Design and Implementation of a DC–DC resonant LLC converter for electric vehicle fast chargers

Academic Edi o : Ahmed Da wish
Recei ed: 30 Decembe 2024
Re ised: 28 Janua y 2025
Accep ed: 14 Feb ua y 2025
Published: 24 Feb ua y 2025
Ci a ion: Rocha, J.; Amin, S.; Coelho,
S.; Rego, G.; A onso, J.L.; Mon ei o, V.
Design and Implemen a ion o a
DC–DC Resonan LLC Con e e o
Elec ic Vehicle Fas Cha ge s. Ene gies
2025,18, 1099. h ps://doi.o g/
10.3390/en18051099
Copy igh : © 2025 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license
(h ps://c ea i ecommons.o g/
licenses/by/4.0/).
A icle
Design and Implemen a ion o a DC–DC Resonan
LLC Con e e o Elec ic Vehicle Fas Cha ge s
Joao Rocha , Saghi Amin , Se gio Coelho , Gonçalo Rego , Joao L. A onso * and Vi o Mon ei o
ALGORITMI Resea ch Cen e, LASI, Uni e si y o Minho, 4800-058 Guima ães, Po ugal;
[email p o ec ed] (J.R.); [email p o ec ed] (S.A.); [email p o ec ed] (S.C.);
[email p o ec ed] (G.R.); [email p o ec ed] (V.M.)
*Co espondence: [email p o ec ed]
Abs ac : This a icle p esen s he design and implemen a ion o a DC–DC powe
con e e o applica ion in elec ic ehicle (EV) as -cha ging sys ems. The p o o-
ype is o he esonan LLC ype and consis s o a high-powe ans o me ope a ing
a high equency, which is an essen ial ea u e o he adequa e beha io o he EV
as -cha ging sys em as a whole. As demons a ed h oughou he a icle, by using
his con e e opology as well as i s speci ic ope a ing modes, such as o achie ing
ze o- ol age swi ching (ZVS) and ze o-cu en swi ching (ZCS), i is possible o enhance
e iciency by educing conduc ion and swi ching losses as well as o inc ease powe densi y.
The de ails o he high-powe high- equency ans o me (HFT), conside ing di e en
designs, a e p esen ed and discussed. Wi h he implemen ed labo a o ial p o o ype ully
de eloped wi h silicon ca bide (SiC) powe semiconduc o de ices, i was possible o
demons a e and alida e he main ea u es o he esonan LLC con e e , including high
e iciency, unde dis inc condi ions o ope a ion.
Keywo ds: elec ic ehicle; as cha ge ; DC–DC esonan LLC con e e ; so swi ching;
high- equency ans o me
1. In oduc ion
Elec ic mobili y and he ongoing ene gy ansi ion a e inc easingly impo an issues
oday. The e is an u gen need o echnological de elopmen in his di ec ion, and people
a e gi ing mo e conside a ion o he use o public anspo a ion and o he u iliza ion o
elec ic ehicles (EVs) [
1
]. This leads o a educ ion in anspo a ion cos s and, om an
en i onmen al pe spec i e, helps o minimize CO
2
emissions and o he pollu an gases [
2
].
As e idence o his, Figu e 1shows a no able inc ease in he numbe o EVs by he end
o 2023, anging om unde 1 million sales o o e 40 million sales [
3
]. Howe e , he e
a e s ill some ac o s ha equi e u he echnological de elopmen o he mass adop ion
o EVs, namely: (i) a educ ion in he EVs’ p ice; (ii) a sho e cha ging ime; and (iii) an
inc ease in he expec ed ba e y li e ime [
4
,
5
]. In addi ion o hese ac o s, he e a e poli ical
and social limi a ions, such as legisla ion ha does no a o he use o hese ehicles o
issues such as he lack o space o cha ging [
6
]. To ha ness he g ow h o elec ic mobili y,
i is equally impo an no only o inc ease he numbe o cha ging s a ions bu also o
de elop imp o ed echnological solu ions o he cha ging p ocess o EVs [
7
]. F om AC
cha ging (on-boa d o o -boa d) o ad anced DC as -cha ging sys ems (o -boa d), as
depic ed in Figu e 2, he e a e a ious opologies ha mee di e en cha ging needs [
8
].
Conce ning he AC–DC s age, whe e se e al opologies a e a ailable, he h ee-phase
boos - ype ec i ie is dis inguished by i s high e iciency, low o al ha monic dis o ion
Ene gies 2025,18, 1099 h ps://doi.o g/10.3390/en18051099
Ene gies 2025,18, 1099 2 o 26
(THD), s aigh o wa dness, cos -e ec i e con igu a ion, and he capaci y o acili a e
bidi ec ional low [9,10].
Ene gies 2025, 18, x FOR PEER REVIEW 2 o 27
needs [8]. Conce ning he AC–DC s age, whe e se e al opologies a e a ailable, he
h ee-phase boos - ype ec i ie is dis inguished by i s high efficiency, low o al ha monic
dis o ion (THD), s aigh o wa dness, cos -effec i e con igu a ion, and he capaci y o a-
cili a e bidi ec ional low [9,10].
Figu e 1. Global EV s ock o e he las 10 yea s (2013–2023) [3].
Howe e , he use o his echnology p esen s a signi ican numbe o challenges, in-
cluding he po en ial o high- ol age s ess, he isk o cu en su ges a he s a , and
ulne abili y o o e cu en du ing sho -ci cui s. Ano he example is he h ee-phase
buck- ype ec i ie , cha ac e ized by he lowe s a ing cu en and ol age s ess on he
componen s. In compa ison, boos ec i ie s esul in g ea e eliabili y and a wide ange
o ou pu ol age egula ion, bu like he boos ype, hey ha e some issues, such as sig-
ni ican conduc ion losses due o he use o diodes and swi ches in se ies [11].
Figu e 2. Composi ion o an EV as cha ge , based on an AC–DC h ee-phase and an isola ed DC–
DC con e e .
Fo he isola ed DC–DC con e e , he li e a u e indica es he use o mul iple opol-
ogies ha may be di ided in o wo main g oups, namely, he isola ed and he non-isola ed
ypes [12]. The in e lea ed h ee-phase LLC esonan con e e is pa icula ly effec i e in
achie ing high efficiency unde ull load condi ions due o he dis ibu ion o powe losses
ac oss he h ee legs [13]. This esul s in a educ ion in he mal s ain and minimiza ion o
s ess on c i ical componen s such as capaci o s and powe swi ches, which con ibu es o
an enhanced le el o eliabili y. Fu he mo e, he leg deac i a ion enables he con e e o
Figu e 1. Global EV s ock o e he las 10 yea s (2013–2023) [3].
Ene gies 2025, 18, x FOR PEER REVIEW 2 o 27
needs [8]. Conce ning he AC–DC s age, whe e se e al opologies a e a ailable, he
h ee-phase boos - ype ec i ie is dis inguished by i s high efficiency, low o al ha monic
dis o ion (THD), s aigh o wa dness, cos -effec i e con igu a ion, and he capaci y o a-
cili a e bidi ec ional low [9,10].
Figu e 1. Global EV s ock o e he las 10 yea s (2013–2023) [3].
Howe e , he use o his echnology p esen s a signi ican numbe o challenges, in-
cluding he po en ial o high- ol age s ess, he isk o cu en su ges a he s a , and
ulne abili y o o e cu en du ing sho -ci cui s. Ano he example is he h ee-phase
buck- ype ec i ie , cha ac e ized by he lowe s a ing cu en and ol age s ess on he
componen s. In compa ison, boos ec i ie s esul in g ea e eliabili y and a wide ange
o ou pu ol age egula ion, bu like he boos ype, hey ha e some issues, such as sig-
ni ican conduc ion losses due o he use o diodes and swi ches in se ies [11].
Figu e 2. Composi ion o an EV as cha ge , based on an AC–DC h ee-phase and an isola ed DC–
DC con e e .
Fo he isola ed DC–DC con e e , he li e a u e indica es he use o mul iple opol-
ogies ha may be di ided in o wo main g oups, namely, he isola ed and he non-isola ed
ypes [12]. The in e lea ed h ee-phase LLC esonan con e e is pa icula ly effec i e in
achie ing high efficiency unde ull load condi ions due o he dis ibu ion o powe losses
ac oss he h ee legs [13]. This esul s in a educ ion in he mal s ain and minimiza ion o
s ess on c i ical componen s such as capaci o s and powe swi ches, which con ibu es o
an enhanced le el o eliabili y. Fu he mo e, he leg deac i a ion enables he con e e o
Figu e 2. Composi ion o an EV as cha ge , based on an AC–DC h ee-phase and an isola ed
DC–DC con e e .
Howe e , he use o his echnology p esen s a signi ican numbe o challenges,
including he po en ial o high- ol age s ess, he isk o cu en su ges a he s a , and
ulne abili y o o e cu en du ing sho -ci cui s. Ano he example is he h ee-phase
buck- ype ec i ie , cha ac e ized by he lowe s a ing cu en and ol age s ess on he
componen s. In compa ison, boos ec i ie s esul in g ea e eliabili y and a wide ange o
ou pu ol age egula ion, bu like he boos ype, hey ha e some issues, such as signi ican
conduc ion losses due o he use o diodes and swi ches in se ies [11].
Fo he isola ed DC–DC con e e , he li e a u e indica es he use o mul iple opolo-
gies ha may be di ided in o wo main g oups, namely, he isola ed and he non-isola ed
ypes [
12
]. The in e lea ed h ee-phase LLC esonan con e e is pa icula ly e ec i e in
achie ing high e iciency unde ull load condi ions due o he dis ibu ion o powe losses
ac oss he h ee legs [
13
]. This esul s in a educ ion in he mal s ain and minimiza ion o
s ess on c i ical componen s such as capaci o s and powe swi ches, which con ibu es o
an enhanced le el o eliabili y. Fu he mo e, he leg deac i a ion enables he con e e o
sus ain i s e iciency ac oss a wide ange o loads, al hough i equi es an ele a ed le el o
design and con ol complexi y due o he necessi y o me iculous leg managemen [
14
].
Ne e heless, he con e e ’s e iciency ends o decline a lowe loads, ende ing i less
Ene gies 2025,18, 1099 3 o 26
sui able o applica ions whe e load le els a e subjec o equen luc ua ions [
15
]. Ano he
opology is he dual ac i e b idge (DAB) con e e , which is pa icula ly well sui ed o
applica ions ha necessi a e bidi ec ional powe low, such as ehicle- o-g id (V2G) and
g id- o- ehicle (G2V) unc ionali ies [
16
]. The modula ion echnique acili a es seamless
swi ching, which con ibu es o a educ ion in swi ching losses and an enhancemen in
o e all e iciency. Fu he mo e, he DAB con e e is capable o e icien ly managing a
