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 secondary protection circuit includes a secondary protection integrated circuit and a secondary current detection component. The secondary protection integrated circuit monitors the current flowing through the battery cell by using the secondary current detection component, and controls the secondary protection component to start 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 achieve 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 and one-parallel batteries (2S1P) used in consumer electronic products such as mobile phones, drones, and robots. Background Art

[0002] 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 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 secondary protection circuit includes a secondary protection integrated circuit and a secondary current detection element. The secondary protection integrated circuit uses the secondary current detection element to monitor the current flowing through the battery cell and controls the start of circuit protection by the secondary protection element according to the monitoring result.

[0006] In a further scheme, the battery cell is composed of a first battery cell and a second battery cell connected in series.

[0007] In a further scheme, it further includes a battery protection logic circuit for starting circuit protection when the voltage or current exceeds the standard. In a further scheme, the secondary current detection element is a resistance element. The positive terminal port and the negative terminal port of the current detection resistor in the secondary protection integrated circuit are respectively connected to both ends of the secondary current detection element to detect the voltage difference across the secondary current detection element. The secondary protection integrated circuit includes an overcurrent comparison circuit for outputting an overcurrent protection signal when the voltage difference signal is greater than the threshold.

[0008] In a further solution, the secondary protection integrated circuit includes a common terminal port, a first battery cell voltage detection port, and a second battery cell voltage detection port; the secondary protection integrated circuit is connected to the first end of the first battery cell through the common terminal port, and is connected to the second end of the first battery cell through the first battery cell voltage detection port, and the second battery cell voltage detection port is connected to the second end of the second battery cell; the secondary protection integrated circuit obtains the maximum value signals of the first battery cell voltage and the second battery cell voltage through the first battery cell voltage detection port and the second battery cell voltage detection port, and the secondary protection integrated circuit further includes an overvoltage comparison circuit for outputting an overvoltage protection signal when the maximum value is greater than the overvoltage threshold.

[0009] In a further solution, the secondary protection integrated circuit obtains the minimum value signals of the voltage of the first battery cell and the voltage of the second battery cell, and the secondary protection integrated circuit further includes an undervoltage comparison circuit for outputting an undervoltage protection signal when the minimum value is lower than the undervoltage threshold.

[0010] In a further solution, the secondary protection integrated circuit includes a charge and discharge state discriminator, a charging overcurrent comparator, and a discharging overcurrent comparator. The charge and discharge state discriminator receives the voltage signal across the current sensing resistor, and determines the charge and discharge states according to the positive and negative polarities of the voltage difference across the current sensing resistor, and outputs a voltage polarity signal. When the charge and discharge state discriminator determines that it is in the charging state according to the voltage difference signal, the charging overcurrent comparator compares the voltage difference across the current sensing resistor with the charging overcurrent protection threshold to output a charging overcurrent protection signal and start circuit protection; when the charge and discharge state discriminator determines that it is in the discharging state according to the voltage difference signal, the discharging overcurrent comparator compares the voltage difference across the current sensing resistor with the discharging overcurrent protection threshold respectively to output a discharging overcurrent protection signal and start circuit protection.

[0011] In a further solution, the secondary protection integrated circuit includes a short-circuit protection circuit for outputting a short-circuit protection signal to start circuit protection when the voltage difference across the current sensing resistor is greater than the short-circuit protection threshold.

[0012] In a further solution, 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 and output terminal. The primary protection circuit includes a coulomb counter integrated circuit, a primary current sensing resistor, and a primary protection element connected in series with the battery cell. The primary protection circuit has an overvoltage protection function and / or an overcurrent protection function.

[0013] In a further embodiment, the primary protection component includes a charging switch and a discharging switch. The coulomb counter integrated circuit is connected to both sides of the primary current sensing resistor through its current sensing negative terminal and current sensing positive terminal to detect the voltage difference across the resistor. The coulomb counter integrated circuit includes an overcurrent judgment circuit, which judges whether an overcurrent has occurred based on the voltage difference, and outputs a control signal to turn off the charging switch and the discharging switch in case of an overcurrent.

[0014] 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 the failure of the primary protection circuit, ensuring the safety of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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:

[0016] Figure 1 It is a circuit schematic diagram of the charging architecture of a conventional 2S1P battery and the battery protection circuit.

[0017] Figure 2 It is a circuit schematic diagram of a battery protection circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] 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. Additionally, it should be noted that for the sake of description, only the parts related to the invention are shown in the drawings.

[0019] The terms "first", "second", and similar terms used in the present application do not denote any order, quantity, or importance, but are only used to distinguish different parts. Terms such as "including" or "comprising" mean that the elements before the term cover the elements listed after the term, and do not exclude the possibility of also covering other elements. Terms such as "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0020] Figure 1 It is a circuit schematic diagram of the charging architecture of a 2S1P battery and the battery protection circuit.

[0021] Figure 1 In the shown battery protection circuit, the battery is a 2S1P two - series - 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).

[0022] The secondary protection circuit (20) mainly realizes the overvoltage protection function through 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 charge and discharge 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.

[0023] 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 unidirectional 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 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.

[0024] It can be seen that Figure 1 the secondary protection circuit (20) in only has the overvoltage protection function and does not have the overcurrent protection function. When the primary protection circuit (10) fails, the secondary protection circuit cannot well protect the battery safety. It cannot meet the comprehensive requirements of LPS for voltage, current, and power, and cannot pass the LPS certification in battery UL2054.

[0025] Such as Figure 2As shown, it is a schematic diagram of a 2S1P battery protection circuit that meets the LPS requirements involved in the present invention. Among them, the battery can be, for example, a battery circuit of two series in parallel (2S1P), which is composed of a first battery cell 43 and a second battery cell 42 connected in series. One end of the first battery cell 43 is connected to the negative pole P- (33) of the power input / output terminal, the other end of the first battery cell 43 is connected in series with one end of the second battery cell 42, and the other end of the second battery cell 42 is connected to the positive pole (P+) 32 of the power input / output terminal. The negative pole (P-) 33 and the positive pole (P+) 32 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 electrical energy to the load in the discharge state, or obtain electrical energy from the charging circuit in the charging state to charge the first battery cell 43 and the second battery cell 42. In an optional implementation manner, the battery can also be a single battery cell or other types of battery circuits.

[0026] Figure 2 Among them, the protection circuit includes a primary protection circuit 30 and a secondary protection circuit 40. One end of the secondary protection circuit 40 is connected to the first and second battery cells, and the other end is connected to the primary protection circuit 30. One end of the primary protection circuit 30 is connected to the secondary protection circuit 40, and the other end is connected to the power input / output terminals 32 and 33. The entire design realizes safety protection such as overcurrent during charging, overcurrent during discharge, overvoltage, undervoltage, and short circuit, and can meet the LPS design.

[0027] The primary protection circuit 30 mainly includes a fuel gauge (Gauge) circuit 31, and the secondary protection circuit 40 mainly includes a secondary protection integrated circuit 41.

[0028] In the primary protection circuit 30, the fuel gauge integrated circuit 31 senses the voltage difference on both sides of the precision resistor 37 by connecting the current sensing negative terminal port (CRN) 313 and the current sensing positive terminal port (CRP) 314 of the fuel gauge integrated circuit 31 to both ends of the precision resistor 37 respectively, and further calculates the current flowing through the precision circuit 37 according to the ratio of the voltage difference to the resistance value of the precision resistor 37. The fuel gauge integrated circuit 31 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 31 realizes the functions of overcurrent protection during charging, overcurrent protection during discharge, and charging and discharging state monitoring of the aforementioned primary battery protection through the fuel gauge software algorithm. In addition, the fuel gauge integrated circuit 31 can also have the first and second battery cell voltage detection ports (VC1, VC2) 317 and 318 for realizing overvoltage and undervoltage protection.

