Fault Circuit; 3- Phase Invert Stage; Power Module - Fujitsu MB9B100A Series User Manual

4.3.3

Fault circuit

DC Bus Over-voltage, this fault signal is generated when the maximum voltage limit on the
DC bus rails is reached. The threshold value is set to 390 V. The comparison of the
threshold value and the amplified DC bus voltage is done by amplifier unit U4C. The
threshold limit is set by R31 and R32.
DC Bus Over-current , this fault signal is generated when the maximum current limit of 16A
is reached. The comparison of the threshold value and the actual current is done by
amplifier unit U4B. The threshold limit is set by R27 and R29.
4.4

3- Phase Invert Stage

4.4.1

Power Module

The three-phase inverter is embedded in a power module (U5). This power module contains:

600V/15A 3-phase IGBT Inverter Bridge

built-in bootstrap diode and VS output

Short-circuit protection

Divided negative dc-link terminals for inverter current sensing applications

Gate Driver Power Supply Under-voltage protection

Single-grounded power supply

Isolation rating of 2000Vrms/min

Maximum switching frequency: 20 kHz
The MCU provides the PWM signals to this power module in order to turn on/off the IGBT,
therefore the power is applied to the motor phases.
Two fault conditions will turn off the low side IGBTs:
a. Under-voltage of 15V (high side).
b. The voltage on CSC pin is higher than 0.5V.
At the same time the module will output low level from VFO pin. A pull-up resister is need on
VFO pin because it is open-collector type.
If you want to know more detail, please refer to the each device's datasheet.
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AN706-00042-1v0-E