di e se ange o ou pu ol ages, he eby o e ing e sa ili y o di e en ypes o ba e -
ies [
17
]. Howe e , bo h sides o he con e e a e suscep ible o high conduc ion losses,
which can be mi iga ed h ough he u iliza ion o a semiconduc o swi ch wi h low on-s a e
d ain- o-sou ce esis ance (RDS(on)) [18,19].
As a inal inpu , he non-isola ed DC–DC mul ile el con e e s ands ou o i s abili y
o gene a e high-quali y powe wi h minimal o al ha monic dis o ion, hus educing
he need o ex ensi e il e ing componen s [
20
]. The con e e is highly scalable and
modula , making i an op imal choice o in eg a ion in o a ious cha ging in as uc u es,
pa icula ly hose equi ing high-powe applica ions. The con e e can e icien ly handle
high ol age le els wi hou he need o ans o me s, which allows a educ ion in bo h
he o e all size and he cos o he cha ging sys em. Howe e , inco po a ing an inc eased
numbe o componen s such as capaci o s and swi ches can esul in a mo e complex sys em
a chi ec u e and highe cos s. In addi ion, he con ol sys em is subjec o g ea e complexi y
due o he need o supe ise a ious ol age le els and swi ching ope a ions [
21
]. In
Table 1, i is possible o see some ad an ages and disad an ages o o he possibili ies o
DC–DC con e e s.
Table 1. Ad an ages and disad an ages o di e en DC–DC powe con e e solu ions o EV
as -cha ging sys ems.
Ad an ages Disad an ages
In e lea ed Th ee-Phase
LLC Resonan •High e iciency in o al load
•Reduc ion in s ess o componen s •Complexi y o design
•Reduced e iciency a low loads
DAB •Bidi ec ional powe low
•So swi ching
•Wide ol age ange
•Loss o con ol
•Complex modula ion
Mul ile el •High powe quali y
•Scalabili y and modula i y •High numbe o componen s
•Complex con ol
LLC Resonan •High e iciency
•So swi ching
•High powe densi y •Complexi y wi h he esonan ank
The dis inguished poin s o his pape a e as ollows: (i) P esen a ion o he con e e
design p ocess showing, s ep by s ep, he mos ele an de ails, including dis inc designs
o he HFT aiming o e i y he in luence o key pa ame e s. (ii) De ailed design and
implemen a ion o a esonan LLC con e e o applica ions in EV as -cha ging sys ems
wi h he main goal o p o ing ha hei use is mo e ad an ageous compa ed wi h he
opologies seen be o e. A compa ison wi h he main simila opologies is also p esen ed and
compa ed in e ms o ad an ages and disad an ages, suppo ing he bene i s o he esonan
LLC con e e . (iii) Compu e alida ion o he mos ele an ope a ion condi ions o
inpu alues o 900 V and wi h a 1:1 con e sion a io a a swi ching equency (
sw
) o
100 kHz, alida ing he ope a ing p inciple and he key ea u es (e.g., ope a ion wi h ZVS
and ZCS). (i ) A labo a o y p o o ype designed o a powe alue o 50 kW, including he
espec i e expe imen al alida ions o di e en scena ios o ope a ion bu o powe alues
Ene gies 2025,18, 1099 4 o 26
only up o 1 kW. ( ) Expe imen al alida ion o a ious HFT con igu a ions o demons a e
ha he de eloped p o o ype achie es high e iciency h ough he imp o emen o he HFT
design as well as he u iliza ion o SiC powe de ices.
This pape is s uc u ed as ollows: Sec ion 2p esen s he LLC esonan con e e ,
while i s ope a ion p inciple is alida ed wi h compu a ional simula ion in Sec ion 3. The
design and de elopmen o he HFT a e p esen ed in Sec ion 4, while he de eloped
labo a o y p o o ype and he espec i e expe imen al alida ions a e p esen ed in Sec ion 5.
The main conclusions a e p esen ed in Sec ion 6.
2. Design o he DC–DC LLC Resonan Con e e
The ini ial concep o a esonan con e e consis s o inco po a ing esonan anks
in o powe con e e s o c ea e oscilla o y ol age and/o cu en wa e o ms, c ea ing
condi ions o ZVS o ZCS. This makes i possible o educe swi ching losses due o so
swi ching [
22
]. Speci ically, isola ed DC–DC LLC esonan con e e s ha e become a good
op ion o EV as -cha ging applica ions, since he use o ZVS and ZCS so -swi ching
echniques helps o educe losses and, consequen ly, signi ican ly inc ease e iciency. This
allows an inc ease in he alue o sw while educing powe densi y [23].
The esonan LLC con e e unde s udy is composed o ou di e en s ages, as
shown in Figu e 3: (i) he ull-b idge in e e , cons i u ing ou swi ching elemen s capable
o gene a ing a squa e wa e wi h he same alue as he inpu ol age, hus suppo ing
a highe cu en ; (ii) he esonan LLC ank, made up o a coil and a capaci o in se ies
and a coil in pa allel wi h he p ima y side o he ans o me ; (iii) he ull-b idge diode
ec i ie ; (i ) an ou pu il e capaci o used o ob ain a cons an ol age a he load [
24
]. In
addi ion o hese ou di e en s ages, he p oposed solu ion also has an HFT (included in
he esonan ank) o ensu e gal anic isola ion be ween he con e e ’s inpu and ou pu ,
so ha i is possible o adjus he ol age h ough he ans o ma ion a io, i necessa y.
Ene gies 2025, 18, x FOR PEER REVIEW 4 o 27
including he espec i e expe imen al alida ions o diffe en scena ios o ope a ion bu
o powe alues only up o 1 kW. ( ) Expe imen al alida ion o a ious HFT con igu a-
ions o demons a e ha he de eloped p o o ype achie es high efficiency h ough he
imp o emen o he HFT design as well as he u iliza ion o SiC powe de ices.
This pape is s uc u ed as ollows: Sec ion 2 p esen s he LLC esonan con e e ,
while i s ope a ion p inciple is alida ed wi h compu a ional simula ion in Sec ion 3. The
design and de elopmen o he HFT a e p esen ed in Sec ion 4, while he de eloped la-
bo a o y p o o ype and he espec i e expe imen al alida ions a e p esen ed in Sec ion
5. The main conclusions a e p esen ed in Sec ion 6.
2. Design o he DC–DC LLC Resonan Con e e
The ini ial concep o a esonan con e e consis s o inco po a ing esonan anks
in o powe con e e s o c ea e oscilla o y ol age and/o cu en wa e o ms, c ea ing
condi ions o ZVS o ZCS. This makes i possible o educe swi ching losses due o so
swi ching [22]. Speci ically, isola ed DC–DC LLC esonan con e e s ha e become a good
op ion o EV as -cha ging applica ions, since he use o ZVS and ZCS so -swi ching
echniques helps o educe losses and, consequen ly, signi ican ly inc ease efficiency. This
allows an inc ease in he alue o
sw
while educing powe densi y [23].
The esonan LLC con e e unde s udy is composed o ou diffe en s ages, as
shown in Figu e 3: (i) he ull-b idge in e e , cons i u ing ou swi ching elemen s capa-
ble o gene a ing a squa e wa e wi h he same alue as he inpu ol age, hus suppo ing
a highe cu en ; (ii) he esonan LLC ank, made up o a coil and a capaci o in se ies and
a coil in pa allel wi h he p ima y side o he ans o me ; (iii) he ull-b idge diode ec i-
ie ; (i ) an ou pu il e capaci o used o ob ain a cons an ol age a he load [24]. In
addi ion o hese ou diffe en s ages, he p oposed solu ion also has an HFT (included
in he esonan ank) o ensu e gal anic isola ion be ween he con e e ’s inpu and ou -
pu , so ha i is possible o adjus he ol age h ough he ans o ma ion a io, i neces-
sa y.
Figu e 3. Block diag am o an EV as -cha ging sys em highligh ing he in e nal cons i u ion o he
esonan LLC con e e .
2.1. Design o he Isola ed DC–DC LLC Resonan Con e e
The unidi ec ional con e e unde s udy, as shown Figu e 4, ope a es in h ee modes
wi h diffe en esonan equencies. Ope a ion o he con e e a an
sw
highe han he
esonan equency (
) is used o he ZVS, which is in a delayed powe ac o mode. Con-
e sely, he ope a ion o he con e e a an
sw
lowe han
is used o he ZCS, which is
in an ad anced powe ac o mode. Ope a ing a
, he ci cui does no ope a e in ei he
ZVS o ZCS; he e o e, o EV cha ging applica ions, i is ecommended ha his LLC
con e e ope a e abo e he 𝑓 o achie e op imal poin o efficiency and s abili y [25]. In
his a icle, a key ocus is ela ed o he design o ope a e abo e he esonance equency,
he e o e op imizing he sys em’s pe o mance in he wides possible equency ange,
wi h a gain alue equal o 1.
Figu e 3. Block diag am o an EV as -cha ging sys em highligh ing he in e nal cons i u ion o he
esonan LLC con e e .
2.1. Design o he Isola ed DC–DC LLC Resonan Con e e
The unidi ec ional con e e unde s udy, as shown Figu e 4, ope a es in h ee modes
wi h di e en esonan equencies. Ope a ion o he con e e a an
sw
highe han he
esonan equency (
) is used o he ZVS, which is in a delayed powe ac o mode.
Con e sely, he ope a ion o he con e e a an
sw
lowe han
is used o he ZCS, which
is in an ad anced powe ac o mode. Ope a ing a
, he ci cui does no ope a e in ei he
ZVS o ZCS; he e o e, o EV cha ging applica ions, i is ecommended ha his LLC
con e e ope a e abo e he
o achie e op imal poin o e iciency and s abili y [
25
]. In
his a icle, a key ocus is ela ed o he design o ope a e abo e he esonance equency,
he e o e op imizing he sys em’s pe o mance in he wides possible equency ange, wi h
a gain alue equal o 1.
Ene gies 2025,18, 1099 5 o 26
Ene gies 2025, 18, x FOR PEER REVIEW 5 o 27
Figu e 4. Topology o he DC–DC esonan LLC con e e .
The inpu DC ol age is con e ed in o a squa e wa e wi h a ull-b idge in e e and
ans e ed o he LLC esonan ank. The esonan ank ci cui consis s o a esonan in-
duc ance (L
), a magne izing induc ance (L
m
), and a esonan capaci o (C
). Diodes D
1
and
D
2
a e used o ec i y he al e na ing ol age a he HFT seconda y side e minals. The
capaci o used as he ou pu load il e is ep esen ed as C
o
. As seen abo e, he isola ed
DC–DC esonan LLC con e e has wo dis inc equencies (
1
and
2
). This can be cal-
cula ed om [26–28] he ollowing:
𝑓

