Broken line detection circuit, battery management chip and broken line detection method

Abstract

A broken line detection method comprises the following steps that chip battery pins and grounding end pins are divided into N sets of battery pins, and the detection method of each set of battery pins comprises the following steps that 1, switches in the sets are switched on, the switches in the sets are switched off after the switching-on time, and a voltage detection device detects the voltage difference between the battery pins in the sets at the moment; step 2, the upper adjacent switches are switched on and switched off after the switching-on time, and the voltage difference between the pins of the group of batteries at the moment is detected after the set switching-off time; 3, detecting a difference value, and if the difference value exceeds a set difference value threshold value, judging that the battery connected between the pins of the current group of batteries is disconnected; when both are smaller than the lower limit threshold, judging that the pins of the current battery pack are short-circuited; and step 4, repeating the step 1 to the step 3 to detect the pins of each group of batteries. According to the invention, no extra configuration pin is needed, the switch array and the voltage detection circuit are utilized to realize broken line detection, and the pin resource is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, relates to battery management chip technology, and particularly relates to a disconnection detection circuit, a battery management chip, and a disconnection detection method. Background Art

[0002] Lithium battery management chips commonly support different battery cell string counts using the same chip model. Currently, the most common solution for pure hardware protection chips is to configure the battery cell string count using a single pin or multiple pins. This configuration is necessary because the chip's internal control logic for disconnect protection, charge overvoltage protection, and discharge undervoltage protection varies depending on the number of battery strings. If the chip lacks disconnect protection, the battery may overcharge or overdischarge, posing a safety hazard.

[0003] like Figure 2 The figure shows the pins used by existing lithium battery management chips during battery configuration. Batteries are connected in series between multiple battery pins VC1 to VC6. For unused battery pins, such as VC6, they are short-circuited with VC5. At the same time, different voltage signals need to be input through the configuration pins SEL0 and SEL1. The lithium battery management chip detects the voltage on these two configuration pins and determines how many batteries are currently connected and how many battery pins are short-circuited.

[0004] Because existing technologies require separate configuration pins to configure the number of lithium-ion batteries, if the chip package pin count is limited and no configuration pins are available, the chip will not have a disconnect protection function. Without disconnect protection, the chip may lead to the risk of overcharging or over-discharging of the lithium-ion batteries, posing a safety hazard. Using separate configuration pins to configure the number of lithium-ion battery strings requires chip pin resources. Summary of the Invention

[0005] In order to overcome the defects of the prior art, the present invention discloses a disconnection detection circuit, a battery management chip and a disconnection detection method.

[0006] The line break detection method of the present invention comprises the following steps: According to the connection relationship of the battery string, all N battery pins and one ground pin of the chip are divided into N groups of battery pins. The first group is the first battery pin and the ground pin, the second group is the second battery pin and the first battery pin, the third group is the third battery pin and the second battery pin, and so on. Define the switch connected between two battery pins in the current group as an intra-group switch. Adjacent switches in the group include upper adjacent switches and lower adjacent switches. Define the intra-group switch in the group below the current battery pin according to the group sequence number as the upper adjacent switch of the current group. Define the intra-group switch in the group above the current battery pin according to the group sequence number as the lower adjacent switch of the current group. Set the difference threshold ΔVT, lower threshold LVT, closing time TON, and opening time TOFF; the detection method for each group of battery pins is as follows Step 1. The switch in the group is closed. After the closing time TON, the switch in the group is opened. After the set opening time, the voltage detection device detects the voltage difference between the pins of the battery group at this time, which is recorded as VT1L. In step 1, the upper adjacent switch remains open. Step 2. The upper adjacent switch is closed. After the closing time TON, the upper adjacent switch is opened. After the set opening time TOFF, the voltage difference between the pins of the battery group is detected and recorded as VT1H. In step 2, the switch K1 in the group remains open. In steps 1 to 2, when a switch is closed, the adjacent switch remains open; Step 3. Detect the difference between VT1L and VT1H. If the difference exceeds the set difference threshold ΔVT, it is determined that the battery connected between the pins of the current battery pack is disconnected. When VT1H and VT1L are both less than the lower threshold LVT, it is determined that the current battery pack pin is short-circuited; Step 4. Repeat steps 1 to 3 in the order of the first group, the second group, the third group, etc. to test the pins of each group of batteries.

