Browse Prior Art Database

Integral Hardware-Software Current Protection

IP.com Disclosure Number: IPCOM000061109D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Kraus, RA: AUTHOR [+2]

Abstract

This article describes a scheme for use when using solid-state switches to connect an external load to ground whereby the current is detected without the addition of sense elements. If excessive current is detected, the switch is then turned off. When using solid-state switches to connect an external load to ground (ground side switching), it is not always practical to insert a sense element in series with the switch to detect the quantity of current flowing through the switch. Too much current passing through the switch may result in damage to the switch and adjacent components. In the scheme disclosed herein, the current is detected without the addition of sense elements. If excessive current is detected, the switch is turned off. Fig. 1 is a block diagram illustrating the present scheme.

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Integral Hardware-Software Current Protection

This article describes a scheme for use when using solid-state switches to connect an external load to ground whereby the current is detected without the addition of sense elements. If excessive current is detected, the switch is then turned off. When using solid-state switches to connect an external load to ground (ground side switching), it is not always practical to insert a sense element in series with the switch to detect the quantity of current flowing through the switch. Too much current passing through the switch may result in damage to the switch and adjacent components. In the scheme disclosed herein, the current is detected without the addition of sense elements. If excessive current is detected, the switch is turned off. Fig. 1 is a block diagram illustrating the present scheme. It consists of a current source (battery), a load (in this case, resistive), a switching device to allow current to pass, a voltmeter to measure the resultant voltage across the switching element, and a microcomputer to detect an over- current/power condition and correct the fault. The switching device shown is a field-effect transistor (FET), although it could be any kind of switch. When the FET is turned on, its internal resistance drops to a small value compared with its off value. Typical on-state values would be 0.1 to 0.5 ohm compared with 1 to 50 Megohms off-state values. Fig. 2 is the equivalent circuit of the switch shown...