Patent ID: 9678166
Date: 2017-06-13
CPC Classifications: G01R

Claim:
1. A voltage detection device for an assembled battery formed of battery cells connected in series, the voltage detection device comprising: an operational amplifier; a first part circuit forming, jointly with the operational amplifier, a level shift circuit, which selects either one of the battery cells of the assembled battery and extracts and holds a voltage representing an inter-terminal voltage of a selected battery cell; an A/D conversion circuit for converting an inputted conversion subject voltage to a digital value; a second part circuit forming, jointly with the operational amplifier, a residual voltage circuit, which generates a residual voltage by amplifying a differential voltage between the conversion subject voltage and an analog voltage corresponding to a conversion result of the A/D conversion circuit, and applies the residual voltage to the A/D conversion circuit as the conversion subject voltage; a switchover circuit for operating the operational amplifier as either one of the level shift circuit and the residual voltage generation circuit, and switching over a state of connection of the first part circuit and the second part circuit so that a voltage held by the level shift circuit is applied to the A/D conversion circuit and the residual voltage generation circuit as the conversion subject voltage; and a control circuit for controlling setting of the switchover circuit and operations of the first part circuit and the second part circuit so that an operation of a cyclic type A/D converter is performed, the control circuit operating the operational amplifier in a level shift mode to operate as the level shift circuit, the control circuit then operating the operational amplifier in an A/D conversion mode to operate as the residual voltage generation circuit, the control circuit circulating through the A/D conversion circuit and the residual voltage generation circuit the conversion subject voltage applied from the level shift circuit, wherein: the first part circuit includes a hold capacitor interposed between an input terminal and an output terminal of the operational amplifier for holding an extracted voltage; the second part circuit includes the switchover circuit includes the control circuit sets the first switchover switch in an on-state and the second switchover switch to a reference line side thereby to operate the operational amplifier as the level shift circuit, and sets the first switchover switch in an off-state and the second switchover switch to an input terminal side of the operational amplifier thereby to operate the operational amplifier as the residual voltage generation circuit, and the first part circuit holds simultaneously the terminal voltages of the battery cells individually; the level shift circuit selects either one of the terminal voltages of the battery cells held by the first part circuit, and generates and holds a pair of voltages, which represents both terminal voltages as a differential voltage; the operational amplifier has an inverting output terminal and a non-inverting output terminal; the first part circuit and the switchover circuit has a part, which is connected to the inverting input terminal and the non-inverting output terminal of the operational amplifier and operates to convert one of the pair of voltages held by the level shift circuit as a first conversion subject voltage, and a part which is connected to the non-inverting input terminal and the inverting output terminal of the operational amplifier and operates to convert an other of the pair of voltages as a second conversion subject voltage; and the A/D conversion circuit A/D-converts the differential voltage between the first conversion subject voltage and the second conversion subject voltage.