How to calculate the overcurrent limit in case of STEVAL-IPM08B and STEVAL-IPMNG8Q: Diodes in OCP path?

[uomo motore]

I am trying to select a board for evaluation for a High Voltage motor control application. Selecting the STEVAL-IPM08B in X-CUBE-MCSDK v5.4.3 shows OCP limit as 8.3 Amps while the STEVAL-IPMNG8Q OCP limit is shown as 12 Amps. This seems strange as the former uses a 12 Amp DBC package IPM while the latter is based on an 8 Amp plastic molded IPM. I tried cross checking the OCP thresholds from the schematics and component values but it is not so straightforward due to the diodes in the OCP comparator signal path.

Can anyone help with the correct formulas for these calculations?

As per my own circuit analysis while considering a diode drop of 0.25V at approx. 0.1mA (from diode datasheet) and worst case CIN internal reference voltage, I am getting 14.4 Amp OCP limit for STEVAL-IPM08B board and 11.97 Amp OCP limit for STEVAL-IPMNG8Q board.

Thanks in advance.

[VSHAR.7]

You can check the associated user manual (UM2280) for STEVAL-IPMNG8Q : 4.3.2 Shunt resistor selection.

according to this user manual : OCP limit is 10.2A

Hope this helps !

[Laurent Ca...]

Adding of "STM32 Motor Control" topic.

Best regards