[0007] Preferably, step 4 is replaced by: Divide each group of battery pins into odd and even groups according to the parity of the serial numbers. The odd and even groups are tested separately. During the test, each group of battery pins in the odd or even group is tested simultaneously through steps 1 to 3.

[0008] Preferably, in step 4, once a disconnection is found, the detection of subsequent groups is terminated.

[0009] A line break detection circuit includes switches connected between adjacent battery pins and a switch connected between a ground pin and one of the battery pins, wherein the switches are connected in series. The circuit also includes a voltage detection device connected between the battery pins and the ground pin, wherein the detection device is used to detect the voltage value on any one of the switches. The line break detection circuit also includes a control circuit for implementing the detection method.

[0010] Preferably, the voltage detection device is a comparator or an analog-to-digital converter.

[0011] A battery management chip comprises a plurality of battery pins and the disconnection detection circuit.

[0012] The battery management chip disconnection detection circuit and detection method of the present invention do not require additional configuration pins, and can implement battery disconnection detection by utilizing a switch array and a voltage detection circuit, thus saving pin resources.

[0013] At the same time, since existing lithium battery management chips usually have their own switch arrays and voltage detection circuits to achieve voltage balance among various batteries, the present invention can use the existing switch arrays and voltage detection circuits to detect pin disconnections in a short period of time after normal power-on. After determining that there is no disconnection, the relevant circuit modules can be released to perform normal operations. Therefore, there is no need to significantly increase additional circuits internally, and only a small amount of logic circuits need to be configured. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1 is a schematic diagram of a specific embodiment of the disconnection detection circuit of the present invention; Figure 2 A schematic diagram of a specific implementation of an existing battery management chip; The names of the reference numerals in the figure are: VC1. first battery pin, VC2. second battery pin, VC3. third battery pin, VC4. fourth battery pin, VC5. fifth battery pin, VC6. sixth battery pin, K1. first switch, K2. second switch, K3. third switch, K4. fourth switch, K5. fifth switch, K6. sixth switch, CP1. first battery, CP2. second battery, CP3. third battery, CP4. fourth battery, CP5. fifth battery, CP6. sixth battery, R1. first resistor, R2. second resistor, R3. third resistor, R4. fourth resistor, R5. fifth resistor, R6. sixth resistor, C1. first capacitor, C2. second capacitor, C3. third capacitor, C4. fourth capacitor, C5. fifth capacitor, C6. sixth capacitor, VSS. ground pin, VCC. power pin, ADC. analog-to-digital converter. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention are described in further detail below.

[0016] like Figure 1As shown, the battery management chip includes a first battery pin VC1, a second battery pin VC2, a third battery pin VC3, a fourth battery pin VC4, a fifth battery pin VC5, a sixth battery pin VC6, a ground pin VSS, and a chip power supply terminal VCC. The six battery pins are all connected to a voltage detection device. The disconnection detection circuit within the chip includes: a first switch K1 connected between the first battery pin and the ground pin, a second switch K2 connected between the first battery pin and the second battery pin, a third switch K3 connected between the second battery pin and the third battery pin, a fourth switch K4 connected between the third battery pin and the fourth battery pin, a fifth switch K5 connected between the fourth battery pin and the fifth battery pin, and a sixth switch K6 connected between the fifth battery pin and the sixth battery pin. The control end of each switch is connected to the control circuit.

[0017] The specific implementation of each switch can be a MOS tube, a triode or a transmission gate circuit.

[0018] Typical circuits for battery management chip applications are as follows: Figure 1 As shown, for each online battery pin that is not short-circuited, a capacitor is connected between the first battery pin and the ground pin, and between two adjacent battery pins; Each online battery pin is also connected to a resistor, and the other end of the resistor is connected to the positive terminal of the battery connected to the online battery pin, such as Figure 1 and 2 As shown, all batteries are connected in series, that is, the positive and negative electrodes of adjacent batteries are connected, the negative electrode of the first battery at the bottom is connected to the ground pin VSS, and the top battery is also connected to the chip power pin VCC.

[0019] After adopting the above connection method, the batteries of each battery power supply circuit are connected in series to supply power to the battery management chip.

