A method for discharging protection of a lithium battery pack and a lithium battery pack using the method

Abstract

This invention discloses a lithium battery pack discharge protection method and a lithium battery pack using this method. When the lithium battery pack enters the working state, the thermistor is in normal working state. At this time, it is first determined whether the lithium battery pack is in charging or discharging working state. When the lithium battery pack is in charging working state, the thermistor is kept in normal working state. When the lithium battery pack is in discharging working state, the voltage of each lithium battery in the lithium battery pack is monitored. If all lithium batteries are not over-discharged, the thermistor is kept in normal working state. If any lithium battery is over-discharged, the thermistor is changed from normal working state to abnormal working state, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal. The advantage is that it still achieves single-cell overcharge protection by using the original charger and single-cell over-discharge protection by using the original discharge controller, thereby improving the service life of the lithium battery pack and reducing the risk of safety accidents.

Description

Technical Field

[0001] This invention relates to a lithium battery pack discharge protection technology, and more particularly to a lithium battery pack discharge protection method and a lithium battery pack using the method. Background Technology

[0002] With the rapid development of the lithium battery power supply industry and the expansion of its application fields, the safety of lithium battery power supply has also received widespread attention. A traditional lithium battery pack typically includes a lithium battery group and a thermistor (usually a negative temperature coefficient thermistor) that senses the temperature of the lithium battery pack. The lithium battery group consists of n lithium batteries (two or more lithium batteries connected in parallel are also counted as one lithium battery), where n is an integer greater than or equal to 3. The positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery pack. The positive terminal of the jth lithium battery and the negative terminal of the (j+1)th lithium battery are connected. The positive terminal of the jth lithium battery is also led out for external connection. The negative terminal of the 1st lithium battery serves as the negative terminal of the lithium battery pack. j = 1, 2, ..., n-1. One end of the thermistor serves as the temperature signal output terminal of the lithium battery pack, and the other end of the thermistor is grounded.

[0003] Traditional lithium battery packs are typically used in conjunction with chargers and discharge controllers. The charger charges the battery pack, providing protection against overcharge and overheating during charging. The discharge controller discharges the battery pack, providing protection against over-discharge and overheating during discharging. The charger has at least n+2 connection ports for connecting to the lithium battery pack. These n+2 ports are: one for connecting to the positive terminal of the battery pack; one for connecting to the negative terminal; n-1 ports for connecting to the positive terminals of the first through (n-1)th lithium batteries in the battery pack; and one port for connecting to the temperature signal output terminal of the battery pack. When the battery pack is connected to the charger for charging, the charger monitors the voltage of each lithium battery cell, the total voltage of the battery pack, and the temperature of the battery pack through the n+2 connection ports. If any lithium battery is detected as overcharged (exceeding its internal charging reference value) or the temperature sensed by the thermistor is too high (exceeding its internal charging reference value), the charger will detect overcharge. The charger stops charging the lithium battery pack and performs overcharge and over-temperature protection when any of the following four conditions occur: the thermistor is open-circuited to ground (below the internal preset lower limit reference value), the thermistor is short-circuited (below the internal preset lower limit reference value), or the thermistor is short-circuited. The thermistor is considered to be in an abnormal working state when it is open-circuited to ground (below the internal preset lower limit reference value) or short-circuited (below the internal preset lower limit reference value). The discharge controller is provided with at least three connection ports connected to the lithium battery pack. These three connection ports are respectively the connection port for connecting to the positive terminal of the lithium battery pack, the connection port for connecting to the negative terminal of the lithium battery pack, and the connection port for connecting to the temperature signal output terminal of the lithium battery pack. When the lithium battery pack is connected to the discharge controller for discharge, the discharge controller monitors the total voltage and temperature of the lithium battery pack through three connection ports. If any of the following four conditions are detected, the discharge controller will control the lithium battery pack to stop discharging and perform over-discharge and over-temperature protection: the lithium battery pack is over-discharged (below its internal preset total voltage reference value, which is 5 times the safe discharge threshold voltage of a single lithium battery); the temperature sensed by the thermistor is too high (exceeding its internal preset upper temperature reference value) or too low (below its internal preset lower temperature reference value); the thermistor has an open circuit to ground (below its internal preset lower temperature reference value); or the thermistor is short-circuited. The circuit diagram of a traditional lithium battery pack including 3 lithium batteries is shown in Figure 1(a), the circuit diagram of a traditional lithium battery pack including 4 lithium batteries is shown in Figure 1(b), the circuit diagram of a traditional lithium battery pack including 5 lithium batteries is shown in Figure 1(c), and the connection diagram of a traditional lithium battery pack including 5 lithium batteries and a charger is shown in Figure 1(c).Figure 2 As shown in the diagram, the connection between a traditional lithium battery pack (including 5 lithium batteries) and a discharge controller is as follows: Figure 3 As shown.

[0004] Currently, the aforementioned combination of lithium batteries, chargers, and discharge controllers is called "single-charge, full-discharge." This means that during the charging process, the charger monitors the voltage of each individual lithium battery cell, while during the discharging process, the discharge controller monitors the overall voltage of the lithium battery pack. The total voltage monitored by the discharge controller is the sum of the voltages of the five individual lithium batteries, only considering whether the average voltage of the five cells is below the safe discharge threshold voltage. However, in reality, voltage imbalances are inevitable among the individual lithium batteries in a lithium battery pack. This results in the total voltage monitored by the discharge controller still being higher than the reference value, but some batteries having high voltage while others have already fallen below the safe discharge threshold voltage. This situation inevitably leads to over-discharge of some lithium batteries in the pack, ultimately shortening the lifespan of the lithium battery pack and increasing the risk of safety accidents. Summary of the Invention

[0005] One of the technical problems to be solved by the present invention is to provide a discharge protection method for a lithium battery pack. This discharge protection method can monitor the voltage of each lithium battery cell during the discharge of the lithium battery pack without changing the structure of the original charger and discharge controller. It can be used in conjunction with the original charger and discharge controller. The original charger can still achieve single-cell overcharge protection and the original discharge controller can achieve single-cell over-discharge protection, thereby improving the service life of the lithium battery pack and reducing the risk of safety accidents.

