| 摘要 |
Adverse effects of switching noise produced by a charge pump circuit on a displayed image are prevented. In a synchronizing separation circuit 18, a synchronizing signal is separated from a video signal. The separated synchronizing signal is subjected to ½ frequency division in a flip-flop 20 to obtain a clock signal having a period which is two times as much as one horizontal period, and this clock signal is utilized to control switching of the charge pump circuit. As a result, a timing at which each switch in the charge pump is changed over can be set in a period close to a horizontal synchronizing signal without a video signal, thereby preventing noise from affecting the video signal.
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