A battery protection circuit

Abstract

The present application discloses a battery protection circuit. The battery protection circuit includes a secondary protection circuit. One end of the secondary protection circuit is connected to the battery cell. The battery cell includes a first battery cell and a second battery cell, and the first battery cell and the second battery cell are connected in series. The secondary protection circuit includes a first integrated circuit for secondary protection and a second integrated circuit for secondary protection, which are respectively used to detect the first battery cell voltage across the first battery cell and the second battery cell voltage across the second battery cell, and implement overvoltage and / or undervoltage protection functions according to the voltages. The secondary protection circuit further includes a secondary current detection component. The first integrated circuit for secondary protection uses the secondary current detection component to monitor the current flowing through the battery cell, and performs circuit protection according to the monitoring result. By adding a current protection function to the secondary protection circuit in the present application, the secondary protection circuit can still implement overvoltage and overcurrent protection functions in the case where the primary protection circuit fails.

Description

Technical Field

[0001] This patent designs battery protection technology, especially the charging architecture and battery protection scheme for two-series-one-parallel (2S1P) batteries used in consumer electronics such as mobile phones, drones, and robots. Background Art

[0002] A limited power source (LPS) is a requirement for power supply safety in safety standards such as IEC60950-1. The design of a power supply that meets the LPS standard should comply with the standards of the maximum allowable output voltage, output current, and output power. It is generally recognized in the industry that a power supply that can be a qualified LPS will not cause electric shock or fire because the output current and voltage it delivers to the load are limited.

[0003] In the current battery series connection (2S1P) scheme, there is no design on the market that can meet the LPS (Limited Power Source) scheme, so the battery cannot pass the relevant battery verification. When the primary battery protection fails, the battery cannot provide overcurrent protection, bringing potential battery safety hazards. Summary of the Invention

[0004] To solve the technical problem that the secondary battery protection circuit in the prior art cannot well protect battery safety, the present invention proposes a battery protection circuit that can meet all aspects of LPS requirements.

[0005] In one scheme, the battery protection circuit includes a secondary protection circuit. One end of the secondary protection circuit is connected to the battery cell. The battery cell includes a first battery cell and a second battery cell, and the first battery cell and the second battery cell are connected in series. The secondary protection circuit includes a first secondary protection integrated circuit and a second secondary protection integrated circuit, which are respectively used to detect the first battery cell voltage across the first battery cell and the second battery cell voltage across the second battery cell, and implement overvoltage and / or undervoltage protection functions according to the voltages. The secondary protection circuit also includes a secondary current detection element. The first secondary protection integrated circuit uses the secondary current detection element to monitor the current flowing through the battery cell and performs circuit protection according to the monitoring results.

[0006] In a further scheme, the secondary current detection element is connected in series with the battery cell.

[0007] In a further scheme, it further includes a battery protection logic circuit, which is used to start circuit protection when the voltage or current exceeds the standard.

[0008] In a further solution, the secondary current detection element is a resistance element. The current detection resistance ports and the common terminal in the first integrated circuit for secondary protection and / or the second integrated circuit for secondary protection are respectively connected to both ends of the secondary current detection element to detect the voltage difference across the secondary current detection element. The first integrated circuit for secondary protection and / or the second integrated circuit for secondary protection includes an overcurrent comparison circuit, which is configured to output an overcurrent protection signal when the voltage difference signal is greater than a threshold value.

[0009] In a further solution, the first integrated circuit for secondary protection includes a first overvoltage comparison circuit and / or the second integrated circuit for secondary protection includes a second overvoltage comparison circuit. The first overvoltage protection circuit is configured to output a first overvoltage protection signal when the voltage of the first battery cell (VC1) is greater than a first overvoltage threshold value. The second overvoltage protection circuit is configured to output a second overvoltage protection signal when the voltage of the second battery cell (VC2) is greater than a second overvoltage threshold value.

[0010] In a further solution, the first integrated circuit for secondary protection (61) includes a first undervoltage comparison circuit and / or the second integrated circuit for secondary protection (62) includes a second undervoltage comparison circuit. Wherein, the first undervoltage comparison circuit is configured to output a first undervoltage protection signal when the voltage of the first battery cell is lower than a first undervoltage threshold value. The second undervoltage comparison circuit is configured to output a second undervoltage protection signal when the voltage of the second battery cell is lower than a second undervoltage threshold value.

