Centralized and distributed sodium ion battery management system
By adopting centralized distributed design and active equalization technology in the sodium ion battery management system, the problems of short battery life and insufficient safety are solved, and higher stability, reliability and accuracy of battery status evaluation are achieved.
Patent Information
- Application Number
- CN202411814517.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-11
- Publication Date
- 2025-03-25
AI Technical Summary
The prior art is difficult to effectively manage sodium ion batteries, resulting in short battery life, insufficient safety and reliability, especially in electric bicycle applications.
The sodium ion battery management system is adopted that combines centralized distribution, and the system is divided into centralized modules and distribution modules, combined with active equalization technology and high-precision measurement units, the battery charge protection, equalization management and SOC/SOH evaluation are achieved.
Simplifies the installation process, improves the overall stability and reliability of the system, extends the battery life, and improves the accuracy of SOC estimation and SOH evaluation.
Smart Images
Figure CN119695307A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an electric vehicle battery management system, in particular to a centralized and distributed combined sodium ion battery management system, belonging to the technical field of electric vehicle battery management. Background Art
[0002] Electric bicycles are a type of electric vehicle. Compared with fuel-powered motorcycles, electric bicycles do not produce exhaust emissions during riding, do not pollute the environment, and help alleviate urban air pollution problems. Electric bicycles do not occupy motor vehicle lanes, and riding is less affected by traffic jams. They are convenient and fast, so they are deeply loved by consumers. As a result, the popularity of electric bicycles is increasing.
[0003] The structure of electric bicycles is relatively simple, with fewer parts, and the failure rate of electric motors is much lower than that of locomotive engines, so the maintenance cost is low. With the rapid development of the electric bicycle industry, the new national standard GB42295 has put forward higher requirements for the safety performance of electric bicycles and their accessories, including the safety of battery management systems such as lithium-ion and sodium-ion batteries. Therefore, it is particularly important to develop a battery management system (BMS) for sodium-ion batteries that is easy and reliable to install and convenient to maintain. Summary of the invention
[0004] The purpose of the present invention is to provide a sodium ion battery management system that combines centralized and distributed management. It adopts a centralized and distributed design and innovatively divides the sodium ion battery management system into centralized and distributed modules, which not only simplifies the installation process, but also improves the overall stability and reliability of the system. The combination of centralized and distributed management and the application of active balancing technology extend the service life of the battery. The high-precision measurement unit improves the accuracy of SOC estimation and SOH evaluation.
[0005] The technical solution adopted by the present invention to solve the above technical problems is: A sodium ion battery management system combining centralized and distributed management, comprising a centralized module and a distributed module, wherein the centralized module is responsible for charging protection and balanced management of the sodium ion battery, and the distributed module is responsible for collecting the cell voltage and temperature; The centralized module includes a master control BMS circuit, and the distributed module includes a sub-control BMS circuit; The master BMS circuit includes a central processing unit, a master communication interface, an active balancing control unit and a data acquisition unit 1; The sub-control BMS circuit includes a cell balancing control unit, a second data acquisition unit, and a sub-control communication interface, the main control communication interface is electrically connected to the sub-control communication interface, the main control BMS circuit is connected to a measuring unit through the first data acquisition unit, and the sub-control BMS circuit is electrically connected to the measuring unit through the second data acquisition unit; The measuring unit includes a voltage detection circuit, a current detection circuit and a temperature detection circuit.
[0006] Furthermore, the centralized module and the distributed module are electrically connected via a communication unit, and data is exchanged via the communication unit.
[0007] Furthermore, the centralized module includes a 16-bit analog-to-digital converter ADC, which is electrically connected to the measuring unit and is used to collect voltage information detected by the voltage detection circuit, current information detected by the current detection circuit, and temperature data detected by the temperature detection circuit.
[0008] Further, the voltage detection circuit includes a plurality of photoelectric coupler chipsets arranged in parallel, and the photoelectric coupler chipsets include chip U11, chip U12, chip U13 and chip U14; The model of the photocoupler chipset is: PC817C, the current detection circuit includes a chip U6, and the chip U6 is provided with resistors RS1 and RS2 in parallel; The temperature detection circuit includes a temperature detector TEMP. A sliding resistor RT is electrically connected to the temperature detector TEMP. A capacitor C8 is arranged in parallel to the sliding resistor RT.
