How to fix the center-aligned problem of the PWM signals?

[DF_MC]

Hello Everybody,

Here are the software and boards in this case:

1. MC workbench 6.4.1
2. STM32 FW V1.28.2

I’m running the code generated by ST MCSDK and noticed that the waveforms on the microcontroller’s U-phase and V-phase channels (see pins Ch. U and Ch. V in picture 2) are not center-aligned—there is a slight offset (see picture 1: the center of the blue waveform is shifted a little to the left relative to the yellow one). How can I fix this? I suspect this mismatch is causing noticeable acoustic noise while the motor is running.

How can I fix the problem? Thank you!

[GMA]

Hello @DF_MC,

For single-shunt topology, a phase shift is applied as described in the Single-shunt with phase-shift current sensing overview chapter of the user manual available through Workbench tool > About > Documentations > Documentation > User manual.

[DF_MC]

Hello, @GMA 

Thanks for your reply. I am using the "isolated current sensor topology" (as shown in the picture below). Should I make any modifications to the generated code to fit my current configuration? Thank you!

[DF_MC]

Hello @GMA ,

Could you please tell me, for an isolated current sensor topology, should the three-phase PWM signals be center-aligned? Thanks!

[GMA]

Hello @DF_MC,

Refer to the Current sampling in three-shunt topology using two A/D converters chapter of the user manual.
For the PWM-centered position, you must consider the high and low sides (only the high side is displayed on your scope) and the effect of the dead time (DT) value that delays the phase switch.