[0020] For the use of less than full load, according to the use specifications of existing battery management chips, some adjacent battery pins are not connected and short-circuited directly when not fully loaded, such as Figure 1 As shown, the fifth and sixth battery pins, serving as the second-highest and highest battery pins, are not connected to a battery power circuit and are directly short-circuited. Because the chip requires at least one battery connection when in use, otherwise the chip will not function properly if the power supply is zero, this invention does not address the case where all battery pins and the ground pin VSS are short-circuited.

[0021] The typical circuit when the above-mentioned battery management chip is used is the conventional existing technology in this field. This application improves the internal circuit of the chip based on this typical circuit.

[0022] During testing, the battery pins are grouped, with the first battery pin VC1 and the ground pin VSS as the first group. Every two adjacent battery pins are grouped for testing, that is, the first battery pin VC1 and the second battery pin VC2 are the second group, the second battery pin VC2 and the third battery pin VC3 are the third group, and so on.

[0023] In the present invention, the voltage detection device detects the intra-group voltage difference between two pins in the same group during detection.

[0024] observe Figure 1 It can be seen that if a battery in the battery string fails and breaks, the chip cannot detect the actual battery voltage, and the entire battery string is not conductive, and the chip cannot work normally. Therefore, the break in the line referred to in this application does not mean that the battery itself is broken, but that the battery is working normally, but due to reasons such as the connection line or the break in the line, the positive electrode of the battery cannot be connected to the battery detection pin; at the same time, if the negative electrode of the first battery is not connected to the ground pin VSS, or the positive electrode of the last battery is not connected to the power pin VCC of the chip, the chip cannot work normally. Therefore, the break in the line described in the present invention does not take this situation into account.

[0025] When testing the first group of battery pins, the switch in the group is the first switch K1, and the upper adjacent switch in the group is the second switch K2. The test is performed according to the following method: Step 1. The first switch K1 is closed. After a set closing time TON, the first switch K1 is opened. After a set opening time TOFF, the voltage detection device detects the voltage difference between the first battery pin VC1 and the ground pin VSS at this time, i.e., the intra-group voltage difference of the first group, which is recorded as VT1L. In step 1, the second switch remains open. Step 2. Close the second switch K2. After the set closing time TON, open the second switch K2. After the set opening time TOFF, measure the internal pressure difference at this time, which is recorded as VT1H. In step 2, the first switch K1 and the third switch K3 remain open. The closing time, TON, must be set to a value sufficient to fully discharge the capacitor connected between the first battery group's pins to near zero, while the opening time, TOFF, must be set to a value sufficient to fully charge the capacitor connected to the first battery group's pins to its maximum value. The specific values ​​of the closing time, TON, and the opening time, TOFF, depend on the selected capacitor value, battery voltage, and internal switch on-resistance.

[0026] Step 3: Detect the difference between VT1L and VT1H. If the difference exceeds the set difference threshold ΔVT, it is determined that the first battery CP1 is disconnected.

[0027] The specific analysis is as follows: Figure 1As shown, it is first assumed that the first battery is not disconnected and the ground terminal pin VSS is grounded; In step 1, K2 remains disconnected, K1 is closed first, the first capacitor C1 is short-circuited and discharged to zero, then K1 is disconnected, the first battery CP1 charges the first capacitor to the positive output voltage VCP1P of the first battery CP1, that is, VT1L=VCP1P; In step 2, K1 remains disconnected, K2 is closed first, and the first capacitor C1 is charged by the first battery and the second battery; Then K2 is disconnected. Since K1 is also disconnected, no matter what the voltage of the first capacitor is before K2 is disconnected, after K2 is disconnected, the first capacitor will be charged to the positive output voltage VCP1P of the first battery CP1, that is, VT1H=VCP1P; That is, when the line is not disconnected, VT1H=VT1L=VCP1P; Then suppose the first battery is disconnected; In step 1, K2 remains disconnected, K1 is closed first, the first capacitor C1 is short-circuited and discharged to zero, then K1 is disconnected. Since the first battery CP1 is disconnected, K2 is also disconnected, and the first capacitor cannot be charged, that is, VT1L=0; Assuming the second battery is connected, K1 remains disconnected in step 2 and K2 is closed first. Since the first battery is disconnected, the first capacitor C1 is charged by the second battery through R2, VC2, and VC1. The charging voltage is the second battery positive electrode voltage VCP2P. Then K2 is disconnected. Since K1 is also disconnected, the first battery is disconnected. After K2 is disconnected, the first capacitor will maintain the voltage before K2 is disconnected, that is, VT1H=VCP2P; That is, when the first battery is disconnected and the second battery is not disconnected, VT1H=VCP2P, VT1L=0; VT1H- VT1L = VCP2P. Assuming the output voltages of the first battery and the second battery are VCP1 and VCP2 respectively, then VCP2P = VCP1 + VCP2. When the first battery is not disconnected, the difference between the two is theoretically zero. ΔVT can be set to a smaller value, such as 0.1V. As long as the difference is greater than 0.1V, the first battery can be considered disconnected.

