Zero crossing detection circuit

The voltage is divided and filtered by resistors, and a square wave signal synchronized with the grid input phase voltage signal is obtained through the zero-crossing comparison circuit composed of LM393. It is turned into a trigger pulse synchronized with the square wave through SN74121N, and is then sent to the DSP control chip for capture. Interface, used to generate edge capture signals to trigger corresponding interrupts, thereby calling the corresponding interrupt service subroutine. Zero-crossing detection circuit: