Cell monitoring unit and cell monitoring method

Abstract

A cell monitoring unit (100) is a cell monitoring unit for monitoring a battery cell (11), the cell monitoring unit comprising: a battery monitoring unit (110) for measuring the state of the battery cell (11); a power supply circuit (111); a second power supply circuit (120) for supplying lower power than the power supply circuit (111); and a radio communication unit (140) including a communication unit (146) for performing radio communication with an upper level system, a time setting circuit (147) for setting the start time and the stop time of the cell monitoring unit (100), and a time measurement unit (148) for measuring an elapsed time from the stop time. The power supply circuit (111) starts at the start time, supplies power to the battery monitoring unit (110) and the communication unit (146), and stops at the stop time, and the second power supply circuit (120) supplies power to the time measurement unit (148) during a period from the stop time to the subsequent start time.

Description

Cell monitoring unit and cell monitoring method

[0001] The present disclosure relates to a cell monitoring unit and a cell monitoring method, and more particularly to a cell monitoring unit and a cell monitoring method used in a battery management system (hereinafter referred to as BMS) that monitors and controls batteries used in electric vehicles and the like.

[0002] Patent Document 1 discloses a battery management system in which a wireless communication unit is disposed in a battery management unit within the battery management system.

[0003] U.S. Pat. No. 1,125,1630

[0004] In some cases, the power required for operation of a cell monitoring unit equipped with a wireless communication unit is supplied from the battery of the monitored device. In such cases, it is desirable to reduce the power consumption of the cell monitoring unit.

[0005] Therefore, the present disclosure provides a cell monitoring unit and a cell monitoring method that can effectively reduce power consumption.

[0006] A cell monitoring unit according to one embodiment of the present disclosure is a cell monitoring unit that monitors battery cells and includes a battery monitoring unit that measures the state of the battery cells, a first power supply circuit, a second power supply circuit that supplies less power than the first power supply circuit, a communication unit for wireless communication with a higher-level system, a first time setting circuit that sets the start time and stop time of the cell monitoring unit, and a first wireless communication unit that has a time measurement unit that measures the elapsed time from the stop time, wherein the first power supply circuit starts up at the start time and supplies power to the battery monitoring unit and the communication unit and stops at the stop time, and the second power supply circuit supplies power to the time measurement unit from the stop time until the next start time.

[0007] A cell monitoring method according to one aspect of the present disclosure is a monitoring method performed by a cell monitoring unit that monitors battery cells, the cell monitoring unit comprising a battery monitoring unit that measures the state of the battery cells, a first power supply circuit, a second power supply circuit that supplies less power than the first power supply circuit, a communication unit for wireless communication with a higher-level system, a time setting circuit that sets the start time and stop time of the cell monitoring unit, and a wireless communication unit having a time measurement unit that measures the elapsed time from the stop time, and the monitoring method includes starting the first power supply circuit at the start time and supplying power to the battery monitoring unit and the communication unit, and stopping the first power supply circuit at the stop time and supplying power from the second power supply circuit to the time measurement unit from the stop time until the next start time.

[0008] According to one aspect of the present disclosure, it is possible to realize a cell monitoring unit or the like that can effectively reduce power consumption.

[0009] Fig. 1 is a diagram showing the configuration of a battery management system according to an embodiment. Fig. 2 is a diagram for explaining power consumption of a power supply circuit according to an embodiment. Fig. 3 is a flowchart showing a first operation of a cell monitoring unit according to an embodiment. Fig. 4 is a flowchart showing a second operation of a cell monitoring unit according to an embodiment.

[0010] (Background to the Invention of the Present Disclosure) Before describing the present disclosure, the background to the invention of the present disclosure will be described.

[0011] The present disclosure relates to a BMS called a wireless Battery Management System (BMS) that connects a cell monitoring unit connected to a battery cell with a higher-level system via wireless communication. The cell monitoring unit is called various names such as a Cell Monitoring (Measurement) Unit (CMU) or a Cell Supervisor (Supervision) Circuit (CSC), but in this specification it will be referred to as a cell monitoring unit or a CMU.

[0012] While BMS cell monitoring units have typically been connected to higher-level systems via wired communication, the application of wireless BMS, which connects wirelessly, is being considered to reduce the weight and space required for wired communication wire harnesses, reduce the number of wire harness connection processes, and facilitate battery reuse.

[0013] Wired communication is typically insulated communication known as Daisy (daisy chain) communication, which can reduce the standby power consumption of a communication circuit to very low or almost zero when waiting to receive communication from a higher-level system.

[0014] On the other hand, in wireless communication, the power consumption in the receivable state is very large, making it difficult to maintain a constant receivable state. Therefore, it is common to reduce average standby power consumption by using intermittent operation that repeats pauses and receivable states within a range that satisfies the required response time.

[0015] However, the cell monitoring unit of a BMS installed in an electric vehicle or the like must be connected to the battery pack from the time the battery is assembled and must be in a receivable state so that it can respond to startup commands sent via wireless communication from a higher-level system. Also, since the cell monitoring unit of a BMS installed in an electric vehicle or the like must obtain power from the battery pack it monitors, it is desirable to reduce standby power consumption to prevent the battery pack from over-discharging during long-term storage or transportation.

[0016] In contrast, the power supply for the wireless communication unit of the cell monitoring unit is preferably designed with transistors with good high-frequency characteristics, and therefore often requires a power supply of 2.5V to 3.3V. Therefore, it is necessary to supply power to the wireless communication unit from a power supply that is stepped down from the battery pack to which the cell monitoring unit is connected. In this case, if standby power is supplied from a specific battery cell in a battery pack consisting of serially connected lithium-ion batteries, only that battery cell will consume power, resulting in an imbalance in the battery pack. Therefore, the cell monitoring unit including the wireless communication unit must be supplied with power from the lowest potential of the negative electrode of the battery pack to which the cell monitoring unit is connected and the highest potential of the positive electrode of the battery pack. For example, in a battery pack consisting of 20 serially connected 3.7V lithium-ion batteries, the voltage must be stepped down from 3.7V x 20 = 74V to 2.5V to supply power to the wireless communication unit.

[0017] Furthermore, cell monitoring units installed in electric vehicles are required to comply with ASIL-D or ASIL-C, which are the high functional safety requirements specified in ISO 26262, so detecting faults in the power supply circuit and fail-operation when detected are extremely important.

[0018] The wireless communication unit is generally composed of a microcontroller called an MCU (Micro Control Unit) and a wireless communication circuit called a PHY, which is a circuit or device component for implementing the functions of the physical layer in the OSI reference model.

[0019] Even short-range wireless communication such as Bluetooth Low Energy (BLE), which consumes relatively little power, requires a current consumption of approximately 10 mA during reception and approximately 20 mA during transmission. In such short-range wireless communication, if a device is to be able to respond to wireless communication from a higher-level system at all times, it is necessary to keep the device in a reception standby state.