[0011] In a further solution, the first integrated circuit for secondary protection and / or the second integrated circuit for secondary protection includes a charge and discharge detection port, a common terminal, a charge and discharge state discriminator, a charge overcurrent comparator, and a discharge overcurrent comparator. Wherein, the charge and discharge detection port and the common terminal are respectively connected to both ends of the secondary current detection element to detect the voltage difference across the secondary current detection element. The charge and discharge state discriminator is configured to receive the voltage difference signal, judge the voltage difference signal, and output a voltage polarity signal. When the charge and discharge state discriminator determines that it is in a charging state according to the voltage difference signal, the charge overcurrent comparator compares the voltage difference across the current detection resistor with a charge overcurrent protection threshold value (Vth1) to determine whether charge overcurrent occurs, and outputs a charge overcurrent protection signal to activate circuit protection. When the charge and discharge state discriminator determines that it is in a discharging state according to the voltage difference signal, the discharge overcurrent comparator compares the voltage difference across the current detection resistor with a discharge overcurrent protection threshold value (Vth2) to determine whether discharge overcurrent occurs, and outputs a discharge overcurrent protection signal to activate circuit protection.

[0012] In a further solution, the first integrated circuit for secondary protection and / or the second integrated circuit for secondary protection includes a short-circuit protection circuit. The short-circuit protection circuit is configured to output a short-circuit protection signal to activate circuit protection when the voltage difference is greater than a short-circuit protection threshold value.

[0013] In a further embodiment, the battery protection circuit further includes a primary protection circuit. One end of the primary protection circuit is connected to the secondary protection circuit, and the other end is connected to the power input / output terminal. The primary protection circuit includes a fuel gauge integrated circuit, a primary current sensing resistor, and a primary protection element connected in series with the battery cell. The primary protection circuit has overvoltage protection function and / or overcurrent protection function.

[0014] In a further embodiment, the primary protection element includes a charging switch and a discharging switch. The fuel gauge integrated circuit is connected to both ends of the primary current sensing resistor through its current sensing negative terminal and current sensing positive terminal respectively to detect the voltage difference across the resistor. The fuel gauge integrated circuit includes an overcurrent judgment circuit, which judges whether an overcurrent has occurred according to the voltage difference, and outputs a control signal to turn off the charging switch and the discharging switch in case of overcurrent.

[0015] In a further embodiment, the current sensing resistor port and the common terminal in the secondary protection second integrated circuit are respectively connected to both ends of the secondary current sensing element to detect the voltage difference across the secondary current sensing element; the current sensing resistor port and the charge / discharge detection port in the secondary protection second integrated circuit are connected to the common terminal of the secondary protection second integrated circuit.

[0016] Advantageous effects: By adding a current protection function to the secondary protection circuit in the present invention, the secondary protection circuit can still achieve overvoltage and overcurrent protection functions in case of failure of the primary protection circuit, ensuring the safety of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0018] Figure 1 It is the circuit schematic diagram of the charging architecture of the existing 2S1P battery and the battery protection circuit.

[0019] Figure 2 It is the circuit schematic diagram of a battery protection circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. In addition, it should be noted that only the parts related to the invention are shown in the drawings for the convenience of description.

[0021] The terms "first", "second" and similar terms used in this application do not denote any order, quantity or importance, but are only used to distinguish different parts. Terms such as "comprising" or "including" mean that the elements before this word cover the elements listed after this word, and do not exclude the possibility of also covering other elements. Terms such as "upper", "lower", "left", "right" are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0022] Figure 1 It is the circuit schematic diagram of the charging architecture for a 2S1P battery and the battery protection circuit.

[0023] Figure 1 In the shown battery protection circuit, the battery is a 2S1P two-series and one-parallel battery, including two series-connected battery cells: the first and second battery cells Cell1 and Cell2 (22, 23). The battery protection circuit includes a primary protection circuit (10) and a secondary protection circuit (20) in three parts.

