A multifunctional novel phase-cut control circuit, characterized by comprising an input interface circuit, a signal detection circuit, a holding current control circuit, a current-limiting protection circuit and a control chip U1;
- The input interface circuit comprises a diode D1 and a diode D3, the anode of the diode D1 is electrically connected to an input terminal L, the anode of the diode D3 is electrically connected to an input terminal N, and the cathodes of the diode D1 and the diode D3 are commonly connected to a high-potential node inside the circuit;
- The signal detection circuit comprises a resistor R1, a resistor R2, a capacitor C1, a resistor R5, a diode D2 and a zener diode Z1;
- one end of the resistor R1 is electrically connected to the high-potential node, and the other end is electrically connected to one end of the resistor R2;
- the other end of the resistor R2 is electrically connected to the anode of the diode D2, and the anode of the diode D2 is electrically connected to the cathode of the zener diode Z1, one end of the capacitor C1, pin 1 of the control chip U1 and one end of the resistor R5;
- the anode of the zener diode Z1, the other end of the resistor R5, the other end of the capacitor C1 and pin 2 of the control chip U1 are grounded;
- The holding current control circuit comprises a triode Q1, a diode D4, a resistor R3, a resistor R4, a resistor R7 and a resistor R8;
- the collector of the triode Q1 is electrically connected to one end of the resistor R4;
- the other end of the resistor R4 is electrically connected to the output end of a signal input interface;
- the emitter of the triode Q1 is electrically connected to one end of the resistor R8 through the resistor R7;
- the other end of the resistor R8 is electrically connected to the ground;
- one end of the resistor R3 is electrically connected to pin 3 of the control chip U1, one end of a resistor R6 and a zener diode Z2;
- the other end of the resistor R3 is electrically connected to the output end of the signal input interface;
- the other pin of the zener diode Z2 is grounded;
- the other end of the resistor R6 is electrically connected to the anode of the diode D4 and the collector of a triode Q2;
- the cathode of the diode D4 is electrically connected to the base of the triode Q1;
- under the control of pin 3 of the control chip U1, current flows from the input interface circuit to the ground through the resistor R4, the triode Q1, the resistor R7 and the resistor R8, and the current flows through a phase-cut dimmer in an external main circuit to serve as holding current to prevent the phase-cut dimmer from false turn-off;
- The current-limiting protection circuit comprises the triode Q2, the resistor R7 and the resistor R8;
- one end of the resistor R7 is electrically connected to the emitter of the triode Q1 and the base of the triode Q2, and the other end is electrically connected to one end of the resistor R8;
- the other end of the resistor R8 is grounded;
- when the current flowing through the resistor R7 and the resistor R8 exceeds a set threshold, a voltage drop generated at the common end of the resistor R7 and the resistor R8 triggers the triode Q2 to conduct;
- after the triode Q2 is conducted, the base voltage of the triode Q1 is pulled down to keep the flowing current at a set value, so as to realize current-limiting protection;
- Pin 4 of the control chip U1 is electrically connected to a capacitor C2, and the other end of the capacitor C2 is grounded.