Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1991-05-10
1992-11-03
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
H04N 318, H04N 563
Patent
active
051610221
ABSTRACT:
A dc-dc converter for converting first to second dc voltages, used for video apparatus, comprising: a self-excited oscillation circuit for producing a clock signal, the self-excited oscillation circuit having a control input for controlling oscillation thereof in response to a control signal; a pulse width modulation circuit responsive to the clock signal and the second dc voltage for controlling duty ratio of the clock signal; a switching circuit responsive the pulse-width-modulated clock signal for switching the first dc voltage; rectifying and smoothing circuit for rectifying and then smoothing an output of the switching circuit to produce the second dc voltage; and a control circuit responsive to a vertical synchronizing signal of a video signal used in the video apparatus for producing the control signal whose pulse width is sufficiently shorter than a vertical retrace period of the vertical synchronizing signal. Oscillation of the self-excited circuit is controlled in response to the vertical synchronizing signal to prevent switching noise of the dc-dc converter from disturbing the reproduced image.
REFERENCES:
patent: 4516169 (1985-05-01), Truskalo
patent: 4891707 (1990-01-01), Dieterle
patent: 4994719 (1991-02-01), Lendaro
Wide-Range and High Efficiency Switching Power Supply for Color TV Receivers, by Toshio Fujimura, et al., IEEE Transactions on Consumer Electronics vol. CE-24, No. 3 Aug., 1978, pp. 473 to 479.
Patent Abstracts of Japan, vol. 91, No. 65 (E-327), Jul. 10, 1985 and JP-60 041372 (Matsushita) Mar. 5, 1985.
Patent Abstracts of Japan, vol. 125, No. 98 (E-698), Dec. 24, 1988 and JP-63 208384 (Matsushita) Aug. 29, 1988.
Ichimura Hiroshi
Katase Wataru
Minema Ikumi
Chin Tommy P.
Victor Company of Japan Ltd.
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