[0009] Furthermore, the analog-to-digital converter ADC collects the total voltage, charging current, and discharging current of the distributed modules after being connected in series, collects the temperature data of the centralized module in real time, and performs SOC estimation and SOH evaluation of the entire battery pack after comprehensive calculation of these information; The SOC estimation algorithm uses a combination of an open circuit voltage method and a current integration method, combined with a Kalman filter algorithm to correct the SOC of the battery pack in real time. The basic formula is as follows: ; Where: SOC represents the battery state of charge at time t; SOC0 represents the initial capacity value of the battery state of charge; CE represents the rated capacity of the battery, usually in ampere-hours Ah; t is the time of charge and discharge; I(τ) is the charge and discharge current of the battery at time τ; It represents the current integral from time 0 to t, which is the accumulated charge and discharge quantity during this time; The SOH evaluation algorithm is the ratio of the current actual capacity of the battery to its nominal rated capacity, and its formula is expressed as: SOH = Qact / Qnom; Among them, Qact represents the actual capacity; Qnom stands for nominal capacity.
[0010] The Kalman filter adaptive filtering algorithm is adopted to continuously estimate the SOH by taking the number and time of balancing in the main control module and the sub-control module as the main parameters and combining the changes in the equivalent internal resistance parameters of the battery pack.
[0011] Further, the sub-control communication interface includes a transistor Q1, a transistor Q2, a transistor Q3 and a transistor Q4, a diode and a resistor R13 are provided in series between the transistor Q1 and the transistor Q2; A resistor R12 and a resistor R14 are connected in parallel between the transistor Q1 and the transistor Q3; A resistor R17 and a resistor R20 are connected in parallel between the transistor Q3 and the transistor Q4.
[0012] Further, the communication interface includes a transistor Q11, a transistor Q11, a transistor Q12 and a transistor Q13, a diode and a resistor R40 are provided in series between the transistor Q10 and the transistor Q11; A resistor R39 and a resistor R42 are connected in parallel between the transistor Q110 and the transistor Q12; A resistor R48 and a resistor R55 are connected in parallel between the transistor Q12 and the transistor Q13.
[0013] Furthermore, the main control BMS circuit includes a field effect transistor Q1, and the field effect transistor Q1 is electrically connected to a photocoupler U2, a photocoupler U4, and a rectifier, and the rectifier is electrically connected to a single-pole double-throw relay.
[0014] Furthermore, the cell balancing control unit includes an active balancing circuit, and the active balancing circuit includes a plurality of battery management chips arranged in parallel, and a capacitor is arranged between every two of the battery management chips.
[0015] Furthermore, the active balancing control unit includes a plurality of photoelectric couplers U1, photoelectric coupler U5 and photoelectric coupler U9 arranged in parallel, the photoelectric coupler U1 is electrically connected to a field effect transistor Q1, the photoelectric coupler U5 is electrically connected to a field effect transistor Q3, and the photoelectric coupler U9 is electrically connected to a field effect transistor Q5.
[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The centralized and distributed design is adopted, and the sodium-ion battery management system is innovatively divided into centralized and distributed modules, which not only simplifies the installation process, but also improves the overall stability and reliability of the system. The combination of centralized and distributed management and the application of active balancing technology extend the battery life. The high-precision measurement unit improves the accuracy of SOC estimation and SOH evaluation.
[0017] 2. When the main control BMS circuit of the battery pack recognizes that the charger is connected, the main control BMS circuit actively sends a communication message. The message contains the voltage and current requested by the battery pack for charging, as well as battery pack information, and has an encrypted field. After receiving the message, the charger confirms that it meets the requirements of the charging voltage and current parameters, and organizes the encrypted fields to reply to the BMS message in the agreed encryption method. After the BMS receives the encrypted fields of the message from the charger and compares them correctly, it turns on the charging switch to allow charging.