[0006] The technical solution adopted by the present invention to solve one of the above-mentioned technical problems is as follows: a discharge protection method for a lithium battery pack, wherein the lithium battery pack includes a lithium battery assembly and a thermistor for sensing the temperature of the lithium battery pack. The lithium battery assembly includes n lithium batteries, where n is an integer greater than or equal to 3. The positive electrode of the nth lithium battery serves as the positive electrode of the lithium battery assembly. The positive electrode of the jth lithium battery and the negative electrode of the (j+1)th lithium battery are connected. The positive electrode of the jth lithium battery is also led out for external connection, j = 1, 2, ..., n-1. The negative electrode of the first lithium battery serves as the negative electrode of the lithium battery assembly. One end of the thermistor serves as the temperature signal output terminal of the lithium battery pack. When the temperature of the lithium battery pack is... When the battery pack enters the working state, the thermistor is in normal working state. At this time, it is first determined whether the lithium battery pack is in charging or discharging state. When the lithium battery pack is in charging state, the thermistor is maintained in normal working state. When the lithium battery pack is in discharging state, the voltage of each lithium battery in the lithium battery pack is monitored in real time. If all lithium batteries are not over-discharged, the thermistor is maintained in normal working state. If any lithium battery is over-discharged, the thermistor is changed from normal working state to abnormal working state, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal.

[0007] By collecting the total voltage of the lithium battery pack, or the voltage of each lithium battery cell in the lithium battery pack, or the total voltage of the lithium battery pack and the voltage of each lithium battery cell in the lithium battery pack, the current state of the lithium battery pack is determined based on the voltage change trend before and after the collection. When the voltage change trend is generally from small to large, it is in the charging state; when the voltage change trend is generally from large to small, it is in the discharging state.

[0008] The direction of the working current of the lithium battery pack in the lithium battery pack is used to determine whether the lithium battery pack is in a charging or discharging state. When the current direction of the lithium battery pack is the normal charging current direction, it is in a charging state; when the current direction of the lithium battery pack is the normal discharging current direction, it is in a discharging state.

[0009] Compared with existing technologies, the discharge protection method for lithium battery packs of the present invention has the advantage of utilizing the characteristics of existing chargers and discharge controllers, which allow normal operation of the current charging or discharging when the thermistor is connected to ground, and which will be considered abnormal operation and protected when the thermistor circuit is disconnected from ground or short-circuited. When the lithium battery pack enters the working state, the thermistor is in normal working state. At this time, it is first determined whether the lithium battery pack is in charging or discharging working state. When the lithium battery pack is in charging working state, the normal working state of the thermistor is maintained. When the lithium battery pack is in discharging working state, the voltage of each lithium battery in the lithium battery pack is monitored. If all lithium batteries are not over-discharged, the normal working state of the thermistor is maintained. If any voltage is found to be over-discharged, the voltage of the thermistor is monitored. If one lithium battery is over-discharged, the thermistor changes from its normal operating state to an abnormal operating state. The temperature signal output terminal of the lithium battery pack outputs an abnormal signal, thus presenting the over-discharge of any lithium battery in the lithium battery pack through the thermistor output signal. This causes the discharge controller to control the lithium battery pack to stop discharging, achieving single-cell over-discharge protection. Therefore, the method of this invention can monitor the voltage of each lithium battery during the discharge of the lithium battery pack without changing the structure of the original charger and discharge controller. It can be used in conjunction with the original charger and discharge controller, still achieving single-cell overcharge protection with the original charger and single-cell over-discharge protection with the original discharge controller, improving the service life of the lithium battery pack and reducing the risk of safety accidents.

[0010] The second technical problem to be solved by the present invention is to provide a lithium battery pack that can monitor the voltage of each lithium battery during discharge without changing the structure of the original charger and discharge controller. It can be used in conjunction with the original charger and discharge controller, and the original charger can still achieve single-cell overcharge protection and the original discharge controller can achieve single-cell over-discharge protection, thereby improving the service life of the lithium battery pack and reducing the risk of safety accidents.

[0011] The technical solution adopted by this invention to solve the second technical problem mentioned above is as follows: a lithium battery pack, comprising a lithium battery assembly and a thermistor for sensing the temperature of the lithium battery pack. The lithium battery assembly comprises n lithium batteries, where n is an integer greater than or equal to 3. The positive electrode of the nth lithium battery serves as the positive electrode of the lithium battery assembly. The positive electrode of the jth lithium battery and the negative electrode of the (j+1)th lithium battery are connected. The positive electrode of the jth lithium battery is also led out for external connection, j = 1, 2, ..., n-1. The negative electrode of the 1st lithium battery serves as the negative electrode of the lithium battery assembly. One end of the thermistor serves as the temperature signal output terminal of the lithium battery pack. The lithium battery pack further includes a signal detection and processing circuit and a switching circuit. The switching circuit has a short-circuit state and an open-circuit state. The signal detection and processing circuit has a sleep mode and a working mode. When the lithium battery pack is in a non-working state, the signal detection and processing circuit enters a sleep mode. When the lithium battery pack enters the charging or discharging state, the signal detection and processing circuit enters the working mode. During the charging state, the signal detection and processing circuit drives the switching circuit to enter the corresponding state, keeping the thermistor in normal working condition. During the discharging state, the signal detection and processing circuit monitors whether each lithium battery in the lithium battery pack is over-discharged. If none of the lithium batteries are over-discharged, the signal detection and processing circuit outputs a no-over-discharge signal to drive the switching circuit to enter the corresponding state, keeping the thermistor in normal working condition. If at least one lithium battery is over-discharged, the signal detection and processing circuit outputs an over-discharge signal to drive the switching circuit to enter the corresponding state, causing the thermistor to change from normal working condition to abnormal working condition, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal.