[0024] The secondary protection circuit (20) mainly realizes the overvoltage protection function by the overvoltage protection chip (21). The common terminal VSS (212) of the overvoltage protection chip (21) is connected to the negative electrode of the first battery cell (23), and the ports VC1 and VC2 are respectively connected to the positive electrodes of Cell1 and Cell2 to measure the voltages of the two battery cells Cell1 and Cell2. The fuse signal output terminal OUT (211) of the overvoltage protection chip (21) controls the fusing of the fuse (25) by controlling the on / off of the MOS switch (24). Thus, during the charging and discharging process, when the voltages borne by the battery cells Cell1 and Cell2 exceed the threshold value, the secondary protection circuit (20) fuses the circuit, thereby activating the circuit protection function and realizing the protection of the battery cells.

[0025] The primary protection circuit 10 mainly includes a fuel gauge chip (11). The fuel gauge chip (11) controls the charge and discharge MOS switch (16) through the charge control port (115) and the discharge control port (116) to realize the one-way conduction control of the charge and discharge circuits. The positive terminal port (114) and the negative terminal port (113) of the current sensing resistor in the fuel gauge chip (11) detect the circuit current according to the voltage across the resistor (17), and the voltage acquisition can be realized in a similar way to that of the secondary protection circuit (20). When the fuel gauge chip (11) detects an overcurrent and / or overvoltage situation, it controls the charge and discharge MOS switch (16) to turn off to protect the charging circuit.

[0026] It can be seen that Figure 1The secondary protection circuit (20) among them only has overvoltage protection function and does not have overcurrent protection function. When the primary protection circuit (10) fails, the secondary protection circuit cannot protect the battery safety well. It cannot meet all aspects of requirements of LPS for voltage, current and power, and cannot pass the LPS certification in battery UL2054.

[0027] As Figure 2 shown, it is the schematic diagram of the battery protection circuit involved in the present invention. This battery can be, for example, a two-series and one-parallel (2S1P) battery circuit, which is composed of a first battery cell 63 and a second battery cell 64 connected in series. One end of the first battery cell 63 is connected to the negative pole P- (53) of the power input / output terminal, the other end of the first battery cell 63 is connected in series with one end of the second battery cell 64, and the other end of the second battery cell 64 is connected to the positive pole (P+) 52 of the power input / output terminal. The negative pole (P-) 53 and the positive pole (P+) 52 of the power input / output terminal are respectively connected to a load or a charging circuit (the load or the charging circuit is not shown), and are used to output electric energy to the load in the discharge state, or obtain electric energy from the charging circuit in the charging state to charge the first battery cell 63 and the second battery cell 64.

[0028] Figure 2 Among them, the protection circuit includes a primary protection circuit 50 and a secondary protection circuit 60. One end of the secondary protection circuit 60 is connected to the first and second battery cells 64 and 63, and the other end is connected to the primary protection circuit 50. One end of the primary protection circuit 50 is connected to the secondary protection circuit 60, and the other end is connected to the power input / output terminals 52 and 53. The whole design realizes safety protections such as overcurrent during charging, overcurrent during discharge, overvoltage, undervoltage, short circuit, etc., and can meet the LPS design.

[0029] The primary protection circuit 50 mainly includes a fuel gauge (Gauge) circuit 51, and the secondary protection circuit 60 mainly includes a first integrated circuit 61 for secondary protection and a second integrated circuit 62 for secondary protection.

[0030] In the primary protection circuit 50, the fuel gauge integrated circuit 51 senses the voltage difference across both sides of the precision resistor 57 by connecting both ends of the precision resistor 57 through its current sensing negative terminal port (CRN) 513 and current sensing positive terminal port (CRP) 514, and further calculates the current flowing through the precision circuit 57 according to the ratio of the voltage difference to the resistance value of the precision resistor 57. The fuel gauge integrated circuit 51 also detects the charging and discharging states of the circuit through the positive and negative polarities of the voltage difference. The fuel gauge integrated circuit 51 realizes the functions of overcurrent protection during charging, overcurrent protection during discharge, and monitoring of charging and discharging states for the aforementioned primary protection of the battery through the fuel gauge software algorithm. In addition, the fuel gauge integrated circuit 51 can also have a voltage detection port to realize overvoltage and undervoltage protection by detecting the voltages of the two battery cells.

