Control method and device for quasi-resonant high-power-factor flyback converter

A device for controlling a driver of a power circuit, comprising:

• a multiplier having a first input configured to receive a first signal based on a feedback signal from the power circuit, a second input configured to receive a second signal based on an input signal from the power circuit, and an output, the multiplier being configured to produce a multiplier signal based on a multiplication of the first and second signals;
• a current generator coupled to the multiplier and configured to produce a current reference signal;
• a capacitor coupled between the first current generator and a supply voltage terminal;
• a first resistor coupled to an output of the first current generator;
• and
• a switch configured to couple the first resistor in parallel with the capacitor when the power transistor is on.

A system, comprising:

• a rectifier having an input and configured to output a rectified voltage;
• a transformer having a primary winding configured to receive a sinusoidal input current from the rectifier;
• a power transistor coupled to the primary winding of the transformer and configured to drive the transformer;
• a driver circuit configured to drive the power transistor based on a voltage reference signal;
• a control circuit configured to produce the voltage reference signal, having:
• a multiplier having a first input configured to receive a first signal, a second input configured to receive a second signal based on the rectified voltage, and an output at which the multiplier is configured to produce a multiplier signal based on a multiplication of the first and second signals;
• a current generator coupled to the multiplier and configured to output a reference current;
• a first resistor coupled to an output of the first current generator;
• a capacitor coupled between the current generator and a supply voltage terminal;
• and
• a switch configured to couple the resistor in parallel with the capacitor when the power transistor is on.