Family of Soft-Switching

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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 62, NO. 6, JUNE 2015 3473

Family of Soft-Switching Single-Switch PWMConverters With Lossless Passive SnubberMehdi Mohammadi,Student Member, IEEE, Ehsan Adib, and Mohammad Rouhollah Yazdani

AbstractTo increase the power conversion density, de-crease switching losses and electromagnetic interference(EMI), and provide safe operating area for a switch, applyingsnubber circuits which provide soft-switching conditions isinevitable. Among different types of snubber circuits, pas-sive snubbers, due to their simplicity and robustness, arepreferred. These snubber circuits can obtain soft-switchingconditions without any additional switch. Thus, gate driveand control circuits remain simple. In this paper, a simplelossless passive snubber circuit which can be applied onisolated and nonisolated converters is introduced. The pro-posed snubber circuit provides zero-current-switching and

zero-voltage-switching conditions at turn-on and turnoffinstants, respectively. The proposed snubber is applied ona boost converter and analyzed. Also, in order to provethe effectiveness of the proposed snubber circuit fromthe converter efficiency and EMI viewpoints, a 200-W pro-totype boost converter is implemented, and experimentalresults are presented. Also, the simulation results of asoft-switched flyback converter with the proposed snubbercell are presented.

Index TermsEfficiency, electromagnetic interference(EMI), lossless passive snubber, soft switching.

I. INTRODUCTION

THESE days, power conversion density is one of the most

important specifications in designing a power electronic

converter which should be taken into account. Generally, in-

creasing the switching frequency is the most effective way

to achieve this goal. If the problems related to increasing the

switching frequency such as switching losses and electromag-

netic interference (EMI) are not solved, in some cases, increas-

ing the switching frequency not only is not effective in reducing

the volume and weight of a converter but also increases the

volume too. Today, power converters are vastly used in various

applications such as power-factor-correction circuits [1], [2],

bidirectional converters as interface for battery charger and

renewable energy sources [3] and also electric vehicles [4],

photovoltaic cells [5], [6], motor drivers [7], fuel cells [8], [9]

and LED drivers [10]. The interest is to provide soft-switching

Manuscript received June 27, 2014; revised September 22, 2014;accepted October 19, 2014. Date of publication November 20, 2014;date of current version May 8, 2015.

M. Mohammadi and E. Adib are with the Department of Electricaland Computer Engineering, Isfahan University of Technology, Isfahan84156-83111, Iran (e-mail: [email protected]; [email protected]).

M. R. Yazdani is with the Department of Electrical and ComputerEngineering, Isfahan (Khorasgan) Branch, Islamic Azad University,Isfahan 86316-56451, Iran (e-mail: [email protected]).

Color versions of one or more of the figures in this paper are availableonline at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIE.2014.2371436

conditions to increase the power conversion density and to

improve the converter efficiency. In pulse width modulation

(PWM) converters, a useful circuit which is able to decrease

the switching losses is the snubber circuit. Basically, snubber

circuits are divided into two categories: active and passive

snubber circuits. In active snubber circuits, an auxiliary switch

is used to control the function of the snubber circuit [11][21].

In some converters, the auxiliary switch needs a floating gate

driver which results in the complexity of the control circuit

[11][16]. However, for the suggested converter in [16], boot-

strap technique can be used which allows the converter gate

drive circuit to be implemented without any additional magneticelement. To obtain soft-switching conditions, scheduling of the

snubber circuit switch is very important which leads to increase

the complexity of the control circuit and needs the value of

the auxiliary circuit components to be determined exactly [22].

Aside from the issues of active techniques, the most important

advantage of theses snubber circuits is that some of them are

able to provide zero voltage switching (ZVS) and zero current

switching (ZCS) conditions at turn-on and turnoff instants,

respectively [21].