[0018] 3. Through the external circuit, the voltage, temperature and other parameters of the battery cells are monitored in real time, and the battery is precisely adjusted to achieve the purpose of balance. The active balancing system can actively intervene in the voltage difference between the battery cells, and transfer the excessive electric energy in the battery string to the low electric energy in the battery string, thereby maintaining the balance state of each string of batteries in the entire battery pack. The advantages of active balancing are fast balancing speed, high efficiency, low temperature rise, and more precise control of the voltage of each string of batteries to reduce energy waste. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 is the electrical schematic diagram of the present invention; Figure 2 This is the main control BMS circuit diagram of the present invention; Figure 3 A partial circuit diagram of a measuring unit of the present invention; Figure 4 The active balancing control unit circuit diagram of the present invention; Figure 5 It is a partial circuit diagram of the main control BMS circuit of the present invention; Figure 6 It is the main control communication interface circuit diagram of the present invention; Figure 7 A circuit diagram of a cell balancing control unit of the present invention; Figure 8 It is the circuit diagram of the sub-control communication interface of the present invention; Fig. 9 It is the temperature detection circuit diagram of the present invention.
[0020] In the figure, 1. centralized module; 2. distributed module; 3. main control BMS circuit; 301. central processing unit; 302. main control communication interface; 303. active balancing control unit; 304. data acquisition unit one; 4. sub-control BMS circuit; 401. cell balancing control unit; 402. data acquisition unit two; 403. sub-control communication interface; 5. communication unit; 6. measurement unit; 601. voltage detection circuit; 602. current detection circuit; 603. temperature detection circuit; 7. analog-to-digital converter ADC. DETAILED DESCRIPTION
[0021] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0022] like Figure 1-Figure 9 As shown, the centralized and distributed sodium ion battery management system provided in this embodiment includes a centralized module 1 and a distributed module 2. The centralized module 1 is responsible for the charging protection and balanced management of the sodium ion battery, and the distributed module 2 is responsible for the collection of the cell voltage and temperature. The centralized module 1 includes a main control BMS circuit 3, and the distributed module 2 includes a sub-control BMS circuit 4. The centralized and distributed design is adopted, and the sodium ion battery management system is innovatively divided into centralized and distributed modules, which simplifies the installation process and improves the overall stability and reliability of the system. The main control BMS circuit 3 includes a central processing unit 301, a main control communication interface 302, an active balancing control unit 303 and a data acquisition unit 304, which are responsible for the double protection of the sodium ion battery for external charging, ensuring that charging is disconnected in the case of unauthenticated, over-temperature, fault and full charge, and charging is allowed only after successful authentication and in compliance with charging conditions; Among them, the main control BMS circuit 3 and the charger are jointly authenticated as follows: When the main control BMS circuit 3 of the battery pack recognizes that the charger is connected, the main control BMS circuit 3 actively sends a communication message, which contains the voltage and current requested by the battery pack for charging, as well as the battery pack information, and has an encrypted field; After receiving the message, the charger confirms that it meets the requirements of the charging voltage and current parameters, and organizes the encrypted fields to reply to the BMS message according to the agreed encryption method. After the BMS receives the encrypted fields of the charger's message and compares them correctly, it turns on the charging switch to allow charging; During the charging process, the main control BMS circuit 3 continuously sends communication messages to the charger, including instructions such as charging continuation, pause, and completion; After charging is completed, disconnect the charging switch; The sub-control BMS circuit 4 includes a cell balancing control unit 401, a data acquisition unit 2 402 and a sub-control communication interface 403. The main control communication interface 302 is electrically connected to the sub-control communication interface 403. The main control BMS circuit 3 is connected to the measurement unit 6 through the data acquisition unit 1 304. The sub-control BMS circuit 4 is electrically connected to the measurement unit 6 through the data acquisition unit 2 402, and is responsible for the active balancing management between each sub-control module and the cell voltage and temperature collection of each distribution module, specifically: The balancing management of the sub-controlled BMS circuit 4 is the premise to ensure the safe and healthy use of the battery pack. The balancing methods include active balancing and passive balancing; The main control BMS circuit 3 includes a field effect tube Q1, and the field effect tube Q1 is electrically connected to a photoelectric coupler U2, a photoelectric coupler