[0020] Therefore, a study is being conducted to reduce the average power consumption in the reception standby state by intermittently switching between a standby state in which a low-speed (e.g., 32 kHz) crystal oscillator and RTC (Real Time Clock) in the wireless communication unit operate to measure the time until the next startup state and a reception-enabled state, with a current consumption of around 10 μA. The standby state is a non-reception-enabled state in which radio waves from a higher-level system cannot be received.

[0021] However, conventionally, the cell monitoring unit has one power supply circuit, so power is supplied to the wireless communication unit from a common power supply circuit both in the standby state and in the reception-enabled state. Therefore, even if the current consumption of the wireless communication unit (i.e., the load) can be reduced, it is difficult to reduce the current consumption of the power supply circuit (see Figure 2 described below).

[0022] Therefore, it has been difficult to keep the average power consumption of a cell monitoring unit including a wireless communication unit in a reception standby state low.

[0023] Therefore, the inventors of the present application have conducted extensive research into reducing the power consumption of a cell monitoring unit including a wireless communication unit, and have devised the cell monitoring unit and cell monitoring method described below.

[0024] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0025] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement positions, connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not described in independent claims are described as optional components.

[0026] Furthermore, in this specification, numerical values ​​and numerical ranges are not expressions that express only the strict meaning, but are expressions that mean that they also include a substantially equivalent range, for example, a difference of about several percent (or about 10%).

[0027] Furthermore, in this specification, ordinal numbers such as "first" and "second" do not refer to the number or order of components unless otherwise specified, but are used for the purpose of avoiding confusion and distinguishing between components of the same type.

[0028] Furthermore, the "connection" of each component means an electrical connection, and includes not only a case where two components are directly connected, but also a case where two components are indirectly connected with another component inserted between them.

[0029] (Embodiment) Hereinafter, a battery management system according to the present embodiment will be described with reference to Figs.

[0030] [1. Configuration of Battery Management System] First, the configuration of a battery management system equipped with cell monitoring units will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing the configuration of a battery management system 1 (hereinafter also referred to as BMS 1) according to this embodiment.

[0031] 1 , the BMS 1 includes an assembled battery 10 configured with a plurality of battery cells 11, a cell monitoring unit 100 (hereinafter also referred to as a CMU 100), and a battery control unit 200 (hereinafter also referred to as a BMU (Battery Management Unit) 200). The CMU 100 and the BMU 200 are configured to be able to communicate with each other, and perform BLE communication using, for example, BLE.

[0032] The battery pack 10 is configured by connecting battery cells 11, which are secondary batteries such as lithium ion batteries, in series. The number of battery cells 11 included in the battery pack 10 is not particularly limited, and may be multiple or one. For convenience, the following description will be given of an example in which the voltage of the battery pack 10 is 75 V, but the voltage of the battery pack 10 is not limited to this.

[0033] The CMU 100 is a unit for monitoring the state of the battery pack 10 (e.g., the voltage of each battery cell 11), and includes a battery monitoring unit 110, a second power supply circuit 120, a power supply circuit 130, a wireless communication unit 140, and an antenna 150. The CMU 100 also includes, for example, a processor and a memory. The memory is a read-only memory (ROM) or a random access memory (RAM), and can store programs executed by the processor. Some or all of the functions of the battery monitoring unit 110 and the wireless communication unit 140 are realized by the processor, which executes programs stored in the memory.

[0034] Although details will be described later, the CMU 100 can switch between a normal mode in which it operates using power supplied from the power supply circuit 111 of the battery monitoring unit 110, and a sleep mode in which it operates using power supplied from a second power supply circuit 120 that supplies less power than the power supply circuit 111. The sleep mode is a low-power consumption mode that consumes less power than the normal mode, and is a mode in which the wireless communication unit 140 operates in a standby state.

[0035] The battery monitoring unit 110 operates using power supplied from the battery pack 10, and performs operations related to monitoring the battery cells 11 (or the battery pack 10) while the power supply circuit 111 is active. For example, the battery monitoring unit 110 measures the state of the battery cells 11 (or the battery pack 10) while the power supply circuit 111 is active. The battery monitoring unit 110 includes a power supply circuit 111, a power supply circuit 112, a voltage measurement circuit 113, and a control circuit 114.

[0036] The power supply circuit 111 is an example of a first power supply circuit, and supplies power to the circuits of the cell monitoring unit 100, including the battery monitoring unit 110 and the wireless communication unit 140. In this embodiment, the power supply circuit 111 is capable of supplying power to, for example, all of the circuits of the cell monitoring unit 100. When the switch SW is turned on, the power supply circuit 111 is started up by receiving power from the battery pack 10, and supplies power to each circuit of the cell monitoring unit 100. The power supply circuit 111 includes, for example, a switching power supply circuit having a DC-DC converter.

[0037] The power supply circuit 111 is connected to the diode 131 and the power supply circuit 112. When the switch SW is on, the power supply circuit 111 supplies power to the wireless communication unit 140 via the diode 131. When the switch SW is on, the power supply circuit 111 also supplies power to the voltage measurement circuit 113 and the control circuit 114 via the power supply circuit 112.

[0038] The power supply circuit 112 is an LDO (Low Drop Out) regulator that outputs a constant voltage lower than the input voltage. The power supply circuit 112 is also called a linear regulator. The power supply circuit 112 steps down the power supply voltage (75 V in this case) from the power supply circuit 111 to a voltage required for the operation of the voltage measurement circuit 113 and the control circuit 114, and outputs the stepped-down constant voltage. If the power supply circuit 111 is a power supply with a large ripple in order to reduce power consumption, the power supply circuit 112 can smooth the current.

[0039] The voltage measurement circuit 113 is a measurement circuit that operates by receiving power from the power supply circuit 112 and measures the voltage of each of the multiple battery cells 11 that make up the battery pack 10. The voltage measurement circuit 113 has a voltage measurement unit that is provided one-to-one with each battery cell 11 and measures the voltage of the connected battery cell 11. The voltage measurement unit may include an ADC unit that converts an analog signal value corresponding to the voltage of the battery cell 11 into a digital signal value, and a calculation unit that calculates a voltage value by performing arithmetic processing on the digital signal value that is the output of the ADC unit.

[0040] The control circuit 114 operates by power supply from the power supply circuit 112 and performs communication with the wireless communication unit 140. The control circuit 114 is connected by wire to the monitoring unit 143 and the start / stop control unit 144. The control circuit 114 may also control each component of the battery monitoring unit 110.

[0041] The control circuit 114 operates by receiving power from the power supply circuit 112 and includes a self-diagnosis circuit 114a that diagnoses whether the battery monitoring unit 110 is operating normally.

[0042] The self-diagnosis circuit 114a diagnoses whether the battery monitoring unit 110 is operating normally while the power supply circuit 111 is running. The diagnostic method of the self-diagnosis circuit 114a is not particularly limited, and any known diagnostic method may be used.

