depletion-mode sicvjfet simplifies high voltage smps · high voltage smps start-up circuits...

Depletion-mode SiC VJFETSimplifies High Voltage SMPS

Nigel Springett, Robin Schrader, and Jeff Casady,SemiSouth Laboratories, Inc.201 Research Blvd.Starkville, MS, USA

PCIM 2012: Nürnberg, Germany

1700V Depletion-mode SiC VJFETSimplify High Voltage SMPS?

Simple start-up Lower switching losses Easy to drive Compact high creapage package. SMD assembly

HOW does a


Depletion-mode SiC VJFETSimplifies High Voltage SMPS

Simple start-up :-

High voltage SMPS start-up circuits required for digital control and gate driver circuits usually have several lossy discrete components.

A depletion-mode SiC VJFET, used in a cascode configuration, supplies the controller/IC start-up current and eliminates high-voltage start-up circuitry


low component count

Simple

robust

Slow start-up at low line

high quiescent power loss

fast start-up at low line

Low quiescent power loss

Mosfet need to be protected against overload

High dissipation in fet under Short Circuit

Vin

R18

C16

R19

C15

D10

12

D21

12

D22

12

C17

D9

12

D16

2 1

D19

21

D20

2 1

Drv

Sns

comp Vcc

VeeInv

Ct5V

IC3

1

2

3

4 5

6

7

8

L3

-A

1

2

L5

-B

3

4

L6

-B

3

4

D

G

S

Q9

g

Q104

231

5

R15

R16

R17

Q114

231

5

17V

1n4148

800V mosfet

200V

200V

10V

18V

500V

500V

Vin

R14

C12

C13

C14

D8

12

D15

2 1

D17

21

D18

2 1

Drv

Sns

comp Vcc

VeeInv

Ct5V

IC2

1

2

3

4 5

6

7

8

L2-A

1

2

L3-B

3

4

L4-B

3

4

D

G

S

Q7

g

Q84

231

5

R12

R13

C1

1

2 1n4148 10V

18V

~2M0.5W

Traditional start up solutions

Solution 1 Using resistor Solution 2 Using mosfet


Alternative using Stackfet ™

Low cost solution

high component count

high switching losses

Best suited low power applications

Pwm with integrated 700V mosfet

600V 4.4Ω mosfet


jfet supplies start-up current

Vin

D11

2 1

Q64

231

5

C9

R11

C10

L2-B

3

4

D7

12

Drv

Sns

comp Vcc

VeeInv

Ct5V

IC1 3

4 5

6

7

8

R9

R10

D

G

S

Q5

g

D12

21

L1-B

3

4

L1-A

1

2

D13

21

C11

D14

2 1

Vout

1n4148 10V

18V

Small bleeder to lift gate

To get high enough voltage

No extra components

Jfet needs no extra heat sink

Fast start-up

Using depletion mode Jfet as start-up cell in 3-phase power supplies


How bleeder works

7

Threshold of jfet GS is~ -4V

Without resistor

gate could be 0V and

source about 4V

Resistor supplies current to

increase gate voltage

Gate rises

Source rises

Gate clamped by zener D7


VeeVcc

TX

1-F

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

XR2100K

TVS1

PESD15VL1BA

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1

D3

0R

XD2LL4148

D12

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

D14

XR1100K

L9951APWM control

CS

gate

1.5KE400A

9V 120µA start-up

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108

ch1 Vds jfet, ch2 gate jfet, Ch3 jfet source ch4 Vcc


SJDP170R1400

l5991A pwm


VeeVcc

TX

1-F

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

XR2100K

TVS1

PESD15VL1BA

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1

D3

0R

XD2LL4148

D12

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

D14

XR1100K

L9951APWM control

CS

gate

1.5KE400A

9V 120µA start-up

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108

ch1 Vds jfet, ch2 gate jfet, Ch3 jfet source ch4 Vcc


Start up independent of line voltage

SJDP170R1400

l5991A pwm


VeeVcc

TX

1-F

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

XR2100K

TVS1

PESD15VL1BA

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1

D3

0R

XD2LL4148

D12

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

D14

XR1100K

L9951APWM control

CS

gate

1.5KE400A

9V 120µA start-up

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108


SJDP170R1400

l5991A pwm

Almost constant current charging of cap, determined by

D2 (26V) and XR2 (100k)


Small SiC chip. Small capacitancesmall losses

Early sample in to-257 (metal to-220)