[0031] The control port 511 of the fuel gauge integrated circuit 51 is the control bus port (SCL) of the I2C bus protocol, and the port 512 of the fuel gauge integrated circuit 51 is the data bus port (SDA) of the I2C bus protocol. The control bus port 511 of the fuel gauge integrated circuit 51 is connected to the control bus port (SCL) 54 of other processors (such as the main processor of the mobile phone), and the data bus port 512 of the fuel gauge integrated circuit 51 is connected to the data bus port (SDA) 55 of other processors (such as the main processor of the mobile phone) for communication with other processors, so as to realize functions such as data feedback to the main processor, receiving control, and data display.

[0032] The primary protection circuit controls the charging and discharging states through the charging MOS and discharging MOS in the MOS switch 56, and shuts off both of them to achieve the primary battery protection function in the case of overvoltage, undervoltage, and overcurrent.

[0033] The primary protection circuit provides temporary safety protection for the battery circuit. The on / off of the MOS switch is controlled by the gate voltage, and the switch state is changeable and not permanently off. In addition, the MOS switch belongs to a semiconductor component and there is a possibility of being broken down. Therefore, the primary protection circuit may fail.

[0034] The secondary protection circuit 60 includes a first secondary protection integrated circuit 61 and a second secondary protection integrated circuit 62, which are used to detect the voltages at both ends of the first battery cell 63 and the second battery cell 64 respectively, to achieve standby protection for secondary protection. When a certain secondary protection integrated circuit is damaged, the other secondary protection integrated circuit can be used as a standby integrated circuit to provide standby protection. Moreover, when the parameters of the two battery cells in the circuit are different, overvoltage and undervoltage protection thresholds can be set separately for each battery cell for independent control.

[0035] The first secondary protection integrated circuit 61 and the second secondary protection integrated circuit 62 include a battery protection logic circuit, which is used to activate circuit protection when the voltage or current exceeds the standard. The battery protection logic circuit may include one or a combination of the first / second overvoltage protection comparison circuit, the first / second undervoltage comparison circuit, the charge and discharge state discriminator, the charging overcurrent comparison circuit, the discharging overcurrent comparison circuit, etc. [zhilin1]

[0036] The secondary protection circuit 60 further includes secondary protection components 66 - 71 and a secondary current detection component 65. The secondary protection components 66 - 71 include first, second, and third switches 66, 67, 71, first and second pull - down resistors 68, 69, and a three - terminal fuse 70. The secondary current detection component 65 uses a precision resistor to implement the current detection function. The first integrated circuit 61 of the secondary protection monitors the current flowing through the battery cells 64, 63 using the secondary current detection component 65, and controls the activation of the protection components 66 - 71 based on the monitoring results, so as to still achieve all - round protection of the battery cell circuit and prevent the occurrence of fire in the event of the failure of the primary protection circuit 60, thus meeting the safety requirements of LPS.

[0037] In the secondary protection circuit 60, the first integrated circuit 61 of the secondary protection is connected to the first end (e.g., the negative electrode) of the first battery cell 63 through the common terminal (VSS) port 613, and is connected to the second end of the first battery cell 63 through the first battery cell voltage detection (VDD) port 614 to detect the voltage of the first battery cell and implement over - voltage and under - voltage protection functions based on the battery cell voltage.

[0038] The over - voltage protection is described below. The first integrated circuit of the secondary protection includes a first over - voltage comparison circuit. After the first integrated circuit 61 of the secondary protection obtains the voltage VC1 of the first battery cell 63, the first over - voltage comparison circuit compares this voltage VC1 with the first over - voltage threshold. When the first over - voltage threshold is exceeded, the first over - voltage comparison circuit outputs a first over - voltage protection signal, and controls the first MOS switch 66 to conduct through the first fuse signal output terminal 615 of the first integrated circuit 61 of the secondary protection, so that the drain of the first MOS switch 66 and the gate of the third switch 71 connected to the drain of the MOS switch 66 are conducted with the upper positive electrode of the battery cell Cell1, thereby controlling the third MOS switch 71 to be in the conducting state, and further enabling the left - hand fuse of the three - terminal fuse element 70 to be directly applied with the total voltage of the first and second battery cells, prompting the fuse to blow and activating the secondary battery protection function. After the primary circuit protection fails, the secondary uses a fuse (Fuse) for protection, and the battery fails permanently to ensure battery safety.

