A HIGH FREQUENCY, HIGH EFFICIENCY,

HIGH POWER FACTORISOLATED ON-BOARD

BATTERY CHARGER FOR ELECTRIC VEHICLE

Yuqi Wei

Professor Adel Nasiri

Contents

01 Introduction

PFC unit02

LLC resonant converter03

Proposed topology04

Magnetic control05

Conclusions and future work06

Design Considerations

Capacitor: Voltage ripple requirement

Inductor: Current ripple requirement

Diodes: Current and voltage stress Input voltage Uin 90V-264V

Output power Po 330W-3.3kW

Switching frequency fs 100kHz

Output voltage Vo 400V

CB

D1

D2 Sm4

LB1uin

Sm1

RL

LB2

Sm2

Sm3

+ -

B

in o inin o

o B

n inin o

o B

, / 2

(1 ) , / 2

s

Li

s

u u uT u uu Li

u uT u uu L

2in o in

B

o,max o

( )20%s

u u uLP f u

13002

oB

L o o

PC uFf V V

, max , max, ,

, min , min

2 2 52in oD peak in peak

in in

P PI I AV V

,, 26

2in peak

D RMSII A

Interleaved technology: Current is evenly sharedMOSFETS: Current and voltage stress

Simulation Verification

0.285 0.29 0.295 0.3Time (s)

0

-10

-20

-30

10

20

30

Vin Iin

0.285 0.29 0.295 0.3Time (s)

0

-20

-40

20

40

Vin Iin

0.285 0.29 0.295 0.3Time (s)

0

-20

-40

20

40

Vin Iin

Input voltage 90V 220V 264V

0 500 1000 1500 2000 2500 3000 35000.98

0.982

0.984

0.986

0.988

0.99

0.992

0.994

0.996

0.998

1

Output power/W

Pow

er fa

ctor

Vin=220VVin=110V

0 500 1000 1500 2000 2500 3000 35002

4

6

8

10

12

14

16

Output power/W

THD

/%

Vin=110VVin=220V

Power factor and THD

Summary

Topology Traditional Boost PFCTotem-pole

bridgeless PFC

SiC based Totem-pole

interleaved bridgeless PFC

Slow Diode 4 2 2

MOSFET 1(Si) 2(Si) 4(SiC)

Fast Diode 1 0 0

Input Inductor 1 1 2

Output Capacitor 1 1 1

Semiconductors in Path 3 2 3

Efficiency Low High Best

Operation Mode CCM DCM CRM CCM CRM CCM CRM DCM

Operation AnalysisD1 D2

t0 t2

0

0

t1 t3

I(Lm) I(LS)

Is

S4

Lr Cr

Lm

T

RL

S1

+

_

uac

Co

S3

S2

VinA

B

iLr

iLm

ip

is

+

_

uo

D2

D3 D4

C1 C2

C3 C4

n:1

Ds1 Ds2

Ds3 Ds4

D1

S4

Lr Cr

Lm

T

RL

S1

+

_

uac

Co

S3

S2

VinA

B

iLr

iLm

ip

is

+

_

uo

D2

D3 D4

C1 C2

C3 C4

n:1

Ds1 Ds2

Ds3 Ds4

D1

S4

Lr Cr

Lm

T

RL

S1

+

_

uac

Co

S3

S2

VinA

B

iLr

iLm

ip

is

+

_

uo

D3 D4

C1 C2

C3 C4

n:1

Ds1 Ds2

Ds3 Ds4

D1 D2

t0-t1

Operation waveforms

t1-t2

t2-t3

Voltage Gain

Region 1: At the right hand of both curves. In this region, the voltage gain is lower than 1, the input impedance is inductive and the switches can achieve ZVS, the diodes at the secondary side are hard switching;Region 2: At the right hand of the resistive curve and the left hand of line fs*=1. In this region, the voltage gain is higher than 1, the input impedance is inductive and the switches can achieve ZVS, the rectifier diodes can achieve ZCS;Region 3: At the left hand of both curves. In this region, the voltage gain can be higher or lower than 1, the input impedance is capacitive and the switches can achieve ZCS, the rectifier diodes can achieve ZCS.

