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Initial on Voltage Tester

IP.com Disclosure Number: IPCOM000077422D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Radcliffe, WE: AUTHOR

Abstract

A test of initial on voltage in power silicon-control rectifiers (SCR) is performed automatically with this circuit and a go/no-go indication of meeting a specification is provided.

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Initial on Voltage Tester

A test of initial on voltage in power silicon-control rectifiers (SCR) is performed automatically with this circuit and a go/no-go indication of meeting a specification is provided.

Pulse generator 1 applies a burst of three 350 microsecond pulses to SCR 2 under test. Power supply 3 supplies a DC signal to the gate to cathode junction of SCR 2, permitting the SCR to fire as soon as the current pulse from generator 1 is applied. The anode to cathode voltage is sensed by differential amplifier 4 and fed to sample-hold circuit 5. Circuit 5 is gated at the 300 microsecond point of the first current pulse, providing an output to operational amplifiers 6 and 7. Amplifiers 6 and 7 amplify the DC value of the 300 microsecond voltage 1.3 and
1.05 times, respectively.

The amplifier voltages provided by circuits 6 and 7 are used as references for voltage comparators 8, g which are strobed from the control logic 10 at the 50 microsecond and 100 microsecond points of the next two current pulses provided by generator 1. If the anode to cathode voltage of SCR 2 is above either of these two voltages, a signal is sent to control logic 10 providing a go/no-go decision, indicative of whether the SCR has failed the test at either or both of the 50 microsecond or 100 microsecond points.

The response curve of time versus initial voltage on, is different for a failed SCR (curve A) as compared to a good SCR (curve B).

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