A lithium iron phosphate battery management system used in garden tools

Abstract

The present invention discloses a lithium iron phosphate battery management system applied to garden tools, including a lithium iron phosphate battery pack, a microcontroller, and a PACK terminal. The microcontroller is connected to an external device through an interface circuit. The lithium iron phosphate battery pack is electrically connected to the microcontroller circuit through a battery monitoring and balancing circuit, a secondary protection circuit, a charge and discharge interface control circuit and a current sampling circuit, a power supply circuit, and a FUSE circuit. The secondary protection circuit is electrically connected to the microcontroller through a FUSE circuit, a charge and discharge interface control circuit, and a current sampling circuit respectively; the battery monitoring and balancing circuit is electrically connected to the microcontroller through a charge and discharge interface control circuit and a current sampling circuit; an external activation signal is used to close the microcontroller circuit; the microcontroller circuit and the battery monitoring and balancing circuit simultaneously realize the control of the charge and discharge interface control circuit and the current sampling circuit. The present invention realizes dual safety protection of the battery pack and modular system design.

Description

Technical Field

[0001] The invention relates to a lithium iron phosphate battery management system applied to garden tools, belongs to the field of battery safety protection, and adopts 12 strings of lithium iron phosphate batteries and a lithium iron phosphate battery management system for the first time in garden tools. Background Art

[0002] Garden tools are divided into three categories: engine (gasoline), mains and battery. Engine (gasoline) is being discontinued in many countries due to environmental issues. Mains garden tools are also decreasing year by year due to safety and portability. Battery power is becoming more and more popular due to its convenience and environmental protection. However, as power batteries and combination batteries are increasingly used in daily work and life, low-cost, high-safety batteries and battery management systems have become an urgent need in the market.

[0003] Currently, ternary lithium batteries and lithium manganese oxide batteries are used in the market. They are not stable when discharged at high rates, and will heat up rapidly, which is a high risk. In addition, the battery capacity is generally between 10AH and 20AH, which is relatively large. The power supply voltage is 36, 48, 56V, and 72V. The battery needs to be discharged at a high rate and has higher safety.

[0004] Especially under high temperature conditions, ternary materials decompose at 200°C, producing violent chemical reactions, releasing oxygen atoms, and are very likely to burn or explode under high temperature. Therefore, based on safety considerations, the use of ternary lithium batteries is temporarily limited to pure electric buses.

[0005] At present, from the public information and chip suppliers, the most widely used is to use the integrated chip analog front end as the core of the battery management system. For example: Chinese patent CN 205985247 U discloses an intelligent lithium battery management system for electric bicycles, which uses the battery management system of the analog front end of the ML5235 chip; CN 206117193U discloses a power lithium battery management system, which uses a battery management system of the control IC; CN 205304339U discloses an intelligent lithium battery management system device based on the BQ7694003 analog front end, and the lithium battery pack is connected to the MCU through a lithium battery analog front end chip BQ7694003; and CN109031151A discloses a low-cost battery string detection device and detection method. Compared with other devices, the device has a simple structure, uses the analog-to-digital converter built into the control CPU, and does not need to use an analog-to-digital front end chip, so the cost is low, and all single battery voltages can be detected at the same time, so the detection speed is fast.

[0006] There are many security loopholes and potential safety hazards in using analog front-end for battery management and detection. When the analog front-end is abnormal, the software may not be able to identify the fault; or, if the microcontroller is abnormal, it will also cause battery accidents, resulting in equipment failure and shutdown, or cause the analog front-end to operate incorrectly and the front-end control to be out of control.

[0007] Failure of the analog front end or the microcontroller will cause an accident. If the analog front end fails, the microcontroller will send a fault message. If the microcontroller fails, the system cannot be controlled normally, overcharging, over-discharging and over-current will occur, and safety cannot be guaranteed.

[0008] How to avoid damage to the battery by external charging equipment and avoid the connection of incompatible equipment, which may cause fire accidents in the battery pack, also requires protection from the battery management system.

[0009] Therefore, the design of the battery management system must consider safety issues in the event of malfunction or failure of each circuit part, and the battery management system must be made safer and more reliable through optimized design. Summary of the invention

[0010] The purpose of the present invention is to provide a lithium iron phosphate battery management system for use in garden tools, and to improve the safety and reliability of the battery management system through optimized design.

