Patent ID: 8760168

Claim:
An assembled battery total voltage detection circuit for detecting a total voltage of an assembled battery configured by connecting a plurality of batteries, comprising: a main control circuit that includes an A/D converter operating with a positive single power supply; a divider resistor connected between a plus terminal and a minus terminal of the assembled battery insulated from the main control circuit; a differential amplifier circuit, including a first buffer, a second buffer and a differential amplifier, that amplifies voltage divided by the divider resistor and that outputs the amplified voltage to the A/D converter, the first buffer, the second buffer and the differential amplifier each being constituted by an operational amplifier operating with a positive single power supply; and a third buffer for applying a bias voltage to the midpoint of the divider resistor, the third buffer being constituted by an operational amplifier that operates with a positive single power supply, wherein the bias voltage is a positive constant electric potential relative to a ground of the main control circuit and is set based upon an operating voltage of the operational amplifier; the amplified voltage output from the differential amplifier circuit and input to the A/D converter varies within a range of the operating voltage of the operational amplifier; and the main control circuit: inputs the voltage divided by the divider resistor, the midpoint of which is biased to the positive electric potential by the third buffer, to the A/D converter via the differential amplifier circuit, and measures the total voltage of the assembled battery; and inputs output voltages of the first and second buffers and the bias voltage to the A/D converter, measures the output voltages of the first and second buffers and the bias voltage, and performs fault diagnosis of the assembled battery total voltage detection circuit based upon the measured total voltage, the measured output voltages of the first and second buffers and the measured bias voltage.