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Quiet Repetition Rate Control of a Gas Panel

IP.com Disclosure Number: IPCOM000051991D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hoffman, HS: AUTHOR

Abstract

For certain display applications or situations, it may be desirable to operate a plasma display at a lower than normal intensity. The most practical way to vary the intensity of light emitted by a plasma display panel is to alter the operating frequency, since the display intensity is a function of frequency. While there are several ways to achieve this variation in repetition rate, when the repetition rate is below the threshold of human hearing, an audible sound is produced which is undesirable from a human factor standpoint.

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Quiet Repetition Rate Control of a Gas Panel

For certain display applications or situations, it may be desirable to operate a plasma display at a lower than normal intensity. The most practical way to vary the intensity of light emitted by a plasma display panel is to alter the operating frequency, since the display intensity is a function of frequency. While there are several ways to achieve this variation in repetition rate, when the repetition rate is below the threshold of human hearing, an audible sound is produced which is undesirable from a human factor standpoint.

In order to minimize the perceived sound level, the sound energy can be distributed over a wide frequency range by dividing the signal into two or more frequency blocks which average into the desired frequency. Because the ear reacts to significantly distinct frequencies of sound in different physical locations, the level of the resultant signals is not cumulative and there is no addition of the sound energy of separated frequencies. The audible noise level is thus either eliminated or substantially reduced below objectionable levels.

In implementation, two or more frequencies are used on successive cycles such that their average repetition rate produces the desired brightness, while splitting the sound energy into corresponding blocks which are not cumulative for hearing perception. Rather than a single frequency signal such as a 10 KHz signal, alternate signals of 5 and 15 KHz will provide the...