Patent Publication Number: US-9853463-B2

Title: Battery monitoring and control integrated circuit and battery system

Description:
TECHNICAL FIELD 
     The present invention relates to a battery monitoring and control integrated circuit and a battery system including the battery monitoring and control integrated circuit. 
     BACKGROUND ART 
     An assembled battery (battery system) configured by connecting a plurality of secondary single cells in series is used for a hybrid electric vehicle (HEV), an electric vehicle (EV), or the like to secure a desired high voltage. Such an assembled battery uses a control IC which monitors the states of the single cells and controls the states of charge and discharge, and a battery controller which controls the control IC to manage each single cell (see PTL 1). 
     In the battery system of PTL 1, four single cells constitute one battery cell group, and a control IC is connected to each battery cell group. A control IC at the highest level connected to a battery cell group on the highest potential side is activated in response to a start signal from the battery controller, and outputs, to a control IC one level below, the start signal at a voltage in accordance with the potential of a battery cell group corresponding to the control IC one level below. Such an operation is performed sequentially from a control IC at a higher level to a control IC at a lower level to activate all the control ICs. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2005-318750 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     At the activation of the battery system, each control IC but a control IC at the highest level is fed a start signal at a higher voltage than its operating power supply from another control IC at a higher level. Therefore, it is necessary for each control IC to be provided with special circuits for inputting/outputting a start signal, such as a dedicated interface circuit and a protection circuit, to enable a normal operation even if such a start signal is input. 
     Solution to Problem 
     A battery monitoring and control integrated circuit according to a first aspect of the present invention is connected to a cell group having a plurality of series-connected single cells for monitoring and controlling the single cells, and includes: a first start input terminal for connecting to a DC signal generation circuit which generates a DC signal based on an AC start signal input from the outside; a start detection unit which detects the DC signal and activates the battery monitoring and control integrated circuit; and a start output unit which outputs the AC start signal to the outside after the activation of the battery monitoring and control integrated circuit. 
     According to a second aspect of the present invention, it is preferred in the battery monitoring and control integrated circuit of the first aspect that the DC signal generation circuit be a doubler rectifier circuit. 
     According to a third aspect of the present invention, it is more preferred in the battery monitoring and control integrated circuit of the second aspect that the doubler rectifier circuit include a rectifying element built in the battery monitoring and control integrated circuit. 
     According to a fourth aspect of the present invention, the battery monitoring and control integrated circuit of any of the first to third aspects may further include a second start input terminal for inputting a DC start signal input from the outside. It is preferred in the battery monitoring and control integrated circuit that the DC start signal input into the second start input terminal be input into the start detection unit not via the DC signal generation circuit. 
     A battery system according to a fifth aspect of the present invention includes a plurality of cell groups each having a plurality of series-connected single cells; a plurality of battery monitoring and control integrated circuits which is respectively connected to the plurality of cell groups and monitors and controls the single cells of the cell groups; and a battery controller which controls the plurality of battery monitoring and control integrated circuits. It is preferred in the battery system that the plurality of battery monitoring and control integrated circuits be connected to each other via capacitors in a predetermined communication order. Moreover, it is preferred that the plurality of battery monitoring and control integrated circuits each include: a first start input terminal for connecting to a DC signal generation circuit which generates a DC signal based on an AC start signal input from the battery controller or a battery monitoring and control integrated circuit at a higher level in the communication order; a start detection unit which detects the DC signal and activates the battery monitoring and control integrated circuit; and a start output unit which outputs the AC start signal to a battery monitoring and control integrated circuit at a lower level in the communication order or the battery controller after the activation of the battery monitoring and control integrated circuit. 
     According to a sixth aspect of the present invention, it is preferred in the battery system of the fifth aspect that the DC signal generation circuit be a doubler rectifier circuit. 
     According to a seventh aspect of the present invention, it is more preferred in the battery system of the sixth aspect that the doubler rectifier circuit include a rectifying element built in the battery monitoring and control integrated circuit. 
     According to an eighth aspect of the present invention, in the battery system of any of the fifth to seventh aspects, the plurality of battery monitoring and control integrated circuits may each further include a second start input terminal for inputting a DC start signal input from the battery controller. It is preferred in the battery system that the DC start signal input into the second start input terminal be input into the start detection unit not via the DC signal generation circuit. 
     Advantageous Effects of Invention 
     According to the invention, the need of special circuits for inputting/outputting a start signal can be eliminated in a battery monitoring and control integrated circuit which monitors and controls a battery. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a hybrid electric vehicle including a battery system according to the present invention. 
         FIG. 2  is a diagram illustrating an example of communication connection between integrated circuits  300  in a cell controller  200  and a microcomputer  504  in a battery controller  500  according to the present invention. 
         FIG. 3  is a diagram illustrating an example of communication connection between the integrated circuits  300  in the cell controller  200  and the microcomputer  504  in the battery controller  500  according to a conventional example. 
         FIG. 4  is a diagram illustrating an internal configuration example of the integrated circuit  300  according to the present invention. 
         FIG. 5  is a diagram illustrating an internal configuration example of the integrated circuit  300  according to the conventional example. 
         FIG. 6  is a diagram illustrating a detailed example of communication connection between an integrated circuit  300   a  on the lowest potential side, an integrated circuit  300   b  one level above the integrated circuit  300   a  in the potential order, and the microcomputer  504 . 
         FIG. 7  is a diagram illustrating the detailed example of communication connection between an integrated circuit  300   d  on the highest potential side, an integrated circuit  300   c  one level below the integrated circuit  300   d  in the potential order, and the microcomputer  504 . 
