Metal halide lamp electronic ballast constant power control circuit diagram

This circuit can increase the power factor λ of the system to above 0.99, effectively suppress the waveform distortion of the input power current in, reach the distortion index lower than L level required by GB15144, and ensure that the current crest factor of the HID lamp is less than 1.7.

Connect the detection resistor Rs in series to the input end of the Buck circuit, and then filter it through the resistor R1 to obtain the average voltage signal. The voltage signal of the lamp is detected from the L2 end. The two amplify the voltage signal through EA, and the output voltage obtained is used as a feedback signal. The relatively strong input is to the PWM controller, and the PWM controller outputs a control signal Vf according to the input feedback voltage signal to control the duty cycle of the switch S2 of the Buck circuit. By appropriately selecting R1, R2, and R3, the output power Po can be well controlled.