Adjustable frequency curve for flyback converter at green mode

A flyback converter with adjustable frequency curve comprising:

• a primary winding configured to receive an input voltage;
• a secondary winding coupled to the primary winding and connected to a rectifier circuit to generate an output DC voltage;
• a feedback circuit coupled to output of the rectifier circuit of the secondary winding to generate a feedback signal;
• a multi-mode control circuit including:
• a voltage input for providing a power to operate the multi-mode control circuit;
• a switching device current sense input for providing a current sense signal of the switching device and generating a control signal;
• a feedback signal input for providing a feedback signal;
• a comparator circuit having an input connected to the exterior adjustable circuit for detecting an input voltage and generating a control voltage;
• a quasi-resonant valley detection circuit having an input connected to the exterior adjustable circuit for performing quasi-resonant valley detection or zero crossing detection;
• a multi-mode control module configured to receive the feedback signal, the quasi-resonant valley detection signal, and the signal from the frequency-reducing curve selection circuit for generating a control signal;
• a pulse width modulation comparator configured to perform a logic operation and generate a corresponding signal by comparing the received current sense signal and feedback signal;
• a SR flip-flop configured to receive the control signal from the multi-mode control module through its set terminal and the logic operation signal through its reset terminal for generating a control signal through its output;
• and
• a gate driver configured to receive the control signal from the SR flip-flop for controlling the switching device;
• an auxiliary winding is configured to provide power for operating the multi-mode control circuit;
• an exterior adjustable circuit connected between the auxiliary winding and the multi-mode control circuit for adjusting the input voltage level of the input feedthrough of the multi-mode control circuit, wherein the multi-mode control circuit is configured to generate a switch control signal based on the information associated with the adjusted input signal through the input feedthrough of the multi-mode control circuit and the feedback signal;
• and
• a switching device connected to the primary winding and the multi-mode control circuit to receive the switch control signal and change a current flowing through the primary winding.