         FIG. 8  is a diagram illustrating a part related to a communication path of an AC start signal between the integrated circuits  300   a  and  300   b  in a readily understandable manner. 
         FIG. 9  is an equivalent circuit diagram corresponding to a cell group connected to diodes  216 , a capacitor  403 , a capacitor  406 , and the integrated circuit  300   a.    
         FIG. 10  is a diagram illustrating a voltage waveform example of a rectangular wave signal output from a start output terminal WU_Tx of the integrated circuit  300   a , and a DC voltage applied to a start detection unit  215  of the integrated circuit  300   b.    
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention is hereinafter described with reference to the drawings. The embodiment described below is an example where the present invention is applied to a battery system used for a hybrid electric vehicle (HEV) or the like. The present invention can be widely applied to various battery systems to be mounted on a plug-in hybrid electric vehicle (PHEV), an electric vehicle (EV), a railway vehicle, and the like, not limited to HEV. 
     In the following example, a lithium-ion battery having voltage within a range of 3.0 to 4.2 V (average output voltage: 3.6 V) is assumed to be an electric storage/discharge device as a minimum unit of control. However, the electric storage/discharge device may be, other than the lithium-ion battery, any electricity storable and dischargeable device which controls its use if the SOC (State of Charge) is too high (overcharge) or too low (over-discharge). Here, it is collectively called an electric cell or a single cell. 
     In the embodiment described below, a plurality of (roughly several to a dozen or so) single cells connected in series is called a cell group. A plurality of the cell groups connected in series is called a battery module. Furthermore, a plurality of the cell groups or battery modules connected in series or series-parallel is designated as an assembled battery. Each cell group is provided with an integrated circuit which detects the cell voltage of each single cell, and monitors and controls the battery status while performing a balancing operation and the like. 
     Firstly, a description is given of an example where the battery system according to the present invention is applied to a drive system for a hybrid electric vehicle with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating a configuration example of a hybrid electric vehicle including the battery system according to the present invention. 
     A battery system  100  is connected to an inverter  700  via relays  600  and  610 . The inverter  700  is connected to a motor  800 . At the start or acceleration of the vehicle, the battery system  100  supplies discharge power through the inverter  700  to the motor  800  to assist an unillustrated engine. At the stop or deceleration of the vehicle, the battery system  100  is charged with the regenerated power from the motor  800  through the inverter  700 . The inverter  700  includes an inverter circuit having a plurality of semiconductor switching elements, a gate driving circuit for the semiconductor switching element, and a motor controller which generates a pulse signal to perform PWM control on the gate driving circuit. However, they are omitted in  FIG. 1   
     The battery system  100  is mainly configured by an assembled battery  102  constituted by a plurality of single cells  101  being lithium-ion batteries, a cell controller  200  including a plurality of battery monitoring and control integrated circuits  300  which detects voltages of the single cells  101  on a cell group basis and performs a balancing discharge operation and the like, and a battery controller  500  which controls the operation of the cell controller  200  and determines the states of the single cells  101 . In the example of the battery system  100  illustrated in the embodiment, 96 series-connected lithium-ion batteries with a rated capacity of 5.5 Ah are used as the single cells  101 . The battery controller  500  communicates with the plurality of integrated circuits  300  via an insulating element group  400  and controls the plurality of integrated circuits  300 . The integrated circuit  300  is provided for each cell group as described above. A voltage detection line between the assembled battery  102  and the cell controller  200  is connected by an unillustrated connector to the cell controller  200 . 
     The battery controller  500  includes a total voltage detection circuit  501  which measures the total voltage of the assembled battery  102 , a charge/discharge current detection circuit  502  which is connected to a current sensor  503  for detecting a charge/discharge current flowing through the assembled battery  102 , and a microcomputer  504  which communicates with the cell controller  200 , the inverter  700 , and an unillustrated high-level vehicle controller, and controls the entire battery controller  500 . The total voltage detection circuit  501  does not need to be provided inside the battery controller  500  as in  FIG. 1  as long as the total voltage of the assembled battery  102  can be measured. 
     A total voltage detection circuit  701  which detects the total voltage of the assembled battery  102  is also provided inside the inverter  700 . Moreover, although not illustrated in  FIG. 1 , the battery controller  500  makes a temperature correction of the parameter of the battery status based on the temperature of the single cell  101  measured by a temperature detection circuit connected to the integrated circuit  300 . 
     Although omitted in  FIG. 1 , the cell controller  200  and the battery controller  500  are provided on one board, and housed in a metal case. Moreover, the assembled battery  102  is also housed in a metal case. The cell controller  200  and the assembled battery  102  are connected by a harness in which a plurality of voltage detection lines, a connection line of a temperature sensor (not illustrated) of the single cell  101 , and the like are tied in a bundle. 
     The following operations are performed after the activation of the battery system  100 . The battery controller  500  transmits an instruction to measure the OCV (open circuit voltage) of the single cells  101  to the cell controller  200  via the insulating element group  400 . Data on the OCV of the single cells  101  measured on the instruction is transmitted on a cell group basis from the cell controller  200  to the battery controller  500  via the insulating element group  400 . 
     The battery controller  500  converts the received OCV of the single cells  101  into the SOC, and calculates the deviations of the SOC of the single cells  101 . The single cell  101  having the deviation of the SOC larger than a predetermined value is targeted for balancing discharge. The time required until the deviation of the SOC of the single cell  101  targeted for balancing discharge becomes zero is calculated. An instruction to perform a control operation to turn on a balancing switch in the integrated circuit  300  only during this time is transmitted from the battery controller  500  to the cell controller  200 . The cell controller  200  performs balancing discharge on the balancing-target single cell  101  on the instruction. 
