| Abstract |
A gate drive circuit for an IGBT inverter power module oriented to electric vehicle traction
applications, has been designed, implemented and tested. The driver board controls two 600V-400A
IGBTs forming one dedicated leg of a three phase traction machine inverter, and in the final version is
directly bonded onto a custom designed water-cooled power module. Its main characteristics are a full
bridge output stage, short circuit protection with soft turn-off sequence, over temperature, transient
over and under voltage, and shoot-through protections. These protection capabilities are prerequisites
for silicon drive stages in traction applications, particularly where the DC supply has dynamic load
variations in the order of 180-320V and 0-400A peak. The full bridge output stage allows positive
gate-to-emitter voltage during the IGBT on-state and negative voltage during the off state using a
single isolated voltage power supply. The decoupling capacitor value associated with the output stage
and the voltage power supply dimensioning, is also analysed. The VCE monitoring circuit detects a
short circuit condition and automatically turns-off the IGBT by reducing the gate voltage from the
positive gate voltage to zero and then from zero to the negative gate voltage. This “soft” turn-off
feature can be very easily implemented using the full bridge output stage topology, and its effect on
the collector-to-emitter peak voltage has been studied during the recovery of short circuit processes.
The dependence and effects of short circuit protection on the most critical components of the circuit
are also experimentally shown. The rest of the protection circuits are also discussed. They have been
designed in order to obtain a very simple and reliable system. The driver has been successfully tested
using an H-bridge converter with 300V applied voltage, sinusoidal output currents up to 120Arms into
an inductive load, at a maximum PWM switching frequency of 20kHz. |
