Battery monitoring device and battery system monitoring device

A battery monitoring device for monitoring a cell group made by connecting a plurality of single battery cells in series including a first switching circuit configured to select, as a measurement target voltage, a type of voltage a differential amplifier circuit including a first input terminal and a second input terminal, configured to convert the measurement target voltage, which is selected by the first switching circuit and input between the first input terminal and the second input terminal, into a voltage in a predetermined range by performing differential amplification, and an AD converter configured to measure the measurement target voltage selected by the first switching circuit and converted by the differential amplifier circuit, and output a digital signal according to the measurement result, wherein an abnormality detection voltage, is output to the AD converter.

TECHNICAL FIELD

The present invention relates to a battery monitoring device and a battery system monitoring device having the same.

BACKGROUND ART

A hybrid electric vehicle (HEV), an electric vehicle (EV), and the like use a assembled battery (battery system) made by connecting, in series, multiple cell groups including multiple single battery cells of secondary batteries connected in series or connecting multiple cell groups in series and parallel in order to ensure a desired high voltage. In such an assembled battery, for calculating residual capacity, protecting and managing each single battery cell, a cell controller, which measures a cell voltage (a voltage between terminals of a single battery cell) and performs balancing discharge for balancing of the state of Charge (SOC) and more specifically for balancing the residual capacity, is provided in a monitoring device of the assembled battery to manage the assembled battery (see PTL 1). This cell controller includes multiple integrated circuits (cell controller ICs) to manage multiple cell groups explained above.

An integrated circuit disclosed in PTL 1 includes a voltage detection circuit constituted by a differential amplifier and an analog digital conversion device, and measures a cell voltage by using this voltage detection circuit. In addition, by causing the voltage detection circuit to measure the voltage of an already-known reference power source, a diagnosis can be done to find as to whether the differential amplifier and the analog digital conversion device are operating normally.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

A conventional diagnosis method using the voltage of the already-known reference power source disclosed in PTL 1 may not be able to detect abnormality when any one of the circuits is in a particular abnormality state in the measurement system for measuring a cell voltage. For example, it is difficult for the conventional method to correctly detect an abnormality state in which the error of the analog digital conversion device increases in a particular voltage range and an abnormality state in which the values of the resistors constituting the differential amplifier change and become unbalanced due to degradation over time which deteriorates the differential amplifier characteristics.

Solution to Problem

A battery monitoring device according to the present invention is for monitoring a cell group made by connecting a plurality of single battery cells in series, including: a first switching circuit configured to select, as a measurement target voltage, any one of a plurality of types of voltages including the cell voltages of the single battery cells in the cell group; a differential amplifier circuit including a first input terminal and a second input terminal, and configured to convert the measurement target voltage, which is selected by the first switching circuit and input to between the first input terminal and the second input terminal, into a voltage in a predetermined range by performing differential amplification; and an AD converter configured to measure the measurement target voltage which is selected by the first switching circuit and converted by the differential amplifier circuit, and output a digital signal according to the measurement result, wherein an abnormality detection voltage, with which abnormality in a differential amplification characteristic of the differential amplifier circuit is detected, is output to the AD converter.

A battery system monitoring device according to the present invention includes the battery monitoring device and a battery controller configured to receive measurement information according to a digital signal which is output from the AD converter of the battery monitoring device from the battery monitoring device. The battery controller detects the abnormality of the differential amplifier characteristics of the differential amplifier circuit on the basis of the measurement information when the abnormality detection voltage is measured by the AD converter.

Advantageous Effects of Invention

According to the invention, the abnormality state in the measurement system for measuring a cell voltage can be correctly detected.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present invention will be explained with reference to drawings. The embodiments explained below is examples in which the present invention is applied to a battery system monitoring device used for a hybrid electric vehicle (HEV). It should be noted that the present invention is not limited to the HEV, and the present invention can be widely applied to various types of battery systems provided on a plug-in hybrid electric vehicle (PHEV), an electric vehicle (EV), a railroad vehicle, and the like.

In the embodiments explained below, an electric storage/discharge device serving as the minimum unit of control is considered to be a Lithium ion (Li-ion) battery of which voltage is in a range of 3.0 to 4.2 V (average output voltage: 3.6V), but the electric storage/discharge device may be other than the above and may be any device capable of accumulating and discharging electricity and restricting usage when the SOC (State of Charge) is too high (overcharge) or too low (overdischarge). In this case, such device is collectively referred to as a single battery, a single battery cell, or simply a cell.

In the embodiments explained below, a set of multiple single battery cells (about several to some dozen single battery cells) connected in series will be referred to as a cell group, and a set of multiple cell groups connected in series will be referred to as a battery module. Further, a set of multiple cell groups or multiple battery modules connected in series or in series and parallel will be referred to as an assembled battery. A cell controller IC serving as a battery monitoring device detecting the cell voltage of each single battery cell and monitoring the battery state while performing balancing operation and the like is provided for each cell group.

(Configuration of Electric Motor Driving Device)

FIG. 1is a view illustrating an example of a configuration of an electric motor driving device for a hybrid electric vehicle equipped with an electric storage device having a battery system monitoring device according to the present invention. This electric motor driving device includes a vehicle controller400, a motor controller300, a battery controller200, multiple cell controller ICs100, a battery system130, an inverter340, a motor350, and the like. Among them, the vehicle controller400, the motor controller300, the battery controller200, and the cell controller IC100and the inverter340exchange information with each other via a communication circuit provided in the vehicle.

The battery system130has multiple cell groups120connected in series. Further, each cell group120is configured by connecting multiple single battery cells110of secondary batteries such as Li-ion batteries connected in series.

The battery system monitoring device10includes a battery controller200, multiple cell controller ICs100, and connection circuits provided between each cell controller IC100and the cell group120and including a resistor, a capacitor, and the like. The electric storage device includes the battery system monitoring device10and the battery system130.

A communication circuit between the battery controller200and the multiple cell controller ICs100is connected in a loop form. When a signal is transmitted from the battery controller200to the most-upstream cell controller IC100via a signal isolator201, the signal is transmitted in series in order from the most-upstream cell controller IC100to the most-downstream cell controller IC100. Finally, the signal is transmitted from the most-downstream cell controller IC100to the battery controller200via a signal isolator202. The battery controller200can exchange information with all the cell controller ICs100via the communication circuit in the loop form.

In this case, for example, signal transmission is done between the battery controller200and each cell controller IC100via the communication circuit in the loop form. Alternatively, the signal transmission can be done using a bidirectional communication circuit. In this case, the signal isolator202is unnecessary. Still alternatively, although not shown, a communication circuit may be connected in parallel from the battery controller200to all the cell controller ICs100, so that the signal transmission can be done in parallel.

The vehicle controller400controls the cruising speed and the traction/braking force of the vehicle on the basis of an operation signal given by vehicle driving operation devices such as a an accelerator pedal, a brake pedal, or a gear lever which are operated by the driver of the hybrid vehicle. The motor controller300controls the battery controller200and the inverter340on the basis of a speed command and a traction/braking force command given by the vehicle controller400, and controls the rotation speed and the torque of the vehicle cruising driving motor350.

