Browse Prior Art Database

ULTRASONIC FREQUENCY AC BIAS FOR AC CORONA GENERATING APPLICATIONS

IP.com Disclosure Number: IPCOM000027172D
Original Publication Date: 1995-Aug-31
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 121K

Publishing Venue

Xerox Disclosure Journal

Abstract

A typical corona generating device is provided with a high voltage AC bias operating in the frequency range of 400 to 600 Hz. At this frequency, a power supply must incorporate transformers that are physically large and heavy. Such low frequency transformers are typically very expensive and also represent a significant barrier to modulaFization, and miniaturization of xerographic power supplies. In addition, such large transformers are characterized by high load capacitances and stray capacitances which result in excessive power losses. Since these capacitive power losses do not contribute to the corona generating current, the losses represent a large portion of the power delivered by the power supply. The present disclosure is directed toward reducing capacitive power losses in a corona generating power supply by utilizing ultrasonic frequency AC bias for an AC corona generating device. The use of such ultrasonic frequency devices permit a substantial reduction in physical size and weight of the power supply so that the cost of the high voltage AC power supply may be substantially reduced.

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XEROX DISCLOSURE JOURNAL

ULTRASONIC FREQUENCY AC Proposed Classification BIAS FOR AC CORONA
GENERATING APPLICATIONS
Thomas I. Yeh
Cliff K. Friend

U.S. C1.355/221 Int. C1. G03g 15/02

CH.l

I I I I I I I I

I I I I I I I I I I I I

XEROX DISCLOSURE JOURNAL - VOI. 20, NO. 4 July/August 1995 319

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ULTRASONIC FREQUENCY AC BIAS FOR AC CORONA GENERATING APPLICATIONS (Cont'd)

A typical corona generating device is provided with a high voltage AC bias operating in the frequency range of 400 to 600 Hz. At this frequency, a power supply must incorporate transformers that are physically large and heavy. Such low frequency transformers are typically very expensive and also represent a significant barrier to modulaFization, and miniaturization of xerographic power supplies. In addition, such large transformers are characterized by high load capacitances and stray capacitances which result in excessive power losses. Since these capacitive power losses do not contribute to the corona generating current, the losses represent a large portion of the power delivered by the power supply. The present disclosure is directed toward reducing capacitive power losses in a corona generating power supply by utilizing ultrasonic frequency AC bias for an AC corona generating device. The use of such ultrasonic frequency devices permit a substantial reduction in physical size and weight of the power supply so that the cost of the high voltage AC power supply may be substantially reduced.

Referring to the accompanying figure, an exemplary circuit is illustrated in schematic form for providing an ultrasonic frequency AC bias voltage to a corona generating device. It can be seen from this figure, that an inductor L is coupled in parallel across the primary of a transformer, forming a parallel resonant network across the transformer for managing capacitive currents including stray capacitances and load capacitances. The network is biased wi...