3 years, 11 months ago.

When I update my LCD in an interrupt timer it influences my SPWM to a 3-phase induction motor.

I'm using a stm32f429zi controller to drive a VFD. When I update the LCD in an interrupt timer it influences my SPWM signals going to the VFD. Why does this happen?

1 Answer

3 years, 11 months ago.

If you are using a SPWM (software generated PWM) it probably uses timer based interrupts to set/reset the PWM outputs. The timer interrupt could collide with the interrupt driven updates for the display which could take some time. The solution should be a hardware controlled PWM that needs no interaction from the processor until you make a change to the PWM duty cycle or period. An alternative solution could be to adapt the interrupt priorities to make sure the SPWM will always override the display handler.

Thank you very much, but with SPWM I meant sinusoidal PWM. I'm implementing volts/hertz control which requires me to constantly update the duty cycles of 3 PWM signals ( 3 phase ). I think your last mentioned solution will probably be the best way to go about solving the problem.

posted by Michael Heyns 25 Sep 2017