1
2𝜋𝐿

𝐶

(1)
𝑓

1
2𝜋󰇛𝐿

𝐿

󰇜 𝐶

(2)
The load esis ance ans e ed o he esonan equi alen ci cui (R
ac
), which depends
on he ans o ma ion a io (n), is gi en by
𝑅

8 𝑛

𝑅

𝜋

(3)
The quali y ac o (Q) o he LLC con e e is calcula ed using
𝑄𝐿/𝐶
𝑅 (4)
The no malized equency (
n
) is calcula ed by
𝑓

𝑓

𝑓
 (5)
The ela ionship be ween he wo induc ances (m) is gi en by
𝑚𝐿𝐿
𝐿 (6)
Finally, in he equi alen ci cui o he LLC con e e wi h a non-ideal ans o me ,
he a io be ween he ou pu and inpu ol ages (G
d
) co esponds o he gain o he eso-
nan ci cui and is gi en by
Figu e 4. Topology o he DC–DC esonan LLC con e e .
The inpu DC ol age is con e ed in o a squa e wa e wi h a ull-b idge in e e
and ans e ed o he LLC esonan ank. The esonan ank ci cui consis s o a esonan
induc ance (L
), a magne izing induc ance (L
m
), and a esonan capaci o (C
). Diodes D
1
and D
2
a e used o ec i y he al e na ing ol age a he HFT seconda y side e minals. The
capaci o used as he ou pu load il e is ep esen ed as C
o
. As seen abo e, he isola ed
DC–DC esonan LLC con e e has wo dis inc equencies (
1
and
2
). This can be
calcula ed om [26,27] he ollowing:
1=1
2π√L C
(1)
2=1
2πp(L +Lm)C
(2)
The load esis ance ans e ed o he esonan equi alen ci cui (R
ac
), which depends
on he ans o ma ion a io (n), is gi en by
Rac =8n2Rou
π2(3)
The quali y ac o (Q) o he LLC con e e is calcula ed using
Q=√L /C
Rac (4)
The no malized equency ( n) is calcula ed by
n= 2
1
(5)
The ela ionship be ween he wo induc ances (m) is gi en by
m=L +Lm
L (6)
Finally, in he equi alen ci cui o he LLC con e e wi h a non-ideal ans o me , he
a io be ween he ou pu and inpu ol ages (G
d
) co esponds o he gain o he esonan
ci cui and is gi en by

Ene gies 2025,18, 1099 6 o 26
Gd=Vou
Vin
=
 2
12pm(m−1)

22−1+j
12 2
12−1(m−1)Q

. (7)
Thus, i is possible o see ha he pa ame e m ep esen s he ela ionships be ween
he induc o s o he esonan ank, in luencing he maximum gain (G
dmax
) o he con e e .
La ge alues o mallow g ea e lexibili y in he ci cui , enabling highe gains, while
smalle alues es ic he esonan beha io . Figu e 5illus a es how di e en alues o
ma ec he sys em’s pe o mance in e ms o e iciency, s abili y, and ampli ica ion ca-
pabili y, making i an essen ial pa ame e o op imizing he esonan con e e . The
same igu e shows he e ec o Q, which di ec ly in luences he G
d
pa ame e o he
esonan ci cui . Lowe alues o Q esul in wide , la e gain cu es, indica ing
a less selec i e esponse and lowe peak gain. On he o he hand, highe alues o
Qp oduce na owe cu es wi h highe peaks, e lec ing g ea e selec i i y and ampli-
ica ion a ound F
.Hence, he Qe ec demons a es how he quali y ac o con ols
he bandwid h and esonan beha io o he sys em, and i is essen ial o de ining he
pe o mance and e iciency o he esonan con e e .
Ene gies 2025, 18, x FOR PEER REVIEW 6 o 27
𝐺

