Power supply system for vehicle, and control method of power supply system

A control method of a power supply system, the power supply system including:

• a main power supply;
• an electric power converter including a capacitor connected between a positive electrode of the main power supply and a negative electrode of the main power supply, the electric power converter being configured to convert output electric power of the main power supply;
• a relay configured to switch connection and disconnection between the electric power converter and the main power supply;
• a sub power supply having an output voltage lower than an output voltage of the main power supply;
• a boost converter having a low voltage end connected to the sub power supply and a high voltage end connected to the capacitor;
• a cooler configured to cool the boost converter;
• and a processor programmed to cause the sub power supply and the boost converter to precharge the capacitor when a main switch is turned on, such that the sub power supply and the boost converter precharge the capacitor before the relay is closed to connect the electric power converter to the main power supply, the control method being performed by the processor and comprising:
• determining whether the main switch is turned on;
• and
• when the main switch is turned on, performing one of a control i) and a control ii), when one of a temperature of the boost converter and a temperature of a coolant in the cooler is higher than a specified temperature threshold, the control i) being to start the precharging while starting the cooler, and the control ii) being to start the cooler before the precharging.