High voltage pulse width modulation (PWM) LED driver controller circuit diagram analysis

1. Start-up input surge current limiting resistor;

2. It is a flow-by-flow passive power factor correction (PPFC) circuit that improves the power factor of the circuit by extending the conduction angle of the AC input mains rectifier diode. It is lower in cost than the active power factor correction circuit (APFC). advantage;

3. Filter capacitor. When the rectified AC input is close to zero-crossing, the energy stored in the storage capacitor C3 supplies power to the IC. The IC is a high-voltage power supply IC;

4. Oscillation control. A resistor connecting this pin to ground will set the PWM frequency. The IC can be switched to constant off-time (PFM) operating mode by connecting the ROSC pin between the external MOSFET gate and the external oscillation resistor;

5. LED light string and external MOSFET switch tube Q1 current detection resistor. If the voltage on the current sensing resistor R _SENSE exceeds the threshold voltage of the current sensing pin CS, the external MOSFET switch Q1 is turned off. The electrical energy stored in the inductor will cause the current to continue to power the load LED through the freewheeling diode D1;

6. BUCK converts the power switch Q1, and the AC mains rectified output DC voltage passes through the load, inductor L1, BUCK converts the power switch Q1` and the current detection resistor RSENSE to the ground, forming a loop. Once the BUCK conversion power switch Q1 is turned off, the magnetic energy stored in the BUCK inductor forms a gray path through the freewheeling diode D1 and the load, and continues to supply power to the load;

7. BUCK inductor. When the BUCK conversion power switch Q1 is turned on, the AC mains rectified output DC voltage forms a loop through the load and the BUCK inductor to store energy for the BUCK inductor. Once the BUCK conversion power switch Q1 is turned off, the BUCK inductor stores energy. The energy is needed to power the load;

8. Output filter capacitor to stabilize the supply voltage on the load;

9. Freewheeling diode D1. Once the BUCK conversion power switch is turned off, the energy stored in the BUCK inductor forms a loop through the load and D1 to continue supplying power to the load.