ON-BOARD POWER SUPPLY APPARATUS

An on-board power supply apparatus is for use in an on-board power supply system. The on-board power supply system includes a battery, an electric power path to which electric power based on the battery is supplied, and a capacitor that is connected to the electric power path. The on-board power supply apparatus includes a mechanical system main relay (first SMR), a parallel circuit, and a second relay. The system main relay (first SMR) is provided on the electric power path in a position on the battery side from the capacitor. The parallel circuit has a configuration in which a first relay and a resistance portion are connected in series, and is connected in parallel with the system main relay (first SMR). The second relay is provided in parallel with the resistance portion.