A power supply circuit, comprises a booster circuit that boosts the voltage supplied from a power supply to produce an output voltage; a voltage divider circuit that divides said output voltage by resistive division and outputs a monitored voltage; a comparator circuit that compares said monitored voltage with a reference voltage and outputs a signal to activate said booster circuit if said monitored voltage is lower than said reference voltage and a signal to deactivate said booster circuit if said monitored voltage is higher than said reference voltage; an auxiliary instruction circuit that outputs an auxiliary signal to control the timing of the activation of said booster circuit; and an arithmetic circuit that performs a calculation using said auxiliary signal and the output signal of said comparator circuit and outputs an enable signal to activate said booster circuit if the output signal of said comparator circuit is a signal to activate said booster circuit, or said auxiliary signal is a signal to activate said booster circuit.