[0039] The under - voltage protection is described below. The first integrated circuit 61 of the secondary protection includes a first under - voltage comparison circuit. After the first integrated circuit 61 of the secondary protection obtains the voltage of the first battery cell 63, the first under - voltage comparison circuit compares this voltage value with the under - voltage threshold. When under - voltage occurs, the first under - voltage comparison circuit outputs a protection signal, and sends a shutdown command and other first under - voltage protection signals to the device through the communication port (not shown) of the first integrated circuit 61 of the secondary protection to prevent the battery from consuming further power and avoid permanent damage to the battery.

[0040] The secondary current detection component 65 in the secondary protection circuit 60 is preferably a precision current detection resistor. The current detection resistor port (VINI) 612 and the common terminal (VSS) 613 in the first integrated circuit 61 of the secondary protection are respectively connected to both ends of the current detection resistor 65 to detect the voltage difference across the current detection resistor 65.

[0041] The overcurrent protection is described below. The first integrated circuit 61 of the secondary protection uses a comparator to compare the voltage difference across the current detection resistor 65 to detect whether it exceeds the set overcurrent threshold, and then determines whether protection occurs. At the same time, the first integrated circuit 61 of the secondary protection includes a charge and discharge state judge, which can judge the charge and discharge states based on the positive and negative polarities of the voltage difference and output a voltage polarity signal, thereby realizing overcurrent protection during charging, overcurrent protection during discharging, and short - circuit protection for the secondary battery protection.

[0042] In addition, the charge and discharge state detection port (VM) 611 can be separately set. One end of a precision resistor is connected at the same connection position as the current detection resistor port (VINI) 612 to specifically detect the charge and discharge states.

[0043] The specific current protection process is as follows. The first integrated circuit 61 of the secondary protection includes a memory that stores the charging overcurrent protection threshold Vth1, the discharging overcurrent protection threshold Vth2, and the short - circuit protection threshold Vth3. After the charge and discharge state judge judges the charge and discharge states, the voltage difference across the current detection resistor 65 is compared with the thresholds Vth1, Vth2, and Vth3 of the charging overcurrent protection, discharging overcurrent protection, and short - circuit protection respectively to determine whether charging overcurrent, discharging overcurrent, or short - circuit occurs, and accordingly outputs a charging overcurrent protection signal, a discharging overcurrent protection signal, or a short - circuit protection signal to initiate circuit protection. Since overcurrent thresholds are separately set for the charge and discharge states, the overcurrent thresholds for charging and discharging can be set differently and independently, realizing independent protection for charging overcurrent protection and discharging overcurrent protection of the battery. In the above - mentioned embodiment, the threshold is a voltage value threshold. In another embodiment, the overcurrent and short - circuit protection thresholds can adopt current value thresholds. At this time, the voltage detected at the port VINI needs to be converted into a current value and then compared with the current value threshold.

[0044] Since overcurrent protection during charging, overcurrent protection during discharging, and short - circuit protection are set in the secondary protection circuit, multiple battery safety protections such as overcurrent during charging, overcurrent during discharging, overvoltage, undervoltage, and short - circuit are provided in the secondary protection, which can comprehensively improve the circuit safety and thus pass the LPS certification in the battery UL2054 standard.

[0045] It should be noted that the secondary protection circuit 60 further includes a secondary protection second integrated circuit 62 to detect the voltage and current of the second battery cell, achieve an independent and comprehensive circuit protection function, and form a backup. Thus, when one of the secondary protection first and second integrated circuits fails or malfunctions, the other secondary protection integrated circuit becomes a backup circuit to achieve backup circuit safety protection.

[0046] Similarly to the secondary protection first integrated circuit 61, the secondary protection second integrated circuit 62 is connected to the first end (e.g., the negative electrode) of the second battery cell 64 through the common terminal (VSS) port 623 and is connected to the second end of the second battery cell 64 through the second battery cell voltage detection (VDD) port 624 to detect the voltage of the second battery cell 64 and achieve overvoltage and undervoltage protection functions according to the battery cell voltage.

