United States Patent [19] [li] Patent Number: 4,951,171
Tran et al. [45] Date of Patent: Aug. 21,1990
US. Patent Aug. 21,1990 Sheet 1 of 3 4,951,171
[54] POWER SUPPLY MONITORING
CIRCUITRY FOR COMPUTER SYSTEM
[75] Inventors: Thanh T. Tran, Tomball; Richard E.
Walker, Spring; Richard A. Faulk,
Cypress, all of Tex.
[73] Assignee: Compaq Computer Inc., Houston, Tex.
[21] Appl. No.: 350,595
[22] Filed: May 11,1989
[51] Int. CI.' H02H3/24
[52] U.S. CI 361/90; 361/91;
361/92; 361/93; 390/663; 390/66; 390/664
[58] Field of Search 361/86, 87, 90, 91,
361/92, 93; 240/660, 661, 662, 663, 664
[56] References Cited
U.S. PATENT DOCUMENTS
4,600,962 2/1986 Bliehall 361/92 X
4,638,175 1/1987 Bradford et al 361/90 X
4,772,980 9/1988 Curtis et al 361/90
Primary Examiner—Derek S. Jennings
Attorney, Agent, or Firm—Arnold, White & Durkee
[57] 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.
20 Claims, 3 Drawing Sheets
