Switching power supply and control method thereof

Abstract

A switching power supply comprises a magnetic element, a power tube and a driving circuit located at the input side of the magnetic element, and a feedback circuit located at the output side of the magnetic element; wherein the feedback circuit comprises an isolation device and an error amplification module; the error amplification module is adapted to sample the output voltage of the magnetic element, generate an error signal based on the sampled voltage, and transmit the error signal to the driving circuit through the isolation device, so that the driving circuit adjusts the duty cycle of the driving signal of the power tube based on the error signal to control the on-off time length of the power tube by using the driving signal; the amplitude of the error signal and the output voltage of the magnetic element have opposite change trends. By using the above scheme, the light load or no load power consumption of the switching power supply can be reduced.

Images