Electrical – AC dimming with STM32 timers

dimmingpwmstm32timer

I'm using an STM32 for AC dimming, for which I use a GPIO output (or timer channel out) to drive a triac, whenever I get a zero crossing detection (rising edge). Is there a way to solve this only using timers architecture and without firmware overhead?i.e not using interrupt handlers.

  • Toff -> configurable.
  • Tonn -> remains the same.

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Best Answer

You can put a timer (A) in single shot triggered from an external pin.
This external pin is your zero crossing detector.

You also may need a timer (B) to measure the frequency.

Software still needs to calculate the duty cycle percentage based on the frequency. And set timer A reload to the measured value in timer B.

However, you could use a DMA operation triggered by timer A to copy the capture time of B to the reload register of A. But, you're calculating with those numbers anyway.

Having an ISR called at 50Hz isn't a problem when it doesn't take a lot of time to process it.

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