The battery controller200controls charging/discharging and the SOC (State of Charge) of the battery system130on the basis of the voltage, the electric current, and the temperature of the battery system130detected by the voltage sensor210, the electric current sensor220, and the temperature sensor230, respectively. In addition the battery controller200controls each cell controller IC100to manage the SOCs of the multiple single battery cells (hereinafter simply referred to as cells)110constituting the battery system130, and performs discharging so as to correct variation in the SOC (hereinafter referred to as balancing discharge) so as to avoid overcharged state.

In the embodiment as shown inFIG. 1, for example, the battery system130is configured such that multiple cell groups120having four cells110connected in series are connected in series. However, the number of single battery cells110constituting the cell group120is not limited thereto. Alternatively, the number of single battery cells110may be equal to or more than four or may be less than four. A cell controller IC100suitable for the specification of the cell group120may be used. The battery system130provided on the hybrid vehicle is generally a high-voltage and high-capacity battery system in which many cells or cell groups are connected in series and parallel, and the voltage between the terminals is several hundred voltage. It is to be understood that the present invention can also be applied to such high-voltage and high-capacity battery system.

The cell controller IC100is provided for each cell group120made by dividing the multiple cells110into a predetermined number of cells110constituting the battery system130. For example, suppose that a battery system130having one hundred cells110connected in series is divided into groups each having four cells110, and twenty five cell groups120are provided in the battery system130. In this case, twenty five cell controller ICs100are used, which is the same number of cell groups120.

Each cell controller IC100detects the voltage between terminals of each cell110(cell voltage) constituting each cell group120, and transmits the detection result to the battery controller200. Then, energizing control of the balancing electric current is performed for each cell110in order to correct variation of the SOC of each cell110in accordance with the command given by the battery controller200. As described above, the cell controller IC100monitors the cell group120. It should be noted that the balancing resistor102is a resistor for restricting the electric current of the discharging of each cell110(balancing discharge), and is provided for each cell110.

A direct current electric power charged in the battery system130is provided to a smoothing capacitor330and an inverter340via a positive electrode-side contactor310and a negative electrode-side contactor320. The direct current electric power provided from the battery system130is converted by the inverter340into an alternate current electric power to be applied to an alternate current motor350, so that the alternate current motor350is driven. The conversion from the direct current electric power into the alternate current electric power is done by switching of a switching device (not shown) provided in the inverter340. On the other hand, when the vehicle brakes, the alternate current electric power generated by the alternate current motor350is converted into a direct current electric power by a diode device (not shown) and the smoothing capacitor330provided in the inverter340. This direct current electric power is applied to the battery system130via the positive electrode-side contactor310and the negative electrode-side contactor320, so that the battery system130is charged. More specifically, the direct current electric power is exchanged between the battery system130and the inverter340.

Ripple noise and switching noise are generated by the operation of the inverter340. These noises are somewhat reduced by the smoothing capacitor330, but cannot be completely eliminated, and the noises flow into the battery system130. Therefore, noise voltage in proportion to the noise electric current is superimposed on the cell voltage of each cell110. This noise voltage causes detection error of the cell voltage, and therefore, this is suppressed by using an RC filter and the like in the voltage measurement circuit (not shown) provided in the cell controller IC100.

Subsequently, the details of the cell controller IC100will be explained. As explained in details later, the cell controller IC100provided in the battery system monitoring device10includes a successive conversion-type AD converter and a differential amplifier circuit. Therefore, this may cause an abnormality state in which the error of the analog digital conversion device increases in a particular voltage range and an abnormality state in which the values of the resistors constituting the differential amplifier circuit change and become unbalanced due to degradation over time which deteriorates the differential amplifier characteristics. In the present invention, various improvements have been made on the cell voltage measurement system of the cell controller IC100in order to correctly detect these abnormality states.

In this case, before the cell controller IC100according to the present invention is explained, the conventional cell controller IC will be explained.FIG. 2is a view illustrating an example of a configuration of a cell voltage measurement system of the conventional cell controller IC100′. In this example, a single cell group120is constituted by twelve cells110connected in series. In the explanation below, these twelve cells110will be referred to as a cell 1 to a cell 12 arranged from a low potential side to a high potential side. InFIG. 2, the cells 3 to 10 are not shown. The positive/negative electrode terminals of the cells 1 to 12 are connected to the cell controller IC100′ via totally thirteen voltage detection lines.

In the cell controller IC100′, the voltage detection lines from the positive/negative electrode terminals of the cells 1 to 12 are connected to the input-side of the switching circuit501. The input-side of the switching circuit501is also connected to a voltage reference504generating a reference voltage Vref1using the negative terminal voltage of the cell 1 as the ground voltage. The switching circuit501selectively switches a combination of any two of them in accordance with a switching signal which is output from a logic unit, not shown, and outputs the combination to input terminals T1, T2of the differential amplifier circuit502. With such operation of the switching circuit501, any one of the cell voltages of the cells 1 to 12 and the reference voltage Vref1generated by the voltage reference504is selected as a measurement target voltage.

FIG. 3is a list table illustrating connection in the switching circuit501when selecting the cell voltages of the cells 1 to 12 and the reference voltage Vref1given by the voltage reference504. As shown in the table, the connections of the upper side and the lower side of the switching circuit501are switched respectively, the cell voltages of the cells 1 to 12 and the reference voltage Vref1can be selectively applied to between the input terminal T1and the input terminal T2of the differential amplifier circuit502. For example, when the cell voltage of the cell 12 is selected, the switching circuit501selects the terminal A1and the terminal B1at the input side and connects them to the terminals C1, C2at the output side. Therefore, the cell voltage between the positive electrode terminal and the negative electrode terminal of the cell 12 is output to between the input terminal T1and the input terminal T2of the differential amplifier circuit502. Likewise, the switching circuit501successively selects the terminals A1to A12and the terminals B1to B12at the input side and connects them to the terminals C1, C2, respectively, at the output side, so that the cell voltages of the cells 12 to 1 are selected and output to the differential amplifier circuit502. When the terminal A13and the terminal B12at the input side are selected and connected to the terminals C1, C2, respectively, at the output side, the reference voltage Vref1from the voltage reference504is output to the differential amplifier circuit502. InFIG. 2, the terminals A4to A10and the terminals B4to B10are not shown.

The differential amplifier circuit502includes resistors R1, R2provided at the side of the input terminal T1, resistors R3, R4provided at the side of the input terminal T2, and a differential amplifier U1having a + input terminal and a − input terminal. The + input terminal of the differential amplifier U1is connected between the resistor R1and the resistor R2, and the − input terminal is connected between the resistor R3and the resistor R4. The measurement target voltage, which is selected by the switching circuit501and is input to the input terminals T1, T2of the differential amplifier circuit502, is differentially amplified by the differential amplifier U1of the differential amplifier circuit502, so that it is converted into a voltage in a predetermined range using the negative terminal voltage of the cell 1 as the reference. The converted measurement target voltage is output from the differential amplifier circuit502to the input side of the AD converter503.

