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Matrix Print Head Decay Circuit

IP.com Disclosure Number: IPCOM000034196D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kruppa, RW: AUTHOR

Abstract

The article describes an improved print head circuit which includes a zener paralleled with an active device (FET/bipolar transistor). With reference to Fig. 1, a zener paralleled with an active device (FET/bipolar transistor), the zener voltage is chosen to be high enough (greater than 25 volts) to obtain a rapid decay of the print head current during the decay period. The wire is driven in a normal fashion. However, at turnoff, the active device across the coil is turned "on." This controls the coil voltage to a value of less than 1.0 volt, which, in turn, causes the current decay to be lengthened and at a high value. This results in a significantly higher print force and lower flight time.

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Matrix Print Head Decay Circuit

The article describes an improved print head circuit which includes a zener paralleled with an active device (FET/bipolar transistor). With reference to Fig. 1, a zener paralleled with an active device (FET/bipolar transistor), the zener voltage is chosen to be high enough (greater than 25 volts) to obtain a rapid decay of the print head current during the decay period. The wire is driven in a normal fashion. However, at turnoff, the active device across the coil is turned "on." This controls the coil voltage to a value of less than 1.0 volt, which, in turn, causes the current decay to be lengthened and at a high value. This results in a significantly higher print force and lower flight time. As the wire approaches or strikes the platen, this current must decay to "0" amps as quickly as possible or else it becomes counter-productive and works against the rebound force. At this time the active device is turned "off" and the zener now takes over. A high voltage zener is used to decay the current as rapidly as possible. The current now being "0" results in no forces that will retard the rebound force caused by the wire striking the platen. Fig. 2 illustrates the three periods of operation of the design. The first period (P1) is the normal pulse caused by the primary driver. The second period (P2) is a result of device T2 being in the "on" state. Period three (P3) is determined by the conduction of the zener diode.

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