Granted Patent B2

US 9,252,671 · App. 13/923,290 · Granted Feb 2, 2016

Abstract

Claims (32)

1. A power adapter, comprising:

a rectifier and filter configured to be coupled to an input alternating current (AC) source and to generate a direct current (DC) transformer input signal;

a transformer, the transformer comprising a primary winding coupled to the transformer input signal and a secondary winding coupled to an output of the power adapter;

a current sensor configured to enable determination of an output current drawn at the output of the power adapter and to generate a current sense signal; and

a controller configured to a) regulate a voltage at the output of the power adapter by controlling current flowing through the primary winding of the transformer and b) select an output voltage from at least a first voltage and a second voltage based upon the current sense signal.

2. The power adapter of claim 1 , further comprising a first switch coupled to the controller and to the secondary winding of the transformer, the first switch being configured to control which of the at least first and second voltages is presented at the output of the power adapter based upon the output voltage selected by the controller.

3. The power adapter of claim 2 , wherein the secondary winding of the transformer comprises a first tap and a second tap, wherein the controller is further configured to generate a first control signal based upon the current sense signal and wherein the first switch selectively couples the output of the power adapter to the first or second tap based upon the first control signal.

4. The power adapter of claim 3 , wherein the controller is further configured to change a state of the first control signal when the output current sensed by the current sensor exceeds a predetermined threshold.

5. The power adapter of claim 1 , further comprising an isolated second control signal that is fed back from the output of the power adapter to the controller.

6. The power adapter of claim 2 , further comprising an output circuit coupled between the first switch and the output of the power adapter, wherein the output circuit comprises a voltage divider circuit.

7. The power adapter of claim 6 , wherein the output circuit further comprises a second switch that is configured to selectively change a ratio of the voltage divider circuit.

8. The power adapter of claim 7 , wherein at least one of the first and second switches comprises a field effect transistor (FET).

9. The power adapter of claim 3 , wherein the controller is further configured to change a state of the first control signal when an averaged output current sensed by the current sensor exceeds the predetermined threshold for a predetermined period of time.

10. A method for a power adapter to selectively provide a first and a second output voltage, comprising:

coupling a direct current (DC) input signal to a primary winding of a transformer, a secondary winding thereof comprising a first tap associated with the first output voltage and a second tap associated with the second output voltage, each of the first and second taps being configured to be selectively coupled to and uncoupled from an output of the power adapter;

determining an output current drawn at the output of the power adapter;

determining when the sensed output current exceeds a predetermined threshold; and

switching the output of the power adapter from the first to the second tap of the transformer by uncoupling the first tap from the output of the power adapter and coupling the second tap to the output of the power adapter when the sensed output current is determined to have exceeded the predetermined threshold.

11. The method of claim 10 , further comprising changing a ratio of a voltage divider coupled to the output of the power adapter when the sensed output current is determined to have exceeded the predetermined threshold.

12. The method of claim 11 , wherein changing the ratio of the voltage divider comprises controlling a field effect transistor (FET) into and out of conduction.

13. The method of claim 10 , further comprising starting a timer when the sensed averaged output current is determined to have exceeded a predetermined threshold and wherein switching comprises switching the output of the power adapter from the first to the second tap when the timer reaches a predetermined value.

14. The method of claim 10 , wherein switching further comprises switching a terminal of a field effect transistor (FET) from the first tap to the second tap.

15. A method of selectively providing a standby voltage or an operating voltage to an electronic device, comprising:

coupling a rectified and filtered direct current (DC) transformer input signal to a primary winding of a transformer, a secondary winding thereof comprising a first tap associated with the standby voltage and a second tap associated with the operating voltage, each of the first and second taps being configured to be selectively coupled to and uncoupled from the electronic device;

determining a current drawn by the electronic device;

determining when the sensed current exceeds a predetermined threshold that is indicative of the electronic device switching from a standby state to an operating state; and

switching from providing the standby voltage to providing the operating voltage by uncoupling the first tap from the electronic device and coupling the second tap to the electronic device when the sensed output current is determined to have exceeded the predetermined threshold.

16. The method of claim 15 , further comprising coupling a voltage divider to the electronic device and changing a ratio of the voltage divider when the sensed current is determined to have exceeded the predetermined threshold.

17. The method of claim 16 , wherein changing the ratio of the voltage divider comprises controlling a field effect transistor (FET) into and out of conduction.

18. The method of claim 15 , wherein switching comprises uncoupling the first tap from the electronic device and coupling the second tap to the electronic device when an averaged sensed current is determined to have exceeded a predetermined threshold for a predetermined period of time.

19. The method of claim 15 , wherein switching further comprises switching a terminal of a field effect transistor from being coupled to the first tap to being coupled to the second tap.

20. The method of claim 15 , wherein the electronic device comprises a data storage device.

Assignments (9)