Latent fault detection in redundant power supply systems

• US 20040039536A1
• Filed: 06/04/2003
• Published: 02/26/2004
• Est. Priority Date: 06/06/2002
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Garnett, Paul J.
• Granted Patent: US 6,947,864 B2
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 31/30 Marginal testing, e.g. by varying supply voltage testing computers during standby operation or idle time G06F11/22
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
• CPC Class Codes: G06F 11/2015 Redundant power supplies power supply failure G06F1/30
• CPC Class Codes: H02J 1/108 using diodes blocking reverse current flow H02J1/12 takes precedence

Abstract

Latent faults are detected by a testing system in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices. The testing system selects as a subject for a test procedure one isolation device and its corresponding power supply. The power supplies are controlled during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value.

Claims

1. A method of testing for latent faults in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state, the method performed by a testing system comprising:

selecting as a subject for a test procedure, one isolation device and its corresponding power supply;

controlling the power supplies during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value;

measuring current through the selected isolation device; and

determining whether the measured current is consistent with the existence of a fault condition in the selected isolation device.

2. A method as claimed in claim 1 wherein the test procedure includes a short circuit detection test in which each of the power supplies other than the selected power supply has a first output voltage greater than a second output voltage of the selected power supply such that the differential voltage is applied for changing the conductive state of the selected isolation device to a non-conductive state in the absence of a fault condition and wherein, if the measured current is non zero and in a direction towards the power supply, the measured current is determined to be consistent with a short circuit fault condition in the selected isolation device.

3. A method as claimed in claim 1 wherein the test procedure includes an open circuit detection test in which the selected power supply has a first output voltage greater than a second output voltage of the remaining power supplies such that the differential voltage is applied for changing the conductive state of each isolation device other then the selected isolation device to a non-conductive state in the absence of a fault condition and wherein, if the measured current is substantially zero, the measured current is determined to be consistent with an open circuit fault condition in the selected isolation device.

4. A method as claimed in claim 3 when dependent from claim 2 wherein the method comprises performing a test cycle comprising a sequence of test procedures such that in a completed test cycle respective short circuit tests and open circuit tests are performed for each of the isolation devices.

5. A method as claimed in claim 4 wherein the number of power supplies is two, the method comprising a first phase in which first and second power supplies output first and second voltages respectively with the first voltage being greater than the second voltage to apply the differential voltage, the currents in corresponding first and second isolation devices being measured to perform the open circuit test on the first isolation device and the short circuit test on the second isolation device;

and a second phase in which the first and second power supplies output the second and first voltages respectively to reverse the applied differential voltage, currents in the first and second isolation devices being measured to perform the short circuit test in the first isolation device and the open circuit test in the second isolation device.

6. A method as claimed in claim 1 comprising operating a system controller to output command signals for controlling the power supplies;

each isolation device having a respective sensing circuit transmitting signals representative of the measurement of current to the system controller; and

further comprising operating the system controller to determine whether the measured currents are consistent with the existence of a fault condition.

7. A method as claimed in claim 6 wherein the system controller initiates the test cycle at predetermined intervals.

8. A method as claimed in claim 7 including the system controller receiving and storing input data representative of the predetermined intervals and initiating the test cycle at intervals determined by the data.

9. A method as claimed in claim 6 comprising the system controller generating an alarm signal in response to detection of a fault condition.

10. A method as claimed in claim 1 wherein each power supply comprises a respective margin arm input and wherein the controlling step comprises inputting a respective logic level signal to the margin arm input of the each power supply.

11. A method as claimed in claim 1 wherein each isolation device comprises a respective diode.

12. A method as claimed in claim 1 wherein the differential voltage is applied such that, during the test procedure and in the absence of fault conditions, the load is supplied by at least one of the power supplies operating at a first output voltage and having a respective isolation device operating in a normal conductive state, and such that each remaining power supply operates at a second output voltage less than the first output voltage by the differential amount and in respect of which power supply the resulting forward voltage across its respective isolation device is less than the forward bias voltage level of the isolation device so that conduction is inhibited.

13. A method as claimed in claim 12 wherein the differential voltage is applied such that, during the test procedure and in the presence of a fault condition requiring the load to be supplied by one or more of the remaining power supplies operating at the second voltage, the resulting load voltage is greater than a minimum operational limit required for operation of the load.

14. A testing system for testing for latent faults in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state, the testing system comprising:

a system controller for selecting as a subject for a test procedure, one isolation device and its corresponding power supply;

control circuitry for controlling the power supplies during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value;

measuring circuitry for measuring current through the selected isolation device; and

wherein the system controller is operable to determine whether the measured current is consistent with the existence of a fault condition in the selected isolation device.

15. A testing system as claimed in claim 14 wherein the test procedure includes an open circuit detection test in which the control circuitry is operable to control the selected power supply to have a first output voltage greater than a second output voltage of the remaining power supplies such that the differential voltage is applied for changing the conductive state of each isolation device other then the selected isolation device to a non-conductive state in the absence of a fault condition and wherein, if the measured current is substantially zero, the system controller is operable to determine the measured current to be consistent with an open circuit fault condition in the selected isolation device.

