igbt driving aspect zhou yizheng. copyright © infineon technologies 2009. all rights reserved. igbt...

IGBT driving aspectZhou Yizheng

Copyright © Infineon Technologies 2009. All rights reserved.

IGBT driving

Driving voltage level

Effect of turn on/off

¬ Rge, Cge, Lg

¬ Driving capability

Isolation

Thermal

Protection

¬ Parasitic turn on

¬ Over voltage

¬ Short circuit/over current



Effect to Vcesat

Vge ， Vcesat

Tvj=125C

Tvj=125C

Effect to short cicuit

Vge ， Isc （ tsc）

note ： max. allowed Vge is 20V

Positive voltage



Miller capability effect

Negative voltage

¬ To guarantee safety off state, avoid parasitic miller turn on

¬ Turn on delay increase (dead time)

¬ Slightly reduce tf and Eoff

¬ Increase driving power



Rgon

Control of dv/dt and di/dt with gate resistor

Turn-on with nominal gate resistor (datasheet value):

dv/dt = 0.9kV/µsdi/dt = 6.4kA/µsICpeak = 2.4kAEon = 816mWs

Turn-on with smaller than nominal gate resistor:


Turn-on with larger than nominal gate resistor:




Rgoff

Control of dv/dt and di/dt with gate resistor

•dv/dt is controllable with gate resistor. A larger resistor will result in a smaller dv/dt.•di/dt is only controllable if the gate voltage doesn’t drop below the Miller Plateau level before IC starts to decrease. This is in general the case for a gate resistor value close to the datasheet value. With larger resistors a control of di/dt starts to work.



Range Determined by

Condition Influenced by Influence on

1 VGE < VGEth Ciss = const RG, CGE tdon

2 VGEth < VGE < VGEM Ciss = const RG, CGEdi/dt

3 VGE = VGEM VGE = const RG, CGCdv/dt

Cge

Independently control of dv/dt and di/dt


For similar Eon, we can:

Rge Cge Eon Di/dt Ipeak tdon Vge_p

4.6ohm 0nf 650mJ 3283kA/us

1.487kA 1.76us 13.6V

1.7ohm 200nf 635mJ 2492kA/us

1.386kA 1.67us 13.7V

4.6ohm0nF 1.7ohm200nF


For similar di/dt, we can:

Rge Cge Eon Di/dt Ipeak tdon Vge_p


1.639kA 1.29us 14.0V


1.635kA 1.23us 15.0V

2.6ohm0nF 1.7ohm46nF


Rge vs. Cge

Using Cge shows better Eon*di/dt coefficient

Using Cge can significantly increase driving power

P=∆U*(Qge+Cge*∆U)*f

Using Cge can significantly increase driving peak current, require more powerful driver (output peak current capability)

The tolerance of Cge should be taken care when used in IGBT paralleling application

Using Cge may cause gate current oscillation, which leads to higher gate peak voltage.


Cable length influence

With short cable With long cable

Calbe Rge Cge Eon Di/dt Ipeak tdon Vge_p

Short 0.9ohm 0nf 196mJ 6128kA/us

1.978kA

0.92us 14.7V

Long 0.9ohm 0nf 87mJ 6920kA/us

2.220kA

0.92us 18.3V


For similar Eon, we can:

With fixed Cge

With fixed Rge



1.908kA

0.92us 17.0V


1.874kA

1.21us 17.5V



1.711kA

1.17us 15.8V


1.673kA

1.39us 15.6V


Cable length influence

Cable length (Lg) shows similar Eon*di/dt coefficient as Rge, This mainly due to Lg effect both during di/dt period and dv/dt period (same as Rge)

Long cable significantly induce the turn on delay time

Long cable is a EMI receiver, which can cause Vge spike and unstable.

Loosing gate cable inductance will significantly increase Eon, which should especially paid attention in active adaptor design.

Adaptor board Rge Cge Eon Di/dt Ipeak

Active 1.0ohm 0nf 332mJ 5650kA/us 1.708kA

Passive(8mm) 1.0ohm 0nf 187mJ 7700kA/us 1.895kA

Long cable should be avoid to be used. But loosing gate inductance should also be paid attention



Driving capability

¬ Peak current capability

¬ Power capability

Maximum driver peak current

U = 30V @ 15V switching

Driver power

internGexternGG(min)Gmax RR

ΔU

R

ΔUI

2issGate

Gate

GateDrivertot

ΔUC3...5fPor

ΔUQfP

PPP

Slow down turn on/off speed

Driver losses

Vge goes down

Power supply losses



Turn on/off criteria

Redundant information on di/dt and dv/dt

2000

1000

0

1000

2000

3000

time [400ns/div]

VR

[5

00

V/d

iv]

IR

[5

00

A/d

iv]

1

23

!

