IN-VEHICLE POWER SUPPLY DEVICE AND VEHICLE HAVING IN-VEHICLE POWER SUPPLY DEVICE MOUNTED THEREIN

An in-vehicle power supply device includes a boost converter configured to perform a boosting operation to boost a voltage supplied from an input terminal; a connection-assist diode connected in parallel to the boost converter; and a switch element connected in parallel to the boost converter and the connection-assist diode. A controller detects a voltage output from an output terminal as a first voltage while instructing the switch element to open and instructing the boost converter to stop an operation of the boost converter. After detecting the first voltage of the output terminal, the controller detects a voltage output from the output terminal as a second voltage while instructing the switch element to continuously open and instructing the boost converter to perform the boosting operation. Based on the difference between the first and second voltages, the controller judges whether the boost converter is normal or abnormal.