The AD converter503operates using the reference voltage Vref0generated by the voltage reference505, and converts the input analog signal into a digital signal, thus outputting an AD converted value. With this operation, the AD converter503measures the measurement target voltage converted by the differential amplifier circuit502, and outputs the digital signal according to the measurement result. This digital signal is sent to a logic unit, not shown, and is converted into measurement information in a predetermined data format by communication control performed by the logic unit, and the measurement information is sent to the battery controller200ofFIG. 1.

The battery controller200receives the measurement information from the cell controller IC100′, so that the battery controller200can obtain the measurement result of the cell voltages of the cells 1 to 12 and the reference voltage Vref1given by the voltage reference504. When the measurement result of the reference voltage Vref1thus obtained is determined to be within a predetermined range, the battery controller200can confirm that the cell voltage measurement system of the cell controller IC100′ is operating normally. More specifically, the battery controller200can determine that all of the differential amplifier circuit502, the AD converter503, and the voltage reference505are normal.

FIG. 4is an explanatory diagram illustrating an internal configuration of an AD converter503. In this case, a configuration is shown in a case where a successive conversion-type AD converter capable of performing measurement with a high degree of accuracy at a relatively high speed is used.

InFIG. 4, the sample and hold circuit601samples the measurement voltage, which is input by the AD converter503, by holding it at a certain level during AD conversion. The sample-and-hold output voltage given by the sample and hold circuit601as well as the output voltage of the DA converter603are applied to the input side of the comparator602. The comparator602compares the sample-and-hold output voltage and the output voltage of the DA converter603, and outputs information indicating which of the voltage values is larger to the control logic604. The control logic604outputs a digital signal of a predetermined number of bits on the basis of the output from the comparator602. The DA converter603outputs the voltage according to the digital signal which is output from the control logic604on the basis of the reference voltage Vref0given by the voltage reference505. With such operation, the measurement voltage sampled and held by the sample and hold circuit601and the output voltage provided by the DA converter603are repeatedly compared by the comparator602, the digital signal according to the comparison result is determined by the control logic604. This digital signal is output from the AD converter503, so that the AD converter503converts the measurement voltage into the digital signal. The AD converter503performs such successive conversion operation, and outputs the measurement voltage as a logic value.

FIG. 5is an explanatory diagram illustrating a configuration of the DA converter603provided in the successive conversion-type AD converter503shown inFIG. 4. As shown inFIG. 5, the DA converter603includes a ladder resistor unit605in which multiple ladder resistors606are connected, and a switching SW unit607for switching connection of each ladder resistor606of the ladder resistor unit605in accordance with the control of the control logic604ofFIG. 4. The switching SW unit607is connected to the voltage reference505. In accordance with the value of each bit of the digital signal from the control logic604, each switch of the switching SW607is controlled, whereby the connection between each ladder resistor606and the voltage reference505is turned ON or OFF. Therefore, the voltage according to the digital signal from the control logic604is output from the DA converter603to the comparator602as an analog output.

(Problems Associated with a Case where there is a Malfunction in the Successive Conversion-Type AD Converter in the Conventional Cell Controller IC)

Subsequently, problems associated with a case where there is a malfunction in the successive conversion-type AD converter503in the conventional cell controller IC100′ explained above will be explained.FIG. 6is a figure illustrating an example of cell voltage detection characteristics in a case where there is a malfunction in the successive conversion-type AD converter503in the conventional cell controller IC100′. This case shows an example of voltage detection characteristics in a case where there is a malfunction that one of the switches of the switching SW unit607is fixed to the side of the voltage reference505in the configuration of the DA converter603in the AD converter503as shown inFIG. 5.

InFIG. 6, as compared with normal voltage detection characteristics610indicated by reference symbol610, malfunctioning voltage detection characteristics indicated by reference symbol611are such that the voltage detection error is larger in each of the voltage ranges in which the input voltage is about 600 to 1200 mV, about 1800 to 2500 mV, about 3100 to 3700 mV, about 4300 to 5000 mV. This is because, in a voltage range in which the switch fixed to the side of the voltage reference505due to malfunction should be originally expected to be in the OFF state, the output voltage from the DA converter603is not output according to the control of the control logic604, and therefore, the successive conversion operation of the AD converter503is not performed normally. This voltage range is different according to the position of the switch fixed in the switching SW unit607. More specifically, when the switch corresponding to the LSB-side of the digital signal from the control logic604is fixed, the problem is no more than a reduction in the resolution, but if the switch corresponding to the MSB side is fixed, a larger error may occur.

In this case, as shown inFIG. 2, the conventional cell controller IC100′ includes a voltage reference504for diagnosing the malfunction of the cell voltage measurement system including the AD converter503. However, in a case where the error peculiar to the successive conversion-type AD converter503explained above occurs, and more specifically, there is a malfunction in which the error increases only in a particular voltage range, the malfunction of the AD converter503cannot be correctly detected unless the reference voltage Vref1given by the voltage reference504is within this voltage range. When there is a malfunction in the successive conversion-type AD converter503, such problem may occur with the conventional cell controller IC100′.

(Problems Associated with a Case where there is a Malfunction in Differential Amplifier Circuit in Conventional Cell Controller IC)

Subsequently, problems associated with a case where there is a malfunction in the differential amplifier circuit502in the conventional cell controller IC100′ will be explained.FIG. 7is a figure illustrating an example of a characteristics chart representing a relationship between a cell position and a voltage detection error that occurs when there is a change in the resistance values of the resistors R1to R4of the differential amplifier circuit502. In this case,FIG. 7shows the relationship between the voltage detection error and the cell position in a case where the voltage dividing ratio at the + input terminal of the differential amplifier U1and the voltage dividing ratio at the − input terminal of the differential amplifier U1each change from 50% by ±0.2% when the cell voltage of each cell is 4.1 V in the configuration of the differential amplifier circuit502shown inFIG. 2using each of the characteristics charts indicated by reference symbols701to704. More specifically, the characteristics charts701,702indicate the relationship between the voltage detection error and the cell position when the voltage dividing ratio at the + input terminal of the differential amplifier U1is 49.8% and 50.2%, respectively. On the other hand, the characteristics charts703,704indicate the relationship between the voltage detection error and the cell position when the voltage dividing ratio at the − input terminal of the differential amplifier U1is 49.8% and 50.2%, respectively.

InFIG. 7, in any one of the characteristics charts701to704, it is understood that a cell connected upstream and having a higher potential has a larger voltage detection error. In this example, in the most-downstream cell 1, the voltage detection error is about ±20 mV, but in the most-upstream cell 12, the voltage detection error increases to about ±200 mV.FIG. 7shows an example of voltage detection error in a case where the number of cells is twelve, but as the number of cells connected in series increases, the voltage detection error becomes higher in the most-upstream cell.

