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Gate Resistor Information
IGBT Gate Driver Calculation
Norbert Pluschke 30.11.2004
1
Which gate driver is suitable for the module SKM 200 GB 128D ?
Design parameters:
fsw = 10 kHz
Rg = 7 
Driver

Example for design parameters
Norbert Pluschke 30.11.2004
2

The suitable gate driver must provide the required

Gate charge (QG)

Average current (IoutAV)

Gate pulse current (Ig.pulse)
Driver

at the applied switching frequency (fsw)
Demands for the gate driver
Norbert Pluschke 30.11.2004
3

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
15
VGG+ = +15V
 QG = 1390nC
Driver
VGG- = -8V
-8
1390
Determination of Gate Charge
Norbert Pluschke 30.11.2004
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
Calculation of average current:

IoutAV = P / U

with P = E * fsw = QG * U * fsw
 IoutAV = QG * fsw
Driver

U = +Ug – (-Ug)
= 1390nC * 10kHz = 13.9mA
Calculation of the average current
Norbert Pluschke 30.11.2004
5

Examination of the peak gate current with minimum
gate resistance

E.g. RG.on = RG.off = 7
≈ U / RG = 23V / 7 = 2.3A
Driver
 Ig.puls
Calculation of the peak gate current
Norbert Pluschke 30.11.2004
6
 P tot – Gate resistor
 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.
The Philips resistor data book has a good section on peak power ratings.
Driver
 Ptot Gate resistor = I out AV x U
Power explication of the Gate Resistor
Norbert Pluschke 30.11.2004
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
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 = 2.3A

Switching frequency fsw = 10kHz

Collector Emitter voltage VCE = 1200V
Driver

Number of driver channels: 2 (GB module)
 dual driver
Choice of the suitable gate driver
Norbert Pluschke 30.11.2004
8

According to the applied and calculated values, the driver e. g.
SKHI 22A is able to drive SKM200GB128D
Calculated and
applied values:

Ig.pulse = 2.3A

IoutAV = 13.9mA

fsw = 10kHz

VCE = 1200V

QG = 1390nC
Driver
@ Rg = 7
Comparison with the parameters in the driver data sheet
Norbert Pluschke 30.11.2004
9
PCB Driver and PCB mountable Driver for single, half bridge, six pack modules

integrated potential-free power supply

switching frequency up to 100kHz

output peak current up to 30A

Gate charge up to 30µC

dv/dt capability up to 75kV/µs

high EMI immunity

TTL- an CMOS-compatible inputs and outputs with potential isolation via opto
coupler or transformer (isolation up to 4kVAC)

protection (interlock, short pulse suppression, short circuit protection via VCE monitoring, under voltage monitoring, error memory and error feedback)
Driver

SEMIDRIVER
Norbert Pluschke 30.11.2004
10
Driver
Product overview (important parameters)
Norbert Pluschke 30.11.2004
11
Driver
 Many thanks for your attention.
Norbert Pluschke 30.11.2004
12