[0028] The above analysis does not consider the case where the second battery is disconnected at the same time. If the second battery is disconnected at the same time, the first capacitor cannot be charged by the second battery even when K2 is closed in step 2, and VT1H = 0. In this case, it is impossible to determine whether the first battery is disconnected when testing the first group of battery pins. However, in the subsequent testing process, since the chip is working normally, at least one battery is connected to the battery pins normally, and a disconnected battery will inevitably be detected.

[0029] This application can detect whether a battery in a battery string is disconnected, and when only one battery is disconnected, it can also detect which battery is disconnected. In the unlikely event that two or more batteries are disconnected at the same time, the disconnection can also be detected and the user can be alerted. In reality, as long as a disconnection occurs, the entire battery power supply system needs to be inspected and replaced.

[0030] Assume that the pins of the first battery group are short-circuited. Since the ground pin VSS is grounded, the voltage on the first battery pin VC1 is always zero, that is, VT1H=VT1L=0.

[0031] Set a suitable lower threshold LVT, such as 0.1V. When VT1H and VT1L are both less than the lower threshold LVT, it is determined that the pins of the current battery pack are short-circuited.

[0032] When short circuit and disconnection are determined to occur simultaneously, it is necessary to stop the chip operation, check the circuit disconnection point and repair it.

[0033] If a disconnection is detected in the first battery pin group, no subsequent detection is performed, the system shuts down, and the detected disconnection fault is processed. In the present invention, the detection of each subsequent battery pin group assumes that no disconnection fault was found before the detection of the battery pin group.

[0034] When testing the pins of the second battery group, the switch in the group is the second switch K2, the upper adjacent switch of the switch K2 is the second switch K3, and the lower adjacent switch is the first switch K1. The following method is used: Step 1. The second switch K2 is closed. After a set closing time TON, the second switch K2 is opened. After a set opening time TOFF, the voltage difference between the second battery pin VC2 and the first battery pin VC1 is detected, which is recorded as VT2L. In step 1, the first switch K1 and the third switch K3 remain open. Step 2. Close the third switch K3. After the set closing time TON, open the third switch K3. After the set opening time TOFF, measure the voltage difference between the second battery pin VC2 and the first battery pin VC1 at this time, and record it as VT2H. In step 2, the second switch K2 and the fourth switch K4 remain open. The closing time, TON, must be set to a value sufficient to fully discharge the capacitor connected between the pins of the second battery group to near zero, while the opening time, TOFF, must be set to a value sufficient to fully charge the capacitor between the pins of the second battery group to its maximum value. The specific values ​​of the closing time, TON, and the opening time, TOFF, are determined by the selected capacitor value, battery voltage, and internal switch on-resistance.

[0035] Step 3: Detect the difference between VT2L and VT2H. If the difference exceeds the set threshold value ΔVT, it is determined that the second battery CP2 is disconnected.

[0036] like Figure 1 As shown, it is first assumed that the second battery is not disconnected; the first switch K1 remains open; In step 1, K3 remains open, K2 is closed first, and the second capacitor C2 is short-circuited and discharged to a voltage equal to the voltage of the first battery pin VC1. Then K2 is disconnected, and the second battery CP2 charges the second capacitor C2. The voltage difference between the pins of the second battery group is the voltage VCP2 of the second battery, that is, VT2L=VCP2; In step 2, K2 remains disconnected and K3 is closed first. When the third battery is disconnected, the second capacitor C2 is charged by the second battery until the voltage difference between the pins of the second battery group is equal to the voltage VCP2 of the second battery. When the third battery is online, the second capacitor C2 is charged by both the third battery and the second battery. Then K3 is disconnected. Since the second battery is used as the power source, no matter what the voltage difference between the pins of the second battery group is before K3 is disconnected, after K3 is disconnected, the second capacitor will be charged until the voltage difference between the pins of the second battery group is the voltage VCP2 of the second battery, that is, VT2H=VCP2; That is, when the second battery is not disconnected, VT2H=VT2L=VCP2; During the detection process from step 1 to step 2, whether the first battery CP1 is online or the first battery pin is short-circuited, it only affects the absolute value of the voltage of the first battery pin VC1, and does not affect the voltage difference VCP2 between the second battery pins.