In this case, the conventional cell controller IC100′ measures the reference voltage Vref1given by the voltage reference504independent and different from the voltage reference505of the AD converter503explained above, thus detecting abnormality in the cell voltage measurement system. However, the reference voltage Vref1given by the voltage reference504is a voltage where the ground voltage of the cell controller IC100′ is adopted as the reference. More specifically, the negative terminal voltage of the cell 1 is adopted as the reference. Therefore, even if the reference voltage Vref1from the voltage reference505is measured when there is a change in the resistance values of the resistors R1to R4of the differential amplifier circuit502, only the voltage detection error corresponding to the most-downstream cell 1 in each of the characteristics charts701to704ofFIG. 7can be measured. More specifically, with the malfunction diagnosis method performed by the conventional cell controller IC100′, the sensitivity for the change in the resistance value of the differential amplifier circuit502is low, and it is difficult to correctly detect the error explained above as a malfunction. In the conventional cell controller IC100′, such problem may occur when there is a malfunction in the differential amplifier circuit502.

When there is a malfunction in the AD converter503and the differential amplifier circuit502explained above, the cell voltage cannot be correctly measured, and therefore, each cell may be overcharged or overdischarged. In particular, with a Li-ion battery, there is a risk of explosion, smoke, and combustion of a cell when the cell is overcharged, and therefore, it is absolutely necessary to avoid such situation. Even if the cell is not overcharged or overdischarged, a cell is charged and discharged in an expected voltage range, and this may degrade the characteristics of the battery system130in a shorter time.

Therefore, in the cell controller IC100according to the present invention, various types of improvements have been made in the cell voltage measurement system in order to correctly detect malfunction in the AD converter503and the differential amplifier circuit502explained above. Each of the contents of the improvements will be explained in each of the first to the seventh embodiments below.

First Embodiment

FIG. 8is a view illustrating an example of a configuration of a cell controller IC100according to the first embodiment of the present invention. The configuration ofFIG. 8is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 8includes not only the voltage reference504but also a reference voltage generation circuit500A having a voltage reference506and a terminal A14provided in the switching circuit501.

In the reference voltage generation circuit500A, the voltage reference504and the voltage reference506generate reference voltages Vref1, Vref2, respectively, which are different from each other. More specifically, the − terminal of the voltage reference504is connected to the negative electrode terminal of the cell 1, and the voltage reference504generates a reference voltage Vref1using the negative terminal voltage of the cell 1 as the reference. On the other hand, the + terminal of the voltage reference506is connected to the positive electrode terminal of the cell 12, and the voltage reference506generates a reference voltage Vref2using the positive terminal voltage of the cell 12 as the reference.

When the cell controller IC100of the present embodiment determines whether the cell voltage measurement system is operating normally, the switching circuit501selects the terminal A13and the terminal B12at the input side, and selects the terminal A1and the terminal B13at the input side, which are to be connected with the terminals C1, C2at the output side. In this manner, the voltage reference504and the voltage reference506are switched and selected, and the reference voltages Vref1and Vref2are output to the differential amplifier circuit502, so that this changes the reference voltage which is output from the reference voltage generation circuit500A. Each measurement result for the reference voltages Vref1and Vref2at this occasion is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

When the measurement result of at least one of the measurement results of the reference voltages Vref1and Vref2is out of a predetermined range with respect to the reference voltages Vref1, Vref2determined in advance, the battery controller200determines that there is a malfunction in the cell voltage measurement system of the cell controller IC100. Therefore, even when there is such a malfunction that the error increases only in a particular voltage range in the successive conversion-type AD converter503, the abnormality of the AD converter503can be detected correctly if any one of the reference voltages Vref1and Vref2stays within the voltage range.

It should be noted that at least one of the voltage reference504and the voltage reference506is preferably generated using a voltage substantially matching the overcharge voltage for each cell as the reference voltage Vref1or Vref2. By doing so, the malfunction detection performance is improved at a voltage around the overcharge voltage, and therefore, the safety in the entire electric storage device can be further improved.

According to the first embodiment of the present invention explained above, the actions and effects as shown in the following (1) to (3) can be achieved.

(1) The cell controller IC100monitors the cell group120including multiple single battery cells110connected in series. This cell controller IC100includes the reference voltage generation circuit500A configured to generate a variable reference voltage, a switching circuit501configured to select, as a measurement target voltage, any one of multiple types of voltages including the reference voltage and the cell voltages of the single battery cells110of the cell group120, and an AD converter503configured to measure the measurement target voltage selected by the switching circuit501and output a digital signal according to the measurement result. The battery controller200receives the measurement information according to the digital signal which is output from the AD converter503from the cell controller IC100. Then, the abnormality of the AD converter503is detected on the basis of the measurement information when the AD converter503measures the reference voltage. In this configuration, the abnormality state can be correctly detected in the measurement system for measuring the cell voltage in the cell controller IC100.

(2) The reference voltage generation circuit500A includes the voltage references504and506generating the reference voltages Vref1, Vref2different from each other. The cell controller IC100causes the switching circuit501to switch and select the voltage references504,506, so that the reference voltage from the reference voltage generation circuit500A is changed. In this configuration, the reference voltage can be easily changed with a simple circuit configuration.

(3) At least one of the voltage reference504and the voltage reference506may generate, as the reference voltage Vref1or the reference voltage Vref2, a voltage substantially matching the predetermined overcharge voltage for determining overcharging of the single battery cell110. In this configuration, in a voltage range around the overcharge voltage, the abnormality of the cell voltage measurement system can be detected reliably. Therefore, the safety in the entire electric storage device can be further improved.

In the first embodiment explained above, for example, the reference voltage generation circuit500A has two voltage references504and506, and generates the reference voltages Vref1, Vref2from these voltage references using the negative terminal voltage of the cell 1 and the positive terminal voltage of the cell 12 as the references. However, the reference voltages respectively generated by the voltage references504,506are not limited thereto. The reference voltage generation circuit500A may have three or more voltage references, and may generate the reference voltages different from each other from these voltage references. More specifically, as long as the reference voltage generation circuit500A has multiple voltage references generating reference voltages different from each other, the reference voltage generation circuit500A is not limited to the aspect as shown inFIG. 8. Various configurations may be applied as the reference voltage generation circuit500A.

Second Embodiment

FIG. 9is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the second embodiment of the present invention. The configuration ofFIG. 9is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 9includes a reference voltage generation circuit500B having a DA converter508instead of the voltage reference504.

In the reference voltage generation circuit500B, the DA converter508generates any reference voltage which is set by a logic unit, not shown, on the basis of a reference voltage Vref3from the voltage reference507. More specifically, the DA converter508operates as a voltage reference generating any reference voltage that is set.

When the cell controller IC100of the present embodiment determines whether the cell voltage measurement system is operating normally, the switching circuit501selects the terminal A13and the terminal B12at the input side which are to be connected with the terminals C1, C2at the output side. By changing the setting value of the DA converter508, the reference voltage which is output from the reference voltage generation circuit500B is changed within a range in which the cell voltage may take. The measurement result of the reference voltage at this occasion is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

When the measurement result of the reference voltage is out of a predetermined range with respect to the setting value of the DA converter508, the battery controller200determines that there is a malfunction in the cell voltage measurement system of the cell controller IC100. Therefore, even when there is such a malfunction that the error increases only in a particular voltage range in the successive conversion-type AD converter503, the abnormality of the AD converter503can be detected correctly by causing the DA converter508to change the reference voltage in the entire range in which the cell voltage may take.