𝑉

𝑉


󰈑
󰈑
󰇧
𝑓

𝑓

󰇨𝑚󰇛𝑚1󰇜
󰇧
𝑓
𝑓

1󰇨
𝑗
𝑓
𝑓

󰇧
𝑓

𝑓

1󰇨󰇛𝑚1󰇜𝑄
󰈑
󰈑
.
(7)
Thus, i is possible o see ha he pa ame e 𝑚 ep esen s he ela ionships be ween
he induc o s o he esonan ank, in luencing he maximum gain (𝐺
dmax
) o he con e e .
La ge alues o 𝑚 allow g ea e lexibili y in he ci cui , enabling highe gains, while
smalle alues es ic he esonan beha io . Figu e 5 illus a es how diffe en alues o
𝑚 affec he sys em’s pe o mance in e ms o efficiency, s abili y, and ampli ica ion capa-
bili y, making i an essen ial pa ame e o op imizing he esonan con e e . The same
igu e shows he effec o 𝑄, which di ec ly in luences he 𝐺
d
pa ame e o he esonan
ci cui . Lowe alues o 𝑄 esul in wide , la e gain cu es, indica ing a less selec i e
esponse and lowe peak gain. On he o he hand, highe alues o 𝑄 p oduce na owe
cu es wi h highe peaks, e lec ing g ea e selec i i y and ampli ica ion a ound F
.
Hence, he 𝑄 effec demons a es how he quali y ac o con ols he bandwid h and eso-
nan beha io o he sys em, and i is essen ial o de ining he pe o mance and efficiency
o he esonan con e e .
Figu e 5. Plo s o diffe en effec s in he cu e gain: (a) m effec ; (b) Q effec .
2.2. Ad an ages and Disad an ages o he Isola ed DC–DC Resonan LLC Con e e
The LLC esonan con e e is a popula choice o high-efficiency and high-powe -
densi y applica ions such as as cha ge s o EVs. I offe s se e al signi ican ad an ages
Figu e 5. Plo s o di e en e ec s in he cu e gain: (a)me ec ; (b)Qe ec .
2.2. Ad an ages and Disad an ages o he Isola ed DC–DC Resonan LLC Con e e
The LLC esonan con e e is a popula choice o high-e iciency and high-powe -densi y
applica ions such as as cha ge s o EVs. I o e s se e al signi ican ad an ages o e
o he DC–DC con e e opologies. By inc easing he
sw
o alues abo e 100 kHz, his ype
o con e e manages o inc ease he powe densi y, which in u n leads o a educ ion in
Ene gies 2025,18, 1099 7 o 26
he size o he magne ic componen s. Consequen ly, his esul s in a mo e compac and
ligh weigh EV cha ging s a ion design. Gi en his, some ad an ages o he LLC esonan
con e e a e as ollows [
28
]: (i) An inc eased
sw
ansla es in o inc eased powe densi y
and educed size and weigh o he componen s, making he p o o ype ligh e and smalle .
(ii) A highe swi ching e iciency, wi h he use o so -swi ching echniques such as ZVS
and ZCS, minimizes swi ching losses, educing he mal s ess and consequen ly inc easing
he use ul li e o he componen s. (iii) Gal anic isola ion p o ided by he HFT isola es he
inpu om he ou pu , imp o ing ope a ional sa e y and allowing lexibili y in sys em
design. (i ) Imp o ed dynamic esponse h ough
ope a ion allows a quick esponse o
load a ia ions. In addi ion o hese ad an ages, he con e e also has some disad an ages
ha can be an obs acle o i s use o o he pu poses [
29
]: (i) The complexi y o he p ojec
inc eases as i equi es a mo e complex design compa ed wi h o he isola ed DC–DC
con e e opologies; allied wi h he high di icul y o adjus ing he esonan componen s,
his can complica e de elopmen and inc ease p ojec ime. (ii) The cos o high- equency
and high-e iciency componen s can be mo e expensi e, and he p oduc ion o he HFT
can also inc ease he cos . (iii) Con olling an LLC esonan con e e is mo e challenging
due o i s highly equency-dependen esponse. (i ) Ensu ing sys em s abili y unde all
ope a ing condi ions can equi e ad anced con ol echniques. ( ) Small a ia ions in he
alues o he esonan componen s can signi ican ly a ec he con e e ’s pe o mance.
2.3. So Swi ching s. Ha d Swi ching
The swi ching p ocess is ex emely impo an in he de elopmen o powe con e e s
and o he elec onic de ices, as i has a di ec impac on he e iciency and eliabili y o he
sys em. Two main app oaches o swi ching ha e been iden i ied: adi ional swi ching and
so swi ching. Each o hese app oaches has i s dis inc i e cha ac e is ics, ad an ages, and
disad an ages depending on he pu pose o each design [28,29].
In he adi ional app oach, elec onic swi ches, such as ansis o s, a e swi ched on
and o ab up ly [
30
]. Ha d swi ching leads o apid ansi ions in cu en and ol age,
which, in u n, lead o highe swi ching losses. Du ing hese ansi ions, cu en and ol age
a e simul aneously p esen in he semiconduc o de ices, which esul s in signi ican powe
losses, as shown in Figu e 6. In addi ion, hese losses esul in he gene a ion o hea , which
equi es he use o hea sinks and addi ional cooling sys ems o keep he componen s
wi hin he speci ied empe a u e ange. In addi ion, adi ional swi ching me hods ha e
been iden i ied as a sou ce o elec omagne ic in e e ence (EMI) [
31
]. This can dis up
he ope a ion o o he elec onic de ices, and he apid ansi ions in ensi y he elec ical
and he mal s ess on he semiconduc o componen s, hus educing hei li espan and
eliabili y. Howe e , ha d swi ching is simple o implemen and con ol, equi ing no
addi ional ci cui y o manage he swi ching ansi ions [32].
Ene gies 2025, 18, x FOR PEER REVIEW 7 o 27
o e o he DC–DC con e e opologies.By inc easing he
sw
o alues abo e 100 kHz, his
ype o con e e manages o inc ease he powe densi y, which in u n leads o a educ-
ion in he size o he magne ic componen s. Consequen ly, his esul s in a mo e compac
and ligh weigh EV cha ging s a ion design. Gi en his, some ad an ages o he LLC es-
onan con e e a e as ollows [29]: (i) An inc eased
sw
ansla es in o inc eased powe
densi y and educed size and weigh o he componen s, making he p o o ype ligh e and
smalle . (ii) A highe swi ching efficiency, wi h he use o so -swi ching echniques such
as ZVS and ZCS, minimizes swi ching losses, educing he mal s ess and consequen ly
inc easing he use ul li e o he componen s. (iii) Gal anic isola ion p o ided by he HFT
isola es he inpu om he ou pu , imp o ing ope a ional sa e y and allowing lexibili y
in sys em design. (i ) Imp o ed dynamic esponse h ough
ope a ion allows a quick
esponse o load a ia ions. In addi ion o hese ad an ages, he con e e also has some
disad an ages ha can be an obs acle o i s use o o he pu poses [30]: (i) The complexi y
o he p ojec inc eases as i equi es a mo e complex design compa ed wi h o he isola ed
DC–DC con e e opologies; allied wi h he high difficul y o adjus ing he esonan com-
ponen s, his can complica e de elopmen and inc ease p ojec ime. (ii) The cos o high-
equency and high-efficiency componen s can be mo e expensi e, and he p oduc ion o
he HFT can also inc ease he cos . (iii) Con olling an LLC esonan con e e is mo e
challenging due o i s highly equency-dependen esponse. (i ) Ensu ing sys em s abil-
i y unde all ope a ing condi ions can equi e ad anced con ol echniques. ( ) Small a -
ia ions in he alues o he esonan componen s can signi ican ly affec he con e e ’s
pe o mance.
2.3. So Swi ching s. Ha d Swi ching
The swi ching p ocess is ex emely impo an in he de elopmen o powe con e -
e s and o he elec onic de ices, as i has a di ec impac on he efficiency and eliabili y
o he sys em. Two main app oaches o swi ching ha e been iden i ied: adi ional swi ch-
ing and so swi ching. Each o hese app oaches has i s dis inc i e cha ac e is ics, ad-
an ages, and disad an ages depending on he pu pose o each design [29,30].
In he adi ional app oach, elec onic swi ches, such as ansis o s, a e swi ched on
and off ab up ly [31]. Ha d swi ching leads o apid ansi ions in cu en and ol age,
which, in u n, lead o highe swi ching losses. Du ing hese ansi ions, cu en and ol -
age a e simul aneously p esen in he semiconduc o de ices, which esul s in signi ican
powe losses, as shown in E o ! Re e ence sou ce no ound. In addi ion, hese losses
esul in he gene a ion o hea , which equi es he use o hea sinks and addi ional cooling
sys ems o keep he componen s wi hin he speci ied empe a u e ange. In addi ion, a-
di ional swi ching me hods ha e been iden i ied as a sou ce o elec omagne ic in e e -
ence (EMI) [32]. This can dis up he ope a ion o o he elec onic de ices, and he apid
ansi ions in ensi y he elec ical and he mal s ess on he semiconduc o componen s,
hus educing hei li espan and eliabili y. Howe e , ha d swi ching is simple o imple-
men and con ol, equi ing no addi ional ci cui y o manage he swi ching ansi ions
[33].
Figu e 6. Rep esen a ion o he p inciple o ope a ion wi h ha d swi ching.
Figu e 6. Rep esen a ion o he p inciple o ope a ion wi h ha d swi ching.
In con as , so swi ching employs modula ion echniques o educe he losses and
s ess associa ed wi h cu en and ol age ansi ions [
33
]. The wo main so -swi ching
echniques a e ZVS and ZCS. In ZVS swi ching, he swi ches a e igge ed when he ol age
ac oss hem is a i s minimum, hus minimizing he ene gy losses ha occu du ing he
Ene gies 2025,18, 1099 8 o 26
swi ching p ocess [
34
]. This is achie ed h ough esonan ci cui s ha gene a e a sinusoidal
ol age a ia ion, as shown in Figu e 7. On he o he hand, o ZCS swi ching, he swi ches
a e ac i a ed when he cu en lowing h ough hem is ze o.
Ene gies 2025, 18, x FOR PEER REVIEW 8 o 27
In con as , so swi ching employs modula ion echniques o educe he losses and
s ess associa ed wi h cu en and ol age ansi ions [34]. The wo main so -swi ching
echniques a e ZVS and ZCS. In ZVS swi ching, he swi ches a e igge ed when he ol -
age ac oss hem is a i s minimum, hus minimizing he ene gy losses ha occu du ing
he swi ching p ocess [35]. This is achie ed h ough esonan ci cui s ha gene a e a si-
nusoidal ol age a ia ion, as shown in Figu e 7. On he o he hand, o ZCS swi ching,
he swi ches a e ac i a ed when he cu en lowing h ough hem is ze o.
Figu e 7. Rep esen a ion o he p inciple o ope a ion wi h so swi ching.
So swi ching offe s se e al signi ican ad an ages. Fi s ly, he educ ion in swi ch-
ing losses signi ican ly imp o es sys em efficiency, esul ing in lowe hea p oduc ion and
educed hea dissipa ion equi emen s. In addi ion, smoo h ansi ions educe he gene -
a ion o elec omagne ic noise [36]. Ano he impo an ad an age is he inc eased li e ime
o he componen s due o he educed elec ical and he mal s ess. Howe e , hese bene-
i s ha e a lo o challenges. Implemen ing so -swi ching echniques equi es addi ional
ci cui s such as esonan ne wo ks, which inc eases he complexi y o he p ojec . Tuning
and calib a ing hese ci cui s can be complica ed and equi e mo e de elopmen ime, and
manu ac u ing cos s can be highe due o he need o addi ional componen s and mo e
complex ci cui s. The efficiency o so -swi ching echniques can also a y wi h he load,
equi ing sophis ica ed con ol o main ain efficiency o e a wide ope a ing ange, as can
be seen in E o ! Re e ence sou ce no ound. [37].
Figu e 8. Examples o swi ching echniques: (a) ZVS swi ching; (b) ZCS swi ching.
Wi h ha , he choice be ween so swi ching and ha d swi ching depends on he spe-
ci ic equi emen s o he applica ion. So swi ching is ideal o applica ions ha equi e
high efficiency and low EMI. Howe e , he addi ional complexi y and cos can be a sig-
ni ican disad an age in such scena ios. A ca e ul assessmen o he sys em equi emen s
and he cha ac e is ics o each swi ching me hod is essen ial o making he igh choice
when designing powe con e e s and o he elec onic de ices.
Figu e 7. Rep esen a ion o he p inciple o ope a ion wi h so swi ching.
So swi ching o e s se e al signi ican ad an ages. Fi s ly, he educ ion in swi ching
losses signi ican ly imp o es sys em e iciency, esul ing in lowe hea p oduc ion and e-
duced hea dissipa ion equi emen s. In addi ion, smoo h ansi ions educe he gene a ion
o elec omagne ic noise [
35
]. Ano he impo an ad an age is he inc eased li e ime o he
componen s due o he educed elec ical and he mal s ess. Howe e , hese bene i s ha e
a lo o challenges. Implemen ing so -swi ching echniques equi es addi ional ci cui s
such as esonan ne wo ks, which inc eases he complexi y o he p ojec . Tuning and
calib a ing hese ci cui s can be complica ed and equi e mo e de elopmen ime, and
manu ac u ing cos s can be highe due o he need o addi ional componen s and mo e
complex ci cui s. The e iciency o so -swi ching echniques can also a y wi h he load,
equi ing sophis ica ed con ol o main ain e iciency o e a wide ope a ing ange, as can
be seen in Figu e 8[36].
Ene gies 2025, 18, x FOR PEER REVIEW 8 o 27
In con as , so swi ching employs modula ion echniques o educe he losses and
s ess associa ed wi h cu en and ol age ansi ions [34]. The wo main so -swi ching
echniques a e ZVS and ZCS. In ZVS swi ching, he swi ches a e igge ed when he ol -
age ac oss hem is a i s minimum, hus minimizing he ene gy losses ha occu du ing
he swi ching p ocess [35]. This is achie ed h ough esonan ci cui s ha gene a e a si-
nusoidal ol age a ia ion, as shown in Figu e 7. On he o he hand, o ZCS swi ching,
he swi ches a e ac i a ed when he cu en lowing h ough hem is ze o.
Figu e 7. Rep esen a ion o he p inciple o ope a ion wi h so swi ching.
So swi ching offe s se e al signi ican ad an ages. Fi s ly, he educ ion in swi ch-
ing losses signi ican ly imp o es sys em efficiency, esul ing in lowe hea p oduc ion and
educed hea dissipa ion equi emen s. In addi ion, smoo h ansi ions educe he gene -
a ion o elec omagne ic noise [36]. Ano he impo an ad an age is he inc eased li e ime
o he componen s due o he educed elec ical and he mal s ess. Howe e , hese bene-
i s ha e a lo o challenges. Implemen ing so -swi ching echniques equi es addi ional
ci cui s such as esonan ne wo ks, which inc eases he complexi y o he p ojec . Tuning
and calib a ing hese ci cui s can be complica ed and equi e mo e de elopmen ime, and
manu ac u ing cos s can be highe due o he need o addi ional componen s and mo e
complex ci cui s. The efficiency o so -swi ching echniques can also a y wi h he load,
equi ing sophis ica ed con ol o main ain efficiency o e a wide ope a ing ange, as can
be seen in E o ! Re e ence sou ce no ound. [37].
Figu e 8. Examples o swi ching echniques: (a) ZVS swi ching; (b) ZCS swi ching.
Wi h ha , he choice be ween so swi ching and ha d swi ching depends on he spe-
ci ic equi emen s o he applica ion. So swi ching is ideal o applica ions ha equi e
high efficiency and low EMI. Howe e , he addi ional complexi y and cos can be a sig-
ni ican disad an age in such scena ios. A ca e ul assessmen o he sys em equi emen s
and he cha ac e is ics o each swi ching me hod is essen ial o making he igh choice
when designing powe con e e s and o he elec onic de ices.
Figu e 8. Examples o swi ching echniques: (a) ZVS swi ching; (b) ZCS swi ching.
Wi h ha , he choice be ween so swi ching and ha d swi ching depends on he
speci ic equi emen s o he applica ion. So swi ching is ideal o applica ions ha equi e
high e iciency and low EMI. Howe e , he addi ional complexi y and cos can be a signi i-
can disad an age in such scena ios. A ca e ul assessmen o he sys em equi emen s and
he cha ac e is ics o each swi ching me hod is essen ial o making he igh choice when
designing powe con e e s and o he elec onic de ices.
2.4. High-F equency T ans o me Design
The HFT design p ocess begins wi h he analysis o i s equi alen ci cui , as shown in
Figu e 9, o unde s and how he L and Lm alues a e ob ained.
Ene gies 2025,18, 1099 9 o 26
Ene gies 2025, 18, x FOR PEER REVIEW 9 o 27
2.4. High-F equency T ans o me Design
The HFT design p ocess begins wi h he analysis o i s equi alen ci cui , as shown
in Figu e 9, o unde s and how he L
and L
m
alues a e ob ained.
Figu e 9. Equi alen elec ic ci cui o he HFT.
A e ob aining he HFT’s equi alen ci cui , some s eps mus be aken in o consid-
e a ion o calcula e he addi ional pa ame e s, including he numbe o u ns and he
numbe o coppe wi es in pa allel in each coil. Thus, he s eps a e as ollows [38]:
1. Selec he co e wi h he “p oduc o a ea” me hod using he ollowing equa ion,
whe e 𝑃

is he inpu powe , 𝐵

is he maximum magne ic lux densi y, k is he
packing ac o , and J is he cu en densi y:
𝐴

𝑃

2 𝐵

𝑘
𝐽
𝑓

. (8)
2. De e mine he numbe o u ns on he p ima y and seconda y sides o he HFT (N
1
and N
2
, espec i ely) using he ollowing equa ions, whe e S ep esen s he c oss-
sec ional a ea o he magne ic co e:
𝑁

𝑉

4 𝐵

𝑆
𝑓

, (9)
𝑁

𝑉

𝑉

(10)
3. Calcula e he c oss-sec ional a ea o he wi e o 𝐴∗𝐽𝐼 and 𝐴∗𝐽𝐼
h ough he ollowing equa ions, whe e I
1
and I
2
ep esen he cu en in he p ima y
and seconda y windings o he ans o me , espec i ely. I
D1
and I
D2
ep esen he
cu en in he diodes, and I
L ms
ep esen s he ms alue o he cu en in he esonan
ank: 𝑖

𝑖

𝑖

2 𝐼

, (11)
𝑖

𝑁

𝑁

𝐼

1
√2𝐼

. (12)
4. Calcula e he winding losses (Pp) and he losses in he HFT co e (Ps) h ough se e al
s eps o de e mine he HFT’s global efficiency.
4.1. Winding losses: 𝑃