[0037] Then suppose the second battery is disconnected; In step 1, K3 remains disconnected and K2 is closed first. The second capacitor C2 is short-circuited and discharged to a voltage equal to the voltage of the first battery pin VC1. The voltage difference between the pins of the second battery group is zero. Then K2 is disconnected. Since the second battery is disconnected and cannot supply power, the second battery CP2 cannot charge the second capacitor. The voltage difference between the pins of the second battery group remains at the original voltage, that is, VT2L=0 at this time. In step 1, when the second switch is closed, the adjacent switches K1 and K3 of the second switch remain open; In step 2, K2 remains open and K3 is closed first; When the third battery and the second battery are both disconnected, the voltage difference between the pins of the second battery group remains at the original value of 0. When the third battery is online, the positive electrode of the second capacitor C2 will be charged by the third battery through R3, VC3, K3, and VC2 to the output voltage VCP3P of the third battery's positive electrode; the negative electrode of the second capacitor C2 maintains the output voltage VCP1P of the first battery's positive electrode; Then K3 is disconnected. Since the second battery is disconnected and K2 is also disconnected, the voltages at the positive and negative electrodes of the second capacitor will remain at their original values; that is, VT2H = VCP3P - VCP1P. It can be seen from this that when the third battery is online and the second battery is disconnected, the difference between VT2H and VT2L is VT2H-VT2L=VCP3P-VCP1P. Since the positive electrode voltage VCP3P of the third battery is equal to the sum of the output voltages of the first, second and third batteries, the positive electrode voltage VCP1P of the first battery is equal to the output voltage of the first battery; that is, VT2H-VT2L=(VCP3+VCP2+VCP1)-VCP1=VCP3+VCP2, where VCP1, VCP2 and VCP3 are the output voltages of the first, second and third batteries respectively.

[0038] When the second battery is online, the difference between the two is zero. By setting ΔVT to a smaller value greater than zero, such as 0.1V, it can be determined whether the second battery is disconnected.

[0039] Similar to the analysis of the first battery string, when both the third and second batteries are disconnected, the voltage of the second capacitor C2 remains at its original value in step 2. At this point, it is impossible to determine whether the second battery is disconnected. However, subsequent determinations will indicate a disconnection in the entire battery string, prompting the user to check the circuit.

[0040] In step 2, when the third switch is closed, the adjacent switches K2 and K4 of the third switch remain open; Assume that the first battery pin VC1 and the second battery pin VC2 are short-circuited; In step 1, K3 remains open. Since the first battery pin VC1 and the second battery pin VC2 are short-circuited, whether K2 is closed or not does not affect the short-circuit state of the first battery pin VC1 and the second battery pin VC2. The positive and negative voltages of the second capacitor are equal and equal to the positive voltage of the first capacitor, that is, VT2L = 0. Since the first battery pin VC1 and the second battery pin VC2 are short-circuited, in step 2, regardless of the status of the internal switches K2 and K3, or whether the third battery is short-circuited, the positive and negative voltages of the second capacitor are always equal, i.e., VT2H=0. It can be seen that when the first battery pin VC1 and the second battery pin VC2 are short-circuited, VT2H=VT2L=0, which is significantly lower than when the battery is connected; When VT2H=VT2L are both smaller than the lower threshold value LVT, it is considered that the first battery pin VC1 and the second battery pin VC2 are short-circuited.

[0041] The analysis of the second group of battery pins covers all possible situations, including disconnection and short circuit of the battery pins in this group, and whether the batteries connected to the next group of battery pins to be tested are online. A similar analysis method can be used for subsequent groups of battery pins to reach similar conclusions.

[0042] Step 4. Repeat steps 1 through 3 for each battery pin group, following the order of the first, second, third, and so on. The voltage detection device can utilize a comparator or a single-channel analog-to-digital converter, switching input terminals using time-division multiplexing to detect the voltages of different battery pin groups at different times.