The malfunction diagnosis of the cell voltage measurement system and the change of the setting value of the DA converter508explained above may be done when the cell group120is charged or discharged during the usage of the electric storage device. In this case, the diagnosis of the cell voltage measurement system is repeated while the predetermined voltage of the DA converter508is changed little by little, so that malfunction of the AD converter503can be detected in real time over a wide voltage range.

According to the second embodiment of the present invention explained above, not only the same actions and effects as those associated with (1) explained in the first embodiment but also the actions and effects as shown in (4) below can be achieved.

(4) The reference voltage generation circuit500B includes the DA converter508operating as the voltage reference generating any reference voltage which has been set. In this configuration, the reference voltage can be easily changed in any given voltage range.

Third Embodiment

FIG. 10is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the third embodiment of the present invention. The configuration ofFIG. 10is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 10includes a reference voltage generation circuit500C having not only a voltage reference504but also an oscillator509.

In the reference voltage generation circuit500C, the oscillator509generates a reference voltage which changes within a predetermined voltage range as the time elapses. The period in which the oscillator509changes the reference voltage is preferably, sufficiently longer than the measurement period of the measurement target voltage of the AD converter503. The range in which the oscillator509changes the reference voltage preferably includes the range which the cell voltage may take. It should be noted that the reference voltage waveform from the oscillator509may be a waveform that changes periodically within a predetermined range such as a triangular wave and a sine wave.

When the cell controller IC100of the present embodiment determines whether the cell voltage measurement system is operating normally, the switching circuit501selects the terminal A13and the terminal B12at the input side, and selects the terminal A14and the terminal B12at the input side, which are to be connected with the terminals C1, C2at the output side. When the terminal A13and the terminal B12are selected, the reference voltage from the oscillator509changing periodically is measured, and when the terminal A13and the terminal B12are selected, the reference voltage Vref1given by the voltage reference504is measured. These measurement results of the reference voltages are transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

When the measurement result of the reference voltage Vref1is within a predetermined range and the measurement result of the reference voltage from the oscillator509monotonically changes in accordance with the reference voltage waveform, the battery controller200determines that the cell voltage measurement system of the cell controller IC100is normal. On the other hand, when measurement result of the reference voltage Vref1is out of a predetermined range, or when the change in the measurement result of the reference voltage from the oscillator509is different from the reference voltage waveform, the battery controller200determines that there is a malfunction in the cell voltage measurement system of the cell controller IC100. Therefore, even when there is a malfunction explained above in which the error of the successive conversion-type AD converter503increases only in a particular voltage range, the oscillator509periodically changes the reference voltage, so that the abnormality of the AD converter503can be detected correctly.

According to the third embodiment of the present invention explained above, not only the same actions and effects as those associated with (1) explained in the first embodiment but also the actions and effects as shown in (5), (6) below can be achieved.

(5) The reference voltage generation circuit500C includes the oscillator509serving as the voltage reference generating the reference voltage that changes within a predetermined voltage range as the time elapses. Therefore, the reference voltage can be easily changed in any voltage range.

(6) The oscillator509periodically changes the reference voltage, and therefore, a determination as to whether the AD converter503is abnormal or not can be easily determined from the change in the measurement result of the reference voltage.

Fourth Embodiment

FIG. 11is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the fourth embodiment of the present invention. The configuration ofFIG. 11is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 11includes a reference voltage generation circuit500D having not only the voltage reference504but also a switching device510and a constant electric current source511, and has a capacitor512provided outside of the cell controller IC100.

In the reference voltage generation circuit500D, the switching device510is provided between the capacitor512and the constant electric current source511. The switching state of the switching device510is controlled so that an electric current is passed from the constant electric current source511to the capacitor512to charge the capacitor512and thereafter an electric current is passed in the opposite direction to discharge the capacitor512. Therefore, the voltage across the capacitor512changes within a predetermined voltage range as the time passes.

In general, many switches and constant electric current sources used for various purposes are provided in the cell controller IC. Therefore, when these are used as the switching device510and the constant electric current source511, the cell voltage measurement system as shown inFIG. 11can be easily made by just externally adding the capacitor512.

When the cell controller IC100of the present embodiment determines whether the cell voltage measurement system is operating normally, the switching circuit501selects the terminal A13and the terminal B12at the input side, and selects the terminal A14and the terminal B12at the input side, which are to be connected with the terminals C1, C2at the output side. When the terminal A13and the terminal B12are selected, the switching state of the switching device510is controlled as described above to charge and discharge the capacitor512, and the voltage across the capacitor512that changes according to the charge/discharge state thereof is measured as the reference voltage. When the terminal A13and the terminal B12are selected, the reference voltage Vref1given by the voltage reference504is measured. The measurement result of the reference voltage is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

When the measurement result of the reference voltage Vref1is within a predetermined range, and the measurement result of the voltage across the capacitor512measured as the reference voltage monotonically changes according to the switching state of the switching device510, the battery controller200determines that the cell voltage measurement system of the cell controller IC100is normal. On the other hand, when the measurement result of the reference voltage Vref1is out of the predetermined range, or when the change in the measurement result of the voltage across the capacitor512does not correspond to the switching state of the switching device510, the battery controller200determines that there is a malfunction in the cell voltage measurement system of the cell controller IC100. Therefore, even when there is a malfunction explained above in which the error of the successive conversion-type AD converter503increases only in a particular voltage range, the capacitor512is charged and discharged to change the voltage across the capacitor512, so that the abnormality of the AD converter503can be detected correctly.

According to the fourth embodiment of the present invention explained above, not only the same actions and effects as those associated with (1) explained in the first embodiment but also the actions and effects as shown in (7) below can be achieved.

(7) The reference voltage generation circuit500D uses the switching device510and the constant electric current source511to output the voltage across the capacitor512that is charged or discharged as the reference voltage, so that the reference voltage is generated, which changes within the predetermined voltage range as the time elapses. Therefore, the reference voltage is changed in accordance with the measurement timing of the reference voltage, and a determination as to whether the AD converter503is abnormal or not can be made easily.

Fifth Embodiment

FIG. 12is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the fifth embodiment of the present invention. The configuration ofFIG. 12is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 12includes a reference voltage generation circuit500A having not only the voltage reference504but also a voltage reference506, and the switching circuit501is provided with a terminal A14for connecting the input terminal T1of the differential amplifier circuit502to the ground voltage. The configuration of the cell voltage measurement system as shown inFIG. 12is the same as the configuration of the cell voltage measurement system of the cell controller IC100according to the first embodiment as shown inFIG. 8.