𝐼

𝑖

, (13)
𝑃

󰇛𝐼

𝑅

󰇜 2 , (14)
Figu e 9. Equi alen elec ic ci cui o he HFT.
A e ob aining he HFT’s equi alen ci cui , some s eps mus be aken in o conside a-
ion o calcula e he addi ional pa ame e s, including he numbe o u ns and he numbe
o coppe wi es in pa allel in each coil. Thus, he s eps a e as ollows [37]:
1.
Selec he co e wi h he “p oduc o a ea” me hod using he ollowing equa ion, whe e
Pin
is he inpu powe ,
Bm
is he maximum magne ic lux densi y, kis he packing
ac o , and Jis he cu en densi y:
AP=Pin
2Bmk J sw . (8)
2.
De e mine he numbe o u ns on he p ima y and seconda y sides o he HFT (N
1
and N
2
, espec i ely) using he ollowing equa ions, whe e S ep esen s he c oss-
sec ional a ea o he magne ic co e:
N1=V1
4BmS sw , (9)
N2=V2
V1
(10)
3.
Calcula e he c oss-sec ional a ea o he wi e o
Aw1∗J=I1 ms
and
Aw2∗J=I2 ms
h ough he ollowing equa ions, whe e I
1
and I
2
ep esen he cu en in he p i-
ma y and seconda y windings o he ans o me , espec i ely. I
D1
and I
D2
ep esen
he cu en in he diodes, and I
L ms
ep esen s he ms alue o he cu en in he
esonan ank:
iL ms =iD1+iD2=2I2, (11)
ip ms =N2
N1
IL
1
√2=I1. (12)
4.
Calcula e he winding losses (Pp) and he losses in he HFT co e (Ps) h ough se e al
s eps o de e mine he HFT’s global e iciency.
4.1. Winding losses:
Pp=I2 ms +iD2, (13)
Ps=(I2
ms +Re 2 , (14)
P =Pp+Ps. (15)
Ene gies 2025,18, 1099 16 o 26
4. HFT De elopmen and P o o ype Assembly
To conduc meaning ul es s on he con e e , i is impe a i e o de elop a angible
and e ec i e p o o ype ha can e ec i ely execu e he concep de eloped in he simula ion
en i onmen wi h op imal e iciency. To achie e his, i is c ucial o accu a ely implemen
he HFT, which is a pi o al componen o his opology. Addi ionally, ensu ing he ap-
p op ia e in e connec ions be ween all sys em componen s is essen ial o he success o
his p o o ype.
4.1. Implemen a ion o a Real HFT
As will be seen in he ollowing sec ions, he mos c ucial aspec o he implemen a ion
o a labo a o y p o o ype o his opology is undoub edly he design o he HFT. While
o he componen s a e equally impo an , i is o he u mos impo ance o comp ehend he
way he HFT is o be wound, he co es ha a e o be employed, and he numbe o u ns in
bo h he p ima y and seconda y ci cui s. I should be no ed ha he HFT u ilized in his
de elopmen was designed o accommoda e powe alues o 25 kW and an
sw
o 100 kHz.
To achie e his, a co e wi h he e e ence UF120/80/40 was selec ed om he company IF
co es, om which he e a e h ee co e op ions: PQ co e, EE co e, and UU co e. The UU co e
(UF120/80/40) was selec ed due o i s supe io isola ion and educed leakage induc ance
compa ed wi h he o he op ions. I s symme ic design and enclosed winding con igu a ion
ensu e a mo e uni o m magne ic pa h, igh e coupling be ween windings, and minimal
lux leakage. These ea u es con ibu e o imp o ed elec omagne ic in e e ence (EMI)
supp ession and highe e iciency. The UU co e is pa icula ly ad an ageous o his ype
o applica ion (EV cha ging s a ions), whe e op imized isola ion, minimal ene gy losses,
and eliable pe o mance a e c i ical [
38
], because o i s wo U-shaped co es. Once he co e
had been selec ed, he hickness o he coppe o be used was de e mined, i.e., 0.1 mm,
using 800 cables in pa allel wi h 12 u ns in he p ima y and 12 u ns in he seconda y and
wi h a 1:1 u n a io, due o he main objec i e o ha ing V
ou
be equal o V
in
. To acili a e
he cons uc ion o he HFT, 3D pa s we e p oduced in which he HFT co es we e ixed, as
show Figu e 20.
Ene gies 2025, 18, x FOR PEER REVIEW 17 o 27
leakage induc ance compa ed wi h he o he op ions. I s symme ic design and enclosed
winding con igu a ion ensu e a mo e uni o m magne ic pa h, igh e coupling be ween
windings, and minimal lux leakage. These ea u es con ibu e o imp o ed elec omag-
ne ic in e e ence (EMI) supp ession and highe efficiency. The UU co e is pa icula ly
ad an ageous o his ype o applica ion (EV cha ging s a ions), whe e op imized isola-
ion, minimal ene gy losses, and eliable pe o mance a e c i ical [39], because o i s wo
U-shaped co es. Once he co e had been selec ed, he hickness o he coppe o be used
was de e mined, i.e., 0.1 mm, using 800 cables in pa allel wi h 12 u ns in he p ima y and
12 u ns in he seconda y and wi h a 1:1 u n a io, due o he main objec i e o ha ing V
ou
be equal o V
in
. To acili a e he cons uc ion o he HFT, 3D pa s we e p oduced in which
he HFT co es we e ixed, as show Figu e 20.
Figu e 20. A 3D mold was implemen ed o c ea e he ‘O’-shaped co e wi h he dimensions 17 cm
long, 12 cm wide, 6 cm deep, and 3 mm ma e ial hickness.
Ten diffe en designs we e ini ially es ed o unde s and how he diffe en ways o
winding he HFT affec ed he alues o he L
and he magne iza ion ield, and conse-
quen ly, he alue o he C
. I is possible o e i y some examples inE o ! Re e ence
sou ce no ound.
• Design 1: W ap 12 u ns o he p ima y and 12 u ns o he seconda y on op on
bo h sides.
• Design 2: W ap 6 u ns plus 6 p ima y u ns, and hen, on op, 6 u ns plus 6 sec-
onda y u ns, epea ing on bo h sides.
• Design 3: Wind 12 p ima y u ns and ano he 12 seconda y u ns.
• Design 4: Wind 12 u ns plus 12 u ns o he p ima y on one side and 12 u ns plus
12 u ns on he o he side o he seconda y.
• Design 5: Wind 12 u ns o he p ima y plus 12 u ns o he seconda y on each side,
using he la ge side.
• Design 6: Wind 12 u ns plus 12 u ns in pa allel o he p ima y plus 12 u ns o he
seconda y on bo h sides.
• Design 7: Wind 12 u ns o he p ima y on one side plus 12 u ns o he seconda y
on he o he side, and hen, on he la ge side, wind 12 u ns o he p ima y plus 12
u ns o he seconda y in pa allel.
• Design 8: Wind 12 u ns o he p ima y plus 12 u ns o he seconda y in pa allel on
one side, and hen, 12 u ns o he p ima y plus 12 u ns o he seconda y on he
o he .
• Design 9: W ap 12 u ns o he seconda y, 12 u ns o he p ima y, 12 u ns o he
seconda y, and 12 u ns o he p ima y di ided among he 4 sides.
Figu e 20. A 3D mold was implemen ed o c ea e he ‘O’-shaped co e wi h he dimensions 17 cm
long, 12 cm wide, 6 cm deep, and 3 mm ma e ial hickness.
Ten di e en designs we e ini ially es ed o unde s and how he di e en ways o
winding he HFT a ec ed he alues o he L
and he magne iza ion ield, and consequen ly,
he alue o he C . I is possible o e i y some examples in Figu e 21.
•
Design 1: W ap 12 u ns o he p ima y and 12 u ns o he seconda y on op on
bo h sides.

