Battery secondary protection circuit and mode switching method thereof

Abstract

The application discloses a battery secondary protection circuit and a mode switching method thereof. The battery secondary protection circuit is connected with a battery primary protection circuit in series and has a power supply pin and a sensing pin. The switching method comprises the following steps: (S1) judging whether a voltage difference between the power supply pin and the sensing pin is greater than a preset value; and (S2) selectively switching the battery secondary protection circuit to a first mode or a second mode according to a judgment result of step (S1). The battery secondary protection circuit performs a circuit protection operation after delaying for a first preset time and a second preset time in the first mode and the second mode respectively, and the first preset time is longer than the second preset time. The application can effectively avoid the assembly noise from starting the overvoltage protection function by mistake and greatly shorten the test time, so as to improve the test efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to a battery protection circuit, and more particularly to a secondary battery protection circuit and a mode switching method thereof. BACKGROUND

[0002] In a general secondary battery protection circuit, once it detects an overvoltage of the battery, it will send an overvoltage protection signal to blow a fuse arranged in a power supply path to provide an overvoltage protection.

[0003] Please refer to Figure 1 In order to avoid the noise generated in the process of assembly or welding from triggering the overvoltage protection function, the existing secondary battery protection circuit will set a filter circuit FC including a debounce circuit DB before the overvoltage protection circuit OVPC in addition to setting a filter circuit composed of a resistor RDD, R1 and a capacitor CDD at the sensing pin PIN2. When the debounce circuit DB detects the state transition of the sensing signal VC1 input from the sensing pin PIN2, the debounce circuit DB will first lock the sensing signal VC1 and then output the filtered sensing signal VC1' after filtering out the noise.

[0004] In order to effectively remove the influence of noise, the existing filter circuit FC will additionally set a delay unit DL to prolong the debounce time of the debounce circuit DB. However, if the debounce time prolonged by the delay unit DL is too short (for example, 4 milliseconds), the noise generated in the assembly stage will still trigger the overvoltage protection function; if the debounce time is greatly prolonged (for example, prolonged to 6 seconds) to avoid this, the test efficiency will be poor because the test result cannot be confirmed until the debounce time ends after each test is completed. The above problems still need to be further solved. SUMMARY

[0005] Therefore, the present application proposes a secondary battery protection circuit and a mode switching method thereof to effectively solve the above problems encountered by the prior art.

[0006] According to an embodiment of the present application, a mode switching method of a secondary battery protection circuit is provided. In this embodiment, the secondary battery protection circuit is connected in series with a primary battery protection circuit and has a power supply pin and a sensing pin. The mode switching method includes the following steps: (S1) determining whether the voltage difference between the power supply pin and the sensing pin is greater than a preset value; and (S2) selectively switching the secondary battery protection circuit to a first mode or a second mode according to the determination result of step (S1). The secondary battery protection circuit performs a circuit protection operation after delaying for a first preset time in the first mode and a second preset time in the second mode, and the first preset time is longer than the second preset time.

[0007] In one embodiment, the first preset time is more than 100 times of the second preset time.

[0008] In one embodiment, if the result of step (S1) is yes, then step (S2) switches the battery secondary protection circuit to the second mode; if the result of step (S1) is no, then step (S2) switches the battery secondary protection circuit to the first mode.

[0009] Another embodiment of the present application is a battery secondary protection circuit. In this embodiment, the battery secondary protection circuit includes a power pin, a sensing pin, a mode switching circuit and a protection circuit. The mode switching circuit is coupled to the power pin and the sensing pin, and judges whether the voltage difference between the power pin and the sensing pin is greater than a preset value, to selectively provide a first time signal or a second time signal, to switch the battery secondary protection circuit to a first mode or a second mode. The protection circuit is coupled to the mode switching circuit, and delays a first preset time or a second preset time before performing a circuit protection operation in the first mode or the second mode, and the first preset time is longer than the second preset time.

[0010] In one embodiment, the first preset time is more than 100 times of the second preset time.

[0011] In one embodiment, when the voltage difference is greater than the preset voltage, the mode switching circuit provides the second time signal.

[0012] In one embodiment, when the voltage difference is less than the preset voltage, the mode switching circuit provides the first time signal.