In contrast, passive snubbers utilize only passive compo-

nents, and they provide soft-switching conditions without any

active components. Therefore, the complexity of the control

and snubber circuits is not increased [23]. Until now, many

passive snubbers have been introduced for power converters

[24][30]. In [24], a lossless passive snubber is introduced

which uses two coupled inductors to provide soft-switching

conditions. The role of the coupled inductors is to discharge

the stored energy in the snubber capacitor. Because one of the

coupled inductors is placed in series with the converter switch,

it results in voltage ringing at the switch turnoff instant. Thus,

the converter switch is turned off under semi-ZVS condition. In

[25], a passive lossless snubber circuit which can be engaged

on some isolated and nonisolated converters is suggested. The

number of the snubber circuit components is relatively high,

and also, it uses two distinct cores for implementing the snubber

inductors. In [26], a lossless passive snubber circuit is offered

which is applied on a double ended flyback converter. How-

ever, the snubber circuit provides ZVS and ZCS conditions

at turn-on and turnoff instants, and it increases the circulation

losses. During switch-on time, the current through the snubber

inductors freewheels through the converter switches, which

causes the conductive losses to increase. Also, Fujiwara and

Nomura [27] introduce a passive snubber applied to a boost

converter in which a diode is added in series with the power

path which leads to higher conduction losses of the converter.

Moreover, two distinct inductors are used in the snubber circuit

which affects the size of the converter. In [28], the introduced

snubber circuit in [27] is modified as it saves two diodes and one

0278-0046 2014IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.


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3474 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 62, NO. 6, JUNE 2015

inductor compared to its counterpart. In [29], a lossless passive

snubber is proposed in which a saturable inductor is used.

Although the saturable inductor causes to obtain ZCS condition

for the converter switch, it results in voltage ringing when

turning off the converter switch. In [30], although the snubber

circuit is successful in providing ZCS condition at turn-on for

the converter switch, it cannot provide soft-switching condition

at the turnoff instant. A family of lossless passive soft-switching

methods is introduced in [31] in which the converter switch

voltage stress is not clamped. The advantage of these converters

is the wide range of duty cycle variation.

In addition to efficiency, losses, and soft-switching condi-

tions, another important parameter of a power converter is the

EMI. Nowadays, electromagnetic compatibility (EMC) stan-

dards such as the International Special Committee on Radio

Interference (CISPR) provide another constraint for power

electronics designers to reduce electromagnetic emissions [32].

Since dv/dt and di/dt of the main switch are reduced insoft-switching converters, electromagnetic emissions can be

lowered with respect to hard-switching converters. However,the reduction of electromagnetic emissions may not be suffi-

cient in some soft-switching topologies due to the unwanted

resonances and additional components that would lead to more

parasitic elements [33]. Consequently, the EMI phenomena of

the new soft-switching converters should be evaluated, which is

considered in this paper.

In this paper, a lossless passive snubber circuit is introduced

which has this ability to be applied on a wide variety of isolated

and nonisolated converters. The proposed snubber circuit can

be applied on boost, buck, buckboost, Sepic, Zeta, Cuk, fly-

back, forward, isolated Sepic, isolated Zeta, and isolated Cuk.

In this snubber, the stored energy in the snubbers capacitor

is delivered to the output voltage that decreases the convertercirculation losses. Usually, passive snubber cells are adopted

for a special converter [26][30]. In this snubber, the stored

energy in the snubbers capacitor is delivered to the output

voltage that decreases the converter circulation losses. In some

cases, for example, in [26], the stored energy in the snubber cell

is delivered to the input voltage which causes the circulation

losses to increase. Another advantage is that the EMI of

the boost converter with the proposed snubber cell can be

considerably reduced by the significant reduction of thedi/dtanddv/dt of the main switch which is achieved by providingZCS and ZVS conditions at turn-on and turnoff instances.

Although the proposed snubber circuit can be engaged on

many converters, in this paper, to explain the function of thesnubber circuit, its behavior on a boost converter is discussed.

The operation of the proposed snubber cell on other converters

is the same as its operation on the boost converter.

This paper is organized as follows. In Section II, the pro-

posed snubber circuit is introduced. In Section III, to evaluate

the operation of the proposed snubber circuit, a soft-switched

boost converter which uses the snubber circuit is discussed.

