ON-BOARD DEVICE

An ECU (on-board device) includes a fuse F and a blown fuse detection circuit. The blown fuse detection circuit monitors a fuse voltage between two connection nodes respectively located upstream and downstream of the fuse in a current path of a current flowing from a positive electrode of a DC power supply through the fuse. The blown fuse detection circuit outputs a voltage lower than a reference voltage if the fuse voltage is lower than a voltage threshold value. The blown fuse detection circuit outputs a voltage higher than or equal to the reference voltage if the fuse voltage is higher than or equal to the voltage threshold value.