[0047] Similarly to the secondary protection first integrated circuit 61, the secondary protection second integrated circuit 62 also includes a current detection resistor port (VINI) 622 and a charge and discharge state detection port (VM) 621 to detect the voltage and current of the second battery cell 64. And the overvoltage, undervoltage, overcurrent, and short-circuit protection during the charging stage and the overvoltage, undervoltage, overcurrent, and short-circuit protection functions during the discharging stage can also be implemented in a similar manner to the secondary protection first integrated circuit 61. And in a similar way, the second fuse signal output terminal 625, the second and third MOS switches 67, 71, the pull-up resistor 68, and the three-terminal fuse 70 are used to achieve fuse melting and circuit protection.

[0048] In this embodiment, the secondary protection circuit includes two secondary protection integrated circuits 61 and 62 for separately detecting the voltages of the two battery cells. The backup protection of the secondary protection is realized. When one integrated circuit is damaged, the other integrated circuit can serve as a backup integrated circuit to provide backup protection. And when the parameters of the two battery cells in the circuit are different, the overvoltage and undervoltage protection thresholds can be set separately for each battery cell for independent control to achieve precise control.

[0049] In one implementation, when the secondary protection first integrated circuit 61 has a current detection function, the secondary protection second integrated circuit 62 does not include a current detection function, and the current detection resistor port (VINI) 622 and the charge and discharge state detection port (VM) 621 of the secondary protection second integrated circuit 62 are respectively connected to the common terminal VSS to simplify the circuit structure.

[0050] The above description is only a preferred embodiment of the present application and an explanation of the technical principles applied. Those skilled in the art should understand that the scope of disclosure involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the foregoing disclosure concept. For example, other auxiliary functional circuits are provided in the above protection circuit, such as a filtering circuit, a biasing circuit, a data communication circuit, etc. For example, a technical solution formed by mutually replacing the above features with technical features having similar functions (but not limited to) disclosed in the present application. For example, the battery in the present invention is not limited to two series-connected and one parallel-connected battery, and those skilled in the art can design a protection circuit for a battery with multiple battery cells connected in series based on this solution. Each integrated circuit in the present invention can be implemented in the form of an FPGA, a DSP, a custom chip, etc.

Claims

1. A battery protection circuit, characterized in that, The battery protection circuit includes a secondary protection circuit (60), wherein, One end of the secondary protection circuit (60) is connected to the battery cells (64, 63); The battery cells (64, 63) include a first battery cell (63) and a second battery cell (64), and the first battery cell and the second battery cell are connected in series; The secondary protection circuit (60) includes a first secondary protection integrated circuit (61) and a second secondary protection integrated circuit (62), which are respectively used to detect the first battery cell voltage (VC1) across the first battery cell (63) and the second battery cell voltage (VC2) across the second battery cell (64), and implement overvoltage and / or undervoltage protection functions according to the voltages; The secondary protection circuit (60) further includes a secondary current detection element (65); The first secondary protection integrated circuit (61) monitors the current flowing through the battery cells (63, 64) by using the secondary current detection element (65), and performs circuit protection according to the monitoring result; The secondary current detection element (65) is connected in series with the battery cells (63, 64); The secondary current detection element (65) is a resistance element, The current detection resistance ports (612, 622) and the common terminals (613, 623) in the first secondary protection integrated circuit (61) and / or the second secondary protection integrated circuit (62) are respectively connected to both ends of the secondary current detection element (65) to detect the voltage difference across the secondary current detection element (65); The first secondary protection integrated circuit (61) and / or the second secondary protection integrated circuit (62) includes an overcurrent comparison circuit, which is used to output an overcurrent protection signal when the voltage difference signal is greater than a threshold value; The secondary protection circuit (60) further includes secondary protection elements; the secondary protection elements include a first switch (66), a second switch (67), a third switch (71), a first pull-down resistor (68), a second pull-down resistor (69) and a three-terminal fuse (70); the first secondary protection integrated circuit (61) monitors the current flowing through the second battery cell (64) and the first battery cell (63) by using the secondary current detection element (65), and controls the secondary protection elements to start protection according to the monitoring result.