Section IV provides a simple procedure to design the pro-

posed snubber circuit. In order to show the effectiveness of

the snubber circuit, the experimental results of a 200-W boost

converter are offered in Section V. The experimental conducted

EMI measurement is presented in Section VI, and the con-

ducted electromagnetic emissions of the proposed converterand its hard-switching counterpart are compared. Also, other

Fig. 1. Proposed lossless passive snubber cell.

Fig. 2. Soft-switched boost converter with the proposed lossless pas-sive snubber.

power converters that the snubber circuit can be engaged on

are introduced in Section VII. To validate the operation of

the snubber circuit in providing soft-switching conditions in

another converter, the simulation results of an 80-W flyback

converter are offered in Section VII too.

II. THE P ROPOSEDL OSSLESS PASSIVE S NUBBERC EL L

Fig. 1shows the proposed lossless passive snubber cell. The

snubber circuit comprises LS1, LS2, LS3, CS, and four snubberdiodesDS1 throughDS4. The snubber inductorsLS2 and LS3are coupled together. The turn ratio of the coupled inductors

LS2 and LS3 can be calculated using the following equation:

na=

LS2LS3

. (1)

The operation of the proposed snubber circuit is based on

the operation of the flyback converter. The role ofCSandLS1is to provide ZVS and ZCS conditions at turnoff and turn-oninstants, respectively. Other snubber components are used to

recover the stored energy in the snubber capacitor.

After turning the converter switch off, CS is charged. Inthe next switching period, to provide ZVS condition for the

converter switch, it is necessary to discharge the voltage ofCS.While the converter switch is on, the stored energy in CS istransferred toLS2under a resonant process. When the converterswitch is turned off, the stored energy in LS2 is transferredto the output voltage. In cases where the current through LS1is larger than the maximum current through LS2, DS4 is notnecessary. It depends on the converter operating power. In fact,

DS4does not allow the voltage ofCSto become negative in low

output powers. The operation of the snubber cell is discussed indetail in Section III.


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MOHAMMADIet al.: FAMILY OF SOFT-SWITCH IN G SINGLE-SWITCH PWM CO NVERTERS WITH PASSIVE SN UBBER 3475

Fig. 3. Equivalent circuits of each operating mode.

III. PRINCIPLEO PERATION OF THES OF T-S WITCHEDBOOST C ONVERTER

In this section, the operating modes of a soft-switched boost

converter using the proposed snubber circuit are explained.

Fig. 2shows the soft-switched boost converter. LS1,LS2,LS3,

CS, andDS1 throughDS4 are the snubber components. Also,Lin, S, DO, and CO are the main components of the boostconverter. In each switching cycle, the proposed boost converter

has seven operating modes in continuous-conduction mode.

The equivalent circuits of each operating mode are shown in

Fig. 3. Also,Fig. 4shows the key waveforms of the converter.

Prior to Mode 1, it is considered that Sand all snubber diodesare off, the stored energy in LS2and LS3is zero, DO is on, andVCS isVCS(t0).

Mode 1 [t0 t1]: At t0, the converter switch S is turnedon under ZCS due to LS1 and LS2. By turning S on, DS1turns on under ZCS. In this mode, since the current through

LS1 is smaller than the input current iin,DO remains on, and

thus,VO is placed across LS1. Therefore, the current throughLS1 increases linearly with the slope ofVO/LS1. Also, sincethe snubber capacitor CS was charged up to a voltage largerthanVO, turningSon starts a resonance betweenLS2 and CS.During this resonance, VCS reduces, and iLS2 increases. Theimportant equations of this mode are as follows:

iLin(t) = iLin(t0) VO Vin

Lin(t t0) (2)

iLS1(t) = VoLs1

(t t0) (3)

iLS2(t) =VCS(t0)CSLS2

sin((t t0)) (4)

VCS(t) =VCS(t0)cos((t t0)) . (5)

Fig. 4. Key waveforms of the soft-switched boost converter.

