Power supply monitoring circuitry for computer system

• US 4,951,171 A
• Filed: 05/11/1989
• Issued: 08/21/1990
• Est. Priority Date: 05/11/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Tran, Thanh T., Walker, Richard E., Faulk, Richard A.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/350,595
• Time in Patent Office: 467 Days
• Field of Search: 361/86, 361/87, 361/90, 361/91, 361/92, 361/93, 240/660, 240/661, 240/662, 240/663, 240/664
• US Class Current: 361/90
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: G06F 11/0754 by exceeding limits
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A computer system having a power supply monitoring arrangement employs a number of comparators for detecting whether or not various supply voltages produced by the power supply for use in the computer are above or below a reference level, or whether an overcurrent condition exists. These detected conditions are used to determine whether or not the power supply should be shut down, or during power-up to determine whether the initialization routine can be started by the CPU. Delays are included to prevent an undervoltage condition from indicating shut down of the power supply during power-up.

Claims

1. A method of operating a computer comprising the steps of:

(a) generating in a power supply at least one supply voltage for use in said computer;

(b) monitoring said supply voltage and producing a first signal if said supply voltage is below a selected value;

(c) detecting an overvoltage condition of said supply voltage;

(d) detecting an overcurrent condition which persists for longer than a selected time for said supply voltage;

(e) shutting off said power suply if either said overvoltage condition or said overcurrent condition is detected; and

(f) preventing said computer from being reset until said first signal has not been present for a selected time.

2. A method according to claim 1 wherein said power supply generates a plurality of supply voltages use in said computer.

3. A method according to claim 2 including the step of shutting off said power supply if said first signal is present after a selected time from applying power to said power supply.

4. A method according to claim 1 wherein said step of monitoring includes monitoring a plurality of supply voltages produced by said power supply.

5. A method according to claim 1 including the step of generating a separate voltage for use as a voltage supply in said steps of monitoring and detecting.

6. A computer having a power supply monitor, comprising:

(a) a power supply generating at least one supply voltage for use in said computer;

(b) means for monitoring said supply voltage and producing a first signal if said supply voltage is below a selected value;

(c) means for detecting an overvoltage condition of said supply voltage;

(d) means for detecting an overcurrent condition which persists for longer than a selected time for said supply voltage;

(e) means for shutting off said power supply if either said overvoltage condition or said overcurrent condition is detected;

(f) said computer having a reset input responsive to said first signal to inhibit the computer from reset until said first signal has not been present for a selected time.

7. A device according to claim 6 wherein said power supply generates a plurality of supply voltages use in said computer.

8. A device according to claim 7 including means for shutting off said power supply if said first signal is present after a selected time from applying power to said power supply.

9. A device according to claim 8 wherein said means for monitoring monitors all of said supply voltages.

10. A circuit for monitoring a power supply for a computer or the like, the power supply producing a plurality of supply voltages, comprising:

(a) a plurality of undervoltage detectors, each one of said undervoltage detectors being responsive to a separate one of said plurality of supply voltages and producing an output indicating whether one of said supply voltages is above or below a selected reference level;

(b) means responsive to all of said outputs from all of said plurality of undervoltage detectors to produce a first signal when all of said supply voltages are above the selected reference level;

(c) at least one overvoltage detector responsive to one of said plurality of supply voltages and producing an overvoltage indication if said one of the supply voltages exceeds a selected value;

(d) a current detector responsive to current flow in a conductor for one of said supply voltages and producing an overcurrent indication if excess current flow is detected;

(e) and means for negating said first signal and for generating a second signal upon occurrence of said overvoltage indication or said overcurrent indication.

11. A circuit according to claim 10 wherein said undervoltage detectors and said overvoltage detector compare said supply voltages to references voltage generated from a voltage supply separate from said supply voltages.

12. A circuit according to claim 10 wherein said supply voltages include both positive voltages and negative voltages.

13. A circuit according to claim 10 wherein said overcurrent indication is produced only if excess current is detected for longer than a selected time period.

14. A circuit according to claim 10 wherein said first signal is produced only if said undervoltage detectors produce said output for longer than a selected time period.

15. A method of monitoring a power supply for a computer or the like, the power supply producing a plurality of supply voltages, comprising the steps of:

(a) detecting undervoltage for each one of said plurality of supply voltages and producing a first signal indicating whether or not all of said supply voltages are above selected reference levels;

(b) detecting overvoltage for at least one of said supply voltages,

(c) detecting overcurrent for at least one of said supply voltages,

(d) producing a second signal when said overvoltage or said overcurrent is detected or when said first signal indicates undervoltage occurring after a selected time folowing power-up, and

(e) shutting down said power supply to prevent said computer from operating in response to said second signal.

16. A method according to claim 15 wherein said steps of detecting undervoltage and overvoltage include comparing said supply voltages to reference voltages generated from a voltage supply separate from said supply voltages.

17. A method according to claim 15 including the step of resetting said computer only in response to the level of said first signal.

18. A method according to claim 15 including the step of shutting down said power supply in response to said second signal.

19. A method according to claim 15 wherein said step of detecting overcurrent includes delaying an output indicating overcurrent for a selected time period.

20. A method according to claim 15 including the step of generating a delayed signal in producing said first signal.