Ripple suppression circuit and a ripple suppression method for quasi-resonant flyback power supply

1 . A ripple suppression circuit for quasi-resonant flyback power supply, the ripple suppression circuit comprising:

a compensation circuit configured to generate a compensation signal, wherein the compensation signal is generated based on bus voltage; and

a control circuit configured to compare a first signal with a second signal to provide a control signal, wherein the control signal is configured to control a power switch of the quasi-resonant flyback power supply turning from an on state to an off state, and the first signal is compensated by the compensation signal;

wherein the ripple suppression circuit further comprises a reference circuit, the reference circuit configured to generate a reference signal, the reference signal generated based on an output voltage of the quasi-resonant flyback power supply;

wherein the first signal represents sum of the reference signal and the compensation signal, and the second signal represents primary side current of a transformer of the quasi-resonant flyback power supply;

wherein the control circuit comprises:

an addition circuit having a first input terminal, a second input terminal and an output terminal, the first input terminal of the addition circuit coupled to the compensation circuit, the second input terminal of the addition circuit coupled to the reference circuit, the addition circuit configured to add the compensation signal and the reference signal to generate the first signal; and

a comparison circuit having a first input terminal and a second input terminal, the first input terminal of the comparison circuit coupled to the second signal, the second input terminal of the comparison circuit coupled to the output terminal of the addition circuit;

when the second signal is greater than the first signal, the control circuit controls the power switch of the quasi-resonant flyback power supply turning from the on state to the off state; and

wherein a relation between the compensation signal and the bus voltage is: CS_comp=K0+K1/Vbus; wherein CS_comp is the compensation signal, K0 is a constant, K1 is a non-zero constant, and Vbus is the bus voltage.

2 . The ripple suppression circuit according to claim 1 , wherein the ripple suppression circuit further comprises a first sampling circuit, the first sampling circuit configured to obtain a circuit signal representing the bus voltage.

3 . The ripple suppression circuit according to claim 2 , wherein the first sampling circuit comprises:

an auxiliary winding having a first terminal and a tail terminal, the tail terminal of the auxiliary winding coupled to a ground;

a third resistor having a first terminal and a second terminal, the first terminal of the third resistor coupled to the first terminal of the auxiliary winding;

a fourth resistor having a first terminal and a second terminal, the first terminal of the fourth resistor coupled to the second terminal of the third resistor, the second terminal of the fourth resistor coupled to the ground; and

a current acquisition circuit having a first terminal and a second terminal, the first terminal of the current acquisition circuit coupled to the first terminal of the fourth resistor, the second terminal of the current acquisition circuit coupled to the ground; the current acquisition circuit configured to obtain a current signal representing the bus voltage by collecting a current flowing through the third resistor.

4 . A ripple suppression method for quasi-resonant flyback power supply, the ripple suppression method comprising:

generating, using a compensation circuit, a compensation signal, wherein the compensation signal is generated based on bus voltage; and

comparing, using a control circuit, a first signal with a second signal to provide a control signal, wherein the control signal is configured to control a power switch of the quasi-resonant flyback power supply turning from an on state to an off state, and the first signal is compensated by the compensation signal;

wherein the ripple suppression method further comprises generating, using a reference circuit, a reference signal, the reference signal generated based on an output voltage of the quasi-resonant flyback power supply;

wherein the first signal represents sum of the reference signal and the compensation signal, and the second signal represents primary side current of a transformer of the quasi-resonant flyback power supply;

wherein the control circuit comprises:

an addition circuit having a first input terminal, a second input terminal and an output terminal, the first input terminal of the addition circuit coupled to the compensation circuit, the second input terminal of the addition circuit coupled to the reference circuit, the addition circuit configured to add the compensation signal and the reference signal to generate the first signal; and

a comparison circuit having a first input terminal and a second input terminal, the first input terminal of the comparison circuit coupled to the second signal, the second input terminal of the comparison circuit coupled to the output terminal of the addition circuit;

when the second signal is greater than the first signal, the control circuit controls the power switch of the quasi-resonant flyback power supply turning from the on state to the off state; and

wherein a relation between the compensation signal and the bus voltage is: CS_comp=K0+K1/Vbus; wherein CS_comp is the compensation signal, K0 is a constant, K1 is a non-zero constant, and Vbus is the bus voltage.