Mode 2 [t1 t2]: At t1, iLS1 reaches iin, and thus, DOturns off under ZCS. Therefore,Vinplaces acrossLinand LS1and causes their currents to increase in a linear manner. The

resonance started in Mode 1 betweenLS2 and CScontinues inthis mode.iLS2 andVCS can be calculated via (4) and (5), andiLS1 can be computed with the following equation:

iLin(t) =iLS1(t) =iLs1(t1) + VinLs1+ Lin

(t t1). (6)


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Mode 3 [t2 t3]: At t2, the voltage ofCS becomes zero.The operation of the proposed snubber cell in this mode

depends on the converter operating power. Based on the

current which passes through LS1, two scenarios can occur[Mode 3 (A) and Mode 3 (B)].

Mode 3 (A): If the current through LS1is larger than the current

through LS2which is calculated in (4), DS2turns on underZVS. Because, in this mode, both DS1 and DS2 are onand back to back, the voltage across LS2 is zero, so itscurrent freewheels through DS1 and DS2. This does notallow the current through LS2 to reduce gradually due tothe diode forward voltage. During this mode, the voltage

ofCSremains zero.Mode 3 (B): If the current through LS1is smaller than iLs2(t2),

DS4 turns on under ZVS, and VCs remains zero. Thecurrent throughLS2 freewheels throughDS4 and S.

Mode 4[t3 t4]: Att3,Sis turned off under ZVS. There-fore,iin and iLS1 pass throughDS2 and CS. In this mode, thecurrent ofLincan be considered almost constant, and thus, VCSis charged linearly. Also, at t3, DS3 turns on and provides anopportunity for the stored energy in the core of the coupled

inductors LS2 and LS3 to be transferred to the output. Also,if Mode 3 (B) occurs, at the beginning of this mode, DS4 turnsoff, andDS2 turns on under ZVS. The important equations ofthis mode are the following:

VCS(t) =iinCS

(t t3) (7)

iDS3 =naiLS2(t2) VOLS3

(t t3). (8)

Mode 5[t4 t5]: Att4,VCS reachesVo(1 + LS1/Lin), so

DO turns on under ZVS. Therefore, a voltage ofVinVO

places across Lin, and this inductor discharges in the output.Also, at t4, a resonance begins between CSand LS1. Under thisresonance, the stored energy inLS1 transfers toCS. The max-imum voltage ofCS att5 can be calculated by the use of (9).In this mode, the current throughDS3 can be obtained via (8)

VCS(t5) =VO

1 +

LS1Lin

+

LS1CS

iin(t4). (9)

Mode 6 [t5 t6]: At t5, the current through LS1 reacheszero, andDS2 turns off under ZCS. In this mode,LS3 is beingdischarged in the output voltage.

Mode 7 [t6t7]: At t6, the stored energy in LS3 is dis-

charged completely, so DS3turns off under ZCS. The operationof the converter in this mode is the same as that of a conven-

tional boost converter when its switch is off.

IV. DESIGN C ONSIDERATIONS

Designing the proposed snubber circuit involves to determine

the values ofCS,LS1,LS2, andLS3. The main components ofthe converter can be designed based on the conventional power

converters [34]. For the design procedure, it is assumed that the

values of the filter inductors and capacitors are chosen, so the

variation of the current filter inductor(I)is known. First, LS1andCSshould be calculated to obtain ZCS and ZVS conditions,respectively. These snubber components can be computed the

TABLE IVOLTAGE A ND C URRENT S TRESSES OF THE S EMICONDUCTOR

ELEMENTS OF THE P ROPOSEDB OOST C ONVERTER

same as any snubber inductor and capacitor [34]. To calculate

LS1 and CS, the following equations can be used:

LS1>Vswtrisw

(10)

CS>iswtf2Vsw

(11)

where Vsw, isw, tr, and tfare the maximum switch voltage andcurrent and the switch current rise and fall times, respectively.

To recover the stored energy in the snubber capacitor, the

value ofLS2 should be chosen properly. For this purpose, thequarter of the period of the resonance started in Mode 1 must

be smaller than the minimum switch-on time

LS2< 1

CS

2Tsw

2(12)

whereTswis the minimum switch-on time.After choosing the value ofLS2,LS3 can be computed.LS3

can be chosen with the following equation:

LS3< 1

CS

VO(T Tsw)

VCs

2(13)

whereT is the switching period, Tsw is the maximum switch-on time, and VCs is the maximum voltage ofCS. Note that VCsdepends on the converter topology, and for the boost converter,

it can be calculated using (9).

