| 摘要 |
<p>PURPOSE:To simplify the constitution of a control circuit by directly controlling a liquid crystal power source with a power fail signal. CONSTITUTION:When a switching transistor (TR) of a power switch of a power control circuit 12 of an AC power source is turned on, a power fail signal 10 due to a diode 29 on the side of a secondary output 18 of a transformer, a capacitor 21, a voltage comparing circuit 22, etc., rises to turn on a TR 28, and a TR 30 is turned on to turn on a negative-output three-terminal regulator 19, and a liquid crystal driving power source 9 is turned on. When the power switch is turned off, the signal 10 immediately falls, and TRs 28 and 30 are turned off, and the TR 29 is turned on, and the power of the power source 9 goes to the same level as a logic power source 8, and thereafter, the power source 9 falls simultaneously with fall of the power source 8, and the liquid crystal power supply sequence is directly controlled by the power fail signal, and thus, the liquid crystal power fail signal, and thus, the liquid crystal power control circuit which does not require software and has a simple constitution is obtained.</p> |