FIG. 13is a list table illustrating connection in the switching circuit501when the cell voltages of the cells 1 to 12, the reference voltages Vref1, Vref2from the voltage references504,506, and the negative terminal voltage of the cell 1, i.e., the ground voltage are selected in the cell controller IC100according to the fifth embodiment of the present invention. As shown in the table, by switching the connections of the upper side and the lower side of the switching circuit501, the cell voltages of the cells 1 to 12 and the reference voltages Vref1, Vref2can be selectively applied to between the input terminal T1and the input terminal T2of the differential amplifier circuit502. Both of the input terminal T1and the input terminal T2are connected to the ground voltage, and they can be short-circuited.

In the cell controller IC100of the present embodiment, the AD converter503measures the voltage into which the differential amplifier circuit502converts the reference voltage Vref2from the voltage reference506as the abnormality detection voltage for detecting the abnormality of the differential amplifier characteristics of the differential amplifier circuit502. At this occasion, the switching circuit501selects the terminal A1and the terminal B13at the input side which are connected to the terminals C1, C2at the output side. Therefore, the reference voltage Vref2from the voltage reference506is selected and input into the differential amplifier circuit502, and the voltage into which the differential amplifier circuit502converts the reference voltage Vref2is output to the AD converter503as the abnormality detection voltage. The measurement information obtained when the AD converter503measured the abnormality detection voltage is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

Further, in the cell controller IC100of the present embodiment, when the measurement result of the abnormality detection voltage indicates abnormality, an offset error and a gain error are measured in order to determine whether the abnormality occurs in the differential amplifier characteristics of the differential amplifier circuit502. The offset error is an error caused by an offset voltage of the differential amplifier circuit502and the AD converter503, and the gain error is an error for the gain of the differential amplifier circuit502and the AD converter503. When all the measurement values of these errors are within a predetermined error range, and the measurement result of the abnormality detection voltage indicates abnormality, then the resistance values of the resistors R1to R4of the differential amplifier circuit502change as described above and it can be determined that there is an abnormality in the differential amplifier characteristics.

When the offset error is measured, the switching circuit501selects the terminal A14and the terminal B12at the input side which are connected to the terminals C1, C2at the output side. Therefore, both of the input terminals T1and T2of the differential amplifier circuit502are connected to the negative electrode-side of the cell 1 at the lowest potential in the cell group120, so that the input terminal T1and the input terminal T2are short-circuited. The output voltage from the differential amplifier circuit502at this occasion, i.e., the output when the ground voltage is input into the differential amplifier circuit502, is output to the AD converter503as the offset error voltage for measuring the offset error. The measurement information obtained when the offset error voltage is measured by the AD converter503is also transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

When the gain error is measured, the switching circuit501selects the terminal A13and the terminal B12at the input side which are connected to the terminals C1, C2at the output side. Therefore, the reference voltage Vref1given by the voltage reference504is selected, and is input into the differential amplifier circuit502. The voltage into which the differential amplifier circuit502converts the reference voltage Vref1is output to the AD converter503as the gain error voltage for measuring the gain error. The measurement information obtained when the AD converter503measures the gain error voltage is also transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

The battery controller200detects the abnormality of the differential amplifier characteristics of the differential amplifier circuit502on the basis of the measurement information of the abnormality detection voltage, offset error voltage and gain error voltage transmitted from the cell controller IC100as described above. At this occasion, the battery controller200measures the offset error and the gain error on the basis of the measurement information from the cell controller IC100when the offset error voltage is measured and the measurement information from the cell controller IC100when the gain error voltage is measured. As a result, when all of these errors are within a predetermined error range, and the value of the measurement information obtained when the abnormality detection voltage is measured is out of a predetermined range with respect to the previously determined reference voltage Vref2, then the battery controller200determines that there is an abnormality in the differential amplifier characteristics of the differential amplifier circuit502in the cell controller IC100. Therefore, the abnormality in the differential amplifier characteristics caused by the change in the resistance values of the resistors R1to R4of the differential amplifier circuit502can be detected correctly.

On the other hand, when the offset error and the gain error are within a predetermined error range, and the value of the measurement information obtained when the abnormality detection voltage is measured is within a predetermined range, then the battery controller200determines that the cell voltage measurement system of the cell controller IC100is normal. When the offset error and the gain error are out of the predetermined error range, it is determined that the offset abnormality or the gain abnormality occurs in at least one of the differential amplifier circuit502and the AD converter503. Therefore, the abnormality of the cell voltage measurement system can be detected in details.

According to the fifth embodiment of the present invention explained above, the actions and effects as shown in the following (8) to (10) can be achieved.

(8) The cell controller IC100monitors the cell group120having multiple single battery cells110connected in series. This cell controller IC100includes a switching circuit501configured to select, as the measurement target voltage, any one of multiple types of voltages including the cell voltages of the single battery cells110of the cell group120, a differential amplifier circuit502including input terminals T1and T2and configured to differential amplifies the measurement target voltage which is selected by the switching circuit501and is input to between the input terminal T1and the input terminal T2, and convert the measurement target voltage into a voltage in a predetermined range, and an AD converter503configured to measure the measurement target voltage which is selected by the switching circuit501and converted by the differential amplifier circuit502, and output a digital signal according to the measurement result, wherein an abnormality detection voltage for detecting abnormality in differential amplifier characteristics of the differential amplifier circuit502is output to the AD converter503. The battery controller200receives the measurement information according to the digital signal which is output from the AD converter503from the cell controller IC100. Then, on the basis of the measurement information obtained when the AD converter503measures the abnormality detection voltage, the abnormality in the differential amplifier characteristics of the differential amplifier circuit502is detected. Therefore, the abnormality state can be detected correctly in the measurement system for measuring the cell voltage.

(9) The cell controller IC100includes the voltage reference506configured to generate the reference voltage Vref2, and causes the switching circuit501to select the reference voltage Vref2, so that the reference voltage Vref2converted by the differential amplifier circuit502is output to the AD converter503as the abnormality detection voltage. Therefore, by using the circuit configuration for detecting the abnormality of the AD converter503explained in the first embodiment, the abnormality detection voltage can be output.

(10) The cell controller IC100includes a voltage reference504connected to the negative electrode-side of the cell 1 of the lowest potential in the cell group120, and configured to generate the reference voltage Vref1using the potential of the negative electrode-side of the cell 1 as the reference. Then, the output voltage from the differential amplifier circuit502obtained when both of the input terminals T1and T2are connected to the negative electrode-side of the cell 1 by the switching circuit501to short-circuit the input terminal T1and the input terminal T2is output to the AD converter503as the offset error voltage. By causing the switching circuit501to select the reference voltage Vref1, the reference voltage Vref1converted by the differential amplifier circuit502is output to the AD converter503as the gain error voltage. The battery controller200measures the offset error of the differential amplifier circuit502and the AD converter503on the basis of the measurement information obtained when the AD converter503measures the offset error voltage. The gain error of the differential amplifier circuit502and the AD converter503is measured on the basis of the measurement information obtained when the AD converter503measures the gain error voltage. Then, when the offset error is within the predetermined error range, and the gain error is within the predetermined error range, and the value of the measurement information obtained when the AD converter503measures the abnormality detection voltage is out of the predetermined range, the differential amplifier characteristics of the differential amplifier circuit502is determined to be abnormal. Therefore, where there is an abnormality in the differential amplifier characteristics of the differential amplifier circuit502, this can be reliably detected.