[0011] The purpose of the present invention is achieved through the following scheme: A lithium iron phosphate battery management system used in garden tools, including a lithium iron phosphate battery pack, a microcontroller, a PACK+ terminal, and a PACK- terminal. The microcontroller is connected to an external device through an interface circuit, wherein:

[0012] The lithium iron phosphate battery pack is electrically connected to the microcontroller circuit via the battery monitoring and balancing circuit or the secondary protection circuit, the charge and discharge interface control circuit and the current sampling circuit, the power supply circuit, and the FUSE circuit, wherein the secondary protection circuit is electrically connected to the microcontroller via the FUSE circuit, the charge and discharge interface control circuit, and the current sampling circuit respectively; the battery monitoring and balancing circuit is electrically connected to the microcontroller via the charge and discharge interface control circuit and the current sampling circuit; the microcontroller circuit and the battery monitoring and balancing circuit simultaneously control the charge and discharge interface control circuit and the current sampling circuit;

[0013] The interface circuit is a UART and RS485 circuit, and the microcontroller circuit is connected to the system external device through the UART and RS485 circuit; the power supply circuit uses an external activation signal in the communication mode of the combination of UART and RS485 to activate the closed-loop control circuit of the microcontroller circuit and control the power supply circuit at the same time;

[0014] The PACK+ terminal is led out by the FUSE circuit, and the PACK- terminal is led out by the charge and discharge interface control circuit and the current sampling circuit.

[0015] The present invention provides a lithium iron phosphate battery management system for garden tools, which is composed of a battery monitoring and balancing circuit, a microcontroller circuit, a charge and discharge interface control circuit, a current sampling circuit, and a power supply circuit to form a first protection system for voltage, current, and temperature protection, and a secondary protection circuit, a FUSE circuit, a power supply circuit, and a microcontroller circuit to form a second protection system, thereby realizing double safety protection for the battery pack. When the battery monitoring and balancing circuit fails to sample the voltage, current, and temperature signals of the battery pack, the secondary protection circuit, the FUSE circuit, and the microcontroller circuit form the second protection system. When the voltage, current, and temperature protection fails, the secondary protection circuit and the microcontroller circuit drive the FUSE circuit, and the FUSE circuit actively fuses to disconnect the charge and discharge circuit, and at this time, Pack+ and Pack- cannot be input and output. The safety of the battery management system is further improved.

[0016] On the basis of the above scheme, the microcontroller circuit is also electrically connected to at least one of the display circuit, the information storage circuit, the watchdog circuit, the real-time clock, the USB output circuit, the charge and discharge identification circuit and the temperature monitoring circuit. The power supply circuit supplies power to the display circuit, the UART and RS485 circuit, the information storage circuit, the watchdog circuit, the real-time clock, the USB output circuit, the charge and discharge identification circuit, and / or the temperature monitoring circuit through the microcontroller circuit. The storage of battery information is realized by the electrical connection between the microcontroller circuit and the information storage circuit; the display of the battery SOC is realized by the electrical connection between the microcontroller circuit and the display circuit; the microcontroller circuit is electrically connected to the watchdog circuit to ensure that the microcontroller circuit is in normal working state. When an abnormality occurs in the program in the microcontroller, the watchdog circuit starts to act and resets the microcontroller to restart work; the microcontroller circuit is electrically connected to the USB output circuit to realize USB charging of external devices; the microcontroller circuit is electrically connected to the charge and discharge identification circuit to wake up the microcontroller circuit during the interface and identify the charge and discharge status at the same time; the microcontroller circuit is electrically connected to the temperature monitoring circuit to realize the detection of battery charge and discharge temperature.

[0017] Furthermore, the communication circuit composed of UART and RS485 is used to connect with external devices, and the relevant information of the battery is sent to the external device that needs power supply. At the same time, the display circuit and information storage circuit connected to the microcontroller circuit read and write the relevant information of the battery, and the battery sleep function can also be activated through communication.

[0018] The principle of the present invention is: the battery monitoring and balancing circuit samples the voltage, current and temperature signals of the battery pack, outputs the charging and discharging control signals according to the protection value, and the signals are output to the microcontroller, the charging and discharging interface control circuit and the current sampling circuit. The microcontroller circuit counts the voltage, current and temperature signals, calculates the voltage, current and SOC and judges the temperature fault, and performs safety protection through the charging and discharging interface control circuit and the current sampling circuit. At the same time, through the communication circuit combined with UART and RS485, the charger or other equipment obtains the battery information through the communication circuit, performs safety work, and sends relevant information to the customer peripheral, mainly including the total battery voltage, the lowest temperature, the highest temperature, the MOSFET temperature, the highest voltage of a single cell, the lowest voltage of a single cell, the remaining capacity, the charging and discharging fault information, the number of charging and discharging cycles, the battery pack serial number and the software version and other information.

[0019] The battery pack of the present invention may also be a battery stack composed of ternary batteries.

[0020] Based on the above solution, the lithium iron phosphate battery pack is a 12-string lithium iron phosphate battery pack, and the capacity of the 12-string lithium iron phosphate battery pack can be 5-25AH, so as to flexibly build a circuit combination battery.

[0021] The microcontroller circuit comprises an MCU circuit, a voltage stabilizing circuit and an ESD surge protection circuit.

[0022] Based on the above solution, the battery monitoring and balancing circuit uses a battery sampling chip (AFE), which involves a balancing function circuit. The battery monitoring and balancing circuit can adjust the monitoring voltage, balancing voltage, balancing current, temperature and other parameters according to market demand, and can also adjust the delay time and recovery time accordingly. It consists of a battery voltage acquisition circuit, a balancing circuit, and a surge protection circuit.