[0012] The other end of the thermistor is grounded through the switching circuit. When the signal detection and processing circuit outputs a non-over-discharge signal, the switching circuit is in a short-circuit state. When the signal detection and processing circuit outputs an over-discharge signal, the switching circuit is in an open-circuit state.

[0013] The lithium battery pack includes five lithium batteries. The switching circuit is implemented using a first field-effect transistor. The signal detection and processing circuit includes a first chip (model AZL05), a second chip (model HT66F0025), a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, and a second field-effect transistor. The second chip has a power port, a ground port, and six I / O ports, which are randomly named the first I / O port, the second I / O port, the third I / O port, the fourth I / O port, the fifth I / O port, and the [missing information - likely a typo]. The sixth I / O port has one end of the first resistor connected to the positive terminal of the lithium battery pack, and the other end of the first resistor connected to one end of the first capacitor and pin 1 of the first chip. The other end of the first capacitor is grounded. The second resistor has one end connected to the positive terminal of the lithium battery pack, and the other end of the second resistor connected to one end of the second capacitor and pin 2 of the first chip. The other end of the second capacitor is grounded. The third resistor has one end connected to the positive terminal of the fourth lithium battery in the lithium battery pack, and the other end of the third resistor connected to one end of the third capacitor and pin 3 of the first chip. The other end of the third capacitor is grounded. One end of the fourth resistor is connected to the positive terminal of the third lithium battery in the lithium battery pack. The other end of the fourth resistor is connected to one end of the fourth capacitor and pin 4 of the first chip. The other end of the fourth capacitor is grounded. One end of the fifth resistor is connected to the positive terminal of the second lithium battery in the lithium battery pack. The other end of the fifth resistor is connected to one end of the fifth capacitor and pin 5 of the first chip. The other end of the fifth capacitor is grounded. One end of the sixth resistor is connected to the positive terminal of the first lithium battery in the lithium battery pack. The other end of the sixth resistor is connected to one end of the sixth capacitor and pin 6 of the first chip. The other end of the sixth capacitor is grounded. Pin 7 of the first chip is grounded; pin 10 of the first chip is connected to one end of the seventh resistor, and the other end of the seventh resistor is grounded; pin 11 of the first chip is connected to one end of the eighth capacitor, and the other end of the eighth capacitor is grounded; pin 12 of the first chip is connected to one end of the ninth capacitor, and the other end of the ninth capacitor is grounded; pin 14 of the first chip is connected to the first I / O port of the second chip; pin 15 of the first chip is connected to the second I / O port of the second chip; pin 16 of the first chip is connected to one end of the seventh capacitor and the power supply port of the second chip, and the other end of the seventh capacitor is grounded.The ground port of the second chip is grounded. The third I / O port of the second chip is connected to the drain of the second field-effect transistor. The source of the second field-effect transistor and one end of the eighth resistor are both grounded. The gate of the second field-effect transistor is connected to the other end of the eighth resistor, and its connection point is connected to the other end of the thermistor. The fourth I / O port of the second chip is connected to the gate of the first field-effect transistor. The drain of the first field-effect transistor is connected to the other end of the thermistor, and the source of the first field-effect transistor is grounded. When the battery pack is disconnected from the charger or discharge controller, or when the battery pack is connected to the charger or discharge controller but the charger or discharge controller is not in operation, the temperature signal output terminal of the battery pack has no effective voltage signal. The second field-effect transistor is cut off, the drain of the second field-effect transistor is at a high level, the second chip stops working, and the signal detection and processing circuit enters sleep mode. During the sleep mode of the signal detection and processing circuit, if the battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation, the temperature signal of the battery pack... When the output terminal has a valid voltage signal, the second field-effect transistor is turned on, and the drain of the second field-effect transistor changes from a high level to a low level. The second chip is awakened and begins to work, and the signal detection and processing circuit enters the working mode. When the signal detection and processing circuit enters the working mode, the second chip immediately controls the first field-effect transistor to remain on for a preset on-time. At this time, the other end of the thermistor remains grounded for the preset on-time. During this period, the second chip determines the overall voltage change trend of each lithium battery cell based on the real-time reading from the first chip. The system determines whether the lithium battery pack is currently charging or discharging. If charging, the first field-effect transistor remains on to facilitate normal charging. If discharging, the voltage of each battery cell is read in real-time from the first chip. If none cell is over-discharged, the first field-effect transistor remains on to facilitate normal discharging. If any battery cell is over-discharged, the first field-effect transistor is turned off to stop discharging, thus providing single-cell protection.

[0014] During the charging or discharging operation of the lithium battery pack, the second chip periodically controls the first field-effect transistor to be off for a set time. This set time is less than the response time of the charger and discharge controller to the abnormal operation of the thermistor. During this period, if the drain of the second field-effect transistor changes from high to low, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation. The signal detection and processing circuit remains in operation. If the drain of the second field-effect transistor remains high, it indicates that the battery pack is disconnected from the charger or discharge controller, or that the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in a non-operating state. The second chip controls the first field-effect transistor to be off and stops working, and the signal detection and processing circuit enters sleep mode.

[0015] The other end of the thermistor is grounded, and the switching circuit is connected in parallel with the thermistor. When the signal detection and processing circuit outputs a non-over-discharge signal, the switching circuit is in an open-circuit state; when the signal detection and processing circuit outputs an over-discharge signal, the switching circuit is in a short-circuit state.

