Detailed explanation of the design of boosted high-brightness LED backlight drive circuit based on HV9911

1. Circuit power supply filter capacitor;

2. C power supply filter capacitor;

3. Bootstrap the voltage output inductor; make the output voltage VO greater than the input voltage VIN;

4. D1 diode is the output boost diode. When D1 diode is turned on, the voltage on the inductor L1 and the input voltage are superimposed and added to the output VO;

5. Output over-voltage and under-voltage sampling detection resistor. Once the circuit has an output over-voltage or under-voltage fault, the circuit enters fault shutdown protection, turning off the Q2 switch and interrupting the load output current;

6. Circuit RC compensation ensures stable operation of the circuit;

7. Output current detection resistor, the detection voltage is added to the FDBK pin to realize output current limiting and over-current protection;

8. Fault protection switch tube. Once an overvoltage, undervoltage or overcurrent fault occurs in the circuit, Q2 turns off and interrupts the circuit output;

9. Q1 is a self-boosting voltage switching tube, which provides a conduction loop for the inductor L1 and realizes energy storage in the inductor L1;

10. The power switch tube source current detection resistor, the detection voltage is sent to the CS pin of HV9911 to complete the current limiting protection control;

11. Cs pin current limiting resistor;

12. The output filter capacitor, capacity and equivalent series resistance (ESR) have a great influence on the ripple current of the load;

13. Timing resistor, the resistance determines the switching operating frequency of the circuit;

14. REF pin output signal filter capacitor;

15. Ramp compensation resistor. Since the circuit works in constant frequency switching mode, the slope compensation signal is added to the current detection signal to ensure that the circuit operates stably and reliably under all peak current operating conditions. This can be achieved by appropriately selecting the resistors RSLOPE and

Parameter implementation of RSC.