[0043] In this way, the voltage measurement circuit 113 and the control circuit 114 are configured to operate while the power supply circuit 111 is activated (i.e., the switch SW is on and power from the battery pack 10 is supplied to the battery monitoring unit 110).

[0044] The second power supply circuit 120 is a power supply circuit that supplies less power than the power supply circuit 111, and when the power supply circuit 111 is stopped (i.e., the switch SW is off), it supplies power to operate at least the time measurement unit 148 among the components of the wireless communication unit 140. The second power supply circuit 120 is connected between the battery pack 10 and the wireless communication unit 140. The second power supply circuit 120 is also connected in parallel with the battery monitoring unit 110.

[0045] The second power supply circuit 120 includes a resistor 121, a Zener diode 122, and a transistor 123. By including the Zener diode 122 and the transistor 123, the second power supply circuit 120 can operate with low power consumption while suppressing the occurrence of ripples.

[0046] The resistor 121 is connected between the battery pack 10 (for example, the power supply terminal T1) and the base of the transistor 123 and the cathode of the Zener diode 122, and is a resistor for applying a predetermined voltage to the transistor 123.

[0047] The Zener diode 122 is a constant voltage diode for limiting the voltage applied to the base of the transistor 123 via the resistor 121. In this embodiment, the Zener diode 122 limits the base potential of the transistor 123 to 5V.

[0048] The transistor 123 has a base connected to the cathode of the Zener diode 122, a collector connected to the power supply terminal T1, and an emitter connected to the diode 132. If the transistor 123 is a silicon transistor, the voltage drop is approximately 0.7 V, so that when the base potential is 5 V, approximately 4.3 V is input to the diode 132. The transistor 123 is, for example, an NPN-type transistor, but is not limited to this.

[0049] In this embodiment, since no switch is provided between the second power supply circuit 120 and the battery pack 10, the second power supply circuit 120 is constantly activated from the moment the CMU 100 is connected to the battery pack 10. In other words, the base potential of the transistor 123 is always 5 V. As a result, the time measurement unit 148 is supplied with power from either the power supply circuit 111 or the second power supply circuit 120, and can continue to operate regardless of the activation and deactivation of the power supply circuit 111 or without controlling the on / off of the second power supply circuit 120.

[0050] The power supply circuit 130 is connected between the power supply circuit 111 and the second power supply circuit 120 and the wireless communication unit 140, and supplies power to the wireless communication unit 140 from only one of the power supply circuit 111 and the second power supply circuit 120 by exclusively switching conduction and non-conduction between the power supply circuit 111 and the second power supply circuit 120 and the wireless communication unit 140. The power supply circuit 130 includes diodes 131 and 132 and a power supply circuit 133.

[0051] The diode 131 is connected between the power supply circuit 111 and the wireless communication unit 140 and receives power from the power supply circuit 111 .

[0052] The diode 132 is connected between the second power supply circuit 120 and the wireless communication unit 140, and receives power from the second power supply circuit 120. The cathode of the diode 132 and the cathode of the diode 131 are connected to each other, forming a diode OR circuit.

[0053] In this way, in the power supply circuit 130, the power supply circuit 111 and the second power supply circuit 120 are connected via the diodes 131 and 132, so that if the voltage of one power supply circuit drops, it is possible to automatically switch to the other power supply circuit. By setting the input voltage of the diode 131 higher than the input voltage of the diode 132, power is supplied from the power supply circuit 111 when the power supply circuit 111 is activated, and power can be supplied from the second power supply circuit 120 when the power supply circuit 111 is stopped. The input voltage of the diode 131 is, for example, 5 V, and the input voltage of the diode 132 is, for example, 4.3 V, but the voltages are not limited thereto. The power supply circuit 130 is configured so that the second power supply circuit 120 supplies power to the wireless communication unit 140 only during a time period when the wireless communication unit 140 is in a standby state and the other circuits of the CMU 100 are in a quiescent state.

[0054] The power supply circuit 133 is an LDO regulator (linear regulator) that outputs a constant voltage that is lower than the power supplied exclusively from one of the diodes 131 and 132. The power supply circuit 133 receives the power supply voltage from the power supply circuit 111 or the second power supply circuit 120, and outputs a constant, smoothed voltage necessary for the operation of the wireless communication unit 140.

[0055] In this way, the power supply circuit 130 is configured to select whether to supply power to the power supply circuit 111 or the second power supply circuit 120, convert the power to a predetermined voltage (e.g., 2.5 V), and supply power to the wireless communication unit 140.

[0056] The wireless communication unit 140 is a communication device that enables the CMU 100 to communicate wirelessly with the BMU 200. The wireless communication unit 140 includes a self-diagnosis circuit 141, a power supply detection unit 142, a monitoring unit 143, a start / stop control unit 144, a non-volatile memory 145, a communication unit 146, a time setting circuit 147, and a time measurement unit 148. The time measurement unit 148 is also connected to a crystal oscillator 149 (the "32 KHz XO" provided in the CMU 100 in FIG. 1 ). The wireless communication unit 140 is an example of a first wireless communication unit.

[0057] The self-diagnosis circuit 141 operates by receiving power from the power supply circuit 111, and diagnoses whether the wireless communication unit 140 is operating normally while the power supply circuit 111 is running.

[0058] The power supply detection unit 142 detects the status (e.g., whether the power supply circuit 111 or the second power supply circuit 120 is normal or abnormal) of at least one of the power supply circuit 111 and the second power supply circuit 120. In this embodiment, the power supply detection unit 142 detects whether the power supply circuit 111 and the second power supply circuit 120 are normal or abnormal. The power supply detection unit 142 detects whether the power supply circuit 111 is normal or abnormal by detecting the current of the power supply circuit 111 based on the monitoring signal s1 of the first power supply, and detects whether the second power supply circuit 120 is normal or abnormal by detecting the current of the second power supply circuit 120 based on the monitoring signal s2 of the second power supply. The power supply detection unit 142 operates by receiving power from at least one of the power supply circuit 111 and the second power supply circuit 120. The power supply detection unit 142 includes, for example, an analog comparator. The power supply detection unit 142 may operate by receiving power from, for example, the second power supply circuit 120.

[0059] The power supply circuit 111 is configured to be able to output a different first power supply monitoring signal s1 depending on whether the power supply circuit 111 is normal or abnormal, and the second power supply circuit 120 is configured to be able to output a different second power supply monitoring signal s2 depending on whether the power supply circuit 111 is normal or abnormal.

[0060] The monitoring unit 143 monitors the battery monitoring unit 110. The monitoring unit 143 obtains the diagnosis result of the self-diagnosis circuit 114a via a signal line.

[0061] The start / stop control unit 144 controls the start and stop of the battery monitoring unit 110. When the battery monitoring unit 110 is to be operated (for example, when communicating with the BMU 200), the start / stop control unit 144 turns on (conducts) the switch SW to start the power supply circuit 111 and outputs a first power supply control signal s3 for starting the control circuit 114. When the battery monitoring unit 110 is to be stopped (for example, when communication with the BMU 200 is to be stopped), the start / stop control unit 144 turns off (non-conducts) the switch SW and outputs a first power supply control signal s3 for stopping the control circuit 114.