Ene gies 2025,18, 1099 17 o 26
•
Design 2: W ap 6 u ns plus 6 p ima y u ns, and hen, on op, 6 u ns plus 6 seconda y
u ns, epea ing on bo h sides.
•Design 3: Wind 12 p ima y u ns and ano he 12 seconda y u ns.
•
Design 4: Wind 12 u ns plus 12 u ns o he p ima y on one side and 12 u ns plus
12 u ns on he o he side o he seconda y.
•
Design 5: Wind 12 u ns o he p ima y plus 12 u ns o he seconda y on each side,
using he la ge side.
•
Design 6: Wind 12 u ns plus 12 u ns in pa allel o he p ima y plus 12 u ns o he
seconda y on bo h sides.
•
Design 7: Wind 12 u ns o he p ima y on one side plus 12 u ns o he seconda y on
he o he side, and hen, on he la ge side, wind 12 u ns o he p ima y plus 12 u ns
o he seconda y in pa allel.
•
Design 8: Wind 12 u ns o he p ima y plus 12 u ns o he seconda y in pa allel on
one side, and hen, 12 u ns o he p ima y plus 12 u ns o he seconda y on he o he .
•
Design 9: W ap 12 u ns o he seconda y, 12 u ns o he p ima y, 12 u ns o he
seconda y, and 12 u ns o he p ima y di ided among he 4 sides.
•
Design 10: Wind 12 u ns o he p ima y, 12 u ns o he p ima y, 12 u ns o he
seconda y, and 12 u ns o he seconda y, changing he o de o Design 9.
Ene gies 2025, 18, x FOR PEER REVIEW 18 o 27
• Design 10: Wind 12 u ns o he p ima y, 12 u ns o he p ima y, 12 u ns o he
seconda y, and 12 u ns o he seconda y, changing he o de o Design 9.
Figu e 21. Th ee diffe en designs acco ding o he shape o he body: (a) Design 5, (b) Design 8, (c)
Design 3.
Fo hese designs, he esul s p esen ed in Table 3 we e ob ained.
Table 3. Values o L
m
and L
we e ob ained o diffe en HFT designs.
𝑳𝒐𝟏 𝑳𝒐𝟐 𝑳𝒔𝟏
Design 1 144 µH 154 µH 1.47 µH
Design 2 179 µH 180 µH 12.86 µH
Design 3 176 µH 177 µH 19.2 µH
Design 4 196 µH 199 µH 70 µH
Design 5 163 µH 175 µH 1.7 µH
Design 6 156 µH 157 µH 1.32 µH
Design 7 163 µH 163 µH 3 µH
Design 8 157 µH 158 µH 2.5 µH
Design 9 158 µH 196 µH 18 µH
Design 10 168 µH 170 µH 32 µH
To ob ain hese alues, speci ic es s we e conduc ed in open and closed ci cui s, so
ha i was possible o isualize he alues, as shown in Figu e 22, Figu e 23 and Figu e
24.
Figu e 22. Values ob ained h ough Design 1 es s: (a) L
o1
equal o 144 µH; (b) L
o2
equal o 154 µH;
(c) L
s1
equal o 1.47 µH.
Figu e 21. Th ee di e en designs acco ding o he shape o he body: (a) Design 5, (b) Design 8,
(c) Design 3.
Fo hese designs, he esul s p esen ed in Table 3we e ob ained.
Table 3. Values o Lmand L we e ob ained o di e en HFT designs.
Lo1Lo2Ls1
Design 1 144 µH 154 µH 1.47 µH
Design 2 179 µH 180 µH 12.86 µH
Design 3 176 µH 177 µH 19.2 µH
Design 4 196 µH 199 µH 70 µH
Design 5 163 µH 175 µH 1.7 µH
Design 6 156 µH 157 µH 1.32 µH
Design 7 163 µH 163 µH 3 µH
Design 8 157 µH 158 µH 2.5 µH
Design 9 158 µH 196 µH 18 µH
Design 10 168 µH 170 µH 32 µH
Ene gies 2025,18, 1099 18 o 26
To ob ain hese alues, speci ic es s we e conduc ed in open and closed ci cui s, so
ha i was possible o isualize he alues, as shown in Figu es 22–24.
Ene gies 2025, 18, x FOR PEER REVIEW 18 o 27
• Design 10: Wind 12 u ns o he p ima y, 12 u ns o he p ima y, 12 u ns o he
seconda y, and 12 u ns o he seconda y, changing he o de o Design 9.
Figu e 21. Th ee diffe en designs acco ding o he shape o he body: (a) Design 5, (b) Design 8, (c)
Design 3.
Fo hese designs, he esul s p esen ed in Table 3 we e ob ained.
Table 3. Values o L
m
and L
we e ob ained o diffe en HFT designs.
𝑳𝒐𝟏 𝑳𝒐𝟐 𝑳𝒔𝟏
Design 1 144 µH 154 µH 1.47 µH
Design 2 179 µH 180 µH 12.86 µH
Design 3 176 µH 177 µH 19.2 µH
Design 4 196 µH 199 µH 70 µH
Design 5 163 µH 175 µH 1.7 µH
Design 6 156 µH 157 µH 1.32 µH
Design 7 163 µH 163 µH 3 µH
Design 8 157 µH 158 µH 2.5 µH
Design 9 158 µH 196 µH 18 µH
Design 10 168 µH 170 µH 32 µH
To ob ain hese alues, speci ic es s we e conduc ed in open and closed ci cui s, so
ha i was possible o isualize he alues, as shown in Figu e 22, Figu e 23 and Figu e
24.
Figu e 22. Values ob ained h ough Design 1 es s: (a) L
o1
equal o 144 µH; (b) L
o2
equal o 154 µH;
(c) L
s1
equal o 1.47 µH.
Figu e 22. Values ob ained h ough Design 1 es s: (a)L
o1
equal o 144
µ
H; (b)L
o2
equal o 154
µ
H;
(c)Ls1equal o 1.47 µH.
Ene gies 2025, 18, x FOR PEER REVIEW 19 o 27
Figu e 23. Values ob ained h ough Design 4 es s: (a) L
o1
equal o 196 µH; (b) L
o2
equal o 199 µH;
(c) L
s1
equal o 70 µH.
Figu e 24. Values ob ained h ough Design 8 es s: (a) L
o1
equal o 157 µH; (b) L
o2
equal o 158 µH;
(c) L
s1
equal o 2.5 µH.
Consequen ly, i was possible o ob ain wo solu ions (chosen due o hei p oximi y
o he alues used in he simula ion en i onmen ) o assess hei pe o mance on he
labo a o y p o o ype. Based on he design o wo ans o me s, as show Figu e 25 i was
possible o iden i y he ad an ages and disad an ages o each.
Figu e 25. HFTs de elopmen : (a) The i s HFT had L
o1
equal o 173 µH, L
o2
equal o 172 µH, and
L
s1
equal o 3 µH. (b) The second HFT had 𝐿

equal o 147 µH, 𝐿

equal o 148 µH, and 𝐿

equal
o 12.5 µH.
4.2. P o o ype Assembly
Following he comple ion o he design p ocess, simula ions, and he implemen a ion
o an HFT, i was possible o c ea e a labo a o y p o o ype capable o handling powe up
o 25 kW. The sys em was subdi ided in o ou disc e e p in ed ci cui boa ds (PCBs),
wi h one PCB dedica ed o he con e e ’s inpu powe sys em (comp ising he inpu
Figu e 23. Values ob ained h ough Design 4 es s: (a)L
o1
equal o 196
µ
H; (b)L
o2
equal o 199
µ
H;
(c)Ls1equal o 70 µH.
Ene gies 2025, 18, x FOR PEER REVIEW 19 o 27
Figu e 23. Values ob ained h ough Design 4 es s: (a) L
o1
equal o 196 µH; (b) L
o2
equal o 199 µH;
(c) L
s1
equal o 70 µH.
Figu e 24. Values ob ained h ough Design 8 es s: (a) L
o1
equal o 157 µH; (b) L
o2
equal o 158 µH;
(c) L
s1
equal o 2.5 µH.
Consequen ly, i was possible o ob ain wo solu ions (chosen due o hei p oximi y
o he alues used in he simula ion en i onmen ) o assess hei pe o mance on he
labo a o y p o o ype. Based on he design o wo ans o me s, as show Figu e 25 i was
possible o iden i y he ad an ages and disad an ages o each.
Figu e 25. HFTs de elopmen : (a) The i s HFT had L
o1
equal o 173 µH, L
o2
equal o 172 µH, and
L
s1
equal o 3 µH. (b) The second HFT had 𝐿

equal o 147 µH, 𝐿

equal o 148 µH, and 𝐿

equal
o 12.5 µH.
4.2. P o o ype Assembly
Following he comple ion o he design p ocess, simula ions, and he implemen a ion
o an HFT, i was possible o c ea e a labo a o y p o o ype capable o handling powe up
o 25 kW. The sys em was subdi ided in o ou disc e e p in ed ci cui boa ds (PCBs),
wi h one PCB dedica ed o he con e e ’s inpu powe sys em (comp ising he inpu
Figu e 24. Values ob ained h ough Design 8 es s: (a)L
o1
equal o 157
µ
H; (b)L
o2
equal o 158
µ
H;
(c)Ls1equal o 2.5 µH.
Consequen ly, i was possible o ob ain wo solu ions (chosen due o hei p oximi y
o he alues used in he simula ion en i onmen ) o assess hei pe o mance on he
labo a o y p o o ype. Based on he design o wo ans o me s, as show Figu e 25 i was
possible o iden i y he ad an ages and disad an ages o each.
Ene gies 2025,18, 1099 19 o 26
Ene gies 2025, 18, x FOR PEER REVIEW 19 o 27
Figu e 23. Values ob ained h ough Design 4 es s: (a) L
o1
equal o 196 µH; (b) L
o2
equal o 199 µH;
(c) L
s1
equal o 70 µH.
Figu e 24. Values ob ained h ough Design 8 es s: (a) L
o1
equal o 157 µH; (b) L
o2
equal o 158 µH;
(c) L
s1
equal o 2.5 µH.
Consequen ly, i was possible o ob ain wo solu ions (chosen due o hei p oximi y
o he alues used in he simula ion en i onmen ) o assess hei pe o mance on he la-
bo a o y p o o ype. Based on he design o wo ans o me s, as show Figu e 25 i was
possible o iden i y he ad an ages and disad an ages o each.
Figu e 25. HFTs de elopmen : (a) The i s HFT had L
o1
equal o 173 µH, L
o2
equal o 172 µH, and
L
s1
equal o 3 µH. (b) The second HFT had 𝐿

