Table of Contents
Advertisement
3. Protection Circuits Design
Since IGBT modules may be destroyed by overcurrent, overvoltage or other abnormality, it is
necessary to design protection circuits.
It is important to fully understand the IGBT modules characteristics when designing these circuits. An
inappropriate circuit will not be able to protect the module. For example, the overcurrent cut-off time
may be too long, or the capacitance of the snubber capacitor may be too small.
For more details on overcurrent and overvoltage protection methods, refer to Chapter 5 'Protection
Circuit Design' of this manual.
4. Cooling Design
IGBT modules have a maximum virtual junction temperature (T
be selected to keep the temperature below this value. When designing heat sink, the operating
conditions of the IGBT module has to be fully considered.
First, calculate the loss of the IGBT module. Based on that loss, select a heat sink that will keep T
below the limit. If the heat sink design is insufficient, the temperature may exceed T
operation and destroy the module. For more information on IGBT power loss calculation and heat sink
selection methods, refer to Chapter 6 'Cooling Design' of this manual.
5. Gate Drive Circuits Design
It is no exaggeration to say that the design of the gate drive circuits ultimately determines the
performance of the IGBT. It is also closely related to the protection circuits design.
Gate drive circuits consists of a forward bias circuit to turn-on the IGBT, and a reverse bias circuit to
turn-off and keep the IGBT in a stable off state. The characteristics of the IGBT change in accordance
with each bias condition.
Insufficient reverse bias gate voltage -V
prevent false turn-on. If the dv/dt is high, false turn-on of the opposing arm IGBT, gate overvoltage, or
noise propagation to the power supply line may occur. Set the optimum drive conditions (+V
R
, C
) to avoid these problems.
G
GE
Also, if the wiring length between the IGBT module and the gate drive circuit is long, the gate voltage
at the product terminal may fluctuate and the product may be destroyed by overvoltage.
For more information on how to design the best gate drive circuits, refer to Chapter 7 'Gate Drive
Circuit Design' of this manual.
REH984f
vj(max)
may cause false turn-on. Set a sufficient -V
GE
© Fuji Electric Co., Ltd. All rights reserved.
). An appropriate heat sink must
vj(max)
value to
GE
GE
vj
during
, -V
,
GE
3-5
Advertisement
Table of Contents
