| 摘要 |
PURPOSE:To prevent the application of a DC voltage to a liquid-crystal display element LCD by detecting the stop of an oscillation source by using a capacitor and a resistance. CONSTITUTION:Switch circuits S1, S2, S3, and S4 turn on when lines 1, 2, 3, and 4 are at ''H'' and turn off when at ''L''. Therefore, when a clock terminal P1 is at ''H'', the S1 and S4 turn on and the S2 and S4 turn off. When the P1 is at ''L'', they operate reversely. A voltage level detecting circuit CP1 has a threshold voltage VT and outputs ''H'' or ''L'' according to the voltage level at 13. An LCD driving circuit 15 receives LCD ON.OFF information inputted to 16 when 17 is at ''H'', and outputs an AC signal to 18 when the information indicates an ON state to turn on an LCD19; when the information shows an OFF state, 18 is grounded and 0V is applied to 19 to turn off the LCD19. When 17 is at ''L'', on the other hand, 0V is applied to 19 regardless of the input information to 16. |
