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Browse Prior Art Database

COROTRON ALTITUDE COMPENSATION

IP.com Disclosure Number: IPCOM000026646D
Original Publication Date: 1993-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 2 page(s) / 60K

Publishing Venue

Xerox Disclosure Journal

Abstract

In Xerox family copiers, a 'tracking' high voltage power supply is used in which the power supply is controlled by feedback from the charge corotron shield, and the currents to the other corotrons are determined by an output network powered from a single transformer. The system works well under most circumstances, but can give large changes in charge level and corotron currents if the atmospheric pressure changes significantly. This can be a problem if, for instance, a machine is set up at a different altitude from install.

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XEROX DISCLOSURE JOURNAL

COROTRON ALTITUDE COMPEN- Proposed Classification SATION U.S. Cl. 355/219
D. J. Milton Int. C1. G03g 15/02

In Xerox family copiers, a 'tracking' high voltage power supply is used in which the power supply is controlled by feedback from the charge corotron shield, and the currents to the other corotrons are determined by an output network powered from a single transformer. The system works well under most circumstances, but can give large changes in charge level and corotron currents if the atmospheric pressure changes significantly. This can be a problem if, for instance, a machine is set up at a different altitude from install.

The present proposal overcomes this by the use of a charge corotron shield bias resistor, chosen so that the mean corotron shield bias is approximately equal to the mean photoreceptor voltage while under the corotron. The high voltage power supply is thus controlling the current to a surface (the shield) which is at the same mean potential as the photoreceptor, and the photoreceptor current becomes insensitive to changes in pressure.

This technique of biassing the surface to which the current is controlled is also applicable to non tracking power supplies. Although a resistor was used in the implementation of this idea, it would also be possible to use a zener diode.

XEROX DISCLOSURE JOURNAL - Vol. 18, No. 1 January/February 1993 45

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