     After the SOC of the assembled battery  102  is calculated from the OCV of the single cells  101  measured above, the inverter  700  or the vehicle controller (not illustrated) being the high-level controller turns on the relays  600  and  610 . The battery system  100  is connected to the inverter  700  and the motor  800 . If the inverter  700  receives a charge/discharge instruction from the vehicle controller, then the inverter  700  operates to drive the motor  800  and the charge/discharge operation of the battery system  100  is performed. 
     After the time when the relays  600  and  610  are turned on and the battery system  100  starts charging/discharging, the battery controller  500  uses the total voltage detection circuit  501  and the charge/discharge current detection circuit  502  to measure the total voltage and the charge/discharge current at every predetermined time interval. The battery controller  500  calculates the state of charge (SOC) and internal resistance (DCR) of the assembled battery  102  in real time from the obtained values of the total voltage and the charge/discharge current. Furthermore, an electric current or electric power with which the assembled battery  102  can be charged or discharged is calculated from these values in real time and transmitted to the inverter  700 . The inverter  700  controls the charge/discharge current or electric power within a range of the current or power. 
       FIG. 2  is a diagram illustrating an example of communication connection between integrated circuits  300   a  to  300   d  in the cell controller  200  and the microcomputer  504  in the battery controller  500  according to the present invention. The integrated circuits  300   a  to  300   d  of  FIG. 2  correspond to the integrated circuits  300  of  FIG. 1 . 
     The microcomputer  504  includes a start signal output port for outputting a start signal to activate the integrated circuits  300   a  to  300   d  in the cell controller  200 , a data transmission port TXD for transmitting a command and data, and an FF signal output port for outputting a data packet (an FF signal) to detect the overcharge state. 
     The example of  FIG. 2  has a configuration in which two battery modules each having two series-connected cell groups each having the plurality of single cells  101  connected in series are arranged, one each above and below a service disconnect switch (SD-SW)  103 . The number of the cell groups configuring the battery module is not limited to two but may be three or more. The integrated circuits  300   a  to  300   d  are provided, corresponding respectively to the cell groups. If simply referred to as the integrated circuit  300  in the following, the integrated circuits  300   a  to  300   d  are not particularly specified. 
     The SD-SW  103  is a switch usually used in a high voltage assembled battery or the like. The SD-SW  103  is opened at the time of a maintenance check to block a current path of the assembled battery  102  and prevent workers from electrical shock. If the SD-SW  103  is opened, the series connection between the battery modules is cut off. Accordingly, even if a person touches the highest and lowest terminals of the assembled battery  102 , his/her body is not subjected to high voltage. Therefore, electrical shock can be prevented. 
     On a communication line of a command and a data signal, a command and a data signal are transmitted from the data transmission port TXD of the microcomputer  504  through a high-speed insulating element  401  to a communication receiving terminal RXD of the integrated circuit  300   a  corresponding to the cell group on the lowest potential side in the assembled battery  102 . On the other hand, on a communication line of a start signal, a start signal is transmitted from the start signal output port of the microcomputer  504  through a low-speed insulating element  402  to a DC start signal input terminal WU_Rx of the integrated circuit  300   a . Moreover, on a communication line of an FF signal, an FF signal is transmitted from the FF signal output port of the microcomputer  504  through the low-speed insulating element  402  to an FF input terminal FFIN of the integrated circuit  300   a.    
     A communication output terminal TXD of the integrated circuit  300   a  corresponding to the cell group on the lowest potential side is connected via the capacitor  403  to a communication receiving terminal RXD of the integrated circuit  300   b  corresponding to the cell group one level above in the potential order. Moreover, an FF output terminal FFOUT and start output terminal WU_Tx of the integrated circuit  300   a  are respectively connected via the capacitors  403  to an FF input terminal FFIN and AC start signal input terminal WU_RxAC of the integrated circuit  300   b.    
     Similarly, a communication output terminal TXD, FF output terminal FFOUT, and start output terminal WU_Tx of the integrated circuit  300   b  are respectively connected via the capacitors  403  to a communication receiving terminal RXD, FF input terminal FFIN, and AC start signal input terminal WU_RxA of the integrated circuit  300   c  corresponding to the cell group one level above in the potential order. Moreover, a communication output terminal TXD, FF output terminal FFOUT, and start output terminal WU_Tx of the integrated circuit  300   c  are respectively connected via the capacitors  403  to a communication receiving terminal RXD, FF input terminal FFIN, and AC start signal input terminal WU_RxAC of the integrated circuit  300   d  corresponding to the cell group one level above in the potential order, in other words, the cell group on the highest potential side. 
     It is necessary to perform communication between the integrated circuit  300   b  connected to the cell group below the SD-SW  103  and the integrated circuit  300   c  connected to the cell group above the SD-SW  103  through isolation. This is because if these communication lines are directly coupled, the battery modules arranged above and below the SD-SW  103  become connected in series through the connection. In this case, even if the SD-SW  103  is detached, the series connection between the battery modules is maintained. Accordingly, the passage of electric current of the assembled battery  102  cannot be blocked. Therefore, if each cell group includes a large number of the single cells  101  and the voltage across each cell group is high, a worker may receive an electrical shock. Hence, in the example of  FIG. 2 , the capacitors  403  are inserted between the integrated circuits  300   b  and  300   c.    