[0062] When the elapsed time since the battery monitoring unit 110 was stopped, measured by the time measurement unit 148, reaches a predetermined time, the start / stop control unit 144 starts the battery monitoring unit 110 with a control signal s3 from the first power supply. It can also be said that the start / stop control unit 144 causes the battery monitoring unit 110 to operate intermittently. The start / stop control unit 144 is an example of a control unit.

[0063] The non-volatile memory 145 stores various types of information. For example, the non-volatile memory 145 may store information related to the operating state of at least one of the battery monitoring unit 110 and the wireless communication unit 140. For example, when the power supply detection unit 142 detects an abnormality in the power supply circuit 111 (that is, when communication with the BMU 200 via the wireless communication unit 140 is not possible), the non-volatile memory 145 may store information indicating that an abnormality has been detected. The non-volatile memory 145 is an example of a storage unit.

[0064] The communication unit 146 is connected to the antenna 150 and communicates wirelessly with the BMU 200 via the antenna 150. The communication unit 146 transmits information to the BMU 200 by radio waves to the BMU 200 and receives radio waves from the BMU 200 via the antenna 150.

[0065] The time setting circuit 147 sets the start time or stop time of the CMU 100 so that the CMU 100 operates in normal mode when the wireless communication unit 140 wirelessly communicates with the BMU 200. The time setting circuit 147 may set both the start time and the stop time, for example. The time setting circuit 147 is an example of a first time setting circuit.

[0066] The time setting circuit 147 may set the start-up time of the cell monitoring unit 100 so that the wireless communication unit 140 starts up at the start-up time of the wireless communication unit 220 set by the time setting circuit 222 , for example.

[0067] The time measurement unit 148 measures the elapsed time from the start-up time or the stop time. The time measurement unit 148 operates using power supplied from the second power supply circuit 120 while operating in sleep mode from the stop time to the next start-up time. The measurement method of the time measurement unit 148 is not particularly limited, but in this embodiment, the time measurement unit 148 measures the time based on the output of the crystal oscillator 149. For example, the time measurement unit 148 measures the time by counting the output of the crystal oscillator 149. By measuring the elapsed time, the time measurement unit 148 can obtain the timing of transition from one of the normal mode and the sleep mode to the other. The time measurement unit 148 is a so-called real-time clock.

[0068] The crystal oscillator 149 is an electronic component that combines a crystal unit and an oscillation circuit in one package, and generates a signal with a stable frequency. The crystal oscillator 149 is also called a clock generation circuit.

[0069] The antenna 150 transmits and receives radio waves for wireless communication.

[0070] The CMU 100 also has a power supply terminal T1 and a GND terminal T2 of the CMU 100. The power supply terminal T1 is connected to the positive terminal of the battery cell 11 that has the highest potential in the battery pack 10, and the GND terminal T2 is connected to the negative terminal of the battery cell 11 that has the lowest potential in the battery pack 10.

[0071] The BMU 200 is capable of wireless communication with the CMU 100 and controls the charging and discharging of the battery pack 10 of the CMU 100. The BMU 200 may be capable of communicating with, for example, a plurality of CMUs 100. The BMU 200 is supplied with power from a power source (for example, a 12 V power source) different from that of the battery pack 10. The BMU 200 is an example of a higher-level system.

[0072] The BMU 200 includes a battery control unit 210, a wireless communication unit 220, and an antenna 230. The BMU 200 also includes, for example, a processor and a memory. The memory is a ROM, a RAM, or the like, and can store programs executed by the processor. The battery control unit 210 and the wireless communication unit 220 are implemented by a processor that executes programs stored in the memory. For example, the battery control unit 210 and the wireless communication unit 220 are implemented by different processors, but may also be implemented by a single processor.

[0073] The battery control unit 210 generates a control signal for controlling the charging and discharging of the battery pack 10 and transmits the control signal to the CMU 100 via the wireless communication unit 220 .

[0074] The wireless communication unit 220 is a communication device that enables the BMU 200 to communicate wirelessly with the CMU 100. The wireless communication unit 220 includes a communication unit 221, a time setting circuit 222, and a time measurement unit 223. The time measurement unit 223 is also connected to a crystal oscillator 224 (the "32 KHz XO" of the BMU 200 in FIG. 1). The wireless communication unit 220 is an example of a second wireless communication unit.

[0075] The communication unit 221 is connected to the antenna 230 and communicates wirelessly with the CMU 100 via the antenna 230. The communication unit 221 transmits information to the CMU 100 by radio waves to the CMU 100 and receives radio waves from the CMU 100 via the antenna 230.

[0076] The time setting circuit 222 sets the start time or stop time of the wireless communication unit 220 for intermittent operation of the BMU 200. The time setting circuit 222 may set both the start time and the stop time, for example. The time setting circuit 222 is an example of a second time setting circuit.

[0077] The time measurement unit 223 measures the elapsed time from the start or stop time of the BMU 200. There are no particular limitations on the measurement method used by the time measurement unit 223, but in this embodiment, the time measurement unit 223 measures the time based on the output of the crystal oscillator 224. For example, the time measurement unit 223 measures the time by counting the output of the crystal oscillator 224. The time measurement unit 223 is a so-called real-time clock.

[0078] The crystal oscillator 224 is an electronic component that combines a crystal resonator and an oscillation circuit in one package, and generates a signal with a stable frequency. The crystal oscillator 224 is also called a clock generation circuit.

[0079] The antenna 230 transmits and receives radio waves for wireless communication.

[0080] The power consumption of each power supply circuit will now be described with reference to Fig. 2. Fig. 2 is a diagram for explaining the power consumption of the power supply circuit according to this embodiment.

[0081] 2, the battery monitoring unit 110 includes, as a control unit, a battery 111a, an error amplifier 111b, a triangular wave generating circuit 111c, a comparator 111d, and a pre-drive 111e. The battery 111a, the error amplifier 111b, the triangular wave generating circuit 111c, the comparator 111d, and the pre-drive 111e form a negative feedback circuit for maintaining the output of the battery monitoring unit 110 at a constant voltage. In other words, the battery 111a, the error amplifier 111b, the triangular wave generating circuit 111c, the comparator 111d, and the pre-drive 111e form a constant voltage source that outputs a constant voltage equivalent to the voltage of the battery 111a (reference voltage). By PWM (Pulse Width Modulation) control, repeated on-off switching is performed to control the power output from the comparator 111d.

[0082] The inductor 161 and the capacitor 162 form a low-pass filter. The current output from the battery monitoring unit 110 and passed through the low-pass filter is supplied to the wireless communication unit 140. For example, the maximum value of the current (maximum load current) is assumed to be 20 mA. Note that the maximum load current is the current consumed when the battery monitoring unit 110 is operating in normal mode and the wireless communication unit 140 is transmitting a signal to the BMU 200.