[0029] The control port 311 of the coulomb meter integrated circuit 31 is the control bus port (SCL) of the I2C bus protocol, and the port 312 of the coulomb meter integrated circuit 31 is the data bus port (SDA) of the I2C bus protocol. The control bus port 311 of the coulomb meter integrated circuit 31 is connected to the control bus port (SCL) 34 of other processors (such as the main processor of a mobile phone), and the data bus port 312 of the coulomb meter integrated circuit 31 is connected to the data bus port (SDA) 35 of other processors (such as the main processor of a 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.

[0030] The primary protection circuit controls the charging and discharging states through the charging MOS and discharging MOS in the MOS switch 36, and in the case of overvoltage, undervoltage, and overcurrent, shuts off both to achieve the primary battery protection function.

[0031] The primary protection circuit's safety protection for the battery circuit is temporary. The on / off of the MOS switch is controlled by the gate voltage, and the switch state is changeable, not permanently disconnected. Additionally, the MOS switch is a semiconductor component and there is a possibility of being broken down. Therefore, the primary protection circuit may fail.

[0032] The secondary protection circuit 40 includes a secondary protection integrated circuit 41, secondary protection elements 44, 45, and a secondary current detection element 46. The secondary protection integrated circuit 41 uses the secondary current detection element 46 to monitor the current flowing through the battery cell and controls the protection elements 44, 45 to start protection according to the monitoring results, so as to still be able to protect the battery cell circuit and prevent the occurrence of fire in the case of the failure of the primary protection circuit 40, thus meeting the safety requirements of LPS.

[0033] The secondary protection integrated circuit 41 includes a battery protection logic circuit for starting circuit protection when the voltage or current exceeds the standard. The battery protection logic circuit may include one or a combination of an overvoltage protection comparison circuit, an undervoltage comparison circuit, a charge and discharge state discriminator, a charging overcurrent comparison circuit, a discharging overcurrent comparison circuit, etc.

[0034] In the secondary protection circuit 40, the secondary protection integrated circuit 41 is connected to the first end (such as the negative electrode) of the first battery cell 43 through the common terminal (VSS) port 412, and is connected to the second end of the first battery cell 43 through the first battery cell voltage detection (VC1) port 413, and is connected to the second end of the second battery cell 42 through the second battery cell voltage detection (VC2) port 414. Through the first battery cell voltage detection (VC1) port 413 and the second battery cell voltage detection VC2 port 414, the voltages of the battery cells Cell1 and Cell2 are detected, and overvoltage and undervoltage protection functions are realized according to the voltages of the battery cells Cell1 and Cell2. Specifically, inFigure 2 In the embodiment, the voltage detected by the VC1 port 413 is the voltage across the first battery cell 43, and the voltage detected by the VC2 port is the total series voltage of the first battery cell 43 and the second battery cell 42. By subtracting the voltage across the first battery cell 43 from the total voltage, the voltage across the second battery cell 42 can be obtained.

[0035] The overvoltage protection is described below. The secondary protection first integrated circuit includes an overvoltage comparison circuit. After the secondary protection integrated circuit 41 obtains the voltages of the first battery cell 43 and the second battery cell 42, the secondary protection integrated circuit 41 further obtains the maximum value of the voltage of the first battery cell 43 and the voltage of the second battery cell 42. The overvoltage comparison circuit compares this maximum value with the overvoltage threshold to ensure that any battery has no overvoltage risk. When this maximum value exceeds the overvoltage threshold, the overvoltage comparison circuit outputs an overvoltage protection signal, and controls the fusing MOS switch 44 to conduct through the fusing signal output terminal 411 of the secondary protection integrated circuit 41, so that the secondary protection element 45 (for example: fuse) takes effect. After the primary circuit protection fails, the secondary uses a fuse (Fuse) for protection, and the battery fails permanently to ensure battery safety.