[0016] The lithium battery pack includes five lithium batteries. The switching circuit is implemented using a first field-effect transistor. The signal detection and processing circuit includes a first chip (model AZL05), a second chip (model HT66F0025), a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, and a second field-effect transistor. One end of the first resistor is connected to the positive terminal of the lithium battery pack, and the other end of the first resistor is connected to one end of the first capacitor and pin 1 of the first chip. The other end of the first capacitor is grounded. One end of the second resistor is connected to the positive terminal of the lithium battery pack. The other end of the second resistor is connected to one end of the second capacitor and pin 2 of the first chip. The other end of the second capacitor is grounded. One end of the third resistor is connected to the positive terminal of the fourth lithium battery in the lithium battery pack. The other end of the third resistor is connected to one end of the third capacitor and pin 3 of the first chip. The other end of the third capacitor is grounded. One end of the fourth resistor is connected to the positive terminal of the third lithium battery in the lithium battery pack. The other end of the fourth resistor is connected to one end of the fourth capacitor and pin 4 of the first chip. The other end of the fourth capacitor is grounded. One end of the fifth resistor is connected to the positive terminal of the second lithium battery in the lithium battery pack. The other end of the fifth resistor is connected to one end of the fifth capacitor and pin 5 of the first chip. The other end of the fifth capacitor is grounded. One end of the sixth resistor is connected to the positive terminal of the first lithium battery in the lithium battery pack. The other end of the sixth resistor is connected to one end of the sixth capacitor and pin 6 of the first chip. The other end of the sixth capacitor is grounded. Pin 7 of the first chip is grounded. Pin 10 of the first chip is connected to one end of the seventh resistor. The other end of the seventh resistor is grounded. Pin 11 of the first chip is connected to one end of the eighth capacitor. The other end of the eighth capacitor is grounded. Pin 12 of the first chip is connected to one end of the ninth capacitor, and the other end of the ninth capacitor is grounded. Pin 14 of the first chip is connected to the first I / O port of the second chip. Pin 15 of the first chip is connected to the second I / O port of the second chip. Pin 16 of the first chip is connected to one end of the seventh capacitor and the power supply port of the second chip, respectively. The other end of the seventh capacitor is grounded. The ground port of the second chip is grounded. The third I / O port of the second chip is connected to the drain of the second field-effect transistor. The source of the second field-effect transistor and one end of the eighth resistor are both grounded.The gate of the second field-effect transistor is connected to the other end of the eighth resistor, and its connection point is connected to the other end of the thermistor. The fourth I / O port of the second chip is connected to the gate of the first field-effect transistor. The drain of the first field-effect transistor is connected to one end of the thermistor, and the source of the first field-effect transistor is grounded. When the battery pack is disconnected from the charger or discharge controller, or when the battery pack is connected to the charger or discharge controller but the charger or discharge controller is not in operation, the temperature signal output terminal of the battery pack has no effective voltage signal, the second field-effect transistor is cut off, the drain of the second field-effect transistor is at a high level, the second chip stops working, and the first field-effect transistor remains cut off. The signal detection and processing circuit enters sleep mode. During the sleep mode of the signal detection and processing circuit, if the battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation, the temperature signal output terminal of the battery pack has an effective voltage signal, the second field-effect transistor is turned on, and the second... When the drain of the field-effect transistor changes from high to low, the second chip is awakened and begins operation. The signal detection and processing circuit enters its working mode. When the signal detection and processing circuit enters its working mode, the second chip immediately controls the first field-effect transistor to remain off for a preset cutoff time period. During this time, the first field-effect transistor does not affect the working state of the thermistor. During this period, the second chip determines whether the lithium battery pack is currently in a charging or discharging state based on the overall voltage change trend of each lithium battery cell read in real time from the first chip. If it is in a charging state, the first field-effect transistor is subsequently controlled to remain off to cooperate with the charger for normal charging. If it is in a discharging state, the voltage of each lithium battery cell is subsequently read in real time from the first chip. If each lithium battery is not over-discharged, the first field-effect transistor is controlled to remain off to cooperate with the discharge controller for normal discharging. If any lithium battery is over-discharged, the first field-effect transistor is controlled to turn on to cooperate with the discharge controller to end the discharge, thus achieving single-cell discharge protection.

[0017] During the charging or discharging operation of the lithium battery pack, the second chip periodically controls the first field-effect transistor to conduct for a set time. This set time is less than the response time of the charger and discharge controller to the abnormal operation of the thermistor. During this period, if the drain of the second field-effect transistor changes from high to low, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation. The signal detection and processing circuit remains in operation. If the drain of the second field-effect transistor remains high, it indicates that the battery pack is disconnected from the charger or discharge controller, or that the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in a non-operating state. The second chip controls the first field-effect transistor to turn off and stops working, and the signal detection and processing circuit enters sleep mode.

[0018] Compared with the prior art, the lithium battery pack of the present invention has the advantage of setting up a signal detection and processing circuit and a switching circuit. The switching circuit has short-circuit and open-circuit states, and the signal detection and processing circuit has a sleep mode and a working mode. When the lithium battery pack is in a non-working state, the signal detection and processing circuit enters the sleep mode. When the lithium battery pack enters the charging or discharging working state, the signal detection and processing circuit enters the working mode. During the charging working state, the signal detection and processing circuit drives the switching circuit to enter the corresponding state, so that the thermistor remains in a normal working state. During the discharging working state, the signal detection and processing circuit monitors whether each lithium battery in the lithium battery pack is over-discharged. If each lithium battery is not over-discharged, the signal detection and processing circuit outputs a no-over-discharge signal to drive the switching circuit to enter the corresponding state, so that the thermistor remains in a normal working state. Maintaining normal operation, if at least one lithium battery is over-discharged, the signal detection and processing circuit outputs an over-discharge signal to drive the switching circuit into the corresponding state, causing the thermistor to change from normal operation to abnormal operation. The temperature signal output terminal of the lithium battery pack outputs an abnormal signal, thereby presenting the over-discharge of any lithium battery in the lithium battery pack through the thermistor output signal, causing the discharge controller to stop discharging the lithium battery pack, realizing single-cell over-discharge protection. Thus, the lithium battery pack of this invention can monitor the voltage of each lithium battery during discharge without changing the structure of the original charger and discharge controller. It can be used in conjunction with the original charger and discharge controller, and the original charger can still achieve single-cell overcharge protection and the original discharge controller can still achieve single-cell over-discharge protection, improving the service life of the lithium battery pack and reducing the risk of safety accidents. Attached Figure Description

[0019] Figure 1(a) is a circuit diagram of a traditional lithium battery pack including three lithium batteries;

[0020] Figure 1(b) is a circuit diagram of a traditional lithium battery pack including four lithium batteries;

[0021] Figure 1(c) is a circuit diagram of a traditional lithium battery pack including 5 lithium batteries;

[0022] Figure 2 This is a schematic diagram showing the connection between a traditional lithium battery pack (containing 5 lithium batteries) and a charger.

