Voltage detection circuit measurement apparatus for use in assembled battery system

1. A voltage detection circuit for measuring a plurality of cell voltages of an assembled battery configured by connecting a plurality of cells in series, the voltage detection circuit comprising:

a plurality of input terminals connected to respective electrodes of the plurality of cells through a plurality of voltage detection lines;

a multiplexer that periodically selects and outputs voltages of a plurality of cells in a group, a plurality of series cells configured as the group;

an analog-to-digital (AD) converter that AD-converts an output voltage from the multiplexer and outputs digital data of the output voltage; and

a control circuit that controls a timing for the selection by the multiplexer and a timing for the AD conversion,

wherein the control circuit switches over a time interval for which the multiplexer selects each of the cells to change a period of the AD conversion, and

wherein the control circuit repeats the AD conversion of the cells in a predetermined order in the group, and switches over a conversion start cell in the group to change the selection time interval.

2. The voltage detection circuit as claimed in claim 1 , wherein the conversion start cell is selected based on a random number from a random number generator that generates a random number.

3. The voltage detection circuit as claimed in claim 2 , further comprising a remainder calculator that performs remainder operation on a random number of an output value from the random number generator to determine and output a start cell number.

4. The voltage detection circuit as claimed in claim 1 ,

wherein, when the conversion start cell is not the lowest cell in the group of the multiplexer,

(A) the multiplexer first selects at least one intermediate cell so as to go through the intermediate cell, and then selects a conversion start cell; or

(B) the multiplexer selects the conversion start cell without any intermediate cell,

and the multiplexer performs a precharge operation, and then the conversion target cell.

5. The voltage detection circuit as claimed in claim 1 ,

wherein, when a cell to be AD-converted is separated by two or more cells,

(A) the multiplexer first selects at least one intermediate cell which is not any next conversion target cell so as to go through the intermediate cell, and then selects the next conversion cell; or

(B) the multiplexer selects the next conversion cell,

and the multiplexer performs a precharge operation, and then select the conversion target cell.

6. The voltage detection circuit as claimed in claim 4 , wherein, in the precharge operation, an input terminal unused by the multiplexer is also a target for selecting the input terminal so as to go through the input terminal.

7. The voltage detection circuit as claimed in claim 1 , comprising a function of AD-converting a monitor voltage other than the cell voltages,

wherein the control circuit switches over a time interval for which the multiplexer selects the monitor voltage to change the period of the AD conversion.

8. The voltage detection circuit as claimed in claim 7 , wherein the monitor voltage is AD-converted during the precharge operation.

9. A voltage measurement apparatus for measure a plurality of cell voltages of an assembled battery configured by connecting a plurality of cells in series, the voltage measurement apparatus comprising:

a voltage detection circuit; and

an apparatus controller,

wherein the voltage detection circuit comprises:

a plurality of input terminals connected to respective electrodes of the plurality of cells through a plurality of voltage detection lines;

a multiplexer that periodically selects and outputs voltages of a plurality of cells in a group, a plurality of series cells connected to the multiplexer configured as the group;

an analog-to-digital (AD) converter that AD-converts an output voltage from the multiplexer and outputs digital data of the output voltage; and

a control circuit that controls a timing for the selection by the multiplexer and a timing for the AD conversion,

wherein the apparatus controller receives and stores the digital data of the output voltage,

wherein the control circuit switches over a time interval for which the multiplexer selects each of the cells to change a period of the AD conversion, and

wherein the control circuit repeats the AD conversion of the cells in a predetermined order in the group, and switches over a conversion start cell in the group to change the selection time interval.

10. An assembly battery system comprising:

a voltage detection circuit;

an apparatus controller; and

an assembly battery configured by connecting a plurality of cells in series,

wherein the assembly battery system is configured to measure a plurality of cell voltages of the assembled battery,

wherein the voltage detection circuit comprises:

a plurality of input terminals connected to respective electrodes of the plurality of cells through a plurality of voltage detection lines;

a multiplexer that periodically selects and outputs voltages of a plurality of cells in a group, a plurality of series cells connected to the multiplexer configured as the group;

an analog-to-digital (AD) converter that AD-converts an output voltage from the multiplexer and outputs digital data of the output voltage; and

a control circuit that controls a timing for the selection by the multiplexer and a timing for the AD conversion,

wherein the apparatus controller receives and stores the digital data of the output voltage,

wherein the control circuit switches over a time interval for which the multiplexer selects each of the cells to change a period of the AD conversion, and

wherein the control circuit repeats the AD conversion of the cells in a predetermined order in the group, and switches over a conversion start cell in the group to change the selection time interval.