[0036] The undervoltage protection is described below. The secondary protection first integrated circuit 61 includes a first undervoltage comparison circuit. After the secondary protection integrated circuit 41 obtains the voltages of the first battery cell 43 and the second battery cell 42, it further obtains the minimum value of the voltage of the first battery cell 43 and the voltage of the second battery cell 42. The first undervoltage comparison circuit compares this minimum value with the undervoltage threshold to ensure that any battery has no undervoltage risk. When it is determined that undervoltage occurs when this minimum value is lower than the undervoltage threshold, the first undervoltage comparison circuit outputs an undervoltage protection signal, and sends an undervoltage protection signal such as a shutdown command to the device through the communication port (not shown) of the secondary protection integrated circuit 41 to prevent the battery from consuming further power and causing permanent damage to the battery.

[0037] The secondary current detection element 46 in the secondary protection circuit 40 is preferably a precision current detection resistor. The positive terminal port (CRP) 415 and the negative terminal port (CRN) 416 of the current detection resistor in the secondary protection integrated circuit 41 are respectively connected to both ends of the current detection resistor to detect the voltage difference across the current detection resistor.

[0038] The overcurrent protection is described below. The secondary protection integrated circuit 41 uses a comparator to compare the voltage difference across the current detection resistor to detect whether it exceeds the set overcurrent threshold, and then determines whether protection occurs. At the same time, the secondary protection first integrated circuit 61 includes a charge and discharge state discriminator, which can judge the charge and discharge states through the positive and negative polarities of the voltage difference and output a voltage polarity signal, so as to realize overcurrent protection for charging, overcurrent protection for discharging and short-circuit protection of the battery secondary protection.

[0039] Specifically, the secondary protection integrated circuit 41 includes a memory that stores a charging overcurrent protection threshold Vth1, a discharging overcurrent protection threshold Vth2, and a short-circuit protection threshold Vth3. After the charge and discharge state discriminator determines the charge and discharge states, by comparing the voltage difference across the current sensing resistor with the thresholds Vth1, Vth2, and Vth3 for charging overcurrent protection, discharging overcurrent protection, and short-circuit protection respectively, it is determined whether charging overcurrent, discharging overcurrent, or short circuit occurs, and accordingly, a charging overcurrent protection signal, a discharging overcurrent protection signal, or a short-circuit protection signal is output to activate 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, achieving independent protection for the battery's charging overcurrent protection and discharging overcurrent protection. In the above embodiment, the threshold is a voltage value threshold. In another embodiment, the overcurrent and short-circuit protection thresholds can adopt current value thresholds.

[0040] Since charging overcurrent, discharging overcurrent protection, and short-circuit protection are provided in the secondary protection circuit, multiple battery safety protections such as charging overcurrent, discharging overcurrent, overvoltage, undervoltage, and short circuit are included in the secondary protection, which can comprehensively improve the circuit safety and thus pass the LPS certification in the battery UL2054 standard.

[0041] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the disclosed scope in the present application is not limited to the technical solution formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the aforementioned disclosed concept. For example, other auxiliary functional circuits such as a filtering circuit, a biasing circuit, a data communication circuit, etc. are provided in the above protection circuit. For example, a technical solution formed by mutually replacing the above features with (but not limited to) technical features with similar functions 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 ways such as FPGA, DSP, custom chips, etc.