[0023] Figure 3 A schematic diagram showing the connection between a lithium battery pack containing five lithium batteries and a discharge controller.

[0024] Figure 4 This is a structural block diagram of a first embodiment of the lithium battery pack of the present invention;

[0025] Figure 5 This is a circuit diagram of a first embodiment of the lithium battery pack of the present invention;

[0026] Figure 6 This is a structural block diagram of a second embodiment of the lithium battery pack of the present invention;

[0027] Figure 7 This is a circuit diagram of a second embodiment of the lithium battery pack of the present invention. Detailed Implementation

[0028] This invention discloses a discharge protection method for lithium battery packs. The invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1: A discharge protection method for a lithium battery pack. The lithium battery pack includes a lithium battery assembly and a thermistor for sensing the temperature of the lithium battery pack. The lithium battery assembly includes n lithium batteries, where n is an integer greater than or equal to 3. The positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery assembly. The positive terminals of the jth and (j+1)th lithium batteries are connected. The positive terminal of the jth lithium battery is also led out for external connection. j = 1, 2, ..., n-1. The negative terminal of the first lithium battery serves as the negative terminal of the lithium battery assembly. One end of the thermistor serves as the temperature signal output terminal of the lithium battery pack. When the lithium battery pack enters... When the device enters the working state, the thermistor is in normal working condition. At this time, it first determines whether the lithium battery pack is in charging or discharging state. When the lithium battery pack is in charging state, the thermistor maintains normal working condition. When the lithium battery pack is in discharging state, the voltage of each lithium battery in the lithium battery pack is monitored. If all lithium batteries are not over-discharged, the thermistor maintains normal working condition. If any lithium battery is over-discharged, the thermistor changes from normal working condition to abnormal working condition, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal.

[0030] In this embodiment, the total voltage of the lithium battery pack, or the voltage of each lithium battery cell in the lithium battery pack, or the total voltage of the lithium battery pack and the voltage of each lithium battery cell in the lithium battery pack are collected. Based on the collected voltage change trend, it is determined whether the lithium battery pack is currently in a charging or discharging state. When the voltage change trend is generally from small to large, it is in a charging state; when the voltage change trend is generally from large to small, it is in a discharging state.

[0031] Example 2: A discharge protection method for a lithium battery pack. The lithium battery pack includes a lithium battery assembly and a thermistor for sensing the temperature of the lithium battery pack. The lithium battery assembly includes n lithium batteries, where n is an integer greater than or equal to 3. The positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery assembly. The positive terminals of the jth and (j+1)th lithium batteries are connected, and the positive terminal of the jth lithium battery is also led out for external connection. The negative terminal of the first lithium battery serves as the negative terminal of the lithium battery assembly, j = 1, 2, ..., n-1. One end of the thermistor serves as the temperature signal output terminal of the lithium battery pack. When the lithium battery pack enters... During operation, the thermistor is in normal working condition. At this time, it first determines whether the lithium battery pack is currently in charging or discharging state. When the lithium battery pack is in charging state, the thermistor maintains normal working condition. When the lithium battery pack is in discharging state, the voltage of each lithium battery in the lithium battery pack is monitored. If all lithium batteries are not over-discharged, the thermistor maintains normal working condition. If any lithium battery is over-discharged, the thermistor changes from normal working condition to abnormal working condition, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal.

[0032] In this embodiment, the direction of the current in the lithium battery pack is used to determine whether the lithium battery pack is in a charging or discharging state. When the direction of the current in the lithium battery pack is the normal charging current direction, it is in a charging state; when the direction of the current in the lithium battery pack is the normal discharging current direction, it is in a discharging state.

[0033] The present invention also discloses a lithium battery pack employing the above-described lithium battery pack discharge protection method. The lithium battery pack of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example 1: As Figure 4As shown, a lithium battery pack includes a lithium battery assembly and a thermistor Rt for sensing the temperature of the lithium battery pack. The lithium battery assembly includes n lithium batteries, where n is an integer greater than or equal to 3. The positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery pack. The positive terminals of the jth and (j+1)th lithium batteries are connected, and the positive terminal of the jth lithium battery is also led out for external connection. j = 1, 2, ..., n-1. The negative terminal of the first lithium battery serves as the negative terminal of the lithium battery pack. One end of the thermistor Rt serves as the temperature signal output terminal of the lithium battery pack. The lithium battery pack also includes a signal detection and processing circuit 1 and a switching circuit 2. The switching circuit 2 has an on state and an off state. The signal detection and processing circuit 1 has a sleep mode and a working mode. When the lithium battery pack is in a non-working state, the signal detection and processing circuit 1 enters the sleep mode. When the lithium battery pack enters the charging or discharging working state, the signal detection and processing circuit 1 enters the working mode. During the charging operation, the signal detection and processing circuit 1 drives the switching circuit 2 to enter the corresponding state, keeping the thermistor Rt in normal working condition. During the discharge operation of the lithium battery pack, the signal detection and processing circuit 1 monitors in real time whether each lithium battery in the lithium battery pack is over-discharged. If each lithium battery is not over-discharged, the signal detection and processing circuit 1 outputs a no-over-discharge signal to drive the switching circuit 2 to enter the corresponding state, keeping the thermistor Rt in normal working condition. If at least one lithium battery is over-discharged, the signal detection and processing circuit 1 outputs an over-discharge signal to drive the switching circuit 2 to enter the corresponding state, causing the thermistor Rt to change from normal working condition to abnormal working condition, and the temperature signal output terminal of the lithium battery pack outputs an abnormal signal. The other end of the thermistor Rt is grounded through the switching circuit 2. When the signal detection and processing circuit 1 outputs a no-over-discharge signal, the switching circuit 2 is in a short-circuit state; when the signal detection and processing circuit 1 outputs an over-discharge signal, the switching circuit 2 is in an open-circuit state.

