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Watch Dog Circuit for Power Supplies

IP.com Disclosure Number: IPCOM000038118D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Steinmetz, MJ: AUTHOR

Abstract

This article describes a circuit arrangement which protects a power supply from microprocessor failure by shutting down the power supply in the event that the microprocessor abnormally halts or "hangs-up".

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 56% of the total text.

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Watch Dog Circuit for Power Supplies

This article describes a circuit arrangement which protects a power supply from microprocessor failure by shutting down the power supply in the event that the microprocessor abnormally halts or "hangs-up".

The use of a microprocessor in power systems for power on/off sequencing and fault isolation presents several advantages. One of the main functions of the microprocessor is to shut down the power supply when an overcurrent or overvoltage condition detected. The power supply is generally in a high noise environment where it is possible for the microprocessor to "hang-up" or stop executing due to noise glitches or due to some other failure of the microprocessor. It is usual, when a hang-up occurs, for the various states within the microprocessor to remain as they were when the hang-up occurs. Therefore, the hang-up may not be apparent to an operator. If this happens, the power supply would be running without any overvoltage or overcurrent protection. A fault on the supply output could result in damage to the power supply.

To protect against this condition, a watch dog circuit as disclosed herein is provided which will shut down the power supply should the microprocessor hang- up. In operation one of the ports of the microprocessor is used to periodically reset the external watch dog circuit. It may be a dedicated port or a port which performs another function requiring a periodic pulse (e.g., a battery check circuit). As long...