Sensor lighting LED driver circuit

Circuit explanation:

1. The input filter circuit plays a two-way filtering role, filtering out the interference from the power grid to the power circuit and the interference from the power circuit to the power grid;

2. C2 filters the DC voltage output from the AC input mains rectifier to make the output DC voltage smoother;

3. Resistor R7, resistor R8 and capacitor C12 form an RC filter circuit to provide the starting operating current for the HT7L2102. Once the circuit completes starting, the HT7L2102 supplies power through the auxiliary winding 4-5 of the D3 flyback transformer, which can reduce the starting resistance of the resistor R7 and the resistor R8. power consumption;

4. The thermistor Rts connected to the HT7L2102 pin TS serves as overheating protection for the circuit. Once the circuit operating temperature is too high, the circuit will be shut down;

5. The capacitor C19 connected to the COMP/FB pin of HT7L2102 compensates for the control loop frequency compensation, making the circuit work more stable;

6. Y capacitor C11 plays the role of filtering the power supply noise signal. It is a high-voltage withstand capacitor, and the power supply noise signal filtering effect is obvious;

7. Optocoupler U2 acts as primary and secondary isolation and ensures reliable transmission of feedback sampling control signals;

8. Q3 is the reference voltage generating circuit, and Q3 provides the current control signal for the current detection control loop composed of the U2 photocoupler loop;

9. Resistor R18 and capacitor C16 form an RC compensation circuit to stabilize the work of the Q3 reference voltage generating circuit ;

10. R28 and resistor R25 are load current sampling resistors. The sampling voltage controls the working current of Q3, and the output constant current control is completed through the photocoupler U2;

11. Resistors R20, R15 and Q3 form an output voltage sampling circuit. The changing output voltage is controlled by the reference voltage Q3, and the output voltage stability control is completed through the photocoupler U2;

12. The source working current sampling resistor of power switch Q1 is sent to the HT7L2102 pin CS to complete the over-current protection control of power switch Q1;

13. The flyback transformer T1 has the primary and secondary isolation function;

14. Resistor R5 and capacitor C3 form an RC absorption loop, which can protect the rectifier diode D1;

15. Resistor R17 is the discharge capacitance of the gate junction capacitance of power switch Q1, which can speed up the working speed of Q1 and reduce the switching power consumption of Q1;

16. Resistor R12 is the gate drive current limiting resistor of power switch Q1;

17. Diode D3 is the rectifier diode of the auxiliary power supply circuit.