In the fifth embodiment explained above, for example, the + terminal of the voltage reference506is connected to the positive electrode-side of the cell 12, and the voltage reference506generates the reference voltage Vref2using the positive terminal voltage of the cell 12 as the reference. However, the embodiment is not limited thereto as long as the reference voltage generated by the voltage reference506is based on a voltage higher than the reference voltage Vref1generated by the voltage reference504. More specifically, the voltage reference506is connected to the positive electrode-side or the negative electrode-side of any one of the cells in the cell group120except the negative electrode-side of the cell 1 of the lowest potential in the cell group120, and can generate, as the reference voltage Vref2, any given voltage using the potential of the positive electrode-side or the negative electrode-side of the cell as the reference.

Sixth Embodiment

FIG. 14is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the sixth embodiment of the present invention. This configuration ofFIG. 14is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the configuration ofFIG. 14includes a voltage dividing circuit514and a switching device513, and the switching circuit501is provided with a terminal A14for connecting the input terminal T1of the differential amplifier circuit502to the ground voltage.

The voltage dividing circuit514is connected between the positive electrode-side of the cell 12 and the negative electrode-side of the cell 1, and outputs the voltage difference, and more specifically, the voltage dividing circuit514outputs the divided voltage according to the voltage of the cell group120constituted by the cells 1 to 12 (cell group voltage). The switching device513selects any one of the divided voltage output from the voltage dividing circuit514and the output voltage from the differential amplifier circuit502, and outputs it to the AD converter503.

FIG. 15is a list table illustrating the connection in the switching circuit501and the connection in the switching device513for selection of the divided voltage according to the cell group voltage when the cell voltages of the cells 1 to 12, the reference voltage Vref1given by the voltage reference504, and the negative terminal voltage of the cell which is the ground voltage are selected in the cell controller IC100according to the sixth embodiment according to the present invention. As shown in the table, the connections of the upper side and the lower side of the switching circuit501are switched, the cell voltages of the cells 1 to 12 and the reference voltage Vref1can be selectively applied to between the input terminal T1and the input terminal T2of the differential amplifier circuit502. Both of the input terminal T1and the input terminal T2can be connected to the ground voltage to be short-circuited. Further, by switching the connection of the switching device513, not only the output voltage from the differential amplifier circuit502but also the divided voltage which is output from the voltage dividing circuit514can be output to the AD converter503.

In the cell controller IC100of the present embodiment, the AD converter503measures the divided voltage given by the voltage dividing circuit514as the abnormality detection voltage for detecting the abnormality in the differential amplifier characteristics of the differential amplifier circuit502. At this occasion, the switching device513selects the terminal D2at the input side which is connected to the terminal D3at the output side. Therefore, the divided voltage from the voltage dividing circuit514is selected, and the divided voltage which is output without passing through the differential amplifier circuit502is output to the AD converter503as the abnormality detection voltage. The measurement information obtained when the abnormality detection voltage is measured by the AD converter503is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

Further, in the cell controller IC100of the present embodiment, similar to what has been explained in the fifth embodiment, the offset error and the gain error are measured. More specifically, the output obtained when the input terminal T1and the input terminal T2are short-circuited to input the ground voltage into the differential amplifier circuit502is output to the AD converter503as the offset error voltage. The voltage obtained when the reference voltage Vref1given by the voltage reference504is converted by the differential amplifier circuit502is output to the AD converter503as the gain error voltage. The measurement information obtained when these voltages are measured is also transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

The battery controller200calculates the cell group voltage on the basis of the measurement information about the abnormality detection voltage transmitted from the cell controller IC100. The cell group voltage and the total summation of the measurement values of the cell voltages are compared, and when the difference is out of a predetermined range, the differential amplifier characteristics of the differential amplifier circuit502in the cell controller IC100is determined to be abnormal. More specifically, the divided voltage from the voltage dividing circuit514is output to the AD converter503as the abnormality detection voltage without passing through the differential amplifier circuit502, so that the cell controller IC100transmits the measurement information not including any error caused by the differential amplifier characteristics of the differential amplifier circuit502. Therefore, the cell group voltage calculated based on the measurement information and the total summation of the measurement values of the cell voltages measured by the differential amplifier circuit502are compared, and a determination can be made as to whether the differential amplifier characteristics of the differential amplifier circuit502is abnormal or not.

Further, the battery controller200measures the offset error and the gain error in accordance with the same method as what has been explained in the fifth embodiment. More specifically, the offset error and the gain error are measured on the basis of the measurement information from the cell controller IC100obtained when the offset error voltage is measured and the measurement information from the cell controller IC100obtained when the gain error voltage is measured.

When all of the offset error and the gain error are within the predetermined error range, and the value of the measurement information when the abnormality detection voltage is measured is out of the predetermined range with respect to the total summation of the measurement values of the cell voltages, the battery controller200determines that the differential amplifier characteristics of the differential amplifier circuit502in the cell controller IC100is abnormal. Therefore, the abnormality of the differential amplifier characteristics caused by the change in the resistance values of the resistors R1to R4of the differential amplifier circuit502can be detected correctly.

On the other hand, when the offset error and the gain error are within the predetermined error range, and the value of the measurement information obtained when the abnormality detection voltage is measured is within the predetermined range, the battery controller200determines that the cell voltage measurement system of the cell controller IC100is normal. When the offset error and the gain error are out of the predetermined error range, it is determined that the offset abnormality or the gain abnormality occurs in at least one of the differential amplifier circuit502and the AD converter503. Therefore, the abnormality of the cell voltage measurement system can be detected in details.

According to the sixth embodiment according to the present invention explained above, not only the same actions and effects as those associated with (8) and (10) explained in the fifth embodiment but also the actions and effects as shown in (11) below can be achieved.

(11) The cell controller IC100includes the voltage dividing circuit514connected between the positive electrode-side of the cell 12 of the highest potential in the cell group120and the negative electrode-side of the cell 1 of the lowest potential therein and configured to output the divided voltage according to the cell group voltage, and the switching device513configured to select anyone of the divided voltage which is output from the voltage dividing circuit514and the output voltage from the differential amplifier circuit502and outputs the selected voltage to the AD converter503. When the switching device513selects the divided voltage, the divided voltage which is output without passing through the differential amplifier circuit502is output to the AD converter503as the abnormality detection voltage. Therefore, the abnormality detection voltage with which it is possible to determine appropriately whether the differential amplifier characteristics of the differential amplifier circuit502is abnormal or not can be output.

Seventh Embodiment

FIG. 16is a view illustrating an example of a configuration of a cell voltage measurement system of a cell controller IC100according to the seventh embodiment of the present invention. The configuration ofFIG. 16is different from the configuration of the conventional cell controller IC100′ as shown inFIG. 2in that the switching circuit501is provided with a terminal A14for connecting the input terminal T1of the differential amplifier circuit502to the ground voltage.

