Power supply apparatus

A power supply apparatus, comprising:

• a power supply;
• a DC/DC converter that includes a switching element of an upper arm, a switching element of a lower arm and a reactor, the switching element of the upper arm and the switching element of the lower arm being connected in series between a positive electrode and a negative electrode of the power supply, one end of the reactor being connected between the switching element of the upper arm and the switching element of the lower arm, other end of the reactor being connected the power supply;
• a lower arm fuse that is provided between the switching element of the lower arm and the negative electrode of the power supply;
• a power supply fuse that is provided between the positive electrode of the power supply and the other end of the reactor;
• a second power supply fuse that is connected to the power supply fuse in parallel;
• a second switch that is connected to the second power supply fuse in series and connected to the power supply in parallel, the second switch being normally opened;
• and
• a controller that closes the second switch upon a short circuit failure of the switching element of the lower arm being detected, wherein
• the lower arm fuse has a fusing characteristic such that the lower arm fuse is fused earlier than the power supply fuse at a time of the short circuit failure of the switching element of the lower arm.