Dear All,
I am developing a high-voltage motor driver using the Nucleo-H563ZI with the STEVAL-IPM30B.
I have set up the entire hardware and want to first verify whether the voltage output is normal (using SVPWM).
My three-phase outputs are not connected to anything; they are floating. I am using a differential probe to check the voltage (specifically, the line voltage UV).
When the duty cycle is below 85%, it appears normal, as shown in the image below.It is a nice sinusoidal voltage.
However, when the duty cycle exceeds 85%, the voltage output starts to show abnormalities, as shown below for the cases of 85% and 100%.
I have confirmed that my PWM signals are still normal at 85% and 100%, so I believe the issue lies with the IPM rather than the control signals.
Since it is a bootstrap circuit, I believe the issue lies in this part. I checked the bootstrap capacitor voltage(TP4 to phase_A). When the system is normal, the bootstrap voltage is around 12.45V.
However, when the duty cycle exceeds 85%, there is a significant voltage drop in the bootstrap voltage.
I believe that as the duty cycle increases, the low side PWM signal does not provide enough time to charge the bootstrap capacitor, which leads to the inability of the switches to operate normally.
I tried changing the bootstrap capacitor from the original 2.2 µF to 30 µF, but it did not improve the situation.
Have anyone know how to resolve this issues?
Best Regards,
(Additionally, if I increase the auxiliary voltage from 15V to 20V, it slightly improves the situation. The abnormalities now only start to appear at around 90% duty cycle. )