Aside from calculating the inductors and capacitors of the

proposed snubber circuit, the other important parameters which

should be taken into account are the semiconductor voltage and

current stresses. For the proposed boost converter, the average

current of the converter switch, the converter switch current

stress, and also the switch voltage stress can be computed byuse of (14)(16), respectively. Also, the voltage and current

stresses of the other semiconductor elements of the proposed

boost converter are shown in Table I

isw(av.) = POVinD

+ CSVswTsw

(14)

isw = POVinD

1 +

LS1LS2

I

2

1

LS1LS2

+ VO

CSLS2

(15)

Vsw = (1 + na)VO+

LS1CS

POVinD

+I2

(16)


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TABLE IIPARAMETERS OF THE I MPLEMENTEDC ONVERTER

Fig. 5. (Top) Voltage and (bottom) current waveforms of (a) the con-verter switchSand (b) the output rectifier diodeDO.

where is the converter efficiency which, at the worst case, canbe considered as 0.8.

V. EXPERIMENTAL R ESULTS

The experimental results of an implemented 200-W proposed

boost converter are presented in this section. The input and

output voltages of the proposed converter are 50 and 100 V,respectively. The switching frequency is 100 KHz. IRF640

andUF4006are engaged as the converter switch S andDS3,respectively. MUR460 is used as the diodesDO, DS1, andDS2,and UF4004 is used for DS4. Also, the values of the otherconverters components are shown in Table II. The parasitic

capacitors of the main switch consist of intrinsic parasitics such

asCossand the parasitic capacitor between the drain and earth(chassis). The Coss typical value is 430 pF according to theIRF640 data sheet.

In order to show that soft-switching conditions are achieved

via the proposed snubber circuit for the implemented boost

converter, the voltages and currents of the converter switch S,

rectifier diodeDO, and snubber diodes DS1 through DS3 areshown inFigs. 5and 6 at the nominal output power. In Fig. 5,

Fig. 6. Voltages and currents of the converter semiconductor elements.(a)DS1, (b)DS2, and (c)DS3.

it can be seen that the voltage waveforms of the semiconductor

components are a little different with the theoretical waveforms.

It is due to the imperfect behavior of these components and

their parasitic capacitors. In Fig. 5(a), it can be seen that the

switch voltage stress is higher than the output voltage. It is

because of the energy of the snubber inductor LS1 whichdepends on the output power and input and output voltages.

Generally, the basic boost topology is not engaged in high step-

up applications. Thus, if the output voltage is high, the input

voltage is relatively high, too. Therefore, the input current is

low, and the energy ofLS1 will not result in an unreasonablevoltage stress. Also, the voltage and current of the main switch

under light load (20 W) output power are shown in Fig. 7.

Fig. 7 clarifies that the proposed snubber is able to provide

soft-switching conditions not only in nominal output power but

in light loads as well. To show the differences between the

proposed soft-switched boost converter and a hard-switching

conventional boost converter which is in the same condition,

in Fig. 8, the voltage and current of the conventional hard-switching boost converter switch are shown under 200- and


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Fig. 7. Voltage and current of the converter switch under 20-W outputpower (volt div.= 50V/dec; current div.= 0.5A/dec).

Fig. 8. Voltage and current of the conventional hard-switching boostconverters switch under (a) 200 W and (b) 20 W output powers.

20-W output powers. InFig. 9, the efficiency diagrams of the

proposed boost converter, a conventional boost converter with

an RCD snubber circuit, and a hard-switching boost converterare shown. The diagrams depicted inFig. 9show that the pro-

posed snubber improves the converter efficiency. In Fig. 10, the

photograph of the implemented soft-switching boost converter

is shown.