U4, and a rectifier, and the rectifier is electrically connected to a single-pole double-throw relay. The battery cell balancing control unit 401 includes an active balancing circuit, and the active balancing circuit includes a plurality of battery management chips arranged in parallel, and a capacitor is arranged between each two battery management chips. Passive balancing: The battery with a higher voltage is discharged by means of resistance discharge, and the electricity is released in the form of heat to achieve the balance of the voltage of the whole group. The advantages of this method are low cost and simple circuit design. However, the disadvantage of passive balancing is that the balancing speed is slow, and because the electrical energy is directly converted into heat energy, the temperature inside the battery pack rises, and the energy is also wasted. The active balancing control unit 303 includes a plurality of photoelectric couplers U1, photoelectric coupler U5 and photoelectric coupler U9 arranged in parallel. The photoelectric coupler U1 is electrically connected to a field effect transistor Q1, the photoelectric coupler U5 is electrically connected to a field effect transistor Q3, and the photoelectric coupler U9 is electrically connected to a field effect transistor Q5. Active balancing: the voltage, temperature and other parameters of the battery cells are monitored in real time through an external circuit, and the battery is precisely adjusted to achieve the purpose of balancing. The active balancing system can actively intervene in the voltage difference between the battery cells, and transfer the excessive electric energy in the battery string to the low electric energy in the battery string, so as to maintain the balance state of each string of batteries in the entire battery pack. The advantages of active balancing are fast balancing speed, high efficiency, low temperature rise, and more accurate control of the voltage of each string of batteries to reduce energy waste. In summary, passive balancing achieves voltage balancing at a lower cost and with a simple circuit, but it is inefficient and wastes energy; while active balancing, although more expensive and with a complex circuit, can achieve voltage balancing between battery strings in a battery pack more efficiently and energy-efficiently. In the present invention, the sub-control BMS circuit 4 in the main control module adopts active balancing technology to balance the voltage between the distribution modules; the sub-control module also adopts active balancing technology to balance the voltage between the battery strings in the module; The measuring unit 6 includes a voltage detection circuit 601, a current detection circuit 602 and a temperature detection circuit 603. In the main control BMS circuit 3, the centralized module includes a 16-bit analog-to-digital converter ADC7, which is electrically connected to the measuring unit 6, and is used to collect voltage information detected by the voltage detection circuit 601, current information detected by the current detection circuit 602 and temperature data detected by the temperature detection circuit 603. The 16-bit ADC collects the voltage of each module and the total voltage, charging current, and discharging current of each distributed module after being connected in series, collects the temperature data of this module in real time, and performs comprehensive calculations on this information to perform SOC estimation and SOH evaluation of the entire battery pack. The SOC battery state of charge and the SOH battery health state are two important parameters for evaluating the battery state. The analog-to-digital converter ADC7 collects the total voltage, charging current, and discharging current of the distributed module 2 in series, collects the temperature data of the middle module 1 in real time, and performs comprehensive calculations on the information to perform SOC estimation and SOH evaluation of the entire battery pack; The SOC estimation algorithm uses a combination of the open circuit voltage method and the current integration method, combined with the Kalman filter algorithm to correct the SOC of the battery pack in real time. The basic formula is as follows: ; Where: SOCt represents the battery state of charge at time t; SOC0 represents the initial capacity value of the battery state of charge; CE represents the rated capacity of the battery, usually in ampere-hours Ah; t is the time of charge and discharge; I(τ) is the charge and discharge current of the battery at time τ; It represents the current integral from time 0 to t, which is the accumulated charge and discharge quantity during this time; The SOH evaluation algorithm is the ratio of the current actual capacity of the battery to its nominal rated capacity, and its formula is expressed as: SOH = Qact / Qnom; Among them, Qact represents the actual capacity; Qnom stands for nominal capacity.
[0023] The Kalman filter adaptive filtering algorithm is adopted, and the number and time of balancing in the main control module and the sub-control module are continuously used as the main parameters, combined with the change of the equivalent internal resistance parameters of the battery pack, to estimate the SOH. The combination of centralized and distributed management improves the stability and reliability of the system. The application of active balancing technology prolongs the service life of the battery. The high-precision measurement unit improves the accuracy of SOC estimation and SOH evaluation.