[0013] In one embodiment, the protection circuit includes a stabilization circuit. The stabilization circuit is coupled to the sensing pin, and receives a sensing signal from the sensing pin and causes the protection circuit to perform the circuit protection operation after the first preset time or the second preset time.

[0014] In one embodiment, the first time signal corresponds to the first mode and the second time signal corresponds to the second mode.

[0015] In one embodiment, the mode switching circuit includes a comparison circuit, a first time circuit, a second time circuit and a switching circuit. The comparison circuit is coupled to the power pin and the sensing pin, and obtains the voltage difference according to the voltage of the power pin and the voltage of the sensing pin. The first time circuit is used to generate the first time signal. The second time circuit is used to generate the second time signal. The switching circuit selectively turns on the first time circuit or the second time circuit according to the voltage difference, to selectively provide the first time signal or the second time signal.

[0016] Compared with the prior art, the battery secondary protection circuit and the mode switching method thereof can switch modes according to different requirements of assembly and testing, so as to provide preset time (for example, 60 seconds and 4 milliseconds) required for assembly and testing, respectively, thereby effectively avoiding the misactivation of the overvoltage protection function by assembly noise and greatly shortening the testing time, so as to improve the testing efficiency.

[0017] The advantages and spirits of the present application can be further understood through the following detailed description of the application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A schematic diagram of an overvoltage protection circuit in a battery secondary protection circuit in the prior art.

[0019] Figure 2 A schematic diagram of mode switching of a battery secondary protection circuit in an embodiment of the present application.

[0020] Figure 3 An embodiment of a mode switching circuit in the battery secondary protection circuit. Figure 2

[0021] A schematic diagram of a battery secondary protection circuit and a battery primary protection circuit connected in series to provide battery overvoltage protection function. Figure 4

[0022] A schematic diagram of the pin coupling state of the battery secondary protection circuit switched to the second mode. Figure 5

[0023] Waveform timing diagrams of the battery secondary protection circuit in the sleep mode, the test mode and the working mode, respectively. Figures 6A to 6C

[0024] A flowchart of a mode switching method of a battery secondary protection circuit in another embodiment of the present application. Figure 7 MAIN ELEMENT SYMBOL EXPLANATION

[0025] FC filter circuit

[0026] DL delay unit

[0027] OVPC overvoltage protection circuit

[0028] 1 battery secondary protection circuit

[0029] PIN1 power pin

[0030] PIN2-PIN4 sensing pin

[0031] 10 mode switching circuit

[0032]

[0033] ​12 protection circuit

[0034] RDD resistance

[0035] R1 resistance

[0036] CDD capacitance

[0037] PS power supply

[0038] + positive electrode

[0039] - negative electrode

[0040] VTM voltage difference

[0041] TM switching signal

[0042] DLS1 first time signal

[0043] DLS2 second time signal

[0044] DLS time signal

[0045] VDD voltage

[0046] 120 delay circuit

[0047] 122 overvoltage protection circuit

[0048] VC1-VC3 sensing signal

[0049] VC1' filtered sensing signal

[0050] VC1" filtered sensing signal

[0051] IC1 battery primary protection circuit

[0052] IC2 battery secondary protection circuit

[0053] PIN5-PIN9 pin

[0054] OVP overvoltage protection signal

[0055] OVPC overvoltage protection circuit

[0056] DB filter circuit

[0057] LG logic circuit

[0058] 100 comparison circuit

[0059] 102 first time circuit

[0060] 104 second time circuit

[0061] SW switching circuit

[0062] M1-M2 switch

[0063] B1-B2 battery

[0064] FS fuse

[0065] P+ high voltage level

[0066] P- low voltage level

[0067] t0-t2 time

[0068] S10-S14 step DETAILED DESCRIPTION

[0069] Reference will now be made in detail to the exemplary embodiments of the present application, and examples of the exemplary embodiments will be illustrated in the accompanying drawings. Identical or similar components / elements are designated by common reference numerals throughout the drawings and the embodiments. In the following embodiments, a sleep mode is a first mode, a test mode is a second mode, and an operation mode is a third mode. However, the present application is not limited thereto.

[0070] According to one embodiment of the present application, a battery secondary protection circuit is provided. In this embodiment, the battery secondary protection circuit is connected in series with a battery primary protection circuit and a fuse to provide a one-time overvoltage protection.

[0071] