Power supply apparatus for detecting battery voltage and the portions of faults

摘要

A power supply apparatus according to the present invention includes a battery and a voltage detection circuit for detecting the voltage of the battery. The voltage detection circuit includes a differential amplifier which has a first input terminal for receiving a voltage based on the voltage of the battery and a second input terminal for receiving a predetermined triangular wave and outputs a rectangular wave with a pulse width modulated according to the voltage based on the voltage of the battery and a predetermined offset voltage, and an offset circuit which supplies the offset voltage to one of the first input terminal and the second input terminal so that the differential amplifier outputs a particular rectangular wave according to the offset voltage even when the voltage based on the voltage of the battery which is supplied to the first input terminal is 0.