SEMICONDUCTOR DEVICE MOUNTING POWER SOURCE CIRCUIT AND LIQUID CRYSTAL DEVICE, ELECTRONIC APPLIANCE USING IT

摘要

PROBLEM TO BE SOLVED: To prevent malfunction such as instantaneous lighting occurring when a power source is abnormally cut off by discharging a potential charged by the capacity of a boosting circuit before first and second power source potentials are equal to each other based on a signal to be activated in the abnormality of the power source. SOLUTION: When a power source is forcedly cut off and the outputs of a comparator 100 and a buffer 102 vary from HIGH to LOW, the outputs of first and second NAND circuits 91 and 92 become HIGH without regard to the logic of the O output and XO output of a third shift register 34. Thus first to third N-type MOS transistors 81 to 83 are forcedly turned on. When the capacity of the first to third transistors 81 to 83 is increased to reduce on resistance at this time, electric charges charged in the second and third capacitors C2 and C3 are discharged before VSS and VDD become equal, and the absolute value of an output potential VOUT is speedily lowered.