[0023] Furthermore, the battery monitoring and balancing circuit is combined with a 12-string lithium iron phosphate battery pack and a microcontroller circuit.

[0024] Based on the above scheme, the power supply circuit adopts a 9-100V wide voltage input high-voltage step-down circuit.

[0025] Preferably, the power supply circuit includes a 9-75V input high-voltage step-down circuit, a micro-power consumption 5V power supply circuit and an isolated 5V power supply circuit.

[0026] Further preferably, the input 9-75V high voltage step-down circuit realizes the output of 5V power supply through the MIC28515 chip.

[0027] Among them, the micro-power consumption 5V power supply circuit uses MOSFET and voltage regulator diode for the first stage of pressure reduction, and a diode is connected in series to a three-terminal voltage regulator chip, and the three-terminal voltage regulator chip outputs 3.3V.

[0028] The isolated 5V power supply circuit is realized by the B0505 ​​power isolation module.

[0029] Based on the above scheme, the secondary protection circuit includes a voltage acquisition circuit for each battery cell and a fault trigger circuit. The circuit monitors the battery voltage through three secondary protection chips S8244 in cascade one, two, and three, and controls the fusing of the FUSE (fuse) through the CO terminal output signal; or, the MCU CON signal is used to control the fusing of the FUSE to achieve the purpose of secondary protection.

[0030] Based on the above solution, the communication circuit composed of UART and RS485 is used to connect to external devices, send battery-related information to external devices that need power, and read and write battery-related information through the display circuit and information storage circuit connected to the microcontroller circuit. The battery sleep function can also be activated through communication.

[0031] Furthermore, the communication circuit of the microcontroller circuit combined with UART and RS485 enables the charger or other equipment to obtain battery information through the communication circuit to perform safety work.

[0032] The watchdog circuit comprises a dedicated watchdog circuit, a power supply circuit and a surge protection circuit.

[0033] Based on the above scheme, the microcontroller circuit is electrically connected to the charge and discharge identification circuit and the watchdog circuit to wake up the microcontroller circuit and identify the charge and discharge status at the same time.

[0034] The real-time clock comprises a real-time clock circuit, a power supply circuit and a surge protection circuit.

[0035] The display circuit comprises a display driving circuit, a power supply circuit and a surge protection circuit.

[0036] Based on the above scheme, the combination of the microcontroller circuit, lithium iron phosphate battery pack, FUSE circuit and secondary protection circuit realizes the protection of charging, discharging, temperature and current of the battery pack in the event of failure of the battery monitoring and balancing circuit.

[0037] The information storage circuit includes an EEPROM or a Flash circuit.

[0038] On the basis of the above scheme, the charge and discharge interface control circuit and the current sampling circuit include a current sampling circuit, a discharge control circuit, a charging control circuit and a driving circuit. The main loop of the current sampling circuit is connected to the lithium iron phosphate battery pack and the secondary protection circuit on the left, and is connected to the battery monitoring and balancing circuit and the microcontroller circuit through a signal line. The main loop of the current sampling circuit is connected to the discharge control circuit and the charging control circuit on the right. The charging control circuit is connected to the Pack-terminal through the main loop, and the signal line is connected to the driving circuit. The discharge control circuit is connected to the driving circuit through the signal line, and the driving circuit is connected to the battery monitoring and balancing circuit and the microcontroller circuit through the signal line. The current sampling circuit is responsible for sampling the charge and discharge current, the discharge control circuit is responsible for protection control during discharge, the charging control circuit is responsible for protection control during charging, and the driving circuit is responsible for driving and controlling the discharge control circuit and the charging control circuit.

[0039] Based on the above scheme, the USB output circuit includes a DCDC step-down circuit, a USB identification circuit and a current limiting circuit. The USB output circuit realizes USB output through the TPS2511 or CX2889 chip, filters through the inductor, and then connects the WE05-4RVLC chip in parallel to realize ESD protection, and then connects the terminal for external output. The USB output circuit has the functions of identification and current limiting, automatically identifies the type of charging device, has low on-resistance, and the short-circuit protection current can be set externally to prevent external short circuit and overcurrent. At the same time, it has over-temperature protection function, shutdown automatic release function, and can prevent reverse current transmission.

[0040] In order to realize the dual protection of software and hardware, the present invention is provided with a system main program and a self-check monitoring program, and the process is as follows: the system is initialized, and after the initialization is completed, the program starts and the timer interrupt is judged yes or no, if no, the judgment is repeated;

[0041] If yes, start the loop and determine the occurrence time, check whether there is an overflow, if not, repeat the judgment; if yes, start AFE detection, current detection, voltage detection, temperature detection, MOS tube control, SOC estimation, LED drive, communication transceiver control, sleep control in sequence, after sleep control, return to overflow detection and loop detection.

[0042] The present invention is also provided with a self-check monitoring program, which starts from the self-check and sequentially performs: crystal oscillator accuracy detection, interrupt detection, PC register detection, Flash detection, RAM detection, communication detection, and ADC input detection. If there is no accuracy offset, the self-check is completed.