[0035] like Figure 5As shown, in this embodiment, the lithium battery pack includes 5 lithium batteries. The switching circuit 2 is implemented using a first field-effect transistor Q1. The signal detection and processing circuit 1 includes a first chip U1 (model AZL05), a second chip U2 (model HT66F0025), a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a second field-effect transistor Q2. One end of the first resistor R1 is connected to the positive terminal of the lithium battery pack, and the other end of the first resistor R1 is connected to the positive terminal of the lithium battery pack. One end of the first capacitor C1 is connected to pin 1 of the first chip U1, and the other end of the first capacitor C1 is grounded. One end of the second resistor R2 is connected to the positive terminal of the lithium battery pack, and the other end of the second resistor R2 is connected to one end of the second capacitor C2 and pin 2 of the first chip U1, and the other end of the second capacitor C2 is grounded. One end of the third resistor R3 is connected to the positive terminal of the fourth lithium battery in the lithium battery pack, and the other end of the third resistor R3 is connected to one end of the third capacitor C3 and pin 3 of the first chip U1, and the other end of the third capacitor C3 is grounded. One end of the fourth resistor R4 is connected to the positive terminal of the third lithium battery in the lithium battery pack, and the other end of the fourth resistor R4 is connected to one end of the fourth capacitor C4 and pin 4 of the first chip U1, and the fourth... The other end of capacitor C4 is grounded. One end of the fifth resistor R5 is connected to the positive terminal of the second lithium battery in the lithium battery pack. The other end of the fifth resistor R5 is connected to one end of the fifth capacitor C5 and pin 5 of the first chip U1. The other end of the fifth capacitor C5 is grounded. One end of the sixth resistor R6 is connected to the positive terminal of the first lithium battery in the lithium battery pack. The other end of the sixth resistor R6 is connected to one end of the sixth capacitor C6 and pin 6 of the first chip U1. The other end of the sixth capacitor C6 is grounded. Pin 7 of the first chip U1 is grounded. Pin 10 of the first chip U1 is connected to one end of the seventh resistor R7. The other end of the seventh resistor R7 is grounded. Pin 11 of the first chip U1 is connected to one end of the eighth capacitor C8. The other end of the eighth capacitor C8 is grounded. The first chip U1 is grounded. Pin 12 of the first chip U1 is connected to one end of the ninth capacitor C9, and the other end of the ninth capacitor C9 is grounded. Pin 14 of the first chip U1 is connected to pin 3 of the second chip U2. Pin 15 of the first chip U1 is connected to pin 2 of the second chip U2. Pin 16 of the first chip U1 is connected to one end of the seventh capacitor C7 and pin 1 of the second chip U2, and the other end of the seventh capacitor C7 is grounded. Pin 8 of the second chip U2 is grounded. Pin 4 of the second chip U2 is connected to the drain of the second field-effect transistor Q2. The source of the second field-effect transistor Q2 and one end of the eighth resistor R8 are both grounded. The gate of the second field-effect transistor Q2 is connected to the other end of the eighth resistor R8, and its connection terminal is connected to the other end of the thermistor Rt.Pin 5 of the second chip U2 is connected to the gate of the first field-effect transistor Q1. The drain of the first field-effect transistor Q1 is connected to the other end of the thermistor Rt, and the source of the first field-effect transistor Q1 is grounded. When the battery pack is disconnected from the charger or discharge controller, or when the battery pack is connected to the charger or discharge controller but the charger or discharge controller is not in operation, there is no effective voltage signal at the temperature signal output terminal of the battery pack. The second field-effect transistor Q2 is cut off, the drain of the second field-effect transistor Q2 is at a high level, the second chip U2 stops working, and the signal detection and processing circuit 1 enters sleep mode. During the sleep mode of the signal detection and processing circuit 1, if the battery pack is connected to the charger or discharge controller and When the charger or discharge controller is in operation, the battery pack's temperature signal output terminal has a valid voltage signal. The second field-effect transistor Q2 is turned on, and its drain changes from high to low. The second chip U2 is activated and begins operation. The signal detection and processing circuit 1 enters its operating mode. Upon entering this mode, the second chip U2 immediately controls the first field-effect transistor Q1 to remain on for a preset conduction time. Meanwhile, the other end of the thermistor remains grounded for the same preset conduction time. During this period, the second chip U2 determines whether the lithium battery pack is currently charging or discharging based on the overall voltage change trend of each lithium battery cell read in real-time from the first chip. In the operating state, if it is in charging mode, the first field-effect transistor Q1 will remain on to cooperate with the charger to charge according to the normal charging process. If it is in discharging mode, the voltage of each lithium battery is read in real time from the first chip. If each lithium battery is not over-discharged, the first field-effect transistor Q1 will remain on to cooperate with the discharge controller to discharge according to the normal process. If any lithium battery is over-discharged, the first field-effect transistor Q1 will be turned off to cooperate with the discharge controller to end the discharge, realizing the single discharge protection function. During the lithium battery pack is in charging or discharging mode, the second chip U2 periodically controls the first field-effect transistor Q1 to be turned off for a set time. The set time is less than the response time of the charger and discharge controller to abnormal operation of the thermistor. During this period, if the drain of the second field-effect transistor Q2 changes from high to low, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation. The signal detection and processing circuit 1 maintains its operating mode. If the drain of the second field-effect transistor Q2 remains at a high level, it indicates that the battery pack is disconnected from the charger or discharge controller, or that the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in a non-operating state. The second chip U2 controls the first field-effect transistor Q1 to turn off and stop working, and the signal detection and processing circuit 1 enters sleep mode.

