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Alarm Circuit for a Plurality of DC Voltage Sources

IP.com Disclosure Number: IPCOM000049172D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bailleul, D: AUTHOR [+4]

Abstract

In many applications, a circuit arrangement is powered by several regulated DC voltage sources and it is desirable to have a device for indicating an alarm condition whenever one of the voltage sources fails. The figure illustrates a circuit which provides an alarm signal in case of voltage source failure, based on the use of logic gates.

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Alarm Circuit for a Plurality of DC Voltage Sources

In many applications, a circuit arrangement is powered by several regulated DC voltage sources and it is desirable to have a device for indicating an alarm condition whenever one of the voltage sources fails. The figure illustrates a circuit which provides an alarm signal in case of voltage source failure, based on the use of logic gates.

The exemplary circuit shown in the figure monitors for alarm conditions in three DC voltage sources VS1, VS2 and VS3 having typical values of + 5 V, + 5 V, and - 5 V, respectively. The circuit comprises three NOR gates, a voltage level adapter T1-T2, and a voltage source T3 T4 which powers (+ 5 V) the N0R gates from a bulk DC voltage source of -48 V.

The alarm device operates as follows. If, for example, voltage source VS1 fails, NOR 1 provides an up level (ground) to NOR 3 whose output in turn provides a down level (-% V). This down level is converted by transistors Tl-T2 to a ground level which is indicative of an alarm condition. If voltage source VS2 fails, an alarm signal is provided during a time interval whose duration is controlled by the value of capacitance C. A failure of the -48 V voltage source also results in an alarm signal at the collector of T2.

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