2. The battery protection circuit according to claim 1, characterized in that, It further includes a battery protection logic circuit, which is used to start circuit protection when the voltage or current exceeds the standard.

3. The battery protection circuit according to claim 1, wherein The first secondary protection integrated circuit (61) includes a first overvoltage comparison circuit and / or the second secondary protection integrated circuit (62) includes a second overvoltage comparison circuit; The first overvoltage protection circuit is used to output a first overvoltage protection signal when the first battery cell voltage (VC1) is greater than a first overvoltage threshold value; the second overvoltage protection circuit is used to output a second overvoltage protection signal when the second battery cell voltage (VC2) is greater than a second overvoltage threshold value.

4. The battery protection circuit according to claim 1, wherein The first secondary protection integrated circuit (61) includes a first undervoltage comparison circuit and / or the second secondary protection integrated circuit (62) includes a second undervoltage comparison circuit; The second-level protection first integrated circuit (61) includes a first undervoltage comparison circuit for outputting a first undervoltage protection signal when the first cell voltage is lower than the first undervoltage threshold; The second-level protection second integrated circuit (62) includes a second undervoltage comparison circuit for outputting a second undervoltage protection signal when the second cell voltage is lower than the second undervoltage threshold.

5. The battery protection circuit according to claim 1, characterized in that The second-level protection first integrated circuit (61) and / or the second-level protection second integrated circuit (62) include charge and discharge detection ports (611, 621), common terminals (613, 623), a charge and discharge state discriminator, a charging overcurrent comparator, and a discharging overcurrent comparator; Among them, the charge and discharge detection ports (611, 621) and the common terminals (613, 623) are respectively connected to both ends of the second-level current detection element (65) to detect the voltage difference across the second-level current detection element (65). The charge and discharge state discriminator is used to receive the voltage difference signal, judge the voltage difference signal, and output a voltage polarity signal; When the charge and discharge state discriminator determines that it is in a charging state according to the voltage difference signal, the charging overcurrent comparator compares the voltage difference across the second-level current detection element (65) with the charging overcurrent protection threshold (Vth1) to determine whether charging overcurrent occurs, and outputs a charging overcurrent protection signal to activate circuit protection; When the charge and discharge state discriminator determines that it is in a discharging state according to the voltage difference signal, the discharging overcurrent comparator compares the voltage difference across the second-level current detection element (65) with the discharging overcurrent protection threshold (Vth2) to determine whether discharging overcurrent occurs, and outputs a discharging overcurrent protection signal to activate circuit protection.

6. The battery protection circuit according to claim 1, wherein The second-level protection first integrated circuit (61) and / or the second-level protection second integrated circuit (62) include a short-circuit protection circuit, which is used to output a short-circuit protection signal to activate circuit protection when the voltage difference is greater than the short-circuit protection threshold.

7. The battery protection circuit according to claim 1, wherein The battery protection circuit further includes a first-level protection circuit (50). One end of the first-level protection circuit (50) is connected to the second-level protection circuit (60), and the other end is connected to the electrical energy input and output terminals (52, 53). The first-level protection circuit (50) includes a fuel gauge integrated circuit (51), a first-level current detection resistor (57), and a first-level protection element (56) connected in series with the cells (61, 62). The first-level protection circuit (50) has an overvoltage protection function and / or an overcurrent protection function.

8. The battery protection circuit according to claim 7, characterized in that, The first-level protection element (56) includes a charging switch and a discharging switch. The fuel gauge integrated circuit (51) is respectively connected to both ends of the first-level current detection resistor (57) through its current detection negative terminal (513) and current detection positive terminal (514) to detect the voltage difference across the resistor. The fuel gauge integrated circuit (51) includes an overcurrent judgment circuit, which judges whether overcurrent occurs according to the voltage difference, and outputs a control signal to turn off the charging switch and the discharging switch in case of overcurrent.

9. The battery protection circuit according to claim 1, wherein The current detection resistor port (622) in the second-level protection first integrated circuit (62), and the common terminals (613, 623) are respectively connected to both ends of the second-level current detection element (65); The current detection resistor port (622) in the second-level protection second integrated circuit (62), and the charge and discharge detection port (621) are connected to the common terminal (623) of the second-level protection second integrated circuit (62).

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