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Driver Circuit

IP.com Disclosure Number: IPCOM000080926D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Wallace, LJ: AUTHOR

Abstract

The circuit shown in Fig. 1 constitutes an improved arrangement for supplying operating power to a plurality of coils or solenoids, such as the coil #1 and coil #2 shown in the drawing. A common pedestal drive is provided including the transistors T1 and T2, and the zener diode ZD. A common resistor R1 is also connected to the common portion of the circuit as shown. Each of the coils #1 and #2 are provided with their own hold circuit such as that shown in the drawing for coil #1 comprising transistors T3 and T4, and the diode D2.

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Driver Circuit

The circuit shown in Fig. 1 constitutes an improved arrangement for supplying operating power to a plurality of coils or solenoids, such as the coil #1 and coil #2 shown in the drawing. A common pedestal drive is provided including the transistors T1 and T2, and the zener diode ZD. A common resistor R1 is also connected to the common portion of the circuit as shown. Each of the coils #1 and #2 are provided with their own hold circuit such as that shown in the drawing for coil #1 comprising transistors T3 and T4, and the diode D2.

Fig. 2 is a waveform diagram showing the waveforms which occur at various points in the circuit during its operation.

In operation, a pick pulse of relatively short duration is applied to T1, for example, which turns on T2. A hold pulse is also applied at the same time to T3, which in turn causes T4 to turn on.

Current will now flow from +24 volts through transistor T2, the coil 1, and through transistor T4 to ground. After a predetermined time, the pick pulse is terminated while the hold pulse is maintained.

A back voltage is generated at the coil as the coil field decays to the hold voltage level. This negative voltage appears at the collector of T2 and the anode of the zener diode ZD. When the voltage exceeds the zener diode breakdown, base current is supplied to T2 and it starts conduction. As the voltage increases beyond the zener diode breakdown, more base current is supplied to T2. This action continues and results...