Method and apparatus for selecting the output of programmable power adapter

1. A method of programming an output of a programmable power adapter, comprising:

sending a signal to a device;

checking the level of the signal in the programmable power adapter with at least one threshold to set a code; and

determining whether change of an output voltage of the programmable power adapter is required in accordance with the code and programming the output voltage in accordance with the code if required;

wherein a resistor installed in the device is coupled to the signal to determine the level of the signal; the output voltage of the programmable power adapter is coupled to the device to provide a power for a load of the device.

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

filtering the signal for checking the level of the signal;

wherein a de-bounce apparatus is applied to filter the signal; the de-bounce apparatus is in the programmable power adapter.

3. The method as claimed in claim 1 , wherein the device further comprises a capacitor coupled to the resistor in parallel.

4. The method as claimed in claim 3 , wherein the programmable power adapter further comprises a discharge switch coupled to discharge the capacitor, the discharge switch is in the programmable power adapter.

5. The method as claimed in claim 1 , wherein the device further comprises a switch connected to the resistor in serial.

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

providing a bleeder resistor to an output terminal of the programmable power adapter for the discharge of the output voltage of the programmable power adapter when the output voltage of the programmable power adapter is changed from a high voltage to a low voltage.

7. A method of programming an output of a power adapter, comprising:

sending a signal to a device;

checking the level of the signal in the power adapter with at least one threshold to set a code; and

determining whether change of an output voltage of the power adapter is required in accordance with the code and programming the output voltage in accordance with the code if required;

wherein a voltage-clamp device installed in the device is coupled to the signal to determine the level of the signal; the output voltage of the power adapter is coupled to the device to provide a power for a load of the device.

8. The method as claimed in claim 7 , further comprising:

filtering the signal for checking the level of the signal;

wherein a de-bounce apparatus is applied to filter the signal; the de-bounce apparatus is in the power adapter.

9. The method as claimed in claim 7 , wherein the device further comprises a capacitor coupled to the voltage-clamp device in parallel.

10. The method as claimed in claim 9 , wherein the power adapter further comprises a discharge switch coupled to discharge the capacitor, the discharge switch is in the power adapter.

11. The method as claimed in claim 7 , wherein the device further comprises a switch connected to the voltage-clamp device in serial.

12. The method as claimed in claim 7 , further comprising:

providing a bleeder resistor to an output terminal of the power adapter for the discharge of the output voltage of the power adapter when the output voltage of the power adapter is changed from a high voltage to a low voltage.

13. The method as claimed in claim 7 , wherein the device is a mobile device.

14. An apparatus of programming an output of a programmable power adapter, comprising:

a control circuit sending a signal to a device, in which the device is coupled to the signal to determine the level of the signal, the control circuit checks the level of the signal with at least one threshold to set a code, the control circuit determines whether change of an output voltage of the programmable power adapter is required in accordance with the code and programs the output voltage in accordance with the code if required;

wherein an identification circuit installed in the device is coupled to the signal to determine the level of the signal; the output voltage of the programmable power adapter is coupled to the device to provide a power for a load of the device.

15. The apparatus as claimed in claim 14 , wherein the device further comprises a switch connected to the identification circuit in serial.

16. A programmable power adapter, comprising:

a control circuit sending a signal to a device, in which the device is coupled to the signal to determine the level of the signal, the control circuit checks the level of the signal with at least one threshold to set a code, the control circuit determines whether change of an output voltage of the programmable power adapter is required in accordance with the code and programs the output voltage in accordance with the code if required; and

a programmable power supply circuit generating the output voltage of the programmable power adapter and controlled by the control circuit for determining the output voltage in accordance with the code.

17. The programmable power adapter as claimed in claim 16 , wherein the device comprises an identification circuit installed in the device, and the identification circuit is coupled to the signal to determine the level of the signal.

18. The programmable power adapter as claimed in claim 16 , wherein the programmable power supply circuit comprises:

a programmable resistor circuit coupled to the output voltage, in which the resistance of the programmable resistor circuit is programmed in accordance with the code; and

an error amplifier coupled to the programmable resistor circuit and a reference signal for programming the output voltage of the programmable power adapter;

wherein the reference signal and the resistance of the programmable resistor circuit determine the output voltage.