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# Circuit Implementation of Square Wave Referenced Display Drivers

IP.com Disclosure Number: IPCOM000079988D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 32K

IBM

## Related People

Fisher, DE: AUTHOR

## Abstract

Certain matrix addressing systems of liquid crystal displays require power supplies referenced to both phases of a square-wave generator, as well as a power supply for the square-wave generator. An obvious solution to this problem is individual floating-power supplies.

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Circuit Implementation of Square Wave Referenced Display Drivers

Certain matrix addressing systems of liquid crystal displays require power supplies referenced to both phases of a square-wave generator, as well as a power supply for the square-wave generator. An obvious solution to this problem is individual floating-power supplies.

An alternate structure is suggested wherein one waveform is generated by a group of logic circuits, the output of which is amplified to the desired driving level. These circuits, and their power sources, are referenced to a common line which is square-wave driven by a ground referenced square-wave generator, therefore, the power source for the logic circuits is shifting up and down with the square wave. The end accomplished by this circuit is to supply the power for these logic circuits from a ground referenced power supply, which also supplies the square- wave generator. This is accomplished by placing the power source for the logic circuits in series with the open collector of an output transistor T of the square- wave generator. As is shown in the diagram, the total load for this output device is a current limiting resistor R in series with the parallel combination of a zener diode Z and a capacitor C.

In operation, when the square-wave generator output is low, the zener diode Z sets the voltage level which is applied to the logic circuits and charges the capacitor C to this voltage. When the output of the square-wave generator is ...