Download Kein Folientitel

Semikron Hong Kong
Gate Driver Requirement
IGBT Gate Driver Calculation
Norbert Pluschke 07.10.2005
1
for an
IGBT driver ?
Gate Peak current
Norbert Pluschke 07.10.2005
Semikron Hong Kong
What is the most important requirement
2
Which gate driver is suitable for the module SKM 200 GB 128D ?
reverse recovery current Diode should be -
1.5 x I diode by 80 degree case
130A x 1.5 = 195A
Design parameters:
fsw = 10 kHz
Rg = ?
Gate resistor in range of “test – gate resistor”
Semikron Hong Kong

Conditions for a safety operation
Norbert Pluschke 07.10.2005
3
Semikron Hong Kong
195A – max reverse recovery current
Rg = 7 Ohm
Two gate resistors are possible for turn on and turn off
Ron = 7 Ohm
Roff = 10 Ohm
How to find the right gate resistor ?
Norbert Pluschke 07.10.2005
4
 Trench Technology needs a smaller Gate charge
 SPT Technology needs more Gate charge compared to
Trench Technology
 Driver has to provide a higher Gate charge
Semikron Hong Kong
 Driver has to provide a smaller Gate charge
Difference between Trench- and SPT Technology
Norbert Pluschke 07.10.2005
5
Gate charge is 2.3 uC
Semikron Hong Kong
 Trench IGBT with same chip current
Driver performance – different IGBT technologies
needs different gate charge
Norbert Pluschke 07.10.2005
6
Gate charge is 3 uC
Semikron Hong Kong
 SPT IGBT with same chip current
Driver performance – different IGBT technologies
needs different gate charge
Norbert Pluschke 07.10.2005
7

The suitable gate driver must provide the required

Gate charge (QG) – power supply of the driver must
provide the average power

Average current (IoutAV) – power supply

Gate pulse current (Ig.pulse) – most important
Semikron Hong Kong

at the applied switching frequency (fsw)
Demands for the gate driver
Norbert Pluschke 07.10.2005
8
Gate charge (QG) can be determined from fig. 6 of the
SEMITRANS data sheet
The typical turn-on and
turn-off voltage of the
gate driver is
Semikron Hong Kong

15
VGG+ = +15V
VGG- = -8V
 QG = 1390nC
-8
1390
Determination of Gate Charge
Norbert Pluschke 07.10.2005
9
Calculation of average current:

IoutAV = P / U

with P = E * fsw = QG * V * fsw
Semikron Hong Kong

V = +Vg + [-Vg]
Absolute value

 IoutAV = QG * fsw
= 1390nC * 10kHz = 13.9mA
Calculation of the average current
Norbert Pluschke 07.10.2005
10
 The power supply or the transformer must provide the energy
(Semikron is using pulse transformer for the power supply, we
must consider the transformed average power from the
transformer)
 Average current
 Is related to the transformer
Semikron Hong Kong
 Gate charge
Power supply requirements
Norbert Pluschke 07.10.2005
11
Examination of the peak gate current with minimum
gate resistance

Semikron Hong Kong

E.g. RG.on = RG.off = 7
 Ig.puls
≈ V / RG + Rint = 23V / 7 + 1 = 2.9 A
Calculation of the peak gate current
Norbert Pluschke 07.10.2005
12
 Ppulse
Gate resistor
= I out AV x V
 More information:
The problem occurs when the user forgets about the peak power rating
of the gate resistor.
The peak power rating of many "ordinary" SMD resistors is quite small.
There are SMD resistors available with higher peak power
ratings. For example, if you take an SKD driver apart, you will see
that the gate resistors are in a different SMD package to all the other
resistors (except one or two other places that also need high peak power). The
problem was less obvious with through hole components simply because the
resistors were physically bigger.
Semikron Hong Kong
 P total – Gate resistor
The Philips resistor data book has a good section on peak power ratings.
Pulse power rating of the gate resistor
Norbert Pluschke 07.10.2005
13

The absolute maximum ratings of the suitable gate driver
must be equal or higher than the applied and calculated
values

Gate charge QG = 1390nC

Average current IoutAV = 13,9mA

Peak gate current Ig.pulse = 2.9 A

Switching frequency fsw = 10kHz

Collector Emitter voltage VCE = 1200V
Semikron Hong Kong

Number of driver channels: 2 (GB module)
 dual driver
Choice of the suitable gate driver
Norbert Pluschke 07.10.2005
14
According to the applied and calculated values, the driver e. g.
SKHI 22A is able to drive SKM200GB128D
Calculated and
applied values:

Ig.pulse = 2.9 A
@ Rg = 7 + R int

IoutAV = 13.9mA

fsw = 10kHz

VCE = 1200V

QG = 1390nC
Semikron Hong Kong

Comparison with the parameters in the driver data sheet
Norbert Pluschke 07.10.2005
15
Semikron Hong Kong
Product overview (important parameters)
Norbert Pluschke 07.10.2005
17
 Adaptable
 Expandable
 Short time to market
 Two versions
 SKYPER™ (standard version)
 SKYPER™ PRO (premium version)
Semikron Hong Kong
 Simple
Driver core for IGBT modules
Norbert Pluschke 07.10.2005
18
 Driver board
 SEMIX 3 IGBT
half bridge
with spring
contacts
Semikron Hong Kong
 SKYPER
Assembly on SEMiXTM 3 – Modular IPM
Norbert Pluschke 07.10.2005
19
with adapter
board
solder directly in
your main board
Semikron Hong Kong
take 3
for 6-packs
modular IPM
using SEMiX®
SKYPER™ – more than a solution
Norbert Pluschke 07.10.2005
20
Advice
Norbert Pluschke 07.10.2005
Semikron Hong Kong
Selection of the right IGBT driver
21
Semikron Hong Kong
Low impedance
Problem 1--------------------- Cross conduction
Norbert Pluschke 07.10.2005
22
VGG+
VGE, Io
VGE(th)
T1
D1
T2
D2
0
vCE,T1(t)
iC,T1(t)
t
VCC
IO
iv,T2
0
vCE,T2(t) = vF,D2(t)
iF,D2(t), iC,T2(t)
t
VCC
IO
0
t
 Why changes
VGE,T2 when T1
switches on?
Semikron Hong Kong
vGE,T1(t)
vGE,T2(t)
Cross conduction behavior
Norbert Pluschke 07.10.2005
23
 When the outer voltage potential V changes, the load Q has to follow
 This leads to a displacement current iV
Semikron Hong Kong
Q  CV
dv
iv  C 
dt
IGBT - Parasitic capacitances
Norbert Pluschke 07.10.2005
24
vCE,T2(t)
VCC
CGC,T2
iC,T2
t
iC,T2(t)
iv,T2(t)
iv,T2
vCE,T2
0
t
vGE,T2(t) VGG+
RGE,T2
vGE,T2
dvCE,T2
iv,T2  CGC,T2 
dt
v GE,T2  iv,T2  RGE,T2
VGE(th)
0
t





Diode D2 switches off and takes over the voltage
T2 “sees” the voltage over D2 as vCE,T2
With the changed voltage potential, the internal capacitances change their charge
The displacement current iv,T2 flows via CGC,T2, RGE,T2 and the driver
iv,T2 causes a voltage drop in RGE,T2 which is added to VGE,T2
Semikron Hong Kong
0
 If vGE,T2 > VGE(th) then T2 turns on (Therefore SK recommends: VGG- = -5…-8…-15 V)
Switching: Detailed for T2
Norbert Pluschke 07.10.2005
25
Semikron Hong Kong
Z 16 -18
Problem 2 ----------------------------- gate protection
Norbert Pluschke 07.10.2005
26
Semikron Hong Kong
Z18
PCB design because no cable
close to the IGBT
Gate clamping ---- how ?
Norbert Pluschke 07.10.2005
27
Semikron Hong Kong
Use MOSFET for the booster
For small IGBTs is ok
Problem 3 -----------------booster for the gate current
Norbert Pluschke 07.10.2005
28
 1200V ----- is chip level ---- consider internal stray inductance
 +/- 20V----- gate emitter voltage ---- consider switching behavior of
freewheeling diode
 Over current
 Power dissipation of IGBT (short circuit current x time)
 Chip temperature level
Semikron Hong Kong
 Over voltage
Problem 4 ---------------------------- Short circuit
Norbert Pluschke 07.10.2005
29
Semikron Hong Kong
Turn on and turn off delay must be
symetrical
Problem 5 – dead time between top and bottom IGBT
Norbert Pluschke 07.10.2005
30
Semikron Hong Kong
Dead time explanation
Norbert Pluschke 07.10.2005
31
 Example:
Semikron Hong Kong
 Dead time = 3 us logic level
 Turn on delay 1 us
 Turn off delay 2.5 us
– Td – toff delay + ton delay = real dead time
– Real dead time: 3us – (2.5us+1us) = 1.5 us
Dead time explanation
Norbert Pluschke 07.10.2005
32
 Peak current
 Gate charge
Semikron Hong Kong
 IGBT driver must provide the peak Gate current
 The stray inductance should be very small in the gate driver
circuit
 Gate/Emitter resistor and Gate/Emitter capacitor (like Ciss)
very close to the IGBT
 Turn off status must have a very low impedance
 High frequency capacitors very close to the IGBT driver
booster
 Don’t use bipolar transistors for the booster
 Protect the Gate/Emitter distance against over voltage
 Don’t mix;
Our final recommendation
Norbert Pluschke 07.10.2005
33
Semikron Hong Kong
Norbert Pluschke 07.10.2005
34