Browse Prior Art Database

INTEGRATION OF LINE VOLTAGE FOR LAMP CONTROL

IP.com Disclosure Number: IPCOM000026565D
Original Publication Date: 1992-Oct-31
Included in the Prior Art Database: 2004-Apr-06
Document File: 2 page(s) / 127K

Publishing Venue

Xerox Disclosure Journal

Abstract

The present invention is a technique which may be employed to precisely control the intensity of illumination of such a lamp. As depicted in the figure, microprocessor 12, preferably an Intel 8051@ microcontroller, is used in conjunction with analog-to-digital (ND) converter 14, digital-to-analog (D/A) converter 16, comparator 18, integrator 20, and power MOSFET 22 to implement the control algorithm.

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XEROX DISCLOSURE JOURNAL

ND CONVERTER

INTEGRATION OF LINE VOLTAGE FOR LAMP CONTROL
John M. Magde, Jr.

Jason T. Stone

Proposed Classification
U.S. C1.355/228 Int. C1. G03G 15/04

INPUT + INTEGRATOR

20 1.

ELECTROMETER COMPARATOR

b MICROPROCESSOR

30 22 32

OUTPUT TO LAMP

- I

I I I I I I I I I I I

I I I

                I INTERRUPT I 4- - - - - - - - - - -1


INPUT POWER

XEROX DISCLOSURE JOURNAL - Vo1.17 No. 5 September/October 1992 331

MOSFET

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INTEGRATION OF LINE VOLTAGE FOR LAMP CONTROL(Cont'd)

As described in the Xerox Disclosure Journal, Vol. 13, No. 4 p.211 (July/August 19881, a power MOSFET may be used to control a document illumination lamp in a copier or scanner. The present invention is a technique which may be employed to precisely control the intensity of illumination of such a lamp. As depicted in the figure, microprocessor 12, preferably an Intel 8051@ microcontroller, is used in conjunction with analog-to-digital (ND) converter 14, digital-to-analog (D/A) converter 16, comparator 18, integrator 20, and power MOSFET 22 to implement the control algorithm.

Generally, the system operates by selectively switching the input full-wave rectified line voltage on input line 30 to produce the switched, or phase controlled, output on line 32. While MOSFET 22 enables the switching of the output power which is supplied to the lamp, it is ultimately the signal from microprocessor 12 which controls the power delivered to the lamp.

Initially, a setup procedure is used to "seed" the lamp control algorithm, and produce an initial conduction angle, or "on time" for the output waveform. Operating with the seed value, the microprocessor begins controlling the output via MOSFET 22, so as to expose a photoreceptor (not shown). Shortly thereafter, the exposed region of the photoreceptor is advanced past electrometer 24, where the the voltage potential on the photoreceptor is measured. Electrometer 24 may be any commonly known electrostatic voltmeter suitable for measurement of the photoreceptor electros...