[0083] The power supply circuit 133 includes a battery 133a, an operational amplifier 133b, and a transistor 133c. The battery 133a, the operational amplifier 133b, and the transistor 133c form a negative feedback circuit for maintaining the output of the power supply circuit 133 at a constant voltage. In other words, the battery 133a, the operational amplifier 133b, and the transistor 133c form a constant voltage source that outputs a constant voltage equivalent to the voltage of the battery 133a (reference voltage).

[0084] In the cell monitoring unit 100 configured as described above, if the maximum current consumption of the wireless communication unit 140 during transmission, 20 mA, is supplied to 2.5 V from the 75 V of the 20 series-connected battery pack 10 via the power supply circuit 112 (linear regulator), the resulting power consumption is 75 V × 20 mA = 1.5 W, and (75 V - 2.5 V) × 20 mA = 1.45 W is lost as heat. To reduce this power loss, a switching regulator can be used. However, even if the current consumption of the control unit (control unit current) is assumed to be 1 mA and switching loss is assumed to be zero, this results in a very low power efficiency of (20 mA × 2.5 V) / (1 mA × 75 V + 20 mA × 2.5 V) × 100 = 40%, which is only 1.5 W × 40% = 0.6 W. Conventionally, power consumption can only be reduced to 1.5 W × 40% = 0.6 W.

[0085] On the other hand, in a sleep mode in which only the time measurement unit 148 and the low-speed (for example, 32 KHz) crystal oscillator 149 of the wireless communication unit 140 are operating, the current consumption is about 10 μA.

[0086] However, in a switching regulator, the current consumption of the power supply circuit 111 is significantly greater. On the other hand, even in a linear regulator, the power consumption is much greater than the power consumption of the wireless communication unit 140 in a standby state. For example, when the wireless communication unit 140 is in a standby state but the control unit is operating, power consumption is as much as (1 mA x 75 V) = 75 mW.

[0087] 1 , the CMU 100 according to this embodiment includes a second power supply circuit 120 different from the power supply circuit 111, and when the wireless communication unit 140 is in a standby state, power is supplied from the second power supply circuit 120 to the wireless communication unit 140. As described above, the second power supply circuit 120 can operate with lower power consumption than the power supply circuit 111 due to its circuit configuration.

[0088] 2, a current of 50 μA is input to the second power supply circuit 120, a current of, for example, 20 μA flows through the resistor 121 depending on the resistance value, and a current of 30 μA is input to the collector of the transistor 123. Then, 10 μA is supplied to the wireless communication unit 140 via the power supply circuit 133.

[0089] In this way, the CMU 100 is configured to use the power supply circuit 111 to supply a load current (20 mA) that enables the wireless communication unit 140 to start up and send and receive radio waves, and is also configured to use the second power supply circuit 120 to supply a load current (10 μA) during sleep mode (standby state).

[0090] The power supply circuits of the cell monitoring unit 100, both the power supply circuit 111 (first power supply circuit) and the second power supply circuit 120, need to be operated at the maximum voltage of the battery pack 10 (for example, 75 V). However, by designing the second power supply circuit 120, which supplies power to the wireless communication unit 140 in sleep mode, which consumes a current of about 10 μA, to consume about 50 μA, it is possible to reduce the power consumption in sleep mode to 75 V x 50 μA = 3.75 mW.

[0091] In this way, by switching the power supply circuit that supplies power to the wireless communication unit 140 between normal operation and standby mode, it is possible to significantly reduce the average power consumption of the power supply circuit itself, thereby effectively reducing the current consumption of the CMU 100.

[0092] With the CMU 100 configured as described above, it is possible to keep the standby power consumption of the CMU 100 low in a wireless BMS (BMS1) that is mainly used in electric vehicles, etc., and to enable long-term storage or transportation of electric vehicles or their battery modules.

[0093] [2. Operation of Battery Management System] Next, the operation of the BMS 1 configured as described above will be described with reference to Figures 3 and 4. Figure 3 is a flowchart showing a first operation (cell monitoring method) of the cell monitoring unit 100 according to this embodiment. At the time of step S11, the wireless communication unit 140 is operating in normal mode, and power is supplied to the wireless communication unit 140 from the power supply circuit 111 (first power supply circuit). Furthermore, the power consumption at the time of step S11 is, for example, 1.5 W.

[0094] 3, first, the time setting circuit 147 sets the next startup time (S11). The time setting circuit 147 sets the startup time so that the CMU 100 operates in normal mode at the timing when the wireless communication unit 140 next transmits radio waves to the BMU 200 or the timing when the wireless communication unit 140 next receives radio waves from the BMU 200. Note that in step S11, the time setting circuits 147 and 222 may set the same time as the next startup time.

[0095] Next, the power supply detection unit 142 checks the operation of the second power supply circuit 120 based on the second power supply monitoring signal s2 (S12). For example, before shutting down the power supply circuit 111, the power supply detection unit 142 detects whether the second power supply circuit 120 is operating normally.

[0096] Next, if the power supply detection unit 142 detects that the second power supply circuit 120 is operating normally (OK in S12), the wireless communication unit 140 transitions to low power consumption mode when the CMU 100 shutdown time arrives (S13). The wireless communication unit 140 turns off its wireless function, the MCU goes into low power consumption mode, and the startup time measurement is turned on. This results in a state in which, for example, mainly only the time measurement unit 148 and the crystal oscillator 149 are operating.

[0097] In addition, in the low power consumption mode, the power supply detection unit 142 may operate to monitor the power supply circuit 111 using power supplied from the second power supply circuit 120, or may be stopped to further reduce power consumption.

[0098] Next, the start / stop control unit 144 outputs a first power supply control signal s3 to the battery monitoring unit 110 to turn off the switch SW and the control circuit 114, thereby turning off (stopping) the first power supply circuit (power supply circuit 111) and the battery monitoring unit 110 (S14). If the power supply detection unit 142 detects that the second power supply circuit 120 is operating normally, the power supply circuit 111 stops when the stop time of the CMU 100 arrives. The normal operation of the second power supply circuit 120 may mean, for example, that the output voltage of the second power supply circuit 120 has not substantially decreased.

[0099] As a result, in the power supply circuit 130, the power supply circuit that supplies power to the wireless communication unit 140 switches from the first power supply circuit to the second power supply circuit 120. Also, the battery monitoring unit 110 transitions to a sleep mode in which mainly only the time measurement unit 148 and the crystal oscillator 149 operate. As described in FIG. 2, the CMU 100 can suppress power consumption in the sleep mode to, for example, about 3.75 mW.

[0100] Next, the time measurement unit 148 determines the start-up time based on the output from the crystal oscillator 149 (S15). The time measurement unit 148 may determine that the start-up time has arrived when a predetermined time has elapsed since the transition to the low power consumption mode.