[0024] Furthermore, if Figure 1 and Figure 3 As shown, the centralized module 1 and the distributed module 2 are electrically connected through the communication unit 5, and data is exchanged through the communication unit 5. The main control BMS circuit 3 sends a collection instruction to each sub-control BMS circuit 4 and receives the voltage and temperature information of each sub-control BMS circuit 4; The voltage detection circuit 601 includes a plurality of photoelectric coupler chipsets connected in parallel, the photoelectric coupler chipsets including chips U11, U12, U13 and U14. The voltage detection circuit 601 is used to measure the voltage of the pressure plate, to prevent the short circuit, tripping and other hidden faults of the power distribution equipment caused by improper operation, and to be used for electrical safety inspection, to timely discover potential electrical safety hazards, and to ensure the normal operation of the equipment and product quality; The model of the photocoupler chipset is: PC817C. The current detection circuit 602 includes a chip U6. The chip U6 is provided with resistors RS1 and RS2 in parallel. The current detection circuit 602 can monitor the current in the circuit in real time. When the current exceeds a preset safety threshold, an overload protection mechanism can be triggered, such as cutting off the power supply or reducing the output power, to prevent the circuit and the device from being damaged due to overheating or short circuit. The current detection circuit 602 can quickly detect such abnormal current and take corresponding protection measures. The temperature detection circuit 603 includes a temperature detector TEMP, to which a sliding rheostat RT is electrically connected, and a capacitor C8 is arranged in parallel with the sliding rheostat RT. The temperature detection circuit 603 can monitor and supervise the operating temperature of the circuit or equipment in real time, and converts the temperature into an electrical signal through the temperature detector TEMP, and then converts it into a digital signal through the analog-to-digital converter ADC7, and finally processes it by the processor. This function is crucial to ensuring the stable operation of the equipment and system.
[0025] Furthermore, if Figure 6 and Figure 8 As shown, the sub-control communication interface 403 includes transistors Q1, Q2, Q3 and Q4, a diode and a resistor R13 are arranged in series between the transistors Q1 and Q2, a resistor R12 and a resistor R14 are arranged in parallel between the transistors Q1 and Q3, and a resistor R17 and a resistor R20 are arranged in parallel between the transistors Q3 and Q4; The communication interface 302 includes transistors Q11, Q12, Q13, a diode and a resistor R40 are arranged in series between the transistors Q10 and Q11, resistors R39 and R42 are arranged in parallel between the transistors Q110 and Q12, and resistors R48 and R55 are arranged in parallel between the transistors Q12 and Q13. The sub-control communication interface 403 is electrically connected to the communication interface 302 to receive voltage, temperature and other information of each sub-control BMS circuit 4. It has a simple structure, low production cost, easy installation and convenient maintenance, which improves the safety and efficiency of the battery management system, meets the requirements of the new national standard electric vehicles, and has good market prospects.
[0026] like Figure 1-Figure 9 As shown, the principle of the centralized and distributed sodium ion battery management system provided in this embodiment is as follows: the distribution module 2 is responsible for the collection of the cell voltage and temperature, the centralized module 1 includes the main control BMS circuit 3, and the distribution module 2 includes the sub-control BMS circuit 4. The centralized and distributed design is adopted, and the sodium ion battery management system is innovatively divided into centralized and distributed modules, which simplifies the installation process and improves the overall stability and reliability of the system; The main control BMS circuit 3 includes a central processing unit 301, a main control communication interface 302, an active balancing control unit 303 and a data acquisition unit 304, which are responsible for the double protection of the sodium ion battery for external charging, ensuring that charging is disconnected in the case of unauthenticated, over-temperature, fault and full charge, and charging is allowed only after successful authentication and in compliance with charging conditions; The combination of centralized and distributed management improves the stability and reliability of the system. The application of active balancing technology prolongs the battery life. The high-precision measurement unit improves the accuracy of SOC estimation and SOH evaluation.
[0027] The above description shows and describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein, and that changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should be within the scope of protection of the claims attached to the present invention.
