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Magnet Driver Circuit

IP.com Disclosure Number: IPCOM000080423D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Meinyk, G: AUTHOR

Abstract

When driving a solenoid 10, as shown in Fig. 1, with a conventional single-ended circuit including a transistor T1, some means of suppression is required around the solenoid 10 to prevent the back EMF from destroying the transistor T1. If a diode D is used as shown by the dotted connection, the collapse of the magnetic field of the solenoid 10 single-ended circuit including a transistor T1, some means of suppression is required around the solenoid 10 to prevent the back EMF from destroying the transistor T1. If a diode D is used as shown by the dotted connection, the collapse of the magnetic field of the solenoid 10 is retarded and greatly limits the repetition rate at which the solenoid can be reenergized.

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Magnet Driver Circuit

When driving a solenoid 10, as shown in Fig. 1, with a conventional single- ended circuit including a transistor T1, some means of suppression is required around the solenoid 10 to prevent the back EMF from destroying the transistor T1. If a diode D is used as shown by the dotted connection, the collapse of the magnetic field of the solenoid 10 single-ended circuit including a transistor T1, some means of suppression is required around the solenoid 10 to prevent the back EMF from destroying the transistor T1. If a diode D is used as shown by the dotted connection, the collapse of the magnetic field of the solenoid 10 is retarded and greatly limits the repetition rate at which the solenoid can be reenergized. Zener diodes have been used in series with the clamp diode, but such circuits require transistors with a higher breakdown voltage.

A double-ended circuit is shown in Fig. 2 which limits the voltage the transistor must withstand. As shown transistor T1 is connected between the solenoid 10 and ground, while a second transistor T2 is connected between the solenoid and the plus terminal of the source. These transistors are complementary, T1 being NPN and T2 PNP. A diode D1 is connected across the solenoid and T1, while a second diode D2 is connected across the solenoid and T2. Resistors R3 and R4 provide the base bias to T1, and resistors R1 and R2 provide the base bias for T2.

When T1 is turned on, point B will go towards ground and current...