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Gas Discharge Display Panel Driver

IP.com Disclosure Number: IPCOM000084850D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Davis, GT: AUTHOR

Abstract

Conventional techniques for holding the output stage of a driver off include passive hold-off, with a resistor connected across the base-emitter junction of the output device and an active hold-off, with an active device pulling the base of the output device to ground. A resistive hold-off requires extra drive current which can be very costly in terms of power dissipation for an 80 volt driver circuit.

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Gas Discharge Display Panel Driver

Conventional techniques for holding the output stage of a driver off include passive hold-off, with a resistor connected across the base-emitter junction of the output device and an active hold-off, with an active device pulling the base of the output device to ground. A resistive hold-off requires extra drive current which can be very costly in terms of power dissipation for an 80 volt driver circuit.

For the particular application considered, in the figure, with the high-voltage bus being switched from a low voltage to about 80 volts, no practical resistor sizes are adequate to hold the driver off. An active hold-off pulling to ground is also impractical for the application being considered, since the output of the driver is pulled below ground by external circuitry during the gas panel sustain cycle. The driver must remain off during the sustain cycle to prevent excessive power dissipation, and with the emitter of the output NPN transistor being pulled negative, the device cannot be held off merely by pulling the base to ground.

The circuit of the figure holds off output transistors 11 and 13, by active hold- off transistors 15 and 17 connected across the base-emitter junctions of the output transistors 11 and 13. Hold-off transistors 15 and 17 are driven by PNP transistor 19, which is referenced to the high-voltage bus 21 and switched by differential amplifier transistors 23 and 25. Transistors 27 and 29 and their emitter re...