Circuits and methods for controlling load sharing by multiple power supplies

• US 6,465,909 B1
• Filed: 07/31/2000
• Issued: 10/15/2002
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Soo, David Henry, Reay, Robert Loren
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US09/628,534
• Time in Patent Office: 806 Days
• Field of Search: 307/24, 307/52-63
• US Class Current: 307/52
• CPC Class Codes: H02H 9/004 in connection with live-insertion of plug-in units involving communication with a central processing unit G06F13/40
• CPC Class Codes: H02J 1/001 Hot plugging or unplugging of load or power modules to or from power distribution networks
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence

Abstract

Circuits and methods for controlling load sharing by multiple power supplies are provided. In preferred embodiments, load share controllers utilize multiple voltage control loops to monitor the output voltages that are being provided by multiple power supplies connected to a load. These voltage control loops each generate a voltage control voltage that is proportional to the difference between the actual output voltage of the corresponding power supply and the desired output voltage. The voltage control loop with the highest voltage control voltage then controls a current control voltage generated in a current control loop for each power supply via a share bus. These current control loops then regulate the current provided by the corresponding power supplies so that those currents are all proportional to the voltage on the share bus. By monitoring the current control voltage in each current control loop, the voltage at the output of each power supply, and the direction of the current flowing between each power supply and the load, the circuits and methods of preferred embodiments of the invention can detect and account for out-of-regulation conditions, over voltage conditions, short circuit conditions, and hot-swapping conditions.

Claims

1. A circuit for controlling load sharing by a plurality of power supplies that are providing power to a load, comprising:

a first error amplifier that measures an output voltage provided by one of the plurality of power supplies to the load;

a diode that is couple to the output of the first error amplifier and that provides a voltage control voltage that is proportional to the output voltage of the one of the plurality of power supplies on a share bus;

an amplifier that measures an output current provided by the one of the plurality of power supplies to the load;

a second error amplifier that provides a feedback signal to the one of the plurality of power supplies based upon a comparison of the voltage control voltage and the output current.

2. The circuit of claim 1, further comprising a status output that indicates when the one of the plurality of power supplies is operating outside of a given range.

3. The circuit of claim 2, further comprising a timer that suspends indication of when the one of the plurality of power supplies is operating outside of the given range until the one of the power supplies has been operating outside of the given range for a given period of time.

4. The circuit of claim 2, further comprising a logic circuit that suspends indication of when the one of the plurality of power supplies is operating outside of the given range when the one of the power supplies is providing current below a given level.

5. The circuit of claim 1, further comprising:

a comparator that detects when the output voltage of the one of the plurality of power supplies exceeds a given voltage;

a gate driver that causes the output current provided by the one of the plurality of power supplies to be reduced, and, once the output current provided by the one of the plurality of power supplies has dropped below a given level, causes the output current provided to increase to a desired level; and

a regulator that regulates the output voltage provided by the one of the plurality of power supplies at the desired level.

6. The circuit of claim 5, further comprising a timer that shuts down current flow from the one of the plurality of power supplies to the load after the output voltage provided by the one of the plurality of power supplies has been regulated for a given period of time.

7. The circuit of claim 5, further comprising a status output that indicates a fault condition upon detecting when the output voltage of the one of the plurality of power supplies exceeds the given voltage.

8. The circuit of claim 1, further comprising:

a comparator that detects a reverse current flow into one of the plurality of power supplies; and

a logic circuit that isolates the one of the plurality of power supplies after the reverse current flow has been detected.

9. The circuit of claim 8, further comprising a timer that confirms that the reverse current flow is present for a given period of time before isolating the one of the plurality of power supplies.

10. The circuit of claim 8, further comprising a status output that indicates a fault when the output voltage of the one of the power supplies drops below a given voltage.

11. The circuit of claim 1, further comprising:

a comparator that detects when the output voltage of one of the plurality of power supplies has fallen below a given level; and

a logic circuit that isolates the one of the plurality of power supplies after detecting that the one of the plurality of power supplies has fallen below the given level.

12. The circuit of claim 11, further comprising a status output that indicates a fault when the output voltage of the one of the power supplies drops below the given level.

13. The circuit of claim 11, further comprising a timer that prevents the one of the plurality of power supplies from providing power to the load for a given period of time after the output voltage of the one of the plurality of power supplies has been restored.

14. The circuit of claim 11, further comprising a gate driver that ramps up current provided from the one of the plurality of power supplies to the load after the output voltage of the one of the plurality of power supplies has been restored.

15. A method for controlling load sharing by a plurality of power supplies that are providing power to a load, comprising:

measuring an output voltage provided by one of the plurality of power supplies to the load;

providing a voltage control voltage that is proportional to the output voltage of the one of the plurality of power supplies on a share bus;

measuring an output current provided by the one of the plurality of power supplies to the load;

providing a feedback signal to the one of the plurality of power supplies based upon a comparison of the voltage control voltage and the output current.

16. The method of claim 15, further comprising indicating when the one of the plurality of power supplies is operating outside of a given range.

17. The method of claim 16, further comprising suspending indication of when the one of the plurality of power supplies is operating outside of the given range until the one of the power supplies has been operating outside of the given range for a given period of time.

18. The method of claim 16, further comprising suspending indication of when the one of the plurality of power supplies is operating outside of the given range when the one of the power supplies is providing current below a given level.

19. The method of claim 15, further comprising:

detecting when the output voltage of the one of the plurality of power supplies exceeds a given voltage;

causing the output current provided by the one of the plurality of power supplies to be reduced;

once the output current provided by the one of the plurality of power supplies has dropped below a given level, allowing the output current provided to increase to a desired level; and

regulating the output voltage provided by the one of the plurality of power supplies at the desired level.

20. The method of claim 19, further comprising shutting down current flow from the one of the plurality of power supplies to the load after the output voltage provided by the one of the plurality of power supplies has been regulated for a given period of time.

21. The method of claim 19, further comprising indicating a fault condition upon detecting when the output voltage of the one of the plurality of power supplies exceeds the given voltage.

22. The method of claim 15, further comprising:

detecting a reverse current flow into the one of the plurality of power supplies; and

isolating the one of the plurality of power supplies after the reverse current flow has been detected.

23. The method of claim 22, further comprising confirming that the reverse current flow is present for a given period of time before isolating the one of the plurality of power supplies.

24. The method of claim 22, further comprising indicating a fault when the output voltage of the one of the power supplies drops below a given voltage.

25. The method of claim 15, further comprising:

detecting when the output voltage of the one of the plurality of power supplies has fallen below a given level; and

isolating the one of the plurality of power supplies after detecting that the one of the plurality of power supplies has fallen below the given level.

26. The method of claim 25, further comprising indicating a fault when the output voltage of the one of the power supplies drops below the given level.

27. The method of claim 25, further comprising preventing the one of the plurality of power supplies from providing power to the load for a given period of time after the output voltage of the one of the plurality of power supplies has been restored.

28. The method of claim 25, further comprising ramping up current provided from the one of the plurality of power supplies to the load after the output voltage of the one of the plurality of power supplies has been restored.