[0043] Compared with the prior art, the present invention comprises a first protection system for voltage, current and temperature protection, which is composed of a battery monitoring and balancing circuit, a microcontroller circuit, a charge and discharge interface control circuit, a current sampling circuit and a power supply circuit; a second protection system is composed of a secondary protection circuit, a FUSE circuit, a power supply circuit and a microcontroller circuit; the present invention realizes double safety protection for a ternary battery pack or a lithium iron phosphate battery pack; at the same time, the microcontroller circuit of the present invention realizes dual system operation through software, one way works normally, one way performs tracking measurement, when one way fails, the other way works seamlessly; when both ways have problems, the watchdog circuit is triggered, and the circuit resets the microcontroller circuit. The software implements a monitoring program internally, monitors whether the main program running process is abnormal, mainly monitors the core register bit, verifies whether the MCLK oscillates at a specified frequency, the percentage frequency drifts, checks the memory damage in the non-volatile memory, checks the CRC value of the memory, checks the RAM memory DC fault (using the march C algorithm), checks the reliability of the external EEPROM abnormal detection communication, checks, and checks the ADC reference voltage. The scheme meets the safety protection needs of the battery voltage, current, temperature, etc. in terms of performance, and at the same time, hardware dual system protection and software dual system protection.

[0044] The present invention truly realizes the double safety protection of the battery pack. The system adopts modular design and can be conveniently combined and designed according to the actual needs of customers, which saves costs and is convenient for operators to assemble, repair and replace. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present invention, further description is given below through the accompanying drawings.

[0046] Figure 1 This is a schematic diagram of a logic block diagram of a lithium iron phosphate battery management system used in garden tools according to the present invention;

[0047] Figure 2 It is a 9-75V high voltage step-down circuit for input;

[0048] Figure 3 To isolate the 5V power supply circuit, this is achieved through the B0505 ​​module (19);

[0049] Figure 4 It is a micro-power consumption 5V power supply circuit;

[0050] Figure 5 It is a secondary protection circuit;

[0051] Figure 6 It is the USB output circuit;

[0052] Figure 7 It is the charge and discharge interface control circuit and the current sampling circuit;

[0053] Figure 8 For the main program flow;

[0054] Fig. 9 To monitor the process flow;

[0055] Description of the symbols in the figure

[0056] 1-12 series lithium iron phosphate battery pack;

[0057] 2——Battery monitoring and balancing circuit;

[0058] 3——Secondary protection circuit;

[0059] 4——Microcontroller circuit;

[0060] 5——Charge and discharge interface control circuit and current sampling circuit;

[0061] 6——power supply circuit;

[0062] 7——FUSE circuit;

[0063] 8——display circuit;

[0064] 9——UART and RS485 circuit;

[0065] 10——Information storage circuit;

[0066] 11——Watchdog circuit;

[0067] 12——Real-time clock;

[0068] 13——USB output circuit;

[0069] 14——Charge and discharge identification circuit;

[0070] 15——Temperature monitoring circuit;

[0071] 16——Pack+terminal;

[0072] 17——Pack-terminal;

[0073] 18——MIC28515 chip;

[0074] 19——B0505 ​​module;

[0075] 20——Three-terminal voltage regulator chip;

[0076] 21, 22, 23——Secondary protection chip S8244 one, two, three;

[0077] 24, 25——FUSE 1, 2

[0078] 26——CX2889 chip;

[0079] 27——WE05-4RVLC chip;

[0080] 28——Current sampling circuit;

[0081] 29——discharge control circuit;

[0082] 30——Charging control circuit;

[0083] 31——Drive circuit. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention and do not have any limiting effect on it. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0085] The present invention provides a lithium iron phosphate battery management system for garden tools, such as Figure 1 As shown in the schematic diagram of the logic block diagram of a lithium iron phosphate battery management system used in garden tools of the present invention, it includes a built-in 12-string lithium iron phosphate battery pack 1, a battery monitoring and balancing circuit 2, a secondary protection circuit 3, a microcontroller circuit 4, a charge and discharge interface control circuit and a current sampling circuit 5, a power supply circuit 6, a FUSE circuit 7, a display circuit 8, a UART and RS485 circuit 9, an information storage circuit 10, a watchdog circuit 11, a real-time clock 12, a USB output circuit 13, a charge and discharge identification circuit 14, a temperature monitoring circuit 15, a Pack+ terminal 16 and a Pack-terminal 17; Figure 1 As shown: The present invention adopts modular design, and the connection mode between modules is:

[0086] The battery monitoring and balancing circuit 2 is connected to the 12-string lithium iron phosphate battery pack 1 via a collection line;

[0087] The secondary protection circuit 3 is connected to the 12-string lithium iron phosphate battery pack 1 through the acquisition line;

[0088] The 12 lithium iron phosphate battery packs are connected to the Pack+16 terminal via the FUSE circuit 7;

[0089] The power supply circuit 6 is connected to the 12-string lithium iron phosphate battery pack through a connecting line; the battery monitoring and balancing circuit 2 is connected to the charge and discharge interface control circuit and the current sampling circuit 5; the microcontroller circuit 4 is connected to the charge and discharge interface control circuit and the current sampling circuit 5; the microcontroller circuit 4 is connected to the power supply circuit 7; the microcontroller circuit 4 is connected to the FUSE circuit 7; the following are achieved:

[0090] The 12-string lithium iron phosphate battery pack 1 is electrically connected to the microcontroller circuit 4 via the battery monitoring and balancing circuit 2, the secondary protection circuit 3, the charge and discharge interface control circuit and the current sampling circuit 5, the power supply circuit 6, and the FUSE circuit 7.