VI. CONDUCTEDEMI MEASUREMENT

In this section, experimental measurements of the conducted

EMI for the proposed and regular boost converter prototypes

are presented. For the conducted EMI measurement, the CISPR

22 line impedance stabilization networks (LISNs) are inserted

between input lines and the input of the prototypes as shown

in Fig. 11. The drainearth parasitic capacitor (CDE) is animportant common-mode EMI path. In the prototype converter,

Fig. 9. Efficiency diagrams of the proposed converter, hard-switchingboost converter, and soft-switching boost converter which uses anResistor,Capacitor,Diode(RCD) snubber cell.

Fig. 10. Photograph of the implemented proposed boost converter.

Fig. 11. CISPR 22 LISN.

the heat sink voltage is floating with respect to earth, and CDEis measured around 16 pF.

The measured total conducted EMI (on input lineL1) of theproposed and regular boost converters is shown inFig. 12using

the peak detection mode of the HAMEG-HMS1000 spectrum

analyzer. In addition to electromagnetic emissions, the CISPR

22 class A limit is shown with the dashed line for the 150-KHz

30-MHz frequency band. According to Fig. 12, the two main

EMI peaks of the conventional boost converter are 84 and

86.5 dBV at 270 kHz and 11 MHz, respectively. The cor-responding values for the proposed converter are around 78.5

and 73 dBV at about 270 kHz and 15.6 MHz, respectively.Consequently, the first and second EMI peaks are reduced by

about 6.5 and 13.5 dBV. In other words, the proposed losslesspassive snubber has the benefit of EMI reduction of up to

13.5 dBV with respect to the hard-switching boost converter.For better comparison, the EMI peaks for various frequency


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Fig. 12. Conducted EMI measurement. (a) Hard-switching boost con-verter; vertical axis: 0100 dBV; horizontal axis: 0.15 M30 MHz.(b) Proposed boost converter; vertical axis: 090 dBV; horizontal axis:

0.15 M30 MHz.

Fig. 13. Comparison between experimental results of conducted elec-tromagnetic emissions for the regular and proposed boost converters.

ranges are shown in Fig. 13 for two prototypes. According

to this figure, conducted electromagnetic emissions are sig-

nificantly decreased in many frequency ranges by the use of

the proposed lossless passive snubber due to providing soft-

switching conditions which leads to reduceddi/dt and dv/dtof the converter switch. Although there are boundary levels

for few frequencies with respect to the CISPR 22 class A

limit such as around 15 MHz, this standard can be satisfiedfor the proposed converter. In general, only by providing soft-

Fig. 14. Nonisolated soft-switched converters with the proposed pas-sive snubber. (a) Buck. (b) Buckboost. (c) Cuk. (d) Sepic. (e) Zeta.

switching conditions may the EMC standards not be satisfied by

passive and active methods [33]. Thus, the EMC improvement

is another benefit of the boost converter with the proposed

snubber.

VII. OTHERS OF T-S WITCHEDTOPOLOGIESW IT HTH E P ROPOSEDS NUBBERC EL L

The proposed snubber circuit can be applied on buck, boost,

buckboost, Sepic, Zeta, Cuk, forward, flyback, isolated Sepic,

isolated Zeta, and isolated Cuk. The operation of the proposed

snubber cell is the same as its operation on the boost converter

which is discussed in Section III. In Figs. 14 and 15, the

nonisolated and isolated converters using the proposed snubber

circuit are depicted. In isolated converters, due to the converter

transformer leakage inductor, applying Ls1 is not necessary.In order to put the operation of the isolated soft-switching

converters into perspective, the simulation results of a soft-switched flyback converter with a nominal output power of


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Fig. 15. Isolated soft-switched converters with the proposed passivesnubber. (a) Forward. (b) Flyback. (c) Isolated Cuk. (d) Isolated Sepic.(e) Isolated Zeta.

TABLE IIIVALUES OF THE F LYBACK C ONVERTER SC OMPONENTS

80 W are presented. The values of the soft-switching flyback

converters components are stated in Table III. In Fig. 16,

the simulation voltage and current waveforms of the flyback

converter switch and output rectifier diodeD are shown, whichindicates the obtained soft-switching conditions.

Fig. 16. Simulation waveforms of the soft-switched flyback con-verter with the proposed snubber circuit. (a) Converter switch voltage,

(b) converter switch current, (c) output rectifier diode voltage, and(d) output rectifier diode current (time scale: 0.5 s/dec).

