| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent delays in increase in bias voltage, even when a capacitor with a large capacitance for stabilizing the bias voltage is provided and power is supplied from a battery. SOLUTION: Presence or absence of a commercial power supply is detected from the output voltage of a regulated power supply circuit 20, which converts power from a commercial power supply into direct-current voltage Va, through a power supply detecting circuit 80. When a CPU 60 decides based on the result of the detection that commercial power supply is not provided, an analog switch 100 is opened by a switch control circuit 90 according to an instruction from the CPU 60, only if a capacitor 70 is not charged. Thus, if a switch 40 is closed and power is supplied from a battery 30, a direct-current voltage Vb of the battery 30 is supplied immediately as a bias voltage to the CPU 60, peripheral circuits and the like without charging the capacitor 70.</p> |