[0091] 12 series of lithium iron phosphate battery packs 1 are respectively connected to the battery monitoring and balancing circuit 2, the secondary protection circuit 3, the charge and discharge interface control circuit and the current sampling circuit 5, the power supply circuit 6, the FUSE circuit 7 and the microcontroller circuit 4, wherein:

[0092] The battery monitoring and balancing circuit 2 is electrically connected to the microcontroller 4 via the charge and discharge interface control circuit and the current sampling circuit 5 to form a protection circuit. The microcontroller circuit 4 and the battery monitoring and balancing circuit 2 simultaneously control the charge and discharge interface control circuit and the current sampling circuit 5.

[0093] The secondary protection circuit 3 is electrically connected to the microcontroller 4 via the FUSE circuit 7, the charge and discharge interface control circuit and the current sampling circuit 5 to form another protection circuit;

[0094] The interface circuit is a UART and RS485 circuit 9, the microcontroller circuit 4 is connected to the system external device through the UART and RS485 circuit 9, and the power supply circuit 6 uses an external activation signal in the communication mode of the combination of UART and RS485 to activate the closed-loop control circuit of the microcontroller circuit 4 and control the power supply circuit at the same time;

[0095] The PACK+ terminal 16 is led out from the FUSE circuit 7 , and the PACK− terminal 17 is led out from the charge and discharge interface control circuit and the current sampling circuit 5 .

[0096] like Figure 1As shown, the microcontroller circuit 4 described in this embodiment is also electrically connected to the display circuit 8, the information storage circuit 10, the watchdog circuit 11, the real-time clock 12, the USB output circuit 13, the charge and discharge identification circuit 14 and the temperature monitoring circuit 15, respectively. The power supply circuit 6 supplies power to the display circuit 8, UART and RS485 circuit 9, information storage circuit 10, watchdog circuit 11, real-time clock 12, USB output circuit 13, charge and discharge identification circuit 14 and temperature monitoring circuit 15 through the microcontroller circuit 4. The storage of battery information is realized through the electrical connection between the microcontroller circuit 4 and the information storage circuit 10; the display of battery SOC is realized through the electrical connection between the microcontroller circuit 4 and the display circuit 8; the electrical connection between the microcontroller circuit 4 and the watchdog circuit 11 ensures that the microcontroller circuit 4 is in normal working state; the electrical connection between the microcontroller circuit 4 and the USB output circuit 13 realizes USB charging of external devices; the electrical connection between the microcontroller circuit 4 and the charge and discharge identification circuit 14 wakes up the microcontroller circuit 4 during the interface and identifies the charge and discharge status at the same time; the electrical connection between the microcontroller circuit 4 and the temperature monitoring circuit 15 realizes the detection of battery charge and discharge temperature.

[0097] The capacity of the 12-string lithium iron phosphate battery pack 1 of this embodiment is 5-25AH, so as to flexibly build a circuit combination battery.

[0098] The battery monitoring and balancing circuit 2 uses a battery sampling chip AFE, which includes a balancing function circuit. The battery monitoring and balancing circuit 2 is combined with a 12-string lithium iron phosphate battery pack 1 and a microcontroller circuit 4.

[0099] In this embodiment, the power supply circuit 6 adopts a 9-75V wide voltage input high-voltage step-down circuit, including an input 9-75V high-voltage step-down circuit, a micro-power consumption 5V power supply circuit, and an isolated 5V power supply circuit, wherein:

[0100] like Figure 2 As shown in the 9-75V input high voltage buck circuit, the MIC28515 chip 18 is used to achieve the output of 5V power supply. The MIC28515 is a frequency-adjustable synchronous buck regulator with a unique adaptive on-time control architecture. The MIC28515 can operate in the 4.5V to 75V input voltage range and provide a maximum of 5A of stable output current. The output voltage can be adjusted down to 0.6V with a guaranteed accuracy of ±1%.

[0101] Figure 3 To isolate the 5V power supply circuit, a B0505 ​​power isolation module 19 is used.

[0102] Figure 4It is a micro-power consumption 5V power supply circuit, which uses MOSFET and voltage regulator diode to do the first stage of pressure reduction, and a diode is connected in series to a three-terminal voltage regulator chip 20, which outputs 3.3V.

[0103] Secondary protection circuits, such as Figure 5 As shown, it includes a voltage acquisition circuit for each battery and a fault triggering circuit; the circuit monitors the battery voltage through three secondary protection chips S8244 1, 2, 3 21, 22, 23 cascaded, and controls the fuse 1, 2 24, 25 to be blown through the CO terminal output signal to achieve the secondary protection purpose. At the same time, the fuse control of FUSE 1, 2 24, 25 can also be realized through the MCU CON signal.

[0104] Figure 6 The USB output circuit realizes USB output through TPS2511 or CX2889 chip 26. The circuit has the functions of identification and current limiting, and can automatically identify the type of charging device. The on-resistance is low, and the short-circuit protection current can be set externally to prevent external short circuit and overcurrent. At the same time, it has the functions of over-temperature protection and shutdown automatic release, and can prevent reverse current transmission. The circuit is connected to the right with an inductor for filtering, and then connected in parallel with a WE05-4RVLC chip (27) to realize ESD protection, and then connected to the terminal for external output.

[0105] like Figure 7 As shown in the charge and discharge interface control circuit and the current sampling circuit, it includes a charge control circuit 30, a discharge control circuit 29, a current sampling circuit 28, and a drive circuit 31. The main circuit of the current sampling circuit 28 is connected to the 12-string lithium iron phosphate battery pack 1 and the secondary protection circuit 3 on the left, and is connected to the battery monitoring and balancing circuit 2 and the microcontroller circuit 4 through a signal line. The main circuit of the current sampling circuit 28 is connected to the discharge control circuit 29 and the charge control circuit 30 on the right. The charge control circuit 30 is connected to the Pack-terminal 17 through the main circuit, and the signal line is connected to the drive current 31. The discharge control circuit 29 is connected to the drive current 31 through the signal line. The drive current 31 is connected to the battery monitoring and balancing circuit 2 and the microcontroller circuit 4 through the signal line. The current sampling circuit 28 is mainly responsible for sampling the charge and discharge currents, the discharge control circuit 29 is mainly responsible for the protection control during discharge, the charge control circuit 30 is mainly responsible for the protection control during charging, and the drive current 31 is mainly responsible for driving and controlling the discharge control circuit 29 and the charge control circuit 30.

[0106] This embodiment also adopts dual-soft program control, including a main program and a monitoring program.

[0107] like Figure 8 As shown in the main program flow chart, the main program flow is as follows: the system is initialized. After the initialization is completed, the program starts and the timer interrupt judges whether it is yes or no. If no, repeat the judgment; if yes,

[0108] Start the loop and determine the occurrence time, check whether there is an overflow, if not, repeat the judgment, if it is, start the sequential detection, AFE detection, current detection, voltage detection, temperature detection, MOS tube control, SOC estimation, LED drive, communication transceiver control, sleep control. After sleep control, return to overflow detection and loop.

[0109] The present invention is also provided with a self-check monitoring program, starting from the self-check, the sequence is: crystal oscillator accuracy detection, interrupt detection, PC register detection, Flash detection, RAM detection, communication detection, ADC input detection, if there is no accuracy offset, the self-check is completed.

[0110] The working principle of this embodiment is as follows: the battery monitoring and balancing circuit 2 samples the voltage, current and temperature signals of the battery pack, outputs the charging and discharging control signals according to the protection value, and outputs them to the microcontroller circuit 4, the charging and discharging interface control circuit and the current sampling circuit 5. The microcontroller circuit 4 performs statistics on the voltage, current and temperature signals, calculates the voltage, current and SOC, and judges the temperature fault, and performs safety protection through the charging and discharging interface control circuit and the current sampling circuit 5. At the same time, relevant information is sent to the customer peripherals through the UART and RS485 circuit 9, mainly including the total battery voltage, the lowest temperature, the highest temperature, the MOSFET temperature, the highest voltage of a single cell, the lowest voltage of a single cell, the remaining capacity, the charging and discharging fault information, the number of charging and discharging cycles, the battery pack serial number and the software version. When the battery monitoring and balancing circuit 2 fails to sample the voltage, current, and temperature signals of the battery pack, the secondary protection circuit 3, the FUSE circuit 7, and the microcontroller circuit 4 form a second protection system. When the voltage, current, and temperature fail, the secondary protection circuit 3 and the microcontroller circuit 4 drive the FUSE circuit 7, and the FUSE circuit 7 actively fuses to disconnect the charge and discharge circuit. At this time, the Pack + terminal 16 and the Pack - terminal 17 cannot input or output. When an abnormality occurs in the program in the microcontroller, the watchdog circuit 11 starts to act, and the reset microcontroller starts working again.