Claims
1. A sodium ion battery management system combining centralized and distributed management, comprising a centralized module (1) and a distributed module (2), characterized in that: The centralized module (1) is responsible for charging protection and balancing management of the sodium ion battery, and the distributed module (2) is responsible for collecting the cell voltage and temperature; The centralized module (1) comprises a master control BMS circuit (3), and the distributed module (2) comprises a sub-control BMS circuit (4); The master control BMS circuit (3) comprises a central processing unit (301), a master control communication interface (302), an active balancing control unit (303) and a data acquisition unit 1 (304); The sub-control BMS circuit (4) comprises a cell balancing control unit (401), a second data acquisition unit (402) and a sub-control communication interface (403), the main control communication interface (302) and the sub-control communication interface (403) are electrically connected, the main control BMS circuit (3) is connected to a measuring unit (6) via the first data acquisition unit (304), and the sub-control BMS circuit (4) is electrically connected to the measuring unit (6) via the second data acquisition unit (402); The measuring unit (6) comprises a voltage detection circuit (601), a current detection circuit (602) and a temperature detection circuit (603).
2. A sodium ion battery management system combining centralized and distributed management according to claim 1, characterized in that: The centralized module (1) and the distributed module (2) are electrically connected via a communication unit (5), and data exchange is performed via the communication unit (5).
3. A sodium ion battery management system combining centralized and distributed management according to claim 1, characterized in that: The centralized module comprises a 16-bit analog-to-digital converter ADC (7), the analog-to-digital converter ADC (7) being electrically connected to the measuring unit (6), and the analog-to-digital converter ADC (7) being used to collect voltage information detected by the voltage detection circuit (601), current information detected by the current detection circuit (602), and temperature data detected by the temperature detection circuit (603).
4. A sodium ion battery management system combining centralized and distributed management according to claim 3, characterized in that: The voltage detection circuit (601) comprises a plurality of photoelectric coupler chipsets arranged in parallel, wherein the photoelectric coupler chipsets comprise a chip U11, a chip U12, a chip U13 and a chip U14; The model of the photoelectric coupler chipset is: PC817C, the current detection circuit (602) comprises a chip U6, and a resistor RS1 and a resistor RS2 are arranged in parallel on the chip U6; The temperature detection circuit (603) comprises a temperature detector TEMP, the temperature detector TEMP is electrically connected to a sliding resistor RT, and a capacitor C8 is arranged in parallel with the sliding resistor RT.
5. The centralized and distributed sodium ion battery management system according to claim 3 is characterized in that: The analog-to-digital converter ADC (7) collects the total voltage, charging current and discharging current of the distributed modules (2) connected in series, collects the temperature data of the centralized module (1) in real time, and performs comprehensive calculations on this information to perform SOC estimation and SOH evaluation of the entire battery pack.
6. The sodium ion battery management system according to claim 1, characterized in that: The sub-control communication interface (403) comprises a transistor Q1, a transistor Q2, a transistor Q3 and a transistor Q4, wherein a diode and a resistor R13 are connected in series between the transistor Q1 and the transistor Q2; A resistor R12 and a resistor R14 are connected in parallel between the transistor Q1 and the transistor Q3; A resistor R17 and a resistor R20 are connected in parallel between the transistor Q3 and the transistor Q4.
7. The centralized and distributed sodium ion battery management system according to claim 1 is characterized in that: The communication interface (302) includes a transistor Q11, a transistor Q11, a transistor Q12 and a transistor Q13, and a diode and a resistor R40 are provided in series between the transistor Q10 and the transistor Q11; A resistor R39 and a resistor R42 are connected in parallel between the transistor Q110 and the transistor Q12; A resistor R48 and a resistor R55 are connected in parallel between the transistor Q12 and the transistor Q13.
8. The centralized and distributed sodium ion battery management system according to claim 1 is characterized in that: The main control BMS circuit (3) comprises a field effect transistor Q1, to which a photoelectric coupler U2, a photoelectric coupler U4 and a rectifier are electrically connected, and to which a single-pole double-throw relay is electrically connected.
9. The centralized and distributed sodium ion battery management system according to claim 1 is characterized in that: The cell balancing control unit (401) comprises an active balancing circuit, which comprises a plurality of battery management chips arranged in parallel, and a capacitor is arranged between every two of the battery management chips.
10. The centralized and distributed sodium ion battery management system according to claim 1, characterized in that: The active balancing control unit (303) comprises a plurality of photoelectric couplers U1, photoelectric coupler U5 and photoelectric coupler U9 which are arranged in parallel, the photoelectric coupler U1 is electrically connected to a field effect transistor Q1, the photoelectric coupler U5 is electrically connected to a field effect transistor Q3, and the photoelectric coupler U9 is electrically connected to a field effect transistor Q5.