Adaptive slope compensation programmable by input voltage of power converter

1. A method for controlling a power converter, comprising:

generating a switching signal coupled to switch a transformer for regulating an output of the power converter in accordance with a feedback signal, and a ramp signal;

generating the ramp signal in accordance with a switching current signal and a slope compensation signal;

generating the slope compensation signal in response to an input voltage signal; and

generating the input voltage signal in response to the level of the input voltage of the power converter,

wherein the feedback signal is generated in accordance with the output of the power converter, and the switching current signal is correlated with a switching current of the transformer.

2. The method as claimed in claim 1 , wherein the slope compensation signal is synchronized with the switching signal.

3. The method as claimed in claim 1 , wherein the level of the switching current signal is controlled by the level of the input voltage of the power converter.

4. The method as claimed in claim 1 , wherein the input voltage signal is generated through the detection from a winding of the transformer.

5. The method as claimed in claim 1 , further comprising:

limiting a maximum switching frequency of the switching signal;

switching on the switching signal in response to a signal detected from a winding of the transformer.

6. A power converter, comprising:

a control circuit generating a switching signal;

a first voltage divider coupled to the control circuit; and

a transformer coupled to the first voltage divider, wherein the transformer and the first voltage divider generate an input voltage signal in response to the level of an input voltage of the power converter, and the switching signal is coupled to switch the transformer for regulating an output of the power converter in accordance with a feedback signal and a ramp signal,

wherein the control circuit comprises:

a second voltage divider, wherein the second voltage divider generates the ramp signal in accordance with a switching current signal and a slope compensation signal; and

a signal generation unit coupled to the second voltage divider, wherein the signal generation unit generates the slope compensation signal in response to the input voltage signal,

wherein the feedback signal is generated in accordance with the output of the power converter, and the switching current signal is correlated with a switching current of the transformer.

7. The power converter as claimed in claim 6 , wherein the slope compensation signal is synchronized with the switching signal.

8. The power converter as claimed in claim 6 , wherein the level of the switching current signal is controlled by the level of the input voltage of the power converter.

9. The power converter as claimed in claim 6 , wherein the input voltage signal is generated through the detection from a winding of the transformer.

10. The power converter as claimed in claim 6 , wherein the control circuit further comprises:

a pulse generation circuit switching on the switching signal in response to a signal detected from a winding of the transformer, and the pulse generation circuit comprising an oscillation circuit,

wherein the oscillation circuit comprises a frequency limiting unit for limiting a maximum switching frequency of the switching signal.