Method and apparatus for controlling programmable power converter with low standby power loss

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

generating a programmable reference signal for regulating an output voltage of the power converter;

generating a feedback signal in accordance with the programmable reference signal and the output voltage;

generating a switching signal coupled to switch a transformer for generating the output voltage in accordance with the feedback signal;

generating a first power source; and

generating a second power source;

wherein the voltage level of the second power source is lower than the voltage level of the first power source; the first power source and the second power source provide a power supply for a control circuit generating the programmable reference signal and the feedback signal; the control circuit will use the first power source as its power supply when the voltage level of the first power source is lower than a threshold; the control circuit will use the second power source as its power supply when the voltage level of the first power source is higher than the threshold.

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

generating a first power supply voltage; and

generating a second power supply voltage;

wherein a voltage level of the second power supply voltage is lower than a voltage level of the first power supply voltage; the first power supply voltage and the second power supply voltage provide a power supply for a switching controller for generating the switching signal; the switching controller will use the first power supply voltage as its power supply when the voltage level of the first power supply voltage is lower than a threshold voltage; the switching controller will use the second power supply voltage as its power supply when the voltage level of the first power supply voltage is higher than the threshold voltage.

3. The method as claimed in claim 1 , wherein the control circuit is in a secondary side of the transformer; a switching controller is in a primary side of the transformer for generating the switching signal; the control circuit has a communication interface for communication with an external device.

4. The method as claimed in claim 1 , wherein the programmable reference signal will be reset to an initial value in response to a power-on of the power converter.

5. The method as claimed in claim 1 , wherein the control circuit generates a control signal coupled to program an over-voltage threshold signal in a switching controller for an over-voltage protection of the output voltage.

6. The method as claimed in claim 5 , wherein the over-voltage threshold signal will be reset to an initial value in response to a power-on of the power converter.

7. The method as claimed in claim 1 , wherein the control circuit generates a control signal coupled to control a programmable current reference signal in a switching controller for regulating an output current.

8. The method as claimed in claim 7 , wherein the programmable current reference signal will be reset to an initial value in response to a power-on of the power converter.

9. An apparatus for controlling a programmable power converter, comprising:

a control circuit generating a programmable reference signal for regulating an output voltage of the power converter, and generating a feedback signal in accordance with the programmable reference signal and the output voltage;

a switching controller generating a switching signal coupled to switch a transformer for generating the output voltage in accordance with the feedback signal; and

a power generator coupled to the transformer for generating a first power source and a second power source;

wherein a voltage level of the second power source is lower than a voltage level of the first power source; the first power source and the second power source provide a power supply for the control circuit; the control circuit will use the first power source as its power supply when the voltage level of the first power source is lower than a threshold; the control circuit will use the second power source as its power supply when the voltage level of the first power source is higher than the threshold.

10. The apparatus as claimed in claim 9 , further comprising:

a voltage generator generating a first power supply voltage and a second power supply voltage;

wherein a voltage level of the second power supply voltage is lower than a voltage level of the first power supply voltage; the first power supply voltage and the second power supply voltage provide a power supply for the switching controller; the switching controller will use the first power supply voltage as its power supply when the voltage level of the first power supply voltage is lower than a threshold voltage; the switching controller will use the second power supply voltage as its power supply when the voltage level of the first power supply voltage is higher than the threshold voltage.

11. The apparatus as claimed in claim 9 , wherein the control circuit is in a secondary side of the transformer; the switching controller is in a primary side of the transformer; the control circuit has a communication interface for communication with an external device.

12. The apparatus as claimed in claim 9 , wherein the switching controller is coupled to detect a reflected signal of the transformer for regulating an output current of the power converter in accordance with demagnetizing time of the transformer.

13. The apparatus as claimed in claim 9 , wherein the switching controller is coupled to detect a reflected signal for performing an over-voltage protection in the switching controller.

14. The apparatus as claimed in claim 9 , wherein the control circuit comprises:

a threshold generation circuit generating a programmable over-voltage threshold for an over-voltage protection in the control circuit; and

an over-voltage protection circuit coupled to generate an over-voltage signal by comparing the output voltage and the programmable over-voltage threshold;

wherein the over-voltage signal is transferred to the switching controller; the over-voltage signal is coupled to disable the switching signal.

15. The apparatus as claimed in claim 14 , wherein the programmable over-voltage threshold will be reset to a minimum threshold in response to a power-on of the power converter.

16. The apparatus as claimed in claim 9 , wherein the control circuit further comprises:

a micro-controller for generating the programmable reference signal.

17. The apparatus as claimed in claim 9 , wherein the control circuit further comprises:

an analog-to-digital converter coupled to detect the output voltage of the power converter;

wherein an output of the analog-to-digital converter is coupled to a micro-controller of the control circuit.

18. The apparatus as claimed in claim 9 , wherein the control circuit comprises:

a reference generation circuit coupled to generate the programmable reference signal; and

a feedback circuit coupled to detect the output voltage for generating the feedback signal in accordance with the programmable reference signal.