LLC power supply current-sharing and frequency locking mechanism

1. A method for controlling a power supply, the method comprising:

providing, by a first power supply, a first output-current determined at least in part by an output voltage of the first power supply; and

regulating the output voltage through a control node, said regulating comprising:

when an external control signal provided by an external source is present at an input node:

generating an internal control signal based at least on the external control signal; and

decoupling the internal control signal from the control node and coupling the input node to the control node; and

when the external control signal is not present at the input node:

maintaining the internal control signal independently from the external control signal; and

decoupling the input node from the control node and coupling the internal control signal to the control node.

2. The method of claim 1 , wherein the external source is a second power supply.

3. The method of claim 2 , further comprising:

providing, by the second power supply, a second output-current, wherein the first output-current and the second output-current represent respective portions of a total output-current provided by a current sharing configuration that comprises the first power supply and the second power supply.

4. The method of claim 3 , further comprising:

balancing the total output-current to have the first output-current and the second output-current represent equal portions of the total output-current.

5. The method of claim 1 , wherein the first power supply is a multiphase power supply, wherein the first output-current comprises two or more portion currents.

6. The method of claim 5 , further comprising:

balancing the first output-current to have the two or more portion currents represent equal portions of the first output-current.

7. The method of claim 1 , wherein said generating the internal control signal comprises:

detecting a phase difference between the external control signal and the internal control signal; and

causing an operating frequency of the internal control signal to match an operating frequency of the external control signal, using the phase difference.

8. The method of claim 1 , further comprising:

detecting whether the external control signal is present; and

operating the first power supply as:

a slave device in response to detecting that the external control signal is present; and

a master device in response to detecting that the external control signal is not present.

9. A power supply comprising:

a switching output stage configured to provide an output voltage to source a first output-current; and

a control circuit coupled to the switching stage and configured to regulate the output voltage through a control node, wherein to regulate the output voltage through the control node the control circuit is configured to:

when an external control signal provided by an external source is present at an input node:

generate an internal control signal based at least on the external control signal; and

decouple the internal control signal from the control node and couple the input node to the control node; and

when the external control signal is not present at the input node:

maintain the internal control signal independently from the external control signal; and

decouple the input node from the control node and couple the internal control signal to the control node.

10. The power supply of claim 9 , wherein the external source is a second power supply.

11. The power supply of claim 10 , wherein the second power supply provides a second output-current, and wherein the first output-current and the second output-current represent respective portions of a total output-current provided by a current sharing configuration that comprises the first power supply and the second power supply.

12. The power supply of claim 11 , wherein the control circuit is further configured to:

receive a second external control signal from the second power supply; and

achieve balanced output-current sharing between the first power supply and the second power supply, using the external control signal.

13. The power supply of claim 9 , wherein the first power supply is a multiphase power supply, wherein the first output-current comprises two or more portion currents.

14. The power supply of claim 13 , wherein the control circuit is further configured to:

balance the first output-current to have the two or more portion currents represent equal portions of the first output-current.

15. The power supply of claim 9 , wherein the control circuit comprises:

a voltage-controlled oscillator having an output configured to provide the internal control signal;

a first integrator having a first input, a second input, and an output, the first input configured to be driven by a signal representative of the output voltage, and the output coupled to an input of the voltage controlled oscillator to drive the input of the voltage-controlled oscillator;

a phase detector coupled to the voltage controlled oscillator to detect a phase difference between the external control signal and the internal control signal; and

a second integrator coupled to the second input of the first integrator to drive the second input of the first integrator according to the phase difference to cause an operating frequency of the internal control signal to match an operating frequency of the external control signal.

16. The power supply of claim 9 , wherein the control circuit is further configured to:

detect whether the external control signal is present; and

operate the first power supply as:

a slave device in response to detecting that the external control signal is present; and

a master device in response to detecting that the external control signal is not present.

17. A control mechanism for controlling a power supply that supplies an output current determined at least in part by an output voltage of the power supply, the control mechanism comprising:

an input node configured to receive an external control signal from a source external to the control mechanism;

a signal processing circuit configured to generate an internal control signal based at least on the external control signal when the external control signal is present at the input node; and

a control circuit configured to regulate the output voltage through a control node, wherein to regulate the output voltage through the control node the control circuit is configured to:

decouple the internal control signal from the control node and couple the input node to the control node when the external control signal is present at the input node; and

when the external control signal is not present at the input node:

maintain the internal control signal independently from the external control signal; and

decouple the input node from the control node and couple the internal control signal to the control node.

18. The control mechanism of claim 17 , wherein the external source is another power supply.

19. The control mechanism of claim 17 , wherein the signal processing circuit is configured to generate the internal control signal by:

detecting a phase difference between the external control signal and the internal control signal; and

causing an operating frequency of the internal control signal to match an operating frequency of the external control signal, using the phase difference.

20. The control mechanism of claim 17 , wherein the control circuit is further configured to:

detect whether the external control signal is present; and

operate the power supply as:

a slave device in response to detecting that the external control signal is present; and

a master device in response to detecting that the external control signal is not present.