[0101] Next, when the time measurement unit 148 determines that the start time has arrived (OK in S15), the start / stop control unit 144 outputs a first power control signal s3 to the battery monitoring unit 110 to turn on the switch SW and the control circuit 114, thereby turning on (starting up) the first power supply circuit (power supply circuit 111) and the battery monitoring unit 110 (S16). The period from when the first power supply circuit and the battery monitoring unit 110 are turned off until when the first power supply circuit and the battery monitoring unit 110 are turned on is the period during which the device operates in sleep mode.

[0102] In this way, the power supply circuit 111 starts up at the startup time of the CMU 100 and supplies power to the wireless communication unit 140 (for example, the communication unit 146).

[0103] If the time measurement unit 148 determines that the start time has not yet arrived (NG in S15), the process returns to step S15 and the time measurement unit 148 continues to make determinations until the start time arrives.

[0104] Next, the wireless communication unit 140 transitions from the low power consumption mode to the normal mode (S17). In the wireless communication unit 140, the wireless function is switched from OFF to ON, the MCU is switched from the low power consumption mode to ON (here, the normal mode), and the startup time measurement is switched from ON to OFF. As a result, for example, in the CMU 100, each component is switched to the normal mode in which it operates.

[0105] The second power supply circuit 120 can supply power to the time measurement unit 148 from the stop time of the CMU 100 to the next start time (here, the time determined as OK in step S15).

[0106] Next, the battery monitoring unit 110 performs battery monitoring (S18). The voltage measurement circuit 113 of the battery monitoring unit 110 measures the voltage of each battery cell 11 of the battery pack 10.

[0107] Furthermore, if the power supply detection unit 142 determines that the second power supply circuit 120 is not operating normally (NG in S12), the wireless communication unit 140 stops (e.g., prohibits) the transition to the low power consumption mode (S19) and reports the abnormality to the Master (S20). The Master here is the BMU 200. When the second power supply circuit 120 is not operating normally, the state in which power is supplied from the first power supply circuit to the wireless communication unit 140 is maintained, so the wireless communication unit 140 operates in normal mode and is able to communicate wirelessly with the BMU 200. Therefore, the wireless communication unit 140 can report the abnormality to the Master in step S20.

[0108] While FIG. 3 illustrates the mode transition of the CMU 100, the mode of the BMU 200 may also transition in synchronization with the mode transition of the CMU 100. The BMU 200 may be configured to transition between, for example, a normal mode in which the wireless communication unit 220 is capable of communication and a sleep mode, which is a low-power consumption mode in which the wireless communication unit 220 does not communicate wirelessly. In the sleep mode of the BMU 200, the time measurement unit 223 measures the elapsed time. For example, the mode of the BMU 200 may be controlled so that the BMU 200 also enters the normal mode (i.e., enters a state in which wireless communication with the CMU 100 is possible) when the CMU 100 enters the normal mode. This allows the power consumption of the BMS 1 as a whole to be effectively reduced.

[0109] Next, another operation of the CMU 100 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing a second operation (cell monitoring method) of the cell monitoring unit 100 according to this embodiment. Fig. 4 shows an example of the operation when the operation check of the power supply circuit 111 is NG.

[0110] First, when the wireless communication unit 140 is operating in normal mode (S31), the power supply detection unit 142 checks the operation of the first power supply circuit based on the monitoring signal s1 of the first power supply (S32).

[0111] Next, if the power supply detection unit 142 determines that the first power supply circuit is not operating normally (NG in S32), the wireless communication unit 140 transitions to a low power consumption mode (S33). This causes the wireless communication unit 140 to be unable to communicate wirelessly with the BMU 200. In this low power consumption mode, the start / stop control unit 144 also operates using power from the second power supply circuit 120. Note that, for example, if a voltage drop in the first power supply circuit is detected, the determination in step S32 is NG.

[0112] Next, the start-stop control unit 144 restarts the first power supply circuit (S34). The start-stop control unit 144 may restart the first power supply circuit, for example, by turning the switch SW OFF and then ON.

[0113] In this way, when the power supply detection unit 142 detects a voltage drop in the power supply circuit 111, the start / stop control unit 144 transitions to a low power consumption mode in which it can operate only with power supplied by the second power supply circuit 120, and restarts the power supply circuit 111.

[0114] Next, the power supply detection unit 142 checks the operation of the first power supply circuit again based on the monitoring signal s1 of the first power supply (S35).

[0115] Next, if the power supply detection unit 142 determines that the first power supply circuit is operating normally (OK in S35), the wireless communication unit 140 returns from the low power consumption mode to the normal mode (S36). This enables wireless communication with the BMU 200.

[0116] Next, the wireless communication unit 140 notifies the host system (here, the BMU 200) of the restoration (S37). The wireless communication unit 140 may transmit to the BMU 200 information such as that it has been determined that the first power supply circuit is not operating normally, that the first power supply circuit has been restarted, etc. After step S37 is executed, or if step S32 is OK, the process returns to step S31 and continues.

[0117] Furthermore, when the power supply detection unit 142 detects that the first power supply circuit is not operating normally (NG in S35), it determines whether the time that has elapsed since it detected that the first power supply circuit is not operating normally is within a predetermined startup time (S38), and if it is within the predetermined startup time (YES in S38), the processes of steps S34 and S35 are repeatedly executed until the predetermined startup time has elapsed or until OK is obtained in step S35. The predetermined startup time is set in advance and is stored in, for example, the non-volatile memory 145.

[0118] Next, when the predetermined startup time has elapsed (NO in S38), the power supply detection unit 142 records an abnormality state in the non-volatile memory 145 (S39). Because the first power supply circuit is not operating normally and cannot communicate wirelessly with the BMU 200, the power supply detection unit 142 records the abnormality state of the first power supply circuit in the non-volatile memory 145. This allows an operator or the like to use information about the abnormality state when checking the operating state of the CMU 100, for example, in cases where the BMU 200 does not receive wireless communication from the CMU 100 for a predetermined period of time.

[0119] Next, the wireless communication unit 140 maintains the low power consumption mode (S40). In other words, the wireless communication unit 140 does not return to the normal mode. The low power consumption mode here is, for example, the same as step S13 shown in FIG. 3 (for example, the start / stop control unit 144 is stopped).

[0120] In this way, the first power supply circuit or the second power supply circuit 120 has a function of outputting a monitoring signal for the wireless communication unit 140 to monitor the operating state of the power supply circuit, so that the wireless communication unit 140 can obtain the operating state of the power supply circuit before transitioning from one of the normal mode and the sleep mode to the other. The wireless communication unit 140 can stop the mode transition or attempt to restart the power supply circuit depending on the operating state of the power supply circuit, thereby realizing a cell monitoring unit 100 with excellent functional safety.

[0121] While the cell monitoring unit 100 according to one or more aspects has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as the modifications do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included in the present disclosure.