     A communication output terminal TXD of the integrated circuit  300   d  corresponding to the cell group on the highest potential side is connected via the high-speed insulating element  401  to a data receiving port RXD of the microcomputer  504 . Similarly, an FF output terminal FFOUT and start output terminal WU_Tx of the integrated circuit  300   d  are respectively connected via the low-speed insulating elements  402  to an FF signal input port and start signal input port of the microcomputer  504 . 
     The high-speed insulating elements  401  and the low-speed insulating elements  402  used in the communication paths between the microcomputer  504  and the integrated circuits  300   a  and  300   d  are collectively illustrated as the insulating element group  400  in  FIG. 1 . 
     An insulating element such as a photocoupler that can transmit DC signals is used for the low-speed insulating element  402 . The microcomputer  504  outputs a start signal being a DC signal from the start signal output port to the DC start signal input terminal WU_Rx of the integrated circuit  300   a  via the low-speed insulating element  402 . The reason why the start signal is set to be a DC signal is because the influence of noise and a voltage change, which tend to occur at the activation of the battery system  100 , is removed. 
     If the start signal from the microcomputer  504  is input into the DC start signal input terminal WU_Rx, the integrated circuit  300   a  is activated in response to this, and a start signal to activate the next integrated circuit  300   b  is output. At this point in time, the integrated circuit  300   a  outputs an AC start signal from its start output terminal WU_Tx via the capacitor  403  to the AC start signal input terminal WU_RxAC of the integrated circuit  300   b . For example, a rectangular wave signal is output as the start signal. 
     If the start signal from the integrated circuit  300   a  is input into the AC start signal input terminal WU_RxAC, the integrated circuit  300   b  is activated in response to the start signal, and a start signal to activate the next integrated circuit  300   c  is output as in the case of the integrated circuit  300   a . In other words, the integrated circuit  300   b  outputs the start signal being an AC signal from its start output terminal WU_Tx via the capacitor  403  to the AC start signal input terminal WU_RxAC of the integrated circuit  300   c . A similar operation is performed also in the integrated circuit  300   c  afterward. 
     If the start signal from the integrated circuit  300   c  is input into the AC start signal input terminal WU_RxAC, and the integrated circuit  300   d  is activated, a start signal is output from the start output terminal WU_Tx of the integrated circuit  300   d  to the start signal input port of the microcomputer  504 . If receiving the start signal, then the microcomputer  504  can confirm the activation of the integrated circuits  300   a  to  300   d  and recognize that the cell controller  200  has been activated. 
     After the activation of the cell controller  200 , the microcomputer  504  transmits a command signal and data (a data packet) to the receiving terminal RXD of the integrated circuit  300   a  through the high-speed insulating element  401 . The integrated circuit  300   a  receives the command signal and the data packet, and further transmits them from its output terminal TXD to the next integrated circuit  300   b . In this manner, all the integrated circuits  300   a  to  300   d  receive the command signal and the data to perform an operation in accordance with the command signal and the data. In order to obtain data such as the voltage across each single cell  101  (referred to as the cell voltage) of the cell groups controlled respectively by the integrated circuits  300   a  to  300   d , each of the integrated circuits  300   a  to  300   d  adds data to the data packet and transmits the data packet from its transmission terminal TXD to the RXD terminal of the next integrated circuit. The data packet is received by the data receiving port RXD of the microcomputer  504  in the end. The microcomputer  504  receives the data packet containing the command signal that the microcomputer  504  itself transmitted. Accordingly, the microcomputer  504  confirms that the command signal has been transferred normally and, if there is data added by the integrated circuits  300   a  to  300   d , receives the data. 
     The loop of an FF signal passing through the FF input terminals FFIN and FF output terminals FFOUT of the integrated circuits  300   a  to  300   d  is a communication channel for detecting the overcharge or over-discharge state of the single cell  101 . This is for detecting overcharge in a different system from the communication line passing through the TXD terminal and the RXD terminal to improve the reliability of detection of overcharge which is important to ensure the security of the single cell  101  using a lithium-ion battery. The FF signal is assumed to be a rectangular wave signal with a fixed cycle, and has, for example, a rectangular wave of 1 kHz in the normal state, and a rectangular wave of 2 kHz in the overcharge state. 
     If a rectangular wave of 1 kHz is input into the FF input terminal FFIN, the integrated circuit  300  recognizes that the integrated circuit  300  at a higher level in the communication order is in the normal state (not overcharged), and outputs a rectangular wave of 1 kHz to the FF output terminal FFOUT. On the other hand, if the cell voltage detection value of the integrated circuit  300  is detected to be an overcharge voltage, the integrated circuit  300  outputs a rectangular wave of 2 kHz to the FF output terminal FFOUT whether the frequency of the input signal of the FF input terminal FFIN is 1 kHz or 2 kHZ, and outputs the overcharge state to the next integrated circuit  300 . Moreover, it is configured to not output a rectangular wave from the FF output terminal FFOUT if the frequency of the input signal of the FFIN terminal is a signal other than 1 kHz or 2 kHz. 
     Even if a certain integrated circuit  300  does not detect the overcharge voltage of the single cell  101  of the cell group controlled by the integrated circuit  300 , when another integrated circuit  300  inputs a rectangular wave of 2 kHz into the FF input terminal FFIN, the relevant integrated circuit  300  outputs a rectangular wave of 2 kHz to the FF output terminal FFOUT. In this manner, the FF signal loop outputs that any of the integrated circuits  300  has detected overcharge. Consequently, the microcomputer  504  can detect overcharge from a different path from the high-speed communication signal loop. 
     The microcomputer  504  is configured to normally output a 1 kHz rectangular wave indicating the normal state as the FF signal to the integrated circuit  300   a  on the lowest potential side, putting the integrated circuit  300   a  at the highest level in the communication order. On the other hand, a 2 kHz rectangular wave indicating overcharge is required to be output when the operation of the FF loop is checked. In other words, even if all the integrated circuits  300   a  to  300   d  do not detect an overcharge voltage, as long as the rectangular wave of the returned FF signal is 2 kHz, the microcomputer  504  can confirm that the FF loop is in normal operation. Moreover, if a trouble occurs in the FF loop, for example, if a wire has been broken, a rectangular wave is not transmitted. Accordingly, the state can be identified. 
     The battery system according to the present invention described in the embodiment has features in the communication lines of start signals in the integrated circuits  300   a  to  300   d  in the cell controller  200 .  FIG. 3  is a diagram illustrating an example of communication connection between the integrated circuits  300   a  to  300   d  in the cell controller  200  and the microcomputer  504  in the battery controller  500  according to a conventional example, as a comparative example for describing the features of the battery system of the present invention. 
     Comparing  FIGS. 2 and 3 , a difference is in that the communication lines of start signals between the integrated circuits  300   a  to  300   d  are respectively connected via the capacitors  403  in  FIG. 2  while being coupled via the low-speed insulating element  402  or directly coupled in  FIG. 3 . In other words, such a conventional example as illustrated in  FIG. 3  is required to have such a connection form in order to input/output start signals being DC signals between the integrated circuits  300   a  to  300   d.    
     The internal configuration of the integrated circuit  300  is described.  FIG. 4  is a diagram illustrating an internal configuration example of the integrated circuit  300  according to the present invention. In  FIG. 4 , it is configured that 12 single cells  101  (referred to as the cells  1  to  12 ) constitute one cell group. 
     A cell group and the integrated circuit  300  that controls the cell group are connected to CV terminals (terminals CV 01  to CV 12  and CV 12 N) for voltage detection and BS terminals (terminals BS 01 H to BS 12 H and terminals BS 01 L to BS 12 L) for performing a balancing operation via voltage detection lines L 1 P to L 12 P and L 12 N for detecting the voltages of the cells  1  to  12 . Both ends, that is, the positive and negative electrode terminals of each of the cells  1  to  12  are respectively connected to the CV terminals via cell input resistors Rcv. A cell input capacitor Cin is connected between each CV terminal and a GND terminal. 
     Moreover, both ends of each of the cells  1  to  12  are respectively connected to the BS terminals through balancing resistors Rb. In the integrated circuit  300 , balancing switches BSW for passing balancing current are respectively connected between the terminals BS 01 H to BS 12 H and the terminals BS 01 L to BS 12 L. If the balancing switch BSW corresponding to any of the cells is turned on, the balancing current of the cell flows via the balancing resistors Rb. Balancing terminal capacitors Cb are respectively connected between the BS terminals. 
     The CV terminals are connected to a multiplexer  210  in the integrated circuit  300 . The multiplexer  210  is for selecting an arbitrary cell and outputting its positive and negative potentials, and is controlled in accordance with an output from a logic unit  213 . A differential amplifier  211  converts the outputs of the multiplexer  210  into each of the voltages across the cells  1  to  12 . An AD converter  212  then converts each voltage into a digital value. The operation of the AD converter  212  is controlled by the logic unit  213 . The output of the AD converter  212  is processed in the logic unit  213 . In other words, the differential amplifier  211  and the AD converter  212  measure voltage. 
     A multiplexer input short circuit switch MSW is provided between two voltage input lines adjacent to each other, in other words, voltage detection lines connected to a positive and a negative electrode of each cell among voltage input lines connected to the multiplexer  210 . 
     Auxiliary input terminals AUXIN and AGND are provided to the integrated circuit  300 . These auxiliary input terminals AUXIN and AGND are connected to a thermistor  207 , a thermistor dividing resistor Rthp, a thermistor input resistor Rth, and a thermistor input capacitor Cth. 
     The resistance value of the thermistor  207  varies significantly with the temperature of its installed location. The thermistor  207  and the thermistor dividing resistor Rthp in series divide the VDD voltage. The voltage across the thermistor  207  is input from the auxiliary input terminals AUXIN and AGND into the integrated circuit  300 . The thermistor input resistor Rth and the thermistor input capacitor Cth act as an RC filter that removes the noise of the input signal. In other words, the noise of the voltage across the thermistor  207 , the voltage changing depending on temperature, is removed by the RC filter and the voltage is input into the integrated circuit  300 . 
     If the voltage across the thermistor  207  input into the integrated circuit  300  is selected by the multiplexer  210 , the voltage value is digitized via the differential amplifier  211  and the AD converter  212 . The digitized value of the voltage across the thermistor  207  is input into the logic unit  213 . 
     The logic unit  213  transmits the digitized voltage across the thermistor  207  as a data signal from the communication output terminal TXD via a communication output unit  220 . The data signal is transmitted to the battery controller  500  via the above-mentioned communication line and accordingly the digitized voltage across the thermistor  207  is transmitted. The battery controller  500  calculates the temperature of the location where the thermistor  207  is installed based on the voltage across the thermistor  207 . The temperature can be calculated using a relational expression between the voltage across the thermistor  207  and temperature preset based on the resistance-temperature characteristic of the thermistor  207 , or tabulated data of the relationship between the voltage across the thermistor  207  and temperature. 