0.0 µJ

2.0 µJ

4.0 µJ

6.0 µJ

8.0 µJ

10.0 µJ

12.0 µJ

14.0 µJ

0 V 500 V 1000 V 1500 V

Measured Turn-off switching losses Eoss in 120W flyback

Turn-off switchinglosses Eoss


Vee

VeeVcc

TX

1-F

A

K

R IC31TL431CD

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

CO

N2

R312K7

XR2100K

C19

TVS1

PESD15VL1BAC22

CO

N1

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1SFH617

C31100N

R3224K

D3

0R

XD2LL4148

D12

C18

R344K7

R354K7

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

C31N

R2622R

D14

XR1100K

L9951APWM control

fb

CS

gate

1.5KE400A

9V 120µA start-up47µF

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108

input 300-800V DC

24V

SchematicNo high-voltage start up components

Space saving

SJDP170R1400

l5991A pwm


Schematic

Vee

VeeVcc

TX

1-F

A

K

R IC31TL431CD

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

CO

N2

R312K7

XR2100K

C19

TVS1

PESD15VL1BAC22

CO

N1

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1SFH617

C31100N

R3224K

D3

0R

XD2LL4148

D12

C18

R344K7

R354K7

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

C31N

R2622R

D14

XR1100K

L9951APWM control

fb

CS

gate

1.5KE400A


47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108

input 300-800V DC

24V

No high-voltage start up components

Space saving

SJDP170R1400

l5991A pwm


Vee

VeeVcc

TX

1-F

A

K

R IC31TL431CD

C110N 1000V

D13

TX

1-E

TX

1-A

XD1LL4148

C21

CO

N2

R312K7

XR2100K

C19

TVS1

PESD15VL1BAC22

CO

N1

R10147K

R10247K

D4 D8

D5

R25R56 1W

OC1SFH617

C31100N

R3224K

D3

0R

XD2LL4148

D12

C18

R344K7

R354K7

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

C31N

R2622R

D14

XR1100K

L9951APWM control

fb

CS

gate

1.5KE400A


47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

STTH3002CT

stth108stth108

input 300-800V DC

24V

SJDP170R1400

Switching at 800V input

100kHz, 1300V 1.4A pk

l5991A pwm


Low losses: hard switched 400V input

24V 5A output

Irms switch=.511A gives conduction losses of 0.36W

switching losses 18µJ=1.8W @ 100kHz

Total 2.2W losses hard switched at 100kHz, 1.3W@50kHz

Note switching losses not dependent on Temperature

Turn-on 20nS/div Turn-off 20ns/div

12µJ 7µJ


24V 5A output

Irms switch=.402A Conduction losses =0.23W

switching losses 32µJ=3.2W @ 100kHz

Total losses hard-switched @100kHz, 3.5W @50kHz1.8W

Note switching losses independent of Temperature

Low losses: hard switched 800V inputTurn-on Turn-off

10µJ22µJ


Switching waveforms 1000V inTurn-on Turn-off

1350V

1200V

2.5A

20nS/div

dv/dt 60V/nS 27uJ losses ~.2A dv/dt=15V/nS 12uJ losses

Pcond=.23W switching losses 39µJ=3.9W @ 100kHz

switching losses (turn-on) dominant,

Change to quasi-resonant or lower frequency for lower losses

Too much capacitance in trafo


New D2pak 7 pin with 6.85mm creapage

2mm longer than standard d2pak

1.27mm pitchg ks 6*Source

17mm

DRAIN


New D2pak 7 pin with 6.85mm creapage

2mm longer than standard d2pak

1.27mm pitch g ks 6*Source

17mm

DRAIN

Rthj-ambient 45C/W on 1in2 fr4 pcb so @50kHz 2 W losses marginal .

small SMD heatsink FK24408D2PAK smd heatsink has Rth 29.C

Reduce losses by changing to Quasiresonant


Simple to Drive

VeeT

X1

-F

XD1LL4148

C21

XR2100K

TVS1

PESD15VL1BA

D8

R25R56 1W

D3

0R

XD2LL4148

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

XR1100K

L9951APWM control

fb

CS

gate

9V 120µA start-up

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

stth108stth108

Only drive small mosfet

Total gate charge <15nC

Need small gate driver

1500V 2.5ΩMosfet gate charge 100nC

Low driving losses


Simple to drive: control of switching speed

Vee

TX

1-F

XD1LL4148

C21

XR2100K

TVS1

PESD15VL1BA

D8

R25R56 1W

D3

0R

XD2LL4148

C101N

DG

S

T2Q1

R28R56 1W

R271K0

C11

Q10

D2

R234R7

XR1100K

L9951APWM control

fb

CS

gate

9V 120µA start-up

47µF

1n0

26V

SJTP170R1400

16

>30V

IRFU024N

4

stth108stth108

C10 determines turn-on di/dt

Large C10 means slower turn-on

Increase R23 for slower turn-off


Minimal delay due to output capacitance

22

Mosfet GATE

Drain 500V

Drain current

Drain current falls to 200mA

Minimal turn-off delay with low drain current due to low Coss of Jfet (8pF)


Turn-off waveforms

XD1LL4148

TVS1

PESD15VL1BA

C101N

DG

S

T2Q1

R271K0

Q10

D2

R234R7

XR1100K

26V

SJTP170R1400

16

>30V

IRFU024N

4

ch1 Vds jfet, Ch2 source jfet, ch3 gate jfet, ch4 drain current

See 100mA drain current at turn-off, takes 100nS to charge Cds to 1200V, Coss~8.3pF

This includes the energy needed to change the mosfet output from 15 to 20V


XD1LL4148

TVS1

PESD15VL1BA

C101N

DG

S

T2Q1

R271K0

Q10

D2

R234R7

XR1100K

26V

SJTP170R1400

16

>30V

IRFU024N

4

t1

T1 Mosfet gate voltage falls,to Vth

t2

T2 Mosfet start switching source rises jfet still on

T3 jfet start switching, drain and gate jfet rise

T4 jfet blocking

t3

Turn-off waveforms 25MHz filter for clarity

t4

PCIM 2012: Nürnberg, Germany 25

Conclusions

1700V Depletion-mode SiC VJFETSimplify High Voltage SMPS

Have demonstrated

Simple start-up, elimination of HV start-up components Low switching losses 120W PSU with minimal heatsink at

50kHz Easy to drive Compact high creapage package. SMD assembly

depletion-mode sicvjfet simplifies high voltage smps · high voltage smps start-up circuits...

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