Browse Prior Art Database

Cam Operated Inductive Load Driver

IP.com Disclosure Number: IPCOM000096951D
Original Publication Date: 1962-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Gruodis, AJ: AUTHOR

Abstract

This driver has a single power supply for biasing and powering and operates on low power input signals. Any inductive voltage developed in the load circuit is isolated from switching devices in the driver.

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Cam Operated Inductive Load Driver

This driver has a single power supply for biasing and powering and operates on low power input signals. Any inductive voltage developed in the load circuit is isolated from switching devices in the driver.

Hook or thyratron-type transistor T1 has a collector 20, a base 22 and an emitter 24. Collector 20 connects to a source of reference potential 26, by way of a load device, typically, a relay coil. An input circuit including a coupling capacitor 30, a resistor 32 and an asymmetrical device 34, all in series, is connected to the base 22. Device 34 is reversely biased, since its cathode connects through resistor 36 to supply voltage 38. The polarity of 38 is determined by the conductivity of transistor T2 whose emitter 40 connects through cam operated switch 39 to the supply. Its collector 37 connects to emitter 24 of T1. A biasing circuit for T2 includes a resistor 42 connected between base 44 and emitter 40. Also, base 44 directly connects to the base 22 of T1.

With switch 39 open, T1 and T2 are off and capacitor 30 is charged, so device 34 is reversely biased. Closing switch 39 does not turn T1 and T2 on. The T1 base current flows through resistor 42. The voltage developed across 42 is insufficient to turn T2 on. Accordingly, the T1 emitter current is zero and it remains nonconducting. A resistor network including resistors 50 and 52 can be added when it is necessary to supply an emitter current to keep T1 nonconducting.

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