     A balancing switch state detection circuit  223  detects the presence or absence of balancing current and diagnoses the balancing switch BSW. These results are output to the logic unit  213  and stored in a register in the logic unit  213 . 
     The logic unit  213  includes the register which stores data for controlling various switches provided to the integrated circuit  300 . For example, data for selecting the input of the multiplexer  210 , data for controlling the multiplexer input short circuit switch MSW, data for controlling the balancing switch BSW, and data for controlling a switch circuit of the balancing switch state detection circuit  223  are stored in the register. A clock signal from an oscillation circuit  214  is input into the logic unit  213 . The clock signal is used to operate the logic unit  213 . 
     An operating power supply Vcc of the integrated circuit  300  is supplied from a Vcc terminal connected to the voltage detection line L 1 P. A capacitor Cvcc for suppressing noise is connected to the Vcc terminal. The voltage detection line L 1 P is connected to the positive electrode side of the cell  1 . The voltage at the positive electrode of the cell  1  is supplied as the operating power supply Vcc to the integrated circuit  300 . 
     The Vcc terminal is further connected to a power supply unit  226  in the integrated circuit  300 . The power supply unit  226  includes a regulator  227 . The regulator  227  uses the operating power supply Vcc supplied from the Vcc terminal to generate an operating power supply VDD of 3.3 V and supply it to the logic unit  213  and the like. The operating power supply VDD is also supplied to a circuit outside the integrated circuit  300  via a VDD terminal of the integrated circuit  300 . A capacitor Cvdd for stabilizing operation is connected to the VDD terminal. 
     The power supply unit  226  includes also a starting circuit  228  which operates in response to a start detection signal from the start detection unit  215 . If an AC start signal from the integrated circuit  300  at a lower level in the communication order is input into the AC start signal input terminal WU_RxAC, or if a DC start signal from the microcomputer  504  is input into the DC start signal input terminal WU_Rx, the start detection unit  215  detects the signal and outputs a start detection signal into the power supply unit  226 . If the start detection signal is input from the start detection unit  215 , the starting circuit  228  outputs the operating power supply Vcc to the regulator  227  and also activates the integrated circuit  300  to perform a POR (power-on reset) operation. Diodes  216  being rectifying elements for doubling and rectifying the voltage of the AC start signal and outputting the start detection signal to the start detection unit  215  are connected to the AC start signal input terminal WU_RxAC in the integrated circuit  300 . 
     If the integrated circuit  300  is activated, a start output unit  219  operates with the output from the logic unit  213 . The start output unit  219  outputs an AC (rectangular wave) start signal from the start output terminal WU_Tx to the integrated circuit  300  at a higher level in the communication order or the microcomputer  504 . 
     The start detection unit  215  is connected to the Vcc terminal. Consequently, even while the operation of the entire integrated circuit  300  is being suspended, the operating power supply Vcc is supplied to the start detection unit  215 . The start detection unit  215  has such a circuit configuration as to reduce the current consumed as much as possible. 
     The communication output unit  220  outputs a command signal and data from the communication output terminal TXD to the integrated circuit  300  at a higher level in the communication order or the microcomputer  504  based on the output data from the logic unit  213 . If the command signal and data are input into the receiving terminal RXD from the integrated circuit  300  at a lower level in the communication order or the microcomputer  504 , a communication receiving unit  217  receives the command signal and data to output them to the logic unit  213 . 
     An FF output unit  221  outputs such an FF signal as described above from the FF output terminal FFOUT to the integrated circuit  300  at a higher level in the communication order or the microcomputer  504  based on the output data from the logic unit  213 . If the FF signal is input into the FF input terminal FFIN from the integrated circuit  300  at a lower level in the communication order or the microcomputer  504 , the FF input unit  218  receives the FF signal, determines which of the normal state and the overcharge state the FF signal represents, and outputs the determination result to the logic unit  213 . 
     The internal configuration of the integrated circuit  300  according to the conventional example is described as a comparative example.  FIG. 5  is a diagram illustrating an internal configuration example of the conventional integrated circuit  300  used to input/output a start signal being a DC signal in the connection example illustrated in  FIG. 3 . 
     Comparing  FIGS. 4 and 5 , the integrated circuit  300  of  FIG. 5  is provided with terminals CP+ and CP− connected to a charge pump unit  238  and a charge pump capacitor Ccp. The charge pump unit  238  in the integrated circuit  300  generates charge pump voltage using the operating power supply Vcc in cooperation with the charge pump capacitor Ccp connected to the outside of the integrated circuit  300 , and supplies the charge pump voltage to the start output unit  219 . In the conventional example, such a circuit is required to output a start signal at a higher voltage than the operating power supply Vcc in accordance with the potential of the cell group corresponding to the integrated circuit  300  of an output destination. 
     Moreover, the integrated circuit  300  of  FIG. 5  does not include the AC start signal input terminal WU_Rx of  FIG. 4  for receiving an AC start signal, and the diodes  216 . 
       FIG. 5  illustrates the internal configuration example of the integrated circuit  300  of the case of the connection example illustrated in  FIG. 3 , in other words, the case where DC start signals are input/output sequentially from the lowest potential side in the communication order opposite to the potential order of the assembled battery  102 . However, contrary to this, DC start signals may be input/output sequentially from the highest potential side in the same communication order as the potential order of the assembled battery  102 . In this case, a start signal at a higher voltage than the operating power supply Vcc is input into the start detection unit  215  in accordance with the potential of the cell group corresponding to the integrated circuit  300  which has output the start signal. Hence, the need of the charge pump unit  238  and the charge pump capacitor Ccp is eliminated. However, it is necessary to provide an interface circuit, a protection circuit, and the like instead to enable the start detection unit  215  to operate normally even if a high voltage start signal is input. 
