Method for automatically regulating bleeder current and LED silicon-controlled-rectifier dimming circuit

An LED silicon-controlled rectifier (SCR) dimming circuit for automatically regulating a bleeder current, comprising:

• an SCR module (10), a rectifier circuit (20), a constant current control circuit (30), a bleeder circuit and a bleeder current control circuit (40);
• wherein,
• the SCR module (10) is connected to the rectifier circuit (20) to control a cut angle of a circuit;
• the rectifier circuit (20) is connected to the bleeder circuit, the bleeder current control circuit (40) and an LED light source to rectify power supply;
• the constant current control circuit (30) is connected to the LED light source to perform constant current control;
• the bleeder circuit comprises a power tube M1 and a bleeder resistor R3 for providing a current circuit for the SCR module (10) when there is no current in the LED lamp string;
• and
• a first end G1 of the bleeder current control circuit (40) is connected to a control end of the power tube M1, a second end A2 is connected to the bleeder resistor R3 and an output end of the power tube M1, a third end A1 is connected to a direct current power source end and a fourth end A4 is connected to the constant current control circuit (30);
• the bleeder current control circuit is used to perform control for the bleeder current based on the size of the leakage current of the SCR module (10) and the bleeder current is a conduction current of the SCR module when the SCR starts to turn on and a voltage on both ends of an LED lamp string is smaller than a conduction voltage of the LED lamp string.