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Magnet Driver Circuit

IP.com Disclosure Number: IPCOM000091887D
Original Publication Date: 1968-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Hanson, CC: AUTHOR [+2]

Abstract

This magnet driver circuit quickly collapses the field of the magnet after it turns off. Source of pulses 1 controls the setting and resetting of latch 2. The amplified output of latch 2 turns on current switch T1. The latter conditions the anode of silicon controlled rectifier SCR 3. This is turned on by driver 4. Magnet 5 is connected in the anode circuit of SCR 3.

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Magnet Driver Circuit

This magnet driver circuit quickly collapses the field of the magnet after it turns off. Source of pulses 1 controls the setting and resetting of latch 2. The amplified output of latch 2 turns on current switch T1. The latter conditions the anode of silicon controlled rectifier SCR 3. This is turned on by driver 4. Magnet 5 is connected in the anode circuit of SCR 3.

Magnet 5 is de-energized by turning SCR 3 off. This is effected by reverse biasing SCR 3, anode to cathode, by turning T1 off. When T1 is turned off, current continues to flow through SCR 3 for a short time. A back emf is generated when the current in magnet 5 is decreasing. Transistor T3, referenced to a suitable voltage, turns on when the back emf exceeds the reference voltage. T3 provides base current for transistor T2 which, in turn, provides a path for collapsing the field of magnet 5.

This circuit is useful where a plurality of magnets is in the anode circuits of as many SCR's, which are selectively driven by a logic circuitry. By varying the reference voltage of T3, the time required for collapsing the magnet field is controlled.

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