equal o 147 µH, 𝐿

equal o 148 µH, and 𝐿

equal
o 12.5 µH.
4.2. P o o ype Assembly
Following he comple ion o he design p ocess, simula ions, and he implemen a ion
o an HFT, i was possible o c ea e a labo a o y p o o ype capable o handling powe up
o 25 kW. The sys em was subdi ided in o ou disc e e p in ed ci cui boa ds (PCBs),
wi h one PCB dedica ed o he con e e ’s inpu powe sys em (comp ising he inpu
Figu e 25. HFTs de elopmen : (a) The i s HFT had L
o1
equal o 173
µ
H, L
o2
equal o 172
µ
H, and
L
s1
equal o 3
µ
H. (b) The second HFT had
Lo1
equal o 147
µ
H,
Lo2
equal o 148
µ
H, and
Ls1
equal o
12.5 µH.
4.2. P o o ype Assembly
Following he comple ion o he design p ocess, simula ions, and he implemen a ion
o an HFT, i was possible o c ea e a labo a o y p o o ype capable o handling powe
up o 25 kW. The sys em was subdi ided in o ou disc e e p in ed ci cui boa ds (PCBs),
wi h one PCB dedica ed o he con e e ’s inpu powe sys em (comp ising he inpu
capaci o , SiCs, and esonan capaci o s) and a second PCB alloca ed o he ou pu powe
sys em (encompassing he ec i ie b idge and ou pu il e ). Rega ding he con ol sys em
and he way he powe sys em was implemen ed, i was necessa y o di ide he PCB
con ol sys em in o disc e e sec ions. The ini ial main PCB inco po a ed he DSP u ilized
o he p o o ype’s con ol sys em in addi ion o he powe supply sys ems and d i e s
as well as he cu en and inpu ol age senso s. The second PCB, si ua ed nea he
ou pu , inco po a ed solely he signal p ocessing appa a us o he ol age and cu en
ou pu senso s.
Fu he mo e, in addi ion o he implemen a ion o he PCBs, p o ec ion sys ems,
including con ac o s and swi ches, we e inco po a ed in o he p o o ype o acili a e
a mo e s aigh o wa d connec ion be ween he use and he p o o ype. I should be
no ed ha i is possible o isualize he p o o ype in Figu e 26 ha was implemen ed and
subsequen ly es ed.
Ene gies 2025, 18, x FOR PEER REVIEW 20 o 27
capaci o , SiCs, and esonan capaci o s) and a second PCB alloca ed o he ou pu powe
sys em (encompassing he ec i ie b idge and ou pu il e ). Rega ding he con ol sys em
and he way he powe sys em was implemen ed, i was necessa y o di ide he PCB con-
ol sys em in o disc e e sec ions. The ini ial main PCB inco po a ed he DSP u ilized o
he p o o ype’s con ol sys em in addi ion o he powe supply sys ems and d i e s as
well as he cu en and inpu ol age senso s. The second PCB, si ua ed nea he ou pu ,
inco po a ed solely he signal p ocessing appa a us o he ol age and cu en ou pu
senso s.
Fu he mo e, in addi ion o he implemen a ion o he PCBs, p o ec ion sys ems, in-
cluding con ac o s and swi ches, we e inco po a ed in o he p o o ype o acili a e a mo e
s aigh o wa d connec ion be ween he use and he p o o ype. I should be no ed ha i
is possible o isualize he p o o ype in Figu e 26 ha was implemen ed and subsequen ly
es ed.
Figu e 26. Implemen ed p o o ype wi h he diffe en PCBs and all he connec ions wi h he use .
5. Expe imen al Resul s
Once he es s on he con ol ha dwa e we e comple ed, i was possible o mo e on
o he es s on he powe ha dwa e, which we e di ided in o wo phases. These alues
we e dimensioned using he equa ions seen in Sec ion 2 o his a icle. By se ing he sw
alue, conside ing ha he esonan LLC con e e ope a es mo e efficien ly a highe
swi ching equencies, he 100 kHz equency was selec ed based on he ans o me de-
sign p ocess and applied wi hin he simula ion en i onmen . In an ini ial phase, he i s
HFT, designed o an sw o 104 kHz, was es ed wi h a capaci o ank o a ound 600 µH
and wi h ol age alues be ween 30 V and 60 V. These alues we e hen modi ied. In a
second phase, he second HFT was used o an sw be ween 127 kHz and 131 kHz wi h a
capaci o ank o a ound 800 µH and ol age alues be ween 30 V and 110 V. Wi h hese
es s, i was possible o be e unde s and he con e e ’s ope a ion in a labo a o y en i-
onmen and all he adjus men s needed o 1 kW powe . Du ing he es s, no addi ional
con ol me hods we e implemen ed beyond he ha dwa e-le el con ol p o ided by he
so swi ching achie ed h ough he ci cui design. The p o o ype con ained o e cu en
and o e ol age p o ec ion only.
5.1. Tes wi h Fi s HFT Design
The expe imen al alida ion began by wo king wi hin he ini ially calcula ed alues,
i.e., an sw alue o 104 kHz, a 600 µH capaci o bank, and a ol age alue o 60 V, as shown
in Figu e 27. No wi hs anding, he esul s ob ained we e no as expec ed, since he e was
some noise in Vsec, and he inpu and ou pu cu en wa e o ms (Ip im and Isec, espec i ely)
Figu e 26. Implemen ed p o o ype wi h he di e en PCBs and all he connec ions wi h he use .
Ene gies 2025,18, 1099 20 o 26
5. Expe imen al Resul s
Once he es s on he con ol ha dwa e we e comple ed, i was possible o mo e on
o he es s on he powe ha dwa e, which we e di ided in o wo phases. These alues
we e dimensioned using he equa ions seen in Sec ion 2o his a icle. By se ing he
sw
alue, conside ing ha he esonan LLC con e e ope a es mo e e icien ly a highe
swi ching equencies, he 100 kHz equency was selec ed based on he ans o me design
p ocess and applied wi hin he simula ion en i onmen . In an ini ial phase, he i s HFT,
designed o an
sw
o 104 kHz, was es ed wi h a capaci o ank o a ound 600
µ
H and
wi h ol age alues be ween 30 V and 60 V. These alues we e hen modi ied. In a second
phase, he second HFT was used o an
sw
be ween 127 kHz and 131 kHz wi h a capaci o
ank o a ound 800
µ
H and ol age alues be ween 30 V and 110 V. Wi h hese es s, i was
possible o be e unde s and he con e e ’s ope a ion in a labo a o y en i onmen and all
he adjus men s needed o 1 kW powe . Du ing he es s, no addi ional con ol me hods
we e implemen ed beyond he ha dwa e-le el con ol p o ided by he so swi ching
achie ed h ough he ci cui design. The p o o ype con ained o e cu en and o e ol age
p o ec ion only.
5.1. Tes wi h Fi s HFT Design
The expe imen al alida ion began by wo king wi hin he ini ially calcula ed alues,
i.e., an
sw
alue o 104 kHz, a 600
µ
H capaci o bank, and a ol age alue o 60 V, as shown
in Figu e 27. No wi hs anding, he esul s ob ained we e no as expec ed, since he e was
some noise in V
sec
, and he inpu and ou pu cu en wa e o ms (I
p im
and I
sec
, espec i ely)
we e no comple ely sinusoidal as p edic ed, which indica es a discon inuous mode o
ope a ion, because he ans o me was ope a ing below he alue o F .
Ene gies 2025, 18, x FOR PEER REVIEW 21 o 27
we e no comple ely sinusoidal as p edic ed, which indica es a discon inuous mode o
ope a ion, because he ans o me was ope a ing below he alue o F
.
Figu e 27. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side (V
p im
);
ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT inpu side
(I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
To add ess his, an a emp was made o see how he sys em could be al e ed o im-
p o e i s beha io and achie e he esul s ob ained in he simula ion en i onmen . Ini-
ially, a he same
sw
alue, he capaci o ank was inc eased o 800 µF, as shown in Figu e
28. The e was an imp o emen in he sys em’s pe o mance, which was close o he p e-
dic ed beha io , bu i was s ill no in ag eemen , which led o he conclusion ha i would
be necessa y o adjus he
sw
alue o he co ec alue, i.e., 127 kHz.
Figu e 28. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
.
Channel 1 yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu
side (V
p im
); ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT
inpu side (I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
As F
sw
inc eases, i is clea , as shown in Figu e 29E o ! Re e ence sou ce no ound.,
ha he sys em is ge ing close o he desi ed beha io p edic ed in he simula ion en i-
onmen . Taking in o conside a ion he app oach o he ideal beha io , i was also neces-
sa y o unde s and whe he he con e e was achie ing so -swi ching con ol.
Figu e 27. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
. Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side
(V
p im
); ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT
inpu side (Ip im); o ange line: cu en signal a he HFT ou pu side (Isec).
To add ess his, an a emp was made o see how he sys em could be al e ed o
imp o e i s beha io and achie e he esul s ob ained in he simula ion en i onmen .
Ini ially, a he same
sw
alue, he capaci o ank was inc eased o 800
µ
F, as shown in
Figu e 28. The e was an imp o emen in he sys em’s pe o mance, which was close o he
p edic ed beha io , bu i was s ill no in ag eemen , which led o he conclusion ha i
would be necessa y o adjus he sw alue o he co ec alue, i.e., 127 kHz.
Ene gies 2025,18, 1099 21 o 26
Ene gies 2025, 18, x FOR PEER REVIEW 21 o 27
we e no comple ely sinusoidal as p edic ed, which indica es a discon inuous mode o
ope a ion, because he ans o me was ope a ing below he alue o F
.
Figu e 27. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side (V
p im
);
ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT inpu side
(I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
To add ess his, an a emp was made o see how he sys em could be al e ed o im-
p o e i s beha io and achie e he esul s ob ained in he simula ion en i onmen . Ini-
ially, a he same
sw
alue, he capaci o ank was inc eased o 800 µF, as shown in Figu e
28. The e was an imp o emen in he sys em’s pe o mance, which was close o he p e-
dic ed beha io , bu i was s ill no in ag eemen , which led o he conclusion ha i would
be necessa y o adjus he
sw
alue o he co ec alue, i.e., 127 kHz.
Figu e 28. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
.
Channel 1 yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu
side (V
p im
); ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT
inpu side (I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
As F
sw
inc eases, i is clea , as shown in Figu e 29E o ! Re e ence sou ce no ound.,
ha he sys em is ge ing close o he desi ed beha io p edic ed in he simula ion en i-
onmen . Taking in o conside a ion he app oach o he ideal beha io , i was also neces-
sa y o unde s and whe he he con e e was achie ing so -swi ching con ol.
Figu e 28. Expe imen al es using he i s ans o me wi h 1 kW o powe and 100 kHz o
sw
. Channel 1 yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT
inpu side (V
p im
); ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a
he HFT inpu side (Ip im); o ange line: cu en signal a he HFT ou pu side (Isec).
As F
sw
inc eases, i is clea , as shown in Figu e 29, ha he sys em is ge ing close o he
desi ed beha io p edic ed in he simula ion en i onmen . Taking in o conside a ion he
app oach o he ideal beha io , i was also necessa y o unde s and whe he he con e e
was achie ing so -swi ching con ol.
Ene gies 2025, 18, x FOR PEER REVIEW 22 o 27
Figu e 29. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side (V
p im
);
ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT inpu side
(I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
Wi h he same es ed alues, he appea ance o he ZVS con ol was es ed, as shown
in Figu e 30. This si ua ion is no ye isible, which makes i clea ha he e is some pa-
ame e in he con e e ha does no comple ely ma ch wha has been calcula ed wi h
he alues used in he simula ion en i onmen ; he e o e, i was necessa y o eadjus he
alues calcula ed o he p o o ype.
Figu e 30. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o F
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
The i s alues showed ha inco ec sizing o he HFT can affec he sys em’s be-
ha io . So, i was necessa y o change he HFT design by inc easing he alue o he eso-
nance induc ance and he
sw
, as shown in he ollowing sec ion.
5.2. Tes wi h Second HFT Design
As seen abo e, he esul s ob ained using he i s HFT design we e no as expec ed;
he e o e, a second HFT wi h he same cha ac e is ics as he one designed in Figu e 30
was used, changing he alue o he
sw
(50 kHz) and main aining he alue o he capaci o
ank (800 µH). Conside ing and applying a ol age be ween 0 V and 110 V, an imp o e-
men in he sys em’s beha io is isible in Figu e 31 whe e i is no iceable ha bo h he
Figu e 29. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o
sw
. Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side
(V
p im
); ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT
inpu side (Ip im); o ange line: cu en signal a he HFT ou pu side (Isec).
Wi h he same es ed alues, he appea ance o he ZVS con ol was es ed, as shown in
Figu e 30. This si ua ion is no ye isible, which makes i clea ha he e is some pa ame e
in he con e e ha does no comple ely ma ch wha has been calcula ed wi h he alues
used in he simula ion en i onmen ; he e o e, i was necessa y o eadjus he alues
calcula ed o he p o o ype.
The i s alues showed ha inco ec sizing o he HFT can a ec he sys em’s beha io .
So, i was necessa y o change he HFT design by inc easing he alue o he esonance
induc ance and he sw, as shown in he ollowing sec ion.

