| 摘要 |
PURPOSE:To prevent saturation of the core of a switching transformer and to prevent malfunction of an excess current protection circuit by synchronizing to the timing of channel switching and by lowering the image load by lowering brightness and contrast. CONSTITUTION:The luminance control signal outputted from a terminal 33 is inversed and amplified by resistances 35, 37 and 38, and a transistor 39, and it is smoothed by a resistance 41, a diode 40 and a capacitor 42. The signal becomes the luminance control voltage and is added to a luminance control circuit 17. On the other hand, the contrast control signal outputted from a terminal 34 is inverted and amplified by resistances 43, 45 and 47 and a transistor 46, is smoothed by a resistance 49, a diode 48 and a capacitor 50, and becomes the contrast control voltage. At the time of channel switching, the positive mute pulse which synchronized to channel switching occurs from a terminal 32 of a microcomputer 31, is inverted and amplified by the transistors 39 and 46 through diodes 36 and 44, and lowers the contrast control voltage. |