FIG. 17is a list table illustrating connections in the switching circuit501when the cell voltages of the cells 1 to 12, the reference voltage Vref1given by the voltage reference504, the negative terminal voltage of the cell 1, i.e., the ground voltage, and the negative terminal voltage of the cell 12 are selected in the cell controller IC100according to the seventh embodiment of the present invention. As shown in the table, the connections of the upper side and the lower side of the switching circuit501are switched respectively, so that the cell voltages of the cells 1 to 12 and the reference voltage Vref1can be selectively applied to between the input terminal T1and the input terminal T2of the differential amplifier circuit502. In addition, both of the input terminal T1and the input terminal T2can be connected to the ground voltage or the negative electrode terminal of the cell 12 to be short-circuited.

In the cell controller IC100of the present embodiment, both of the input terminals T1and T2of the differential amplifier circuit502are connected to the negative electrode-side of the cell 12 so that the input terminal T1and the input terminal T2are short-circuited. The output voltage from the differential amplifier circuit502at this occasion is measured by the AD converter503as the abnormality detection voltage with which the abnormality of the differential amplifier characteristics of the differential amplifier circuit502is detected. At this occasion, the switching circuit501selects the terminal A2and the terminal B1at the input side which are connected to the terminals C1, C2at the output side. The measurement information obtained when the abnormality detection voltage is measured by the AD converter503is transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

FIG. 18is a figure illustrating an example of a characteristics chart showing a relationship between a voltage detection error and a cell position when there is a change in the resistance values of the resistors R1to R4of the differential amplifier circuit502and the input terminals T1and T2of the differential amplifier circuit502are connected to the negative electrode-side of the same cell to be short-circuited. The characteristics charts indicated by reference symbols801,802indicate the relationships between the voltage detection error and the cell position when the cell voltage of each cell is 4.1 V, and the voltage dividing ratio at the side of the + input terminal of the differential amplifier U1and the voltage dividing ratio at the side of the − input terminal of the differential amplifier U1change from 50% by ±0.2%. More specifically, the characteristics chart801shows the relationship between the voltage detection error and the cell position when the voltage dividing ratio of the + input terminal or the − input terminal of the differential amplifier U1is 49.8%. On the other hand, the characteristics chart802shows the relationship between the voltage detection error and the cell position when the voltage dividing ratio of the + input terminal or the − input terminal of the differential amplifier U1is 50.2%.

InFIG. 18, in each of the characteristics charts801,802, a cell which is connected to an upper side and of which potential is high has a higher voltage detection error. More specifically, it is understood that in a case where the output voltage from the differential amplifier circuit502obtained when both of the input terminals T1and T2are connected to the positive electrode-side or the negative electrode-side of any one of the cells to be short-circuited is output as the abnormality detection voltage, then, the detected error increases when the position of the cell is at an upper side. Therefore, the abnormality of the differential amplifier characteristics of the differential amplifier circuit502can be more easily detected. Therefore, as described above, in the present embodiment, both of the input terminals T1and T2of the differential amplifier circuit502are connected to the negative electrode-side of the most-upstream cell 12, and the output voltage from the differential amplifier circuit502at this occasion is output to the AD converter503as the abnormality detection voltage.

Further, in the cell controller IC100of the present embodiment, similar to what has been explained in the fifth embodiment, the offset error and the gain error are measured. More specifically, the output that occurs when the input terminal T1and the input terminal T2are short-circuited and the ground voltage is input into the differential amplifier circuit502is output to the AD converter503as the offset error voltage. The voltage into which the reference voltage Vref1given by the voltage reference504is converted by the differential amplifier circuit502is output to the AD converter503as the gain error voltage. The measurement information obtained when these voltages are measured is also transmitted from the cell controller IC100to the battery controller200ofFIG. 1.

The battery controller200detects the abnormality of the differential amplifier characteristics of the differential amplifier circuit502on the basis of each measurement information about the abnormality detection voltage, the offset error voltage, and the gain error voltage transmitted from the cell controller IC100. At this occasion, the battery controller200measures the offset error and the gain error in accordance with the same method as that has been explained in the fifth embodiment. More specifically, each of the offset error and the gain error is measured on the basis of the measurement information from the cell controller IC100obtained when the offset error voltage is measured and the measurement information from the cell controller IC100obtained when the gain error voltage is measured.

When both of the offset error and the gain error are within a predetermined error range, and the value of the measurement information obtained when the abnormality detection voltage is measured is out of a predetermined range, then the battery controller200determines that the differential amplifier characteristics of the differential amplifier circuit502is abnormal in the cell controller IC100. Therefore, the abnormality in the differential amplifier characteristics caused by the change in the resistance values of the resistors R1to R4of the differential amplifier circuit502can be correctly detected.

On the other hand, when the offset error and the gain error are within the predetermined error range, and the value of the measurement information obtained when the abnormality detection voltage is measured is within the predetermined range, the battery controller200determines that the cell voltage measurement system of the cell controller IC100is normal. In a case where the offset error and the gain error are out of the predetermined error range, it is determined that the offset abnormality or the gain abnormality occurs in at least one of the differential amplifier circuit502and the AD converter503. Therefore, the abnormality of the cell voltage measurement system can be detected in details.

According to the seventh embodiment of the present invention explained above, not only the same actions and effects as those associated with (8) and (10) explained in the fifth embodiment but also the actions and effects as shown in (12) below can be achieved.

(12) The cell controller IC100causes the switching circuit501to connect both of the input terminals T1and T2to the negative electrode-side of the cell 12, and the output voltage from the differential amplifier circuit502obtained when the input terminal T1and the input terminal T2are short-circuited is output to the AD converter503as the abnormality detection voltage. Therefore, without providing any independent voltage reference such as the voltage reference506explained in the fifth embodiment, the abnormality detection voltage can be output, with which it is possible to determine appropriately whether the differential amplifier characteristics of the differential amplifier circuit502is abnormal or not.

In the seventh embodiment explained above, for example, both of the input terminals T1and T2are connected to the negative electrode-side of the cell 12 to be short-circuited, so that the abnormality detection voltage is output to the AD converter503. However, the position of the cell connected to the input terminals T1and T2is not limited thereto as long as the abnormality voltage detection error according to the change of the resistance value is output as the measurement result of the abnormality detection voltage when the resistance values of the resistors R1to R4of the differential amplifier circuit502change and the differential amplifier characteristics become abnormal. More specifically, both of the input terminals T1and T2are connected to the positive electrode-side or the negative electrode-side of anyone of the cells of the cell group120except the negative electrode-side of the cell 1 of the lowest potential in the cell group120, so that the input terminals T1and T2are short-circuited, and the output voltage from the differential amplifier circuit502at this occasion can be output to the AD converter503as the abnormality detection voltage.

It should be noted that each of the embodiments explained above is an example of embodiments of the present invention. The present invention is not limited to these embodiments. A person skilled in the art can make various modifications without losing the features of the present invention. Therefore, other aspects that can be conceived of within the technical concept of the present invention are also included in the scope of the present invention.