| 摘要 |
PURPOSE:To prevent a direct current voltage from being impressed to a liquid crystal display part and to prevent the deterioration in the liquid crystal by providing a horizontal and vertical synchronizing signal detection means and a means for interrupting the supply of a power to the liquid crystal display part and the peripheral circuit thereof, when the synchronizing signal is not detected. CONSTITUTION:A horizontal synchronization detection circuit 121, while the horizontal synchronizing signal 100 is detected, outputs an H level detection signal to an AND gate 124. A vertical synchronization separating circuit 122 separates the vertical synchronizing signal 200 from the input horizontal synchronizing signal 100 and outputs to a vertical synchronization detection circuit 123. The circuit 124, while the signal 200 is detected, outputs the H level signal to the AND gate 124. In the gate 124, when the AND condition from the circuits 121 and 123 are formed, a synchronization detection signal 700 is outputted to a power source control circuit 13. Accordingly, when either of the signal 100 or 200 is not detected, the gate 124 stops the output of the signal 700. The power source control circuit 13, when the signal 700 is stopped, immediately turns off a supply power off and stops the operation of the liquid crystal part or the like.
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