[0036] Example 2: Figure 6As shown, a lithium battery pack includes a lithium battery assembly and a thermistor Rt for sensing the temperature of the lithium battery pack. The lithium battery assembly includes n lithium batteries, where n is an integer greater than or equal to 3. The positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery pack. The positive terminals of the jth and (j+1)th lithium batteries are connected, and the positive terminal of the jth lithium battery is also led out for external connection. j = 1, 2, ..., n-1. The negative terminal of the first lithium battery serves as the negative terminal of the lithium battery pack. One end of the thermistor Rt serves as the temperature signal output terminal of the lithium battery pack. The lithium battery pack also includes a signal detection and processing circuit 1 and a switching circuit 2. The switching circuit 2 has short-circuit and open-circuit states. The signal detection and processing circuit 1 has a sleep mode and a working mode. When the lithium battery pack is in a non-working state, the signal detection and processing circuit 1 enters the sleep mode. When the lithium battery pack enters the charging or discharging working state, the signal detection and processing circuit 1 enters the working mode. During operation, signal detection and processing circuit 1 drives switching circuit 2 to enter the corresponding state, keeping the thermistor Rt in normal working condition. When the lithium battery pack is in discharge mode, signal detection and processing circuit 1 monitors whether each lithium battery in the lithium battery pack is over-discharged. If each lithium battery is not over-discharged, signal detection and processing circuit 1 outputs a no-over-discharge signal to drive switching circuit 2 to enter the corresponding state, keeping the thermistor Rt in normal working condition. If at least one lithium battery is over-discharged, signal detection and processing circuit 1 outputs an over-discharge signal to drive switching circuit 2 to enter the corresponding state, changing the thermistor Rt from normal working condition to abnormal working condition. The temperature signal output terminal of the lithium battery pack outputs an abnormal signal. The other end of the thermistor Rt is grounded. Switching circuit 2 is connected in parallel with the thermistor Rt. When signal detection and processing circuit 1 outputs a no-over-discharge signal, switching circuit 2 is in an open-circuit state. When signal detection and processing circuit 1 outputs an over-discharge signal, switching circuit 2 is in a short-circuit state.

[0037] like Figure 7As shown, in this embodiment, the lithium battery pack includes 5 lithium batteries. The switching circuit 2 is implemented using a first field-effect transistor Q1. The signal detection and processing circuit 1 includes a first chip U1 (model AZL05), a second chip U2 (model HT66F0025), a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a second field-effect transistor Q2. One end of the first resistor R1 is connected to the positive terminal of the lithium battery pack, and the other end of the first resistor R1 is connected to the positive terminal of the lithium battery pack. One end of the first capacitor C1 is connected to pin 1 of the first chip U1, and the other end of the first capacitor C1 is grounded. One end of the second resistor R2 is connected to the positive terminal of the lithium battery pack, and the other end of the second resistor R2 is connected to one end of the second capacitor C2 and pin 2 of the first chip U1, and the other end of the second capacitor C2 is grounded. One end of the third resistor R3 is connected to the positive terminal of the fourth lithium battery in the lithium battery pack, and the other end of the third resistor R3 is connected to one end of the third capacitor C3 and pin 3 of the first chip U1, and the other end of the third capacitor C3 is grounded. One end of the fourth resistor R4 is connected to the positive terminal of the third lithium battery in the lithium battery pack, and the other end of the fourth resistor R4 is connected to one end of the fourth capacitor C4 and pin 4 of the first chip U1, and the third... The other end of capacitor C4 is grounded. One end of the fifth resistor R5 is connected to the positive terminal of the second lithium battery in the lithium battery pack. The other end of the fifth resistor R5 is connected to one end of the fifth capacitor C5 and pin 5 of the first chip U1. The other end of the fifth capacitor C5 is grounded. One end of the sixth resistor R6 is connected to the positive terminal of the first lithium battery in the lithium battery pack. The other end of the sixth resistor R6 is connected to one end of the sixth capacitor C6 and pin 6 of the first chip U1. The other end of the sixth capacitor C6 is grounded. Pin 7 of the first chip U1 is grounded. Pin 10 of the first chip U1 is connected to one end of the seventh resistor R7. The other end of the seventh resistor R7 is grounded. Pin 11 of the first chip U1 is connected to one end of the eighth capacitor C8. The other end of the eighth capacitor C8 is grounded. One end is grounded. Pin 12 of the first chip U1 is connected to one end of the ninth capacitor C9, and the other end of the ninth capacitor C9 is grounded. Pin 14 of the first chip U1 is connected to pin 3 of the second chip U2. Pin 15 of the first chip U1 is connected to pin 2 of the second chip U2. Pin 16 of the first chip U1 is connected to one end of the seventh capacitor C7 and pin 1 of the second chip U2, and the other end of the seventh capacitor C7 is grounded. Pin 8 of the second chip U2 is grounded. Pin 4 of the second chip U2 is connected to the drain of the second field-effect transistor Q2. The source of the second field-effect transistor Q2 and one end of the eighth resistor R8 are both grounded. The gate of the second field-effect transistor Q2 is connected to the other end of the eighth resistor R8, and its connection point is connected to one end of the thermistor Rt.Pin 5 of the second chip U2 is connected to the gate of the first field-effect transistor Q1. The drain of the first field-effect transistor Q1 is connected to one end of the thermistor Rt. The source of the first field-effect transistor Q1 is grounded.