[0122] For example, in the above embodiment, an example has been described in which the cell monitoring unit 100 is equipped with both the self-diagnostic circuits 114a and 141, but this is not limited to this, and the cell monitoring unit 100 may be equipped with at least one of the self-diagnostic circuits 114a and 141, or may not be equipped with the self-diagnostic circuits 114a and 141.

[0123] Furthermore, for example, the BMS 1 (wireless BMS) according to the above-described embodiment is mainly used in electric vehicles such as electric automobiles, but the application is not limited to this.

[0124] Furthermore, for example, in the BMS 1 according to the above embodiment, an example has been described in which the cell monitoring unit 100 and the battery control unit 200 each include a time setting circuit, but this is not limited to this, and at least one of the cell monitoring unit 100 and the battery control unit 200 may include a time setting circuit. For example, if only the cell monitoring unit 100 includes the time setting circuit 147, the set start time and stop time are transmitted to the battery control unit 200 via wireless communication. For example, if only the battery control unit 200 includes the time setting circuit 222, the set start time and stop time are transmitted to the cell monitoring unit 100 via wireless communication.

[0125] Furthermore, the expression "XX unit" in the above embodiments may be realized by a processor and memory, or may be realized by a circuit (for example, a dedicated circuit).

[0126] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0127] The order in which the steps in the flowchart are executed is merely an example for specifically explaining the present disclosure, and other orders may be used. Some of the steps may be executed simultaneously (in parallel) with other steps, or some of the steps may not be executed.

[0128] The division of functional blocks in the block diagram is an example, and multiple functional blocks may be realized as a single functional block, one functional block may be divided into multiple blocks, or some functions may be moved to another functional block.Furthermore, the functions of multiple functional blocks having similar functions may be processed in parallel or in time-sharing by a single piece of hardware or software.

[0129] Furthermore, each component described in the above embodiments may be implemented as software or, typically, as an LSI, which is an integrated circuit. These components may be individually integrated into a single chip, or some or all of them may be integrated into a single chip. Here, the term "LSI" is used, but depending on the level of integration, it may also be referred to as an IC, system LSI, super LSI, or ultra LSI. Furthermore, the integrated circuit implementation method is not limited to LSI, and may be implemented using a dedicated circuit (a general-purpose circuit that executes a dedicated program) or a general-purpose processor. After LSI fabrication, a field programmable gate array (FPGA) that can be programmed or a reconfigurable processor that can reconfigure the connections or settings of circuit cells within the LSI may also be used. Furthermore, if an integrated circuit technology that replaces LSI emerges due to advances in semiconductor technology or a derivative technology, that technology may naturally be used to integrate the components.

[0130] A system LSI is an ultra-multifunctional LSI manufactured by integrating multiple processing units on a single chip, and is specifically a computer system comprising a microprocessor, ROM, RAM, etc. The ROM stores computer programs. The system LSI achieves its functions when the microprocessor operates in accordance with the computer programs.

[0131] Furthermore, one aspect of the present disclosure may be a computer program that causes a computer to execute each of the characteristic steps included in the cell monitoring method shown in FIG. 3 or FIG.

[0132] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0133] (Technology 1) A cell monitoring unit that monitors battery cells includes a battery monitoring unit that measures the state of the battery cells, a first power supply circuit, a second power supply circuit that supplies less power than the first power supply circuit, a communication unit for wireless communication with a higher-level system, a first time setting circuit that sets a start time and a stop time of the cell monitoring unit, and a first wireless communication unit that has a time measurement unit that measures the elapsed time from the stop time, wherein the first power supply circuit starts up at the start time and supplies power to the battery monitoring unit and the communication unit and stops at the stop time, and the second power supply circuit supplies power to the time measurement unit from the stop time until the next start time.

[0134] As a result, power is supplied from the second power supply circuit, which has a lower power supply, between the time when the cell monitoring unit is stopped and the time when it is started again, so the power consumed by the power supply circuit can be reduced compared to when the first power supply circuit is constantly supplying power, and therefore the power consumption when the cell monitoring unit is stopped (in sleep mode) can be effectively reduced.

[0135] (Technology 2) The battery monitoring unit is the cell monitoring unit of Technology 1 that is activated while the first power supply circuit is activated and measures the state of the battery cells.

[0136] This stops measurement of the state of the battery cells until the first power supply circuit is started up, thereby reducing the power consumed in measuring the state of the battery cells.

[0137] (Technology 3) The cell monitoring unit of Technology 1 or 2 further includes a self-diagnosis circuit that diagnoses whether at least one of the battery monitoring unit and the first wireless communication unit is operating normally while the first power supply circuit is activated.

[0138] As a result, the self-diagnosis by the self-diagnosis circuit is stopped until the first power supply circuit is started up, so that the power consumed in the self-diagnosis can be reduced.

[0139] (Technology 4) The upper system is a cell monitoring unit according to any of technologies 1 to 3, which includes a second time setting circuit that sets the startup time of a second wireless communication unit that the upper system includes, and the first time setting circuit sets the startup time of the cell monitoring unit so that the first wireless communication unit starts up at the startup time of the second wireless communication unit set by the second time setting circuit.

[0140] This prevents the first power supply circuit from activating during times when the host system cannot communicate wirelessly, i.e., prevents unnecessary power consumption, thereby reducing power consumption when the host system cannot communicate wirelessly.

[0141] (Technology 5) The first wireless communication unit is a cell monitoring unit according to any one of technologies 1 to 4, further including a power detection unit that detects the state of at least one of the first power supply circuit and the second power supply circuit that supply power to the first wireless communication unit.

[0142] This makes it possible to prevent the operation of at least one of the first power supply circuit and the second power supply circuit from being controlled when the circuit is not in a normal state. For example, it is possible to prevent the operation of the power supply circuit from being controlled when it is better not to control the operation (start / stop) of the power supply circuit, i.e., to prevent unnecessary power consumption. Therefore, it is possible to reduce power consumption when the power supply circuit is not normal.

[0143] (Technology 6) A cell monitoring unit according to Technology 5, further comprising a control unit that, when the power supply detection unit detects a voltage drop in the first power supply circuit, transitions to a low power consumption mode in which operation is possible only with power supplied from the second power supply circuit, and restarts the first power supply circuit.

[0144] By providing the second power supply circuit, power for restarting the first power supply circuit can be supplied from the second power supply circuit, thereby preventing the cell monitoring unit from failing to function.

[0145] (Technology 7) A cell monitoring unit according to Technology 5 or 6, wherein the power supply detection unit detects whether the second power supply circuit is operating normally before stopping the first power supply circuit, and the first power supply circuit stops at the stop time if the power supply detection unit detects that the second power supply circuit is operating normally.

[0146] This allows the first power supply circuit to be stopped only when the second power supply circuit is operating normally.

[0147] (Technology 8) The cell monitoring unit of Technology 7 further includes a memory unit that stores information indicating that an abnormality has been detected when the power supply detection unit detects an abnormality in the first power supply circuit.

