Patent ID: 8711536

Claim:
A voltage detection apparatus, comprising: an operational amplifier; a first switch coupled between a high potential side terminal of a detection target voltage source and a common node; a second switch coupled between a low potential side terminal of the detection target voltage source and the common node; a first capacitor including a plurality of capacitor elements coupled in series between the common node and an inverting input terminal of the operational amplifier; a third switch coupled between the inverting input terminal and an output terminal of the operational amplifier; a second capacitor coupled between the inverting input terminal and output terminal of the operational amplifier; a reference voltage selection circuit which selects one of a first reference voltage and a second reference voltage differing from one another, and applies a selected reference voltage to a non-inverting input terminal of the operational amplifier; and a controller which is capable of selecting a voltage detection mode and a self-diagnostic mode, wherein in the voltage detection mode, the controller uses the reference voltage selection circuit to select the first reference voltage and sets charge in the first capacitor by closing the third switch and closing the first switch, and subsequently, the controller detects an interterminal voltage of the detection target voltage source based on an output voltage of the operational amplifier after opening the third switch and first switch and closing the second switch, and in the self-diagnostic mode, the controller uses the reference voltage selection circuit to select one of the first reference voltage and the second reference voltage and sets charge in the first capacitor by closing the third switching and closing one of the first switch and the second switch, and subsequently, the controller carries out a fault diagnosis based on an output voltage of the operational amplifier after opening the third switch and selecting the other one of the first reference voltage and second reference voltage using the reference voltage selection circuit.