Ene gies 2025,18, 1099 22 o 26
Ene gies 2025, 18, x FOR PEER REVIEW 22 o 27
Figu e 29. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal a he HFT inpu side (V
p im
);
ed line: ol age signal a he HFT ou pu side (V
sec
); g een line: cu en signal a he HFT inpu side
(I
p im
); o ange line: cu en signal a he HFT ou pu side (I
sec
).
Wi h he same es ed alues, he appea ance o he ZVS con ol was es ed, as shown
in Figu e 30. This si ua ion is no ye isible, which makes i clea ha he e is some pa-
ame e in he con e e ha does no comple ely ma ch wha has been calcula ed wi h
he alues used in he simula ion en i onmen ; he e o e, i was necessa y o eadjus he
alues calcula ed o he p o o ype.
Figu e 30. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o F
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
The i s alues showed ha inco ec sizing o he HFT can affec he sys em’s be-
ha io . So, i was necessa y o change he HFT design by inc easing he alue o he eso-
nance induc ance and he
sw
, as shown in he ollowing sec ion.
5.2. Tes wi h Second HFT Design
As seen abo e, he esul s ob ained using he i s HFT design we e no as expec ed;
he e o e, a second HFT wi h he same cha ac e is ics as he one designed in Figu e 30
was used, changing he alue o he
sw
(50 kHz) and main aining he alue o he capaci o
ank (800 µH). Conside ing and applying a ol age be ween 0 V and 110 V, an imp o e-
men in he sys em’s beha io is isible in Figu e 31 whe e i is no iceable ha bo h he
Figu e 30. Expe imen al es using he i s ans o me wi h 1 kW o powe and 127 kHz o
F
sw
. Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line:
anode- o-ca hode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line:
cu en signal a he HFT ou pu (Isec).
5.2. Tes wi h Second HFT Design
As seen abo e, he esul s ob ained using he i s HFT design we e no as expec ed;
he e o e, a second HFT wi h he same cha ac e is ics as he one designed in Figu e 30 was
used, changing he alue o he
sw
(50 kHz) and main aining he alue o he capaci o ank
(800
µ
H). Conside ing and applying a ol age be ween 0 V and 110 V, an imp o emen
in he sys em’s beha io is isible in Figu e 31 whe e i is no iceable ha bo h he inpu
ol age and ou pu ol age wa es (blue and ed, espec i ely) and he inpu cu en and
ou pu cu en wa es (g een and o ange, espec i ely) a e simila o hose obse ed in he
simula ion en i onmen .
Ene gies 2025, 18, x FOR PEER REVIEW 23 o 27
inpu ol age and ou pu ol age wa es (blue and ed, espec i ely) and he inpu cu en
and ou pu cu en wa es (g een and o ange, espec i ely) a e simila o hose obse ed
in he simula ion en i onmen .
Figu e 31. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
Ha ing concluded ha he sys em was beha ing as in ended, all ha emained was
o con i m he exis ence o so swi ching, which, as e i ied in he p e ious sec ion, was
he bigges p oblem conce ning he HFT. Figu e 32 shows he exis ence o so swi ching
(blue line and yellow line); i.e., i shows ha he ol age passing h ough he diode is
ac i e only when he sou ce ol age o he MOSFET is equal o ze o, which indica es he
co ec ope a ion o he ZVS con ol. By checking his pa ame e , he co ec ope a ion o
he en i e sys em can now be seen in a labo a o y en i onmen using a p o o ype capable
o p o ing he co ec ope a ion o he con e e despi e he small changes i was subjec ed
o du ing he 1 kW es phase.
Figu e 32. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
Figu e 31. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
. Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line:
anode- o-ca hode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line:
cu en signal a he HFT ou pu (Isec).
Ha ing concluded ha he sys em was beha ing as in ended, all ha emained was
o con i m he exis ence o so swi ching, which, as e i ied in he p e ious sec ion, was
he bigges p oblem conce ning he HFT. Figu e 32 shows he exis ence o so swi ching
(blue line and yellow line); i.e., i shows ha he ol age passing h ough he diode is ac i e
only when he sou ce ol age o he MOSFET is equal o ze o, which indica es he co ec
ope a ion o he ZVS con ol. By checking his pa ame e , he co ec ope a ion o he en i e
Ene gies 2025,18, 1099 23 o 26
sys em can now be seen in a labo a o y en i onmen using a p o o ype capable o p o ing
he co ec ope a ion o he con e e despi e he small changes i was subjec ed o du ing
he 1 kW es phase.
Ene gies 2025, 18, x FOR PEER REVIEW 23 o 27
inpu ol age and ou pu ol age wa es (blue and ed, espec i ely) and he inpu cu en
and ou pu cu en wa es (g een and o ange, espec i ely) a e simila o hose obse ed
in he simula ion en i onmen .
Figu e 31. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
Ha ing concluded ha he sys em was beha ing as in ended, all ha emained was
o con i m he exis ence o so swi ching, which, as e i ied in he p e ious sec ion, was
he bigges p oblem conce ning he HFT. Figu e 32 shows he exis ence o so swi ching
(blue line and yellow line); i.e., i shows ha he ol age passing h ough he diode is
ac i e only when he sou ce ol age o he MOSFET is equal o ze o, which indica es he
co ec ope a ion o he ZVS con ol. By checking his pa ame e , he co ec ope a ion o
he en i e sys em can now be seen in a labo a o y en i onmen using a p o o ype capable
o p o ing he co ec ope a ion o he con e e despi e he small changes i was subjec ed
o du ing he 1 kW es phase.
Figu e 32. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
.
Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line: anode- o-ca h-
ode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line: cu en signal
a he HFT ou pu (I
sec
).
Figu e 32. Expe imen al es using he second ans o me wi h 1 kW o powe and 50 kHz o
sw
. Yellow line: PWM signal a MOSFET 1 (V
_S1
); blue line: ol age signal (V
ds
); ed line:
anode- o-ca hode (V
ak
) ol age signal; g een line: cu en signal a he HFT inpu (I
p im
); o ange line:
cu en signal a he HFT ou pu (Isec).
5.3. E iciency Resul s
Finally, i is possible o see in Figu e 33 ha he con e e achie ed high e iciency in a
simula ion en i onmen using dynamic semiconduc o models o ge as close as possible
o he eal alues. In he expe imen al alida ion, an e iciency o 96.6% was achie ed wi h
an ope a ing powe o 1 kW. This e iciency is expec ed o imp o e as he powe inc eases,
aligning wi h he sys em’s design speci ica ions, whe e he so -swi ching beha io will
app oach i s op imal pe o mance and op imal design.
Ene gies 2025, 18, x FOR PEER REVIEW 24 o 27
5.3. Efficiency Resul s
Finally, i is possible o see in Figu e 33 ha he con e e achie ed high efficiency in
a simula ion en i onmen using dynamic semiconduc o models o ge as close as possible
o he eal alues. In he expe imen al alida ion, an efficiency o 96.6% was achie ed wi h
an ope a ing powe o 1 kW. This efficiency is expec ed o imp o e as he powe inc eases,
aligning wi h he sys em’s design speci ica ions, whe e he so -swi ching beha io will
app oach i s op imal pe o mance and op imal design.
Figu e 33. Efficiency o an ope a ing powe ange om 5 kW o 25 kW in he simula ion en i on-
men .
6. Conclusions
The e olu ion o elec ic ehicles (EVs) and hei widesp ead adop ion p esen s con-
side able challenges ela ed o cha ging imes, ehicle au onomy, ba e y du abili y, and
inno a i e as -cha ging sys ems. Aligned wi h such e olu ion, his a icle p esen s he
design and de elopmen o a labo a o y p o o ype o a DC–DC esonan LLC con e e
o elec ic ehicle (EV) as cha ge s. The a ious phases o he design and implemen a-
ion p ocess o a labo a o ial p o o ype a e ou lined, wi h a special emphasis on he design
o he HFT, which p o es o be he mos c ucial pa o he DC–DC esonan LLC con-
e e . The c i ical signi icance o he high-powe , high- equency ans o me (HFT) de-
sign, which exe s a p o ound in luence on he sys em’s beha io , is p esen ed in de ail,
conside ing a ious designs (e.g., in e ms o he possibili ies o he a angemen o he
p ima y and seconda y windings in he HFT), wi h he objec i e o iden i ying hei e -
ec s on he DC–DC esonan LLC con e e . In addi ion, he p o o ype was ully de el-
oped, conside ing he u iliza ion o silicon ca bide (SiC) powe de ices. A se o ele an
simula ion and expe imen al esul s a e p esen ed, alida ing he ope a ing p inciple as
well as he speci ic ope a ing modes o he DC–DC esonan LLC con e e when achie -
ing ze o- ol age swi ching (ZVS) and ze o-cu en swi ching (ZCS). By combining hese
ea u es, i is possible o educe conduc ion and swi ching losses and, he e o e, achie e a
high-efficiency ope a ion unde dis inc condi ions o ope a ion.
Au ho Con ibu ions:
Concep ualiza ion, J.R. and S.A.; me hodology, J.R.; o mal analysis,
V.M.; in es iga ion, J.R. and S.A.; w i ing—o iginal d a p epa a ion, J.R.; w i ing— e-
iew and edi ing, J.R., S.A., S.C., G.R., J.L.A., and V.M. All au ho s ha e ead and ag eed
o he published e sion o he manusc ip .
Figu e 33. E iciency o an ope a ing powe ange om 5 kW o 25 kW in he simula ion en i onmen .
6. Conclusions
The e olu ion o elec ic ehicles (EVs) and hei widesp ead adop ion p esen s con-
side able challenges ela ed o cha ging imes, ehicle au onomy, ba e y du abili y, and
inno a i e as -cha ging sys ems. Aligned wi h such e olu ion, his a icle p esen s he
design and de elopmen o a labo a o y p o o ype o a DC–DC esonan LLC con e e o
elec ic ehicle (EV) as cha ge s. The a ious phases o he design and implemen a ion
Ene gies 2025,18, 1099 24 o 26
p ocess o a labo a o ial p o o ype a e ou lined, wi h a special emphasis on he design o he
HFT, which p o es o be he mos c ucial pa o he DC–DC esonan LLC con e e . The
c i ical signi icance o he high-powe , high- equency ans o me (HFT) design, which
exe s a p o ound in luence on he sys em’s beha io , is p esen ed in de ail, conside ing
a ious designs (e.g., in e ms o he possibili ies o he a angemen o he p ima y and
seconda y windings in he HFT), wi h he objec i e o iden i ying hei e ec s on he
DC–DC esonan LLC con e e . In addi ion, he p o o ype was ully de eloped, conside -
ing he u iliza ion o silicon ca bide (SiC) powe de ices. A se o ele an simula ion and
expe imen al esul s a e p esen ed, alida ing he ope a ing p inciple as well as he speci ic
ope a ing modes o he DC–DC esonan LLC con e e when achie ing ze o- ol age
swi ching (ZVS) and ze o-cu en swi ching (ZCS). By combining hese ea u es, i is pos-
sible o educe conduc ion and swi ching losses and, he e o e, achie e a high-e iciency
ope a ion unde dis inc condi ions o ope a ion.
Au ho Con ibu ions: Concep ualiza ion, J.R. and S.A.; me hodology, J.R.; o mal analysis, V.M.;
in es iga ion, J.R. and S.A.; w i ing—o iginal d a p epa a ion, J.R.; w i ing— e iew and edi ing,
J.R., S.A., S.C., G.R., J.L.A. and V.M. All au ho s ha e ead and ag eed o he published e sion o
he manusc ip .
Funding: This pape was suppo ed by he Alliance o he Ene gy T ansi ion (56) co- inanced by he
Reco e y and Resilience Plan (PRR) h ough he Eu opean Union. This wo k has been suppo ed by
FCT—Fundação pa a a Ciência e Tecnologia wi hin he R&D Uni P ojec o ALGORITMI Cen e. This
wo k is also pa o he p ojec ha has ecei ed unding om he Eu opean Union’s Ho izon Eu ope
esea ch and inno a ion p og am unde he Ma ie Sklodowska-Cu ie Doc o al Ne wo ks g an ag ee-
men No 101072414 (E2GO). João Rocha has a schola ship wi h he e e ence ATE_BI_2023_02_CALG (2).
Gonçalo Rego has a schola ship wi h he e e ence ATE_BI_2024_01_CALG (1). Se gio Coelho is suppo ed
by he doc o al schola ship 2021.08965.BD, g an ed by FCT—Fundação pa a a Ciência e Tecnologia.
Da a A ailabili y S a emen : The o iginal con ibu ions p esen ed in his s udy a e included in he
a icle. Fu he inqui ies can be di ec ed o he co esponding au ho .
Con lic s o In e es : The au ho s decla e no con lic s o in e es .
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