[0148] This eliminates the need for electronic components such as switches between the second power supply circuit and the battery cell, making it possible to reduce the power consumed by the operation of such electronic components.

[0149] (Technology 9) The second power supply circuit is configured to be constantly activated from the moment the cell monitoring unit is connected to the battery cell, and the time measurement unit continues to operate regardless of the activation and cessation of the first power supply circuit, which is a cell monitoring unit of any of Technologies 1 to 8.

[0150] This allows the cell monitoring unit to keep a record of the detected abnormality even if it is not possible to transmit the information to the upper system via wireless communication.

[0151] (Technology 10) The cell monitoring unit according to any one of Technologies 1 to 9, wherein the first wireless communication unit further includes a control unit that controls activation and shutdown of the first power supply circuit.

[0152] This allows the first wireless communication unit to control the activation and deactivation of the first power supply circuit.

[0153] (Technology 11) The first power supply circuit is a switching power supply circuit, and the second power supply circuit is the cell monitoring unit of any one of Technologies 1 to 10, including a resistor, a Zener diode, and a transistor.

[0154] This makes it possible to effectively reduce the power consumption of the second power supply circuit.

[0155] (Technology 12) A monitoring method executed by a cell monitoring unit that monitors battery cells, the cell monitoring unit comprising: a battery monitoring unit that measures the state of the battery cells; a first power supply circuit; a second power supply circuit that supplies less power than the first power supply circuit; a communication unit for wireless communication with a higher-level system; a time setting circuit that sets a start time and a stop time for the cell monitoring unit; and a wireless communication unit having a time measurement unit that measures the elapsed time from the stop time, the monitoring method comprising: at the start time, starting the first power supply circuit and supplying power to the battery monitoring unit and the communication unit; at the stop time, stopping the first power supply circuit and supplying power from the second power supply circuit to the time measurement unit from the stop time until the next start time.

[0156] This provides the same effect as the cell monitoring unit described above.

[0157] These general or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or as any combination of the system, method, integrated circuit, computer program, or recording medium. The program may be pre-stored in the recording medium, or may be supplied to the recording medium via a wide area communication network including the Internet.

[0158] The present disclosure is useful for cell monitoring units and the like included in battery management systems mounted on vehicles.

[0159] 1 Battery management system 10 Assembled battery 11 Battery cell 100 Cell monitoring unit 110 Battery monitoring unit 111 Power supply circuit (first power supply circuit) 111a, 133a Battery 111b Error amplifier 111c Triangular wave generating circuit 111d Comparator 111e Pre-Drive 112, 133 Power supply circuit 113 Voltage measurement circuit 114 Control circuit 114a, 141 Self-diagnosis circuit 120 Second power supply circuit 121 Resistor 122 Zener diode 123, 133c Transistor 130 Power supply circuit 131, 132 Diode 133b Operational amplifier 140 Wireless communication unit (first wireless communication unit) 142 Power supply detection unit 143 Monitoring unit 144 Start / stop control unit (control unit) 145 Non-volatile memory (storage unit) 146, 221 Communication unit 147 Time setting circuit (first time setting circuit) 148, 223 Time measurement unit 149, 224 Crystal oscillator 150, 230 Antenna 200 Battery control unit 210 Battery control unit 220 Wireless communication unit (second wireless communication unit) 222 Time setting circuit (second time setting circuit) s1 First power supply monitoring signal s2 Second power supply monitoring signal s3 First power supply control signal SW Switch T1 Power supply terminal T2 GND terminal

Claims

1. A cell monitoring unit that monitors battery cells, comprising: a battery monitoring unit that measures the state of the battery cells; a first power supply circuit; a second power supply circuit that supplies less power than the first power supply circuit; a communication unit for wireless communication with a higher-level system; a first time setting circuit that sets a start time and a stop time for the cell monitoring unit; and a first wireless communication unit that has a time measurement unit that measures the elapsed time from the stop time, wherein the first power supply circuit starts up at the start time and supplies power to the battery monitoring unit and the communication unit, and stops at the stop time, and the second power supply circuit supplies power to the time measurement unit from the stop time until the next start time.

2. The cell monitoring unit according to claim 1, wherein the battery monitoring section is activated while the first power supply circuit is activated, and measures the state of the battery cells.

3. A cell monitoring unit as described in claim 1 or 2, further comprising a self-diagnosis circuit that diagnoses whether at least one of the battery monitoring unit and the first wireless communication unit is operating normally while the first power supply circuit is activated.

4. A cell monitoring unit as described in claim 1 or 2, wherein the upper system is provided with a second time setting circuit that sets the startup time of a second wireless communication unit provided in the upper system, and the first time setting circuit sets the startup time of the cell monitoring unit so that the first wireless communication unit starts up at the startup time of the second wireless communication unit set by the second time setting circuit.

5. A cell monitoring unit as described in claim 1 or 2, wherein the first wireless communication unit further includes a power detection unit that detects the state of at least one of the first power supply circuit and the second power supply circuit that supply power to the first wireless communication unit.

6. The cell monitoring unit according to claim 5, further comprising a control unit that, when the power supply detection unit detects a voltage drop in the first power supply circuit, transitions to a low power consumption mode in which operation is possible only with power supplied by the second power supply circuit, and restarts the first power supply circuit.

7. The cell monitoring unit of claim 5, wherein the power supply detection unit detects whether the second power supply circuit is operating normally before stopping the first power supply circuit, and the first power supply circuit stops at the stop time if the power supply detection unit detects that the second power supply circuit is operating normally.

8. The cell monitoring unit according to claim 7, further comprising a storage unit that stores information indicating that an abnormality has been detected when the power supply detection unit detects an abnormality in the first power supply circuit.

9. A cell monitoring unit as described in claim 1 or 2, wherein the second power supply circuit is configured to be constantly activated from the moment the cell monitoring unit is connected to the battery cell, and the time measurement unit continues to operate regardless of the activation and cessation of the first power supply circuit.

10. The cell monitoring unit according to claim 1 or 2, wherein the first wireless communication unit further comprises a control unit that controls activation and deactivation of the first power supply circuit.

11. The cell monitoring unit according to claim 1 or 2, wherein the first power supply circuit is a switching power supply circuit, and the second power supply circuit includes a resistor, a Zener diode, and a transistor.

12. A monitoring method executed by a cell monitoring unit that monitors battery cells, the cell monitoring unit comprising: a battery monitoring unit that measures the state of the battery cells; a first power supply circuit; a second power supply circuit that supplies less power than the first power supply circuit; a communication unit for wireless communication with a higher-level system; a time setting circuit that sets a start time and a stop time for the cell monitoring unit; and a wireless communication unit having a time measurement unit that measures the elapsed time from the stop time, the monitoring method comprising: at the start time, starting up the first power supply circuit and supplying power to the battery monitoring unit and the communication unit; at the stop time, stopping the first power supply circuit; and from the stop time until the next start time, supplying power from the second power supply circuit to the time measurement unit.

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