Claims

1. A battery protection circuit, characterized in that, the battery protection circuit includes a secondary protection circuit (40), wherein, one end of the secondary protection circuit (40) is connected to the battery cell; the secondary protection circuit (40) includes a secondary protection integrated circuit (41) and a secondary current detection element (46). The secondary protection integrated circuit (41) monitors the current flowing through the battery cell by using the secondary current detection element (46), and controls the secondary protection elements (44, 45) to start circuit protection according to the monitoring result. The secondary current detection element (46) is a current detection resistor. The positive terminal port (415) and the negative terminal port (416) of the current detection resistor in the secondary protection integrated circuit (41) are respectively connected to both ends of the secondary current detection element (46) to detect the voltage difference across the secondary current detection element (46). The secondary protection integrated circuit (41) includes an overcurrent comparison circuit for outputting an overcurrent protection signal when the voltage difference signal is greater than the threshold value. The secondary protection integrated circuit (41) includes a charge-discharge state discriminator, a charge overcurrent comparator and a discharge overcurrent comparator. The charge-discharge state discriminator judges the charge and discharge states according to the positive and negative polarities of the voltage difference across the current detection resistor, and outputs a voltage polarity signal. When the charge-discharge state discriminator judges it as the charging state according to the voltage difference signal, the charge overcurrent comparator compares the voltage difference across the current detection resistor with the charge overcurrent protection threshold (Vth1) to output a charge overcurrent protection signal and start circuit protection. When the charge-discharge state discriminator judges it as the discharging state according to the voltage difference signal, the discharge overcurrent comparator compares the voltage difference across the current detection resistor with the discharge overcurrent protection threshold (Vth2) respectively to output a discharge overcurrent protection signal and start circuit protection.

2. The battery protection circuit according to claim 1, characterized in that, the battery cell is a battery cell formed by connecting a first battery cell (43) and a second battery cell (42) in series.

3. The battery protection circuit according to claim 1, characterized in that, it further includes a battery protection logic circuit for starting circuit protection when the voltage or current exceeds the standard.

4. The battery protection circuit according to claim 2, characterized in that, the secondary protection integrated circuit (41) includes a common terminal port (412), a first battery cell voltage detection port (413), and a second battery cell voltage detection port (414); the secondary protection integrated circuit (41) is connected to the first end of the first battery cell (43) through the common terminal port (412), and is connected to the second end of the first battery cell (43) through the first battery cell voltage detection port (413). The second battery cell voltage detection port (414) is connected to the second end of the second battery cell (42); The secondary protection integrated circuit (41) obtains the maximum value signal of the voltage of the first battery cell (43) and the voltage of the second battery cell (42) through the first battery cell voltage detection port (413) and the second battery cell voltage detection port (414). The secondary protection integrated circuit (41) further includes an overvoltage comparison circuit for outputting an overvoltage protection signal when the maximum value is greater than the overvoltage threshold.

5. The battery protection circuit according to claim 4, wherein, the secondary protection integrated circuit (41) obtains the minimum value signal of the voltage of the first battery cell (43) and the voltage of the second battery cell (42), and the secondary protection integrated circuit (41) further includes an undervoltage comparison circuit for outputting an undervoltage protection signal when the minimum value is lower than the undervoltage threshold.

6. The battery protection circuit according to claim 1, wherein, the secondary protection integrated circuit (41) includes a short-circuit protection circuit, and the short-circuit protection circuit is used for outputting a short-circuit protection signal to start circuit protection when the voltage difference across the current detection resistor is greater than the short-circuit protection threshold (Vth3).

7. The battery protection circuit according to claim 1, wherein, the battery protection circuit further includes a primary protection circuit (30), one end of the primary protection circuit (30) is connected to the secondary protection circuit (40), and the other end is connected to the power input / output terminals (32, 33). The primary protection circuit (30) includes a fuel gauge integrated circuit (31), a primary current detection resistor (37), and a primary protection element (36) connected in series with the battery cell. The primary protection circuit (30) has an overvoltage protection function and / or an overcurrent protection function.

8. The battery protection circuit according to claim 7, wherein, the primary protection element (36) includes a charging switch and a discharging switch. The fuel gauge integrated circuit (31) is connected to both sides of the primary current detection resistor (37) through its current detection negative terminal port (313) and current detection positive terminal port (314) respectively to detect the voltage difference across the resistor. The fuel gauge integrated circuit (31) includes an overcurrent judgment circuit, and the judgment circuit 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.

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