VIII. CONCLUSION

Providing soft-switching conditions in power converters has

many advantages such as increasing the converter efficiency

and power conversion density and reducing EMI. In this paper,

a lossless passive snubber circuit which is able to be applied

in many isolated and nonisolated converters is introduced. The

experimental results clarify that the converters efficiency is

improved by the use of the proposed lossless snubber circuit.

Also, in order to verify the effectiveness of the proposedsnubber in reducing the conducted EMI, the conducted EMI of

the boost converter with the proposed snubber is measured and

is compared to its hard-switching counterpart, which shows the

significance of the conducted EMI reduction.

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[12] E. Adib and H. Farzanehfard, Family of soft-switching PWM converterswith current sharing in switches,IEEE Trans. Power Electron., vol. 24,no. 4, pp. 979985, Apr. 2009.

[13] E. Adib and H. Farzanehfard, Family of zero-voltage transition pulsewidth modulation converters with low auxiliary switch voltage stress,

IET Power Electron., vol. 4, no. 4, pp. 447453, Apr. 2011.

[14] M. Pavlovsk, G. Guidi, and A. Kawamura, Buck/boost dc-dc convertertopology with soft switching in the whole operating region,IEEE Trans.Power Electron., vol. 29, no. 2, pp. 851862, Feb. 2014.

[15] L. Chen, H. Hu, Q. Zhang, A. Amirahmadi, and I. Batarseh, A boundary-mode forward-flyback converter with an efficient active LC snubbercircuit, IEEE Trans. Power Electron., vol. 29, no. 6, pp. 29442958,Jun. 2014.

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sition PWM converters,IET Power Electron., vol. 1, no. 2, pp. 214223,Jun. 2008.

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Mehdi Mohammadi (S14) was bor n inIsfahan, Iran, in 1989. He received the Asso-ciates in electrical engineering (electronics)from the Shahid Mohajer Technical Institutionof Isfahan, Iran, in 2008, the B.S. degreein electrical engineering (electronics) fromthe Bonyan Institute of Higher Education,Shahinshahr, Iran, in 2010, and the M.S.degree in electrical engineering (electronics)

from the Isfahan University of Technology (IUT),Isfahan, in 2014. He is currently working towardthe Ph.D. degree in electrical engineering at the University of BritishColumbia, Vancouver, BC, Canada, where he works on advancedcontrol methods for power converters and new switching topologies.

He is currently with the Power Switching Laboratory at IUT. Hisresearch interests include advanced control schemes for power con-verters, high-frequency soft-switching converters, their applications, andelectromagnetic interference.

Ehsan Adibwas born in Isfahan, Iran, in 1982.He received the B.S., M.S., and Ph.D. degreesin electrical engineering from the Isfahan Uni-versity of Technology, Isfahan, in 2003, 2006,and 2009, respectively.

He is currently a Faculty Member in the De-partment of Electrical and Computer Engineer-ing, Isfahan University of Technology. He is theauthor of more than 50 papers published in

journals and conference proceedings. His re-search interests include dcdc converters and

their applications and soft-switching techniques.Dr. Adib was the recipient of the Best Ph.D. Dissertation Award from

the IEEE Iran Section in 2010.

Mohammad Rouhollah Yazdani was born inIsfahan, Iran, in 1978. He received the B.S.degree in electrical engineering from the IsfahanUniversity of Technology, Isfahan, in 2001,

the M.S. degree in electrical engineering fromthe Islamic Azad University, Najafabad Branch,Najafabad, Iran, in 2004, and the Ph.D. degreein electrical engineering from the Islamic AzadUniversity, Sciences and Research Branch,Tehran, Iran, in 2011.

Since 2011, he has been a Faculty Memberin the Department of Electrical and Computer Engineering, Isfahan(Khorasgan) Branch, Islamic Azad University. His research interestsinclude soft-switching converters, electromagnetic interference mod-eling and reduction techniques, signal integrity, and electromagneticcompatibility issues.

Documents

Family of Soft-Switching