     A description is given in detail of the input/output of start signals between the integrated circuits  300   a  to  300   d  and the microcomputer  504  of  FIG. 2 .  FIG. 6  is a diagram illustrating a detailed example of communication connection between the integrated circuit  300   a  on the lowest potential side, the integrated circuit  300   b  one level above the integrated circuit  300   a  in the potential order, and the microcomputer  504  in  FIG. 3 . Moreover,  FIG. 7  is a diagram illustrating the detailed example of communication connection between the integrated circuit  300   d  on the highest potential side, the integrated circuit  300   c  one level below the integrated circuit  300   d  in the potential order, and the microcomputer  504  in  FIG. 3 . 
     In  FIG. 6 , the integrated circuit  300   a  on the lowest potential side is at the highest level in the communication order. In the integrated circuit  300   a , the DC start signal input terminal WU_Rx is used to input a DC start signal output from the microcomputer  504 . A photocoupler is connected as the low-speed insulating element  402  to this terminal. The microcomputer  504  passes current through a diode of the photocoupler via a drive transistor  404 , which turns on a transistor side insulated from the diode in the photocoupler. The transistor is connected on its collector side to Vcc of the integrated circuit  300   a  via a resistor, and connected on its emitter side to a ground via a resistor. When the transistor side of the photocoupler is turned on, a voltage obtained by dividing Vcc by the resistor is applied to the DC start signal input terminal WU_Rx of the integrated circuit  300   a . The start detection unit  215  is a comparator including a preset threshold value, and outputs a start detection signal to the power supply unit  226  (see  FIG. 4 ) if detecting a voltage equal to or more than the threshold value. Consequently, the integrated circuit  300   a  is activated. 
     If the integrated circuit  300   a  is activated as described above, the start output unit  219  of the integrated circuit  300   a  outputs an AC start signal from the start output terminal WU_Tx at the instruction of the logic unit  213 . It is assumed here that a rectangular wave signal is output as the AC start signal. The signal is applied through the capacitor  403  to the AC start signal input terminal WU_RxAC of the integrated circuit  300   b  that is one level above in the potential order and one level below in the communication order. 
     In the integrated circuit  300   b , the AC start signal input terminal WU_RxAC is connected to the diodes  216  connected between the ground and the DC start signal input terminal WU_Rx. The diodes  216  and the capacitor  406  connected between the DC start signal input terminal WU_Rx and the ground are part of the components of the doubler rectifier circuit. If being input into the AC start signal input terminal WU_RxAC in the integrated circuit  300   b , the rectangular wave signal as the AC start signal output from the integrated circuit  300   a  is rectified by the doubler rectifier circuit and converted into DC voltage. The DC voltage is input into the start detection unit  215  and accordingly a start detection signal is output from the start detection unit  215  to activate the integrated circuit  300   b.    
     The diodes  216  are connected between the ground and the DC start signal input terminal WU_Rx also in the integrated circuit  300   a , and are connected to the AC start signal input terminal WU_RxAC. However, the DC start signal from the microcomputer  504  input into the DC start signal input terminal WU_Rx of the integrated circuit  300   a  is input into the start detection unit  215  not via the diodes  216 . Hence, the DC start signal can be detected by the start detection unit  215 . 
       FIG. 8  illustrates apart related to the communication path of an AC start signal between the integrated circuits  300   a  and  300   b  in a readily understandable manner. Within the part,  FIG. 9  is an equivalent circuit diagram corresponding to the cell group connected to the diodes  216 , the capacitor  403  connected between the start output terminal WU_Tx of the integrated circuit  300   a  and the AC start signal input terminal WU_RxAC of the integrated circuit  300   b , the capacitor  406 , and the integrated circuit  300   a . The circuit illustrated in  FIG. 9  is a general doubler rectifier circuit. If a rectangular wave signal with an amplitude VDD is output from the start output terminal WU_Tx of the integrated circuit  300   a , a fixed DC voltage Vw is applied by the doubler rectifier circuit to the start detection unit  215  of the integrated circuit  300   b.    
       FIG. 10  illustrates a voltage waveform example of a rectangular wave signal with the amplitude VDD output from the start output terminal WU_Tx of the integrated circuit  300   a , and the DC voltage Vw applied to the start detection unit  215  of the integrated circuit  300   b . In  FIG. 10 , the left vertical axis represents the voltage values of a rectangular wave signal, and the right vertical axis represents the voltage values of DC voltage. As illustrated in the example, if a rectangular wave signal at a frequency of 32 kHz and an amplitude of 3.3 Vp-p is output as the AC start signal from the integrated circuit  300   a , a DC voltage of approximately 2.5 V is applied to the start detection unit  215  of the integrated circuit  300   b . The DC voltage rises up to a voltage equal to or more than approximately 90% in approximately 0.1 ms after the start of the output of the rectangular wave. Consequently, it can be seen that the starting time from the output of the AC start signal by the integrated circuit  300   a  to the activation of the integrated circuit  300   b  is sufficiently short. The capacity of the capacitor  406  is set to 0.01 μF. 
