Circuit for converting alternating current silicon controlled rectifier dimming signal into PWM (Pulse Width Modulation) dimming signal

The utility model discloses a circuit for converting an alternating current silicon controlled rectifier dimming signal into a PWM dimming signal, which is used for providing a dimming signal for an LED driving power supply and comprises a rectifier bridge BD1, a field effect transistor Q3, a photoelectric coupler OP1, a field effect transistor Q4 and a processing chip U1, the first input end and the second input end of the rectifier bridge BD1 are respectively connected with input alternating current, and the first input end and the second input end of the field effect transistor Q3 are respectively connected with the processing chip U1. The first output end of the rectifier bridge BD1 is electrically connected with the drain electrode of the field effect transistor Q3, the second output end of the rectifier bridge BD1 is grounded, a resistor R5 is connected between the grid electrode and the drain electrode of the field effect transistor Q3, and the grid electrode of the field effect transistor Q3 is ground