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TUNGSTEN LAMP SWITCHING POWER SUPPLY

IP.com Disclosure Number: IPCOM000024875D
Original Publication Date: 1982-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 85K

Publishing Venue

Xerox Disclosure Journal

Abstract

The figure shows a circuit diagram for a power supply which supplies a load such as a tungsten lamp for illuminating a document in a scanning copier system. The circuit causes a transistor/photodiode to control duty cycle and to eliminate strobing effects.

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TUNGSTEN LAMP SWITCHING POWER SUPPLY
Lawrence J. Mason

Proposed Classification
U.S. C1. 323/234 Int. CI. G05f 1/10

The figure shows a circuit diagram for a power supply which supplies a load such as a tungsten lamp for illuminating a document in a scanning copier system. The circuit causes a transistor/photodiode to control duty cycle and to eliminate strobing effects.

As shown in the figure, a conventional AC power source is connected to bridge rectifier 20. The rectifier converts the applied AC power to full-wave rectified DC power across output leads 22, 24. The output on lead 22 has a 120 cycles per second ripple component which is filtered by capacitor 26. The full wave rectified and filtered voltage is then applied across lamp 30 in series with inductor 32. Lamp 30 is a 96 volt tungsten lamp. The AC power source is also connected across transformer 34 and a DC rectified signal on lead 36 is filtered and supplied to

Volume 7 Number 4 July/August 1982 235

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TUNGSTEN LAMP SWITCHING POWER SUPPLY (Cont'd)

power to the amplifiers 40 and 42 and the pulse width modulator 60. When the lamp goes on, the light output is sensed by photodiode 41. The output of photodiode 41 is a current proportional to the irradiance from lamp 30 impinging

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thereon. Amplifier 42 provides a current-to-voltage conversion and its output V is proportional to the input photodiode signal and the amplifier gain (controlled by r...