     Return to the description of  FIG. 6 . In the integrated circuit  300   a  of  FIG. 6 , a digital isolator using, for example, a small transformer for communication as the high-speed insulating element  401  is connected to the communication receiving terminal RXD connected to the communication receiving unit  217 . A command and communication data which are transmitted from the microcomputer  504  are input into the communication receiving unit  217  from the communication receiving terminal RXD of the integrated circuit  300   a  through the digital isolator. The VDD terminal of the integrated circuit  300   a  supplies the operating power supply VDD to the digital isolator. The operating power supply VDD is not output during the suspension of the operation of the integrated circuit  300   a . Therefore, dark current does not flow through the digital isolator at this point in time. 
     Moreover, a photocoupler is connected as the low-speed insulating element  402  to the FF input terminal FFIN connected to the FF input unit  218  of the integrated circuit  300   a  as in the case of the DC start signal input terminal WU_Rx. The microcomputer  504  passes current through a diode of the photocoupler via a drive transistor  405 . Accordingly, a transistor side insulated from the diode in the photodiode is turned on to transmit an FF signal. 
     In  FIG. 7 , the integrated circuit  300   d  on the highest potential side is at the lowest level in the communication order. The AC start signal of a rectangular wave output by the start output unit  219  of the integrated circuit  300   d  from the start output terminal WU_Tx is input into the start signal input port of the microcomputer  504  via a drive transistor  409  and a photocoupler being the low-speed insulating element  402 . If receiving the AC start signal output from the integrated circuit  300   d , then the microcomputer  504  can confirm that all the integrated circuits  300   a  to  300   d  have been activated. 
     Moreover, the command and communication data output by the communication output unit  220  of the integrated circuit  300   d  from the communication output terminal TXD are input into the data receiving port RXD of the microcomputer  504  via a digital isolator being the high-speed insulating element  401 . The VDD terminal of the integrated circuit  300   d  supplies the operating power supply VDD to the digital isolator. Furthermore, the FF signal output by the FF output unit  221  of the integrated circuit  300   d  from the FF output terminal FFOUT is input into the FF signal input port of the microcomputer  504  via a drive transistor  410  and a photocoupler being the low-speed insulating element  402 . The microcomputer  504  may confirm that all the integrated circuits  300   a  to  300   d  have been activated by receiving them from the integrated circuit  300   d.    
     The embodiment described above has the following operations and effects. 
     (1) The battery monitoring and control integrated circuit  300  is configured by the diodes  216 , the capacitor  403 , and the capacitor  406 , and includes the AC start signal input terminal WU_RxAC for connecting to the doubler rectifier circuit which generates a DC signal based on an AC start signal input from the integrated circuit  300  at a higher level in the communication order connected via the capacitor  403 , the start detection unit  215  which detects the DC signal and activates the relevant integrated circuit  300 , and the start output unit  219  which outputs the AC start signal to the integrated circuit  300  at a lower level in the communication order or the microcomputer  504  of the battery controller  500  after the activation of the relevant integrated circuit  300 . Consequently, compared with the conventional case using a DC start signal, it is not necessary for the integrated circuit  300  to include a charge pump circuit for outputting a start signal at a higher voltage than the operating power supply Vcc, and an interface circuit, a protection circuit, and the like for enabling the start detection unit  215  to operate normally even if a high voltage start signal is input. Therefore, the need of special circuits to input/output a start signal can be eliminated. 
     (2) The doubler rectifier circuit includes the diodes  216  built in the integrated circuit  300 . Hence, the doubler rectifier circuit can easily be configured by connecting capacitors with an appropriate capacity as the capacitors  403  and  406  outside the integrated circuit  300 . 
     (3) The integrated circuit  300  further includes the DC start signal input terminal WU_Rx for inputting a DC start signal input from the microcomputer  504 . The DC start signal input into the DC start signal input terminal WU_Rx is input into the start detection unit  215  not via the doubler rectifier circuit. Hence, the DC start signal can be detected in the start detection unit  215  in a similar detection method to that of the AC start signal input via the doubler rectifier circuit. 
     An example of the embodiment of the present invention has been described above. However, the present invention is not limited to this. Those skilled in the art can make various modifications without impairing the features of the present invention. 
     For example, in the embodiment, a start signal, a command and communication data, and an FF signal are transmitted between the integrated circuits  300  in the communication order opposite to the potential order of the assembled battery  102 . However, the communication order may be reversed. In other words, a start signal, a command and communication data, and an FF signal can be transmitted between the integrated circuits  300  also in the same communication order as the potential order of the assembled battery  102 . In the present invention, all of these signals are transmitted between the integrated circuits  300  via the capacitors  403 . Accordingly, the relationship between the potential order and the communication order is not particularly limited. 
     Moreover, the communication signal and FF signal, which are described in the embodiment, may be differential signals to make resistant to noise. Furthermore, an AC start signal of a rectangular wave or the like may be output from the battery controller  500 , and input into the AC start signal input terminal WU_RxAC of the integrated circuit  300  at the highest level in the communication order. Alternatively, a start signal and communication signal or FF signal from the battery controller  500  may be shared. Communication signals and FF signals are transmitted from the battery controller  500  all the time during the operation of the battery controller  500 . Hence, it is possible to generate a DC signal from these signals and use the DC signal as a start signal in the integrated circuit  300 . 
     Various modifications described above may be applied individually or may be freely combined to be applied. 
     The scope of the present invention is not limited to a battery system having the configuration described in the embodiment. The present invention can be applied to battery systems having various configurations, and to electrically driven vehicles having various specifications.