A control device of a power supply circuit includes processing circuitry. The processing circuitry includes a state-of-charge calculator and a target calculator. The state-of-charge calculator calculate a state of charge of the first battery. The target calculator calculates a target voltage range. When an output voltage of the first battery detected by a voltage sensor cannot be acquired and an acquisition failure occurs, after the occurrence of the acquisition failure, the state-of-charge calculator is configured to obtain the state of charge of the first battery, as a held state-of-charge, that was calculated before the occurrence of the acquisition failure. When a pre-charge process is performed in a state in which the acquisition failure is occurring, the target calculator is configured to calculate an estimated output voltage of the first battery from the held state-of-charge and calculate the target voltage range based on the estimated output voltage.