[0038] When the battery pack is disconnected from the charger or discharge controller, or when the battery pack is connected to the charger or discharge controller but the charger or discharge controller is not in operation, there is no effective voltage signal at the temperature signal output terminal of the battery pack. The second field-effect transistor Q2 is cut off, its drain is at a high level, the second chip U2 stops working, and the first field-effect transistor Q1 remains cut off. The signal detection and processing circuit 1 enters sleep mode. While the signal detection and processing circuit 1 is in sleep mode, if the battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation, the temperature signal output terminal of the battery pack will have an effective voltage. The signal triggers the second field-effect transistor Q2 to conduct, causing its drain to change from high to low. This wakes up the second chip U2, and the signal detection and processing circuit 1 enters its operating mode. When this mode is activated, the second chip U2 immediately controls the first field-effect transistor Q1 to remain off for a preset cutoff time period. During this time, the first field-effect transistor Q1 does not affect the operating state of the thermistor Rt. During this period, the second chip U2 determines whether the lithium battery pack is currently in a charging or discharging state based on the overall voltage change trend of each lithium battery cell read in real-time from the first chip. If it is in a charging state, the subsequent control... The first field-effect transistor Q1 remains off to allow the charger to charge normally. If the battery is in discharge mode, the voltage of each lithium battery is read in real-time from the first chip. If none of the lithium batteries are over-discharged, the first field-effect transistor Q1 remains off to allow the discharge controller to discharge normally. If any lithium battery is over-discharged, the first field-effect transistor Q1 is turned on to stop the discharge, thus providing single-cell discharge protection. During the charging or discharging phase of the lithium battery pack, the second chip U2 periodically controls the first field-effect transistor Q1 to conduct for a set time, which is less than the time required for the charger and discharge controller to operate. The response time of the controller to the abnormal working state of the sensitive resistor. During this period, if the drain of the second field-effect transistor Q2 changes from high level to low level, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in working state. The signal detection and processing circuit 1 maintains the working mode. If the drain of the second field-effect transistor Q2 remains at a high level, it indicates that the battery pack is disconnected from the charger or discharge controller, or the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in non-working state. The second chip U2 controls the first field-effect transistor Q1 to be turned off and stops working. The signal detection and processing circuit 1 enters sleep mode.

Claims

1. A lithium battery pack employing a discharge protection method, comprising a lithium battery assembly and a thermistor for sensing the temperature of the lithium battery assembly, wherein the lithium battery assembly comprises n lithium batteries, where n is an integer greater than or equal to 3, the positive terminal of the nth lithium battery serves as the positive terminal of the lithium battery assembly, the positive terminal of the jth lithium battery and the negative terminal of the (j+1)th lithium battery are connected, the positive terminal of the jth lithium battery is also led out for external connection, j=1,2,…,n-1, the negative terminal of the 1st lithium battery serves as the negative terminal of the lithium battery assembly, and one end of the thermistor serves as the temperature signal output terminal of the lithium battery pack, characterized in that… The lithium battery pack further includes a signal detection and processing circuit and a switching circuit. The switching circuit has a short-circuit state and an open-circuit state. The signal detection and processing circuit has a sleep mode and a working mode. When the lithium battery pack is in a non-working state, the signal detection and processing circuit enters the sleep mode. When the lithium battery pack enters a charging or discharging state, the signal detection and processing circuit enters the working mode. During the charging state, the signal detection and processing circuit drives the switching circuit to enter the corresponding state, keeping the thermistor in normal working condition. During the discharging state, the signal detection and processing circuit monitors whether each lithium battery in the lithium battery pack is over-discharged. If each lithium battery is not over-discharged, the signal detection and processing circuit outputs a no-over-discharge signal to drive the switching circuit to enter the corresponding state, keeping the thermistor in normal working condition. If at least one lithium battery is over-discharged, the signal detection and processing circuit outputs an over-discharge signal to drive the switching circuit to enter the corresponding state, causing the thermistor to change from normal working condition to abnormal working condition. The temperature signal output terminal of the lithium battery pack outputs an abnormal signal. By collecting the total voltage of the lithium battery pack, or the voltage of each lithium battery cell in the lithium battery pack, or the total voltage of the lithium battery pack and the voltage of each lithium battery cell in the lithium battery pack, the current state of the lithium battery pack is determined based on the voltage change trend before and after the collection. When the voltage change trend is generally from small to large, it is in the charging state; when the voltage change trend is generally from large to small, it is in the discharging state. Alternatively, the direction of the working current of the lithium battery pack in the lithium battery pack can be used to determine whether the lithium battery pack is in a charging or discharging state. When the current direction of the lithium battery pack is the normal charging current direction, it is in a charging state; when the current direction of the lithium battery pack is the normal discharging current direction, it is in a discharging state.

2. A lithium battery pack according to claim 1, characterized in that... The other end of the thermistor is grounded through the switching circuit. When the signal detection and processing circuit outputs a non-over-discharge signal, the switching circuit is in a short-circuit state. When the signal detection and processing circuit outputs an over-discharge signal, the switching circuit is in an open-circuit state.

3. A lithium battery pack according to claim 2, characterized in that... During the charging or discharging operation of the lithium battery pack, a second chip periodically controls the first field-effect transistor to be off for a set time. This set time is less than the response time of the charger and discharge controller to the abnormal operating state of the thermistor. During this period, if the drain of the second field-effect transistor changes from high level to low level, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation. The signal detection and processing circuit remains in operation mode. If the drain of the second field-effect transistor remains at a high level, it indicates that the battery pack is disconnected from the charger or discharge controller, or that the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in a non-operating state. The second chip controls the first field-effect transistor to be off and then stops working. The signal detection and processing circuit enters sleep mode.

4. A lithium battery pack according to claim 1, characterized in that... The other end of the thermistor is grounded, and the switching circuit is connected in parallel with the thermistor. When the signal detection and processing circuit outputs a non-over-discharge signal, the switching circuit is in an open-circuit state; when the signal detection and processing circuit outputs an over-discharge signal, the switching circuit is in a short-circuit state.

5. A lithium battery pack according to claim 4, characterized in that... During the charging or discharging operation of the lithium battery pack, a second chip periodically controls the first field-effect transistor to conduct for a set time. This set time is less than the response time of the charger and discharge controller to the abnormal operation of the thermistor. During this period, if the drain of the second field-effect transistor changes from high to low, it indicates that the lithium battery pack is connected to the charger or discharge controller and the charger or discharge controller is in operation. The signal detection and processing circuit remains in operation. If the drain of the second field-effect transistor remains high, it indicates that the battery pack is disconnected from the charger or discharge controller, or that the battery pack is connected to the charger or discharge controller but the charger or discharge controller is in a non-operating state. The second chip controls the first field-effect transistor to turn off and stops working, and the signal detection and processing circuit enters sleep mode.

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