Cell voltage abnormality detector and cell voltage monitoring device for a multi-cell series battery

• US 8,154,253 B2
• Filed: 09/12/2008
• Issued: 04/10/2012
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Omagari, Kazuya
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Chung, Steve T.
• Application Number:
  US12/209,771
• Publication Number:
  US 20090179650A1
• Time in Patent Office: 1,306 Days
• Field of Search: 320/134, 320/149, 320/155, 324/426, 324/433, 369/30.36, 369/53.12, 369/53.42, 340/636.01, 340/636.21
• US Class Current: 320/134
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/12 Recording operating variables ; Monitoring of operating variables
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A circuit for detecting battery cell abnormalities in a multi-cell series battery for effectively and quickly detecting abnormalities with a simple, small circuit that provides improved reliability, safety and service life of the multi-cell series battery. In the voltage monitoring device 12, immediately after the start of the monitoring cycle of any battery cell BT_i, cell voltage abnormality detector 14 checks whether cell voltage V_i is outside of the normal operating range. The cell voltage abnormality detector 14 has: a group of selection switches 18 for selecting any battery cell BT of multi-cell series battery 10 and retrieving its voltage to first and second monitoring terminals A, B; cell voltage/monitoring current converter 20; monitoring current/monitoring voltage converter 22; comparison/evaluation circuit 24; evaluation signal output circuit 26 and abnormality detection controller 28.

Claims

1. A cell voltage abnormality detector for a multi-cell series battery made up of plural battery cells connected in series that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving cell voltage from between first and second monitoring terminals;

a cell voltage/monitoring current converter, which has a first transistor connected between said first and second monitoring terminals and which converts the voltage of said battery cell selected by said selection switch into a monitoring current;

a monitoring current/monitoring voltage converter, which has a second transistor that, in combination with said first transistor, forms a current mirror circuit, and which converts the monitoring current generated by said cell voltage/monitoring current converter into a monitoring voltage; and

a comparison/evaluation circuit, which compares said monitoring voltage obtained by said monitoring current/monitoring voltage converter with a prescribed reference voltage and which determines whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

4. The cell voltage abnormality detector of claim 1 wherein said cell voltage/monitoring current converter has a resistor connected in series with said first transistor between said first and second monitoring terminals.

5. The cell voltage abnormality detector of claim 1 wherein said cell voltage/monitoring current converter has a resistor connected in series with said first transistor between said first and second monitoring terminals.

20. A cell voltage monitoring device for a multi-cell series battery comprising:

the cell voltage abnormality detector described in claim 1, and

a cell voltage measurement circuit that measures the voltage of each cell of said multi-cell series battery.

21. The cell voltage monitoring device of claim 20 wherein said cell voltage measurement circuit is comprised of the following parts:

a sampling switch for sampling the output voltage of said battery cell selected by said sampling switch;

a capacitor that is charged by the voltage sampled by said sampling switch; and

an A/D converter that converts the charge voltage on said capacitor into a digital signal,

and a transfer switch for transferring the charge voltage on said capacitor to said A/D converter.

22. The cell voltage monitoring device of claim 21 wherein immediately after the start of the first half-period when the voltage of a given battery cell is selected by said sampling switch, said cell voltage abnormality detector is turned on to determine whether the battery cell voltage is normal or abnormal.

2. A cell voltage abnormality detector for a multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving cell voltage from between first and second monitoring terminals,

a cell voltage/monitoring current converter, which has a first transistor connected between said first and second monitoring terminals and which converts the voltage of said battery cell selected by said selection switch into a monitoring current;

a current mirror monitoring current generator, which has a second transistor that, in combination with said first transistor, forms a current mirror circuit, and which proportionally generates a current mirror monitoring current that is in a predetermined ratio to said current monitoring current; and

a comparison/evaluation circuit, which compares said current mirror monitoring current generated by said current mirror monitoring current generator with a predetermined reference current, and which determines whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

6. The cell voltage abnormality detector of claim 2 wherein said cell voltage/monitoring current converter has an on/off switch connected in series with said first transistor between said first and second monitoring terminals.

7. The cell voltage abnormality detector of claim 2 wherein said cell voltage/monitoring current converter has a resistor connected in series with said first transistor between said first and second monitoring terminals.

3. A cell voltage abnormality detector for a multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving cell voltage from between the first and second monitoring terminals,

a cell voltage/monitoring current converter, which has a first transistor connected between said first and second monitoring terminals and which converts the voltage of said battery cell selected by said selection switch into a monitoring current; and

a comparison/evaluation circuit, which has a second transistor that, in combination with said first transistor, forms a current mirror circuit, and which compares said monitoring current generated by said cell voltage/monitoring current converter with a predetermined reference current, and judges whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

8. The cell voltage abnormality detector of claim 3 wherein said cell voltage/monitoring current converter has an on/off switch connected in series with said first transistor between said first and second monitoring terminals.

9. The cell voltage abnormality detector of claim 3 wherein said cell voltage/monitoring current converter has a resistor connected in series with said first transistor between said first and second monitoring terminals.