0.4 0.8 1.2 1.6 20

1

2

3

* 1s

f

Resistive Curve

1

3

2

0.5Q

0Q

2Q

10Q

1

/ /( )1/ / /

o s m acs

AB s r s r s m ac

nV jw L RM H jwV jw L jw C jw L R

2 * 3 * 3 2 * 2 * 2*

2 * 3

2

1 1( ) ( ) (1 ) (1 ( ) )( )( )

ac

s s s ss

s

RZ f j f Q f ff Q Q

fQ

Voltage gain curve with different Q value

Battery charging profile

Proposed topology

VA

CC Charge CV Charge

2.75

4.2

0.78

7.8

D1

D2

Sm4

CB

uin + -

Sm1

Interleaved Totem-pole Bridgeless Boost PFC Unit

S4

Lr1 Cr1

Lm1

RL

S1Co1

S3

S2

T1

Lr2 Cr2

Lm2

Co2T2

Full-Bridge LLC Resonant Converter Unit

Sm2

Sm3

LB1

LB2

Variable Inductor

Why two LLC resonant converters and magnetic control?

1. System efficiency is improved;2. Power handling ability is

improved;3. The EMI design is simplified;4. The complexity of control

circuit is reduced.

Operation point a b c d e f

Charge mode CC CC CC/CV CV CV CV

Output power/W 2070 2333 3319 2002 1140 362

Output voltage of LLC1/V 210.5 210.6 210.5 211.1 212.2 214.3

Output voltage of LLC2/V 58.5 113.3 211.2 208.6 214.4 226.4

Output current/A 7.69 7.20 7.84 4.77 2.67 0.82

Equivalent load

resistance/ohm35 45 54 88 160 538

Simulation Verification

Simulation Verification

0 100 200 300 400 500 60040

60

80

100

120

140

160

180

200

220

Equivalent load resistance/ohm

Out

put v

olta

ge/V

LLC1LLC2

0 100 200 300 400 500 6000

500

1000

1500

2000

2500

3000

3500

Equivalent load resistanc/ohm

Out

put p

ower

/W

Output voltage of LLC1 and LLC2 Output power of the system

Introduction

IND

UC

TAN

CE

VA

LUE

DC BIAS CURRENT

Lmax

Lmin

Inductance value versus dc bias current

CONTROLIDC

NDCL

NAC

g NDC

DCAC AC

Typical structure of a variable inductor

Voltage/Current Reference

Voltage/Current Feedback

ErrorGc

PI Controller

Limiter

Current Control Signal Current

SourceVariable Inductor

A

B

Operation principle for the variable inductor

Spice Modeling and Simulation

Variable inductor model implemented in LTspice

Simulation result for the inductance value versus dc bias current

Conclusions and Future WorkConclusions In this paper, a high frequency, high efficiency and high power factor isolated on-board battery charger is proposed. The topology includes two parts, AC/DC power factor correction (PFC) circuit unit and DC/DC converter unit. The following characteristics are achieved. 1) For AC/DC part, the efficiency is improved by using SiC devices; the inductor volume and input current ripple are reduced due to interleaved technology; and the measured power factor is greater than 0.98 during the whole operation range, the THD of the input current is less than 5% under different operating conditions; 2) For DC/DC part, by carefully designing the resonant tanks for two LLC resonant converters, ZVS operation for the primary switches and ZCS operation for the secondary diodes are achieved during the whole operation range. 3) The EMI design is much easier and system control is simplified due to the magnetic control; therefore, a constant frequency can be implemented. The simulation verifies the operation of variable inductor.

Future Work Hardware implementation and experimental validation are the focus of the future work.