CONTROL METHOD AND DEVICE EMPLOYING PRIMARY SIDE REGULATION IN A QUASI-RESONANT AC/DC FLYBACK CONVERTER

摘要

The present disclosure is directed to a primary-controlled high power factor quasi resonant converter. The converter converts an AC power line input to a DC output to power a load, generally a string of LEDs, and may be compatible with phase-cut dimmers. The power input is fed into a transformer being controlled by a power switch. The power switch is driven by a controller having a shaping circuit. The shaping circuit uses a current generator, switched resistor and capacitor to produce a reference voltage signal. The controller drives the power switch based on the voltage reference signal, resulting in a sinusoidal input current in a primary winding of the transformer, resulting in high power factor and low total harmonic distortion for the converter.

主权项

1. A device for controlling a power transistor of a power stage, comprising:
a divider having a first input, a second input and an output, the divider being configured to produce a voltage reference signal; a first current generator configured to produce an output current; a shaper circuit configured to output to the first input of the divider a first signal based on the output current of the first current generator; a bias circuit configured to output a second signal to the second input of the divider based on the first signal; and a driver circuit having a first input, configured to receive the voltage reference signal, and an output configured to drive the power transistor.