10. A cell voltage abnormality detector for a multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving cell voltage from between the first and second monitoring terminals,

a first transistor connected between said first and second monitoring terminals,

a second transistor which, in combination with said first transistor, forms a first current mirror circuit;

a current/voltage converter that converts the current flowing in said second transistor into a monitoring voltage; and

,

a comparison/evaluation circuit, which compares said monitoring voltage obtained by said current/voltage converter with a predetermined reference voltage and which determines whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

11. The cell voltage abnormality detector of claim 10 wherein:

said current/voltage converter comprises

a third transistor connected in series with said second transistor between said first monitoring terminal and a first power supply voltage terminal,

a fourth transistor which, in combination with said third transistor, forms a second current mirror circuit,

and a first resistor connected in series with said fourth transistor between the second and third power supply voltage terminals that produces the prescribed voltage drop;

said monitoring voltage is retrieved from the node between said fourth transistor and said first resistor;

and wherein said comparison/evaluation circuit comprises;

a first voltage comparator, which compares said monitoring voltage with a first comparison reference voltage for monitoring the lower threshold and outputs a dual-value evaluation signal that indicates the relative high/low relationship between the two voltages,

and a second voltage comparator, which compares said monitoring voltage with the second comparison reference voltage for monitoring the upper threshold and outputs a dual-value evaluation signal indicating the relative high/low relationship between the two voltages.

18. The cell voltage abnormality detector of claim 10 wherein a third resistor is connected in series with said first transistor between said first and second monitoring terminals.

19. The cell voltage abnormality detector of claim 10 wherein it has an on/off switch that is connected in series with said first transistor between said first and second monitoring terminals.

12. A cell voltage abnormality detector for multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving cell voltage from between the first and second monitoring terminals;

a first transistor connected between said first and second monitoring terminals;

a second transistor which, in combination with said first transistor, forms a first current mirror circuit;

a current/voltage converter that converts the current flowing in said second transistor into a first monitoring voltage for monitoring the upper threshold and a second monitoring voltage for monitoring the lower threshold; and

a comparison/evaluation circuit, which compares said first and second monitoring voltages obtained by said current/voltage converter with first and second reference voltages, respectively, and which determines whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

13. The cell voltage abnormality detector of claim 12 wherein:

said current/voltage converter comprises;

a third transistor connected in series with said second transistor between said first monitoring terminal and a first power supply voltage terminal;

a fourth transistor which, in combination with said third transistor, forms a second current mirror circuit;

a first resistor connected in series with said fourth transistor between the second and third power supply voltage terminals that produces the prescribed voltage drop;

a fifth transistor which, in combination with said third transistor, forms a third current mirror circuit;

and a second resistor connected in series with said fifth transistor between said second and third power supply voltage terminals, wherein said first monitoring voltage is retrieved from the node between said fourth transistor and said first resistor, and said second monitoring voltage is retrieved from the node between said fifth transistor and said second resistor.

14. A cell voltage abnormality detector for a multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving its voltage from between the first and second monitoring terminals;

a first transistor connected between said first and second monitoring terminals;

a second transistor which, in combination with said first transistor, forms a first current mirror circuit; and

a comparison/evaluation circuit, which compares the current flowing in said second transistor with a reference current, and which determines whether the voltage of said battery cell selected by said selection switch is outside of a predetermined normal range.

15. The cell voltage abnormality detector of claim 14 wherein said comparison/evaluation circuit comprises:

a third transistor connected in series with said second transistor between said first monitoring terminal and a first power supply voltage terminal;

a fourth transistor which, in combination with said third transistor, forms a second current mirror circuit;

a first constant current source connected in series with said fourth transistor between the second and third power supply voltage terminals that produces a prescribed voltage;

a fifth transistor which, in combination with said third transistor, forms a third current mirror circuit;

and a second constant current source that is connected in series with said fifth transistor between said second and third power supply voltage terminals and that is used to monitor the upper threshold wherein a first evaluation signal indicating whether the voltage of said battery cell is lower than a prescribed lower threshold is retrieved from the node between said fourth transistor and said first constant current source, and a second evaluation signal indicating whether the output voltage of said battery cell exceeds a prescribed upper threshold is retrieved from the node between said fourth transistor and said second constant current source.

16. A cell voltage abnormality detector for multi-cell series battery that is used to detect cell voltage abnormalities in at least a single cell of the multi-cell series battery made up of plural battery cells connected in series comprising:

a selection switch for selecting any of the at least single cells of said multi-cell series battery and retrieving its voltage from between the first and second monitoring terminals,

a first transistor connected between said first and second monitoring terminals,

and a comparison/evaluation circuit, which compares the current flowing in said first transistor with a reference current, and which determines whether the voltage of said battery cell selected by said selection switch is outside of a prescribed normal range.

17. The cell voltage abnormality detector of claim 16 characterized in that

said comparison/evaluation circuit comprises

for monitoring a lower threshold,

a second transistor which, in combination with said first transistor, forms a first current mirror circuit, and

a first constant current source connected in series with said second transistor between said first monitoring terminal and a prescribed power supply voltage terminal,

and for monitoring an upper threshold,

a third transistor which, in combination with said first transistor, forms a second current mirror circuit, and

a second constant current source that is connected in series with said third transistor between said first monitoring terminal and said power supply voltage terminal;

wherein a first evaluation signal indicating whether the voltage of said battery cell is lower than a prescribed lower threshold is retrieved from the node between said second transistor and said first constant current source, and a second evaluation signal indicating whether the output voltage of said battery cell exceeds a prescribed upper threshold is retrieved from the node between said third transistor and said second constant current source.