0

0 1000 2000 30000

1000

2000

VR(t) [V]

IR(t

) [A

]

locus iR(t)*vR(t)

1

2

3

!

0

Diode SOA


Isolation

+ -Optocoupler

Optical Fiber

High isolation capability Aging of electrical characteristic

Reduced reliability due to aging

No energy transmission

MonolithicLevel Shifter

Cost effective

Integration of logic suitable

No galvanic isolation

EMI sensitivity


DiscreteTransformer

Very high isolation Capability

Energy transmission possible

Expensive

Device Volume

CorelessTransformer (CLT)

High isolation capability

Very cost effective

Easy integration of logic function



Isolation

Isolation transformer

¬ Isolation test

¬ Partial discharge test

¬ Parasitic capacitor (Primary - secondary)


Thermal

Influenced parameters

Module case temperature

Driving power (switching frequency, Qg)

Driving peak current

Sensitive parts

Gate resistor

Booster

Power supply

Fiber


Thermal

If system internal ambient temperature is known.

From delt Tca, we can check temperature rise due to module itself heating

Adding temperature rise due to driving signal, real driver board temperature can be gotten.

System cooling can significant improve driver cooling condition


Protection

UVLO

Interlock / generating deadtime

Vge over voltage

Parasitic turn on

Short circuit protection

Over voltage protection (for short circuit off)

¬ Active Clamping

¬ DVRC (Dynamik Voltage Raise Control)

¬ di/dt-Feedback

¬ Soft-Shut-Down

¬ Two-Level Turn-off


Protection

UVLO

¬ Avoid driving IGBT with low voltage causing thermal issue

¬ Avoid series break down

Interlock / generating deadtime

¬ Avoid short through by software mistake

¬ Hardware deadtime should be shorter than software deadtime


Protection

¬ Limitation of increase of gate voltage due to positive feedback over CGC and due to di/dt

¬ Limitation of short circuit currents

Methode 1Gate-Supply Clamping

Methode 2Gate-Emitter Clamping

Vge over voltage


Protection

Parasitic turn on

¬ minus voltage off

¬ separate gate resistors, using small Rgoff and big Rgon

¬ Additional gate emitter capacitor to shunt the Miller current

¬ Active Miller clamping


Protection


Desaturation detect

Ic Vce

OC SC II

Vce

Ic

SC I


Protection


Desaturation detect

Based on fixed reference voltage Based on variable reference voltage


Protection


Desaturation detect

Over current protection?

– Noise immunity is poor

– Blanking time hard to set for fixed reference voltage concept, especially for high voltage module

– Current protect point hard to be accurate

¬ Directly detect collector current

¬ Digital controller to detect di/dt

¬ By system current sensor


Protection

Over voltage protection

¬ Active clamping


Protection


¬ DVRC (Dynamic Voltage Raise Control)

uGE(t)

iC(t)

uCE(t)

dic/dt=11kA/µs@ Tj=25°C

RG=3.6EOFF=0.9J

uGE(t)

iC(t)

uCE(t)

dic/dt=3.4kA/µs@ Tj=25°C

RG=13EOFF=1.95J

+16V

-16V

PWM

IRFD 120

UF4007

UF4007

100pF

RG=1.5

FZ2400R17KE3

47R

15R

ZPD16

RMO

S

56

BYD77

BYD77

44H11

45H11

MFP-D

MFN-D

3xSM6T220A

RAC=15

4xSM6T220A

UAC

URAC


Protection


¬ di/dt protection

Detect & comparison

Gate boost


Protection


¬ Soft shut down

Rg

Rssd


Protection


¬ Two level turn off

VGEDriver Out

VCEIC

VGEDriver Out

VCEIC

Without Two-Level Turn-OffVCE reaches 1000V

With Two-Level Turn-OffVCE reduced to 640V

igbt driving aspect zhou yizheng. copyright © infineon technologies 2009. all rights reserved. igbt...

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