16. A testing system as claimed in claim 14 wherein the test procedure includes a short circuit detection test in which the control circuitry is operable to control each of the power supplies other than the selected power supply to have a first output voltage greater than a second output voltage of the selected power supply such that the differential voltage is applied for changing the conductive state of the selected isolation device to a non-conductive state in the absence of a fault condition and wherein, if the measured current is non zero and in a direction towards the power supply, the system controller is operable to determine the measured current to be consistent with a short circuit fault condition in the selected isolation device.

17. A testing system as claimed in claims 16 wherein the test procedure includes an open circuit detection test in which the control circuitry is operable to control the selected power supply to have a first output voltage greater than a second output voltage of the remaining power supplies such that the differential voltage is applied for changing the conductive state of each isolation device other then the selected isolation device to a non-conductive state in the absence of a fault condition and wherein, if the measured current is substantially zero, the system controller is operable to determine the measured current to be consistent with an open circuit fault condition in the selected isolation device.

18. A testing system as claimed in claim 17 wherein the testing system is operable to perform a test cycle comprising a sequence of test procedures such that in a completed test cycle respective short circuit tests and open circuit tests are performed for each of the isolation devices.

19. A testing system as claimed in claim 18 wherein the number of power supplies is two, the testing system being operable to perform a test cycle comprising a first phase in which first and second power supplies output first and second voltages respectively with the first voltage being greater than the second voltage to apply the differential voltage, the measuring circuitry being operable to measure the currents in corresponding first and second isolation devices to perform the open circuit test on the first isolation device and the short circuit test on the second isolation device;

and a second phase in which the first and second power supplies output the second and first voltages respectively to reverse the applied differential voltage, the measuring circuitry being operable to measure the currents in the first and second isolation devices to perform the short circuit test in the first isolation device and the open circuit test in the second isolation device.

20. A testing system as claimed in claim 14 wherein the system controller is operable to output command signals for controlling the power supplies;

each isolation device having a respective sensing circuit for transmitting signals representative of the measurement of current to the system controller; and

the system controller being further operable to determine whether the measured currents are consistent with the existence of a fault condition.

21. A testing system as claimed in claim 20 wherein the system controller is operable to initiate the test cycle at predetermined intervals.

22. A testing system as claimed in claim 21 wherein the system controller is operable to receive and store input data representative of the predetermined intervals and being operable to initiate the test cycle at intervals determined by the data.

23. A testing system as claimed in claim 14 wherein the system controller is operable to generate an alarm signal in response to detection of a fault condition.

24. A testing system as claimed in claim 14 wherein each power supply comprises a respective margin arm input and wherein the control circuitry comprises control logic operable to input a respective logic level signal to the margin arm input of the each power supply.

25. A testing system as claimed in claim 14 and operable to apply the differential voltage such that, during the test procedure and in the absence of fault conditions, the load is supplied by at least one of the power supplies operating at a first output voltage and having a respective isolation device operating in a normal conductive state, and such that each remaining power supply operates at a second output voltage less than the first output voltage by the differential amount and in respect of which power supply the resulting forward voltage across its respective isolation device is less than the forward bias voltage level of the isolation device so that conduction is inhibited.

26. A testing system as claimed in claim 24 and operable to apply differential voltage such that, during the test procedure and in the presence of a fault condition requiring the load to be supplied by one or more of the remaining power supplies operating at the second voltage, the resulting load voltage is greater than a minimum operational limit required for operation of the load.

27. A system comprising:

a load circuit;

a plurality of DC power supplies each having a respective isolation device via which the power supply is connected to the load circuit, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state; and

a test system for testing for latent faults, the test system comprising;

a system controller for selecting as a subject for a test procedure, one isolation device and its corresponding power supply;

control circuitry for controlling the power supplies to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non-conductive state by reducing its forward voltage to less than its respective forward bias voltage value;

measuring circuitry for measuring current through the selected isolation device; and

wherein the system controller is operable to determine whether the measured current is consistent with the existence of a fault condition in the selected isolation device.

28. A system as claimed in claim 27 wherein the load circuit comprises a computer system.

29. A system as claimed in claim 27 wherein each isolation device comprises a respective diode.

30. A portable storage medium carrying processor implementable instructions for instructing a processor to control a testing system to perform a method of testing for latent faults in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state, the method performed by the testing system comprising:

selecting as a subject for a test procedure, one isolation device and its corresponding power supply;

controlling the power supplies during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value;

measuring current through the selected isolation device; and

determining whether the measured current is consistent with the existence of a fault condition in the selected isolation device.

31. A signal carrying processor implementable instructions for instructing a processor to control a testing system to perform a method of testing for latent faults in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state, the method performed by a testing system comprising:

selecting as a subject for a test procedure, one isolation device and its corresponding power supply;

controlling the power supplies during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value;

measuring current through the selected isolation device; and

determining whether the measured current is consistent with the existence of a fault condition in the selected isolation device.