Zero cross detection circuit

The utility model discloses a zero cross detection circuit composed of a switch triode Q1, a bias resistor R1, a bias resistor R2, a blocking coupling capacitor C1, a pull-up resistor R2, a current limiting resistor R5, a pull-down resistor R3 and a three-end programmable parallel voltage-stabilizing diode. The three-end programmable parallel voltage-stabilizing diode, the bias resistor R1 and the bias resistor R2 form a core detection circuit of the zero cross detection circuit. The pull-down resistor R3 is used for controlling collector electrode current in a controllable range when the switch triode is switched on and pulling output signal lines to a determined low electric level when the switch triode is switched off. The current limiting resistor R5 is connected between diodes D1 and is used for controlling base electrode current within a controllable range when the switch triode is switched on. The zero cross detection circuit is simple in structure, low in cost, high in detection precision, low in power consumption and stable and reliable in use.