[0111] Through the above specific embodiments, the beneficial effects of the present invention are: the combination mode of 12-series lithium iron phosphate battery pack 1, battery monitoring and balancing circuit 2, secondary protection circuit 3, microcontroller circuit 4, charge and discharge interface control circuit and current sampling circuit 5 effectively improves the safety of the lithium iron phosphate battery management system of garden tools, meets the overvoltage, undervoltage, overcurrent and short circuit protection functions of the 12-series lithium iron phosphate battery pack; realizes the performance of secondary protection when the system fails; the internal design of the software realizes two sets of software, one for normal operation and one for tracking measurement, while the external watchdog circuit 11 and real-time clock 12 ensure that the system is restarted when the system is abnormal in an emergency; the charge and discharge identification circuit 14 can prevent the charger from being abused, and ensure that when a charger that does not match the device is inserted, no safety accident will occur. The charge and discharge identification circuit 14 can prevent the insertion and use of non-matching devices, and is connected to the outside through the UART and RS485 communication circuit 9, and displays the battery voltage, temperature, current, number of cycles, fault information, power information, battery health status, and battery serial number in real time. The charge and discharge identification circuit 14 and the UART and RS485 communication circuit 9 are implemented by sharing two interfaces, TXD (ID) and RXD (ID), thus saving connector interfaces.

[0112] The present invention adopts hardware dual system protection and software dual system protection, truly realizing the double safety protection of the battery pack. The system design adopts a modular mode, which can be conveniently combined and designed according to the actual needs of customers, thus saving costs.

[0113] A lithium iron phosphate battery management system for garden tools adopts a modular design, which is convenient for workers to assemble and repair and replace. Various modifications to these embodiments will be obvious to professionals in the field, and the general principles defined in this article can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this article, but will conform to the widest scope consistent with the principles and novel features disclosed in this article.

Claims

1. A lithium iron phosphate battery management system for garden tools, comprising a lithium iron phosphate battery pack, a microcontroller, a PACK+ terminal (16), and a PACK- terminal (17), wherein the microcontroller is connected to an external device via an interface circuit, and ... , The lithium iron phosphate battery pack (1) is electrically connected to a microcontroller circuit (4) via a battery monitoring and balancing circuit (2), a secondary protection circuit (3), a charge and discharge interface control circuit and a current sampling circuit (5), a power supply circuit (6), and a FUSE circuit (7), wherein the secondary protection circuit (3) is electrically connected to the microcontroller circuit (4) via the FUSE circuit (7), the charge and discharge interface control circuit, and the current sampling circuit (5); the battery monitoring and balancing circuit (2) is electrically connected to the microcontroller circuit (4) via the charge and discharge interface control circuit and the current sampling circuit (5); the microcontroller circuit (4) and the battery monitoring and balancing circuit (2) simultaneously control the charge and discharge interface control circuit and the current sampling circuit (5); The interface circuit is a UART and RS485 circuit (9), the microcontroller circuit (4) is connected to the system external device via the UART and RS485 circuit (9), the power supply circuit (6) uses an external activation signal in a communication mode of a combination of UART and RS485 to activate the closed-loop control circuit of the microcontroller circuit and control the power supply circuit at the same time; The PACK+ terminal (16) is led out from the FUSE circuit (7), and the PACK- terminal (17) is led out from the charge and discharge interface control circuit and the current sampling circuit (5); wherein, The microcontroller circuit (4) is also electrically connected to at least one of a display circuit (8), an information storage circuit (10), a watchdog circuit (11), a real-time clock (12), a USB output circuit (13), a charge and discharge identification circuit (14), and a temperature monitoring circuit (15). The power supply circuit (6) supplies power to the display circuit (8), the UART and RS485 circuit (9), the information storage circuit (10), the watchdog circuit (11), the real-time clock (12), the USB output circuit (13), the charge and discharge identification circuit (14) and the temperature monitoring circuit (15) through the microcontroller circuit (4). The storage of battery information is achieved through the electrical connection between the microcontroller circuit (4) and the information storage circuit (10); the display of the battery SOC is achieved through the electrical connection between the microcontroller circuit (4) and the display circuit (8); the microcontroller circuit (4) and the watchdog circuit (11) are electrically connected to ensure that the microcontroller circuit (4) is in a normal working state; the microcontroller circuit (4) and the USB output circuit (13) are electrically connected to realize USB charging of external devices; the microcontroller circuit and the charge and discharge identification circuit are electrically connected to wake up the microcontroller circuit when the interface is connected, and the charge and discharge state is identified at the same time; the microcontroller circuit (4) and the temperature monitoring circuit (15) are electrically connected to detect the charge and discharge temperature of the battery; The communication circuit combined with UART and RS485 is used to connect with external devices, and the relevant information of the battery is sent to the external device that needs power supply. At the same time, the relevant information of the battery is read and written through the display circuit and information storage circuit connected to the microcontroller circuit (4), and the battery dormancy function is activated by communication; The microcontroller circuit (4) is combined with a UART and RS485 communication circuit to enable a charger or other device to obtain battery information through the communication circuit and perform safety work; The USB output circuit (13) realizes USB output through a TPS2511 or CX2889 chip (26), performs ESD protection through inductor filtering, and then connects a WE05-4RVLC chip (27) in parallel, and then connects the terminals for external output; the USB output circuit (13) has the functions of identification and current limiting, automatically identifies the type of charging device, has low on-resistance, and the short-circuit protection current can be set externally to prevent external short circuit and overcurrent. It also has an over-temperature protection function, a shutdown automatic release function, and can prevent reverse current transmission.

2. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that The lithium iron phosphate battery pack (1) is a 12-string lithium iron phosphate battery pack, and the capacity of the 12-string lithium iron phosphate battery pack is 5-25AH, so as to flexibly build a circuit combination battery.

3. A lithium iron phosphate battery management system for garden tools according to claim 1 or 2, characterized in that The battery monitoring and balancing circuit (2) uses a battery sampling chip ( AFE ), which involves balanced Function Circuit.

4. A lithium iron phosphate battery management system for garden tools according to claim 3, characterized in that The battery monitoring and balancing circuit (2) is combined with a 12-string lithium iron phosphate battery pack and a microcontroller circuit (4).

5. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that The power supply circuit (6) adopts a high voltage step-down circuit with a wide voltage input of 9 to 75 V.

6. A lithium iron phosphate battery management system for garden tools according to claim 5, characterized in that The power supply circuit (6) includes a 9-75V input high-voltage step-down circuit, a micro-power consumption 5V power supply circuit, and an isolated 5V power supply circuit.

7. A lithium iron phosphate battery management system for garden tools according to claim 6, characterized in that The input 9-75V high voltage step-down circuit realizes the output of 5V power supply through the MIC28515 chip (18).

8. A lithium iron phosphate battery management system for garden tools according to claim 6, characterized in that The micro-power consumption 5V power supply circuit uses MOSFET and voltage regulator diode to perform first-stage pressure reduction, and a diode is connected in series to a three-terminal voltage regulator chip (20), and the three-terminal voltage regulator chip (20) outputs 3.3V.

9. A lithium iron phosphate battery management system for garden tools according to claim 6, characterized in that , isolate the 5V power supply circuit, which is achieved through the B0505 ​​power isolation module (19).

10. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that The secondary protection circuit (3) includes a voltage acquisition circuit for each battery cell and a fault trigger circuit. The circuit monitors the battery voltage through three secondary protection chips S82441 (21), S82442 (22), and S82443 (23) in cascade connection, and controls the fuse to be blown through the CO terminal output signal; or, controls the fuse to be blown through the MCU CON signal to achieve the purpose of secondary protection.

11. The lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that: The electrically connected combination of the microcontroller circuit (4), the charge and discharge identification circuit and the watchdog circuit (11) wakes up the microcontroller circuit (4) and identifies the charge and discharge status at the same time.

12. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that The combination of the microcontroller circuit (4), the lithium iron phosphate battery pack (1), the FUSE circuit (7) and the secondary protection circuit (3) realizes the protection of the charging, discharging, temperature and current of the battery pack in the event that the battery monitoring and balancing circuit (2) fails.

13. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that , the information storage circuit (10) includes an EEPROM or a Flash circuit.

14. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that The charge and discharge interface control circuit and the current sampling circuit (5) include a current sampling circuit (28), a discharge control circuit (29), a charge control circuit (30) and a drive circuit (31). The main circuit of the current sampling circuit (28) is connected to the lithium iron phosphate battery pack (1) and the secondary protection circuit (3), and is connected to the battery monitoring and balancing circuit (2) and the microcontroller circuit (4) through a signal line. The current sampling circuit (28) The main circuit is connected to the discharge control circuit (29) and the charging control circuit (30) on the right side. The charging control circuit (30) is connected to the PACK-terminal (17) through the main circuit and is connected to the drive circuit (31) through a signal line. The discharge control circuit (29) is connected to the drive circuit (31) through a signal line. The drive circuit (31) is connected to the battery monitoring and balancing circuit (2) and the microcontroller circuit (4) through a signal line. The current sampling circuit (28) is responsible for sampling the charge and discharge current. The discharge control circuit (29) is responsible for protection control during discharge. The charging control circuit (30) is responsible for protection control during charging. The drive circuit (31) is responsible for driving and controlling the discharge control circuit (29) and the charging control circuit (30).

15. A lithium iron phosphate battery management system for garden tools according to claim 1, characterized in that , a main program and a self-check monitoring program are provided, the main program flow is as follows: the system is initialized, after the initialization is completed, the program starts and the timer interrupt is used to judge whether it is yes or no, if not, the judgment is repeated; If yes, start the loop and determine the occurrence time to check whether there is an overflow. If not, repeat the judgment. If yes, start AFE detection, current detection, voltage detection, temperature detection, MOS tube control, SOC estimation, LED drive, communication transceiver control, and sleep control in sequence. After sleep control, return to overflow detection and loop detection.

16. A lithium iron phosphate battery management system for garden tools according to claim 15, characterized in that ,The system has a self-test monitoring program, starting from the self-test, the sequence is: crystal oscillator accuracy test, interrupt test, PC register test, Flash test, RAM test, communication test, ADC input test. If there is no accuracy offset, the self-test is completed.

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