[0043] To save detection time, step 4 can be replaced by: dividing each group of battery pins into odd groups and even groups according to the parity of the serial numbers, and detecting the odd and even groups separately. During the detection, each group of battery pins in the odd or even group is tested simultaneously through steps 1 to 3.

[0044] For example, all odd-numbered groups, i.e., the first, third, fifth, ... battery pins, are tested first. After all tests are completed, all even-numbered groups, i.e., the second, fourth, sixth, ... battery pins, are tested. In this case, the voltage detection device can use a multi-channel ADC to simultaneously input the voltages of multiple groups of battery pins for voltage difference detection and judgment.

[0045] After testing each battery pin group, if no disconnections are detected, the chip begins normal operation. The various switches and voltage detection devices can be used to implement other functions, such as cell balancing, while the chip is operating normally. If a disconnection is detected, the power is turned off to check the battery connection and repair or replace it. The power is then turned back on to test for disconnections, and the chip will continue to operate normally until no disconnections are detected.

[0046] The foregoing are various preferred embodiments of the present invention. Unless the preferred implementation modes in each preferred embodiment are obviously self-contradictory or based on a certain preferred implementation mode, each preferred implementation mode can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for the purpose of clearly describing the inventor's invention verification process, and are not intended to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. Any equivalent structural changes made using the contents of the description of the present invention should also be included in the protection scope of the present invention.

Claims

1. A disconnection detection method, characterized in that: The following steps are involved: According to the connection relationship of the battery string, all N battery pins and one ground pin of the chip are divided into N groups of battery pins. The first group is the first battery pin and the ground pin, the second group is the second battery pin and the first battery pin, the third group is the third battery pin and the second battery pin, and so on. Define the switch connected between two battery pins in the current group as an intra-group switch. Adjacent switches in the group include upper adjacent switches and lower adjacent switches. Define the intra-group switch in the group below the current battery pin according to the group sequence number as the upper adjacent switch of the current group. Define the intra-group switch in the group above the current battery pin according to the group sequence number as the lower adjacent switch of the current group. Set the difference threshold ΔVT, lower threshold LVT, closing time TON, and opening time TOFF; the detection method for each group of battery pins is as follows Step 1. The switch in the group is closed. After the closing time TON, the switch in the group is opened. After the set opening time, the voltage detection device detects the voltage difference between the pins of the battery group at this time, which is recorded as VT1L. In step 1, the upper adjacent switch remains open. Step 2. The upper adjacent switch is closed. After the closing time TON, the upper adjacent switch is opened. After the set opening time TOFF, the voltage difference between the pins of the battery group is detected and recorded as VT1H. In step 2, the switch K1 in the group remains open. In steps 1 to 2, when a switch is closed, the adjacent switch remains open; Step 3. Detect the difference between VT1L and VT1H. If the difference exceeds the set difference threshold ΔVT, it is determined that the battery connected between the pins of the current battery pack is disconnected. When VT1H and VT1L are both less than the lower threshold LVT, it is determined that the current battery pack pin is short-circuited; Step 4. Repeat steps 1 to 3 in the order of the first group, the second group, the third group, etc. to test the pins of each group of batteries.

2. The disconnection detection method according to claim 1, wherein: The step 4 is replaced by: Divide each group of battery pins into odd and even groups according to the parity of the serial numbers. The odd and even groups are tested separately. During the test, each group of battery pins in the odd or even group is tested simultaneously through steps 1 to 3.

3. The disconnection detection method according to claim 1, wherein: In step 4, once a disconnection is found, the detection of subsequent groups is terminated.

4. A disconnection detection circuit, characterized in that: The device comprises a switch connected between adjacent battery pins and a switch connected between a ground pin and one of the battery pins, wherein the switches are connected in series. The device also comprises a voltage detection device connected between the battery pins and the ground pin, wherein the detection device is used to detect the voltage value on any one of the switches. The disconnection detection circuit further comprises a control circuit for implementing the detection method according to any one of claims 1 to 3.

5. The disconnection detection circuit according to claim 1, wherein: The voltage detection device is a comparator or an analog-to-digital converter.

6. A battery management chip comprising a plurality of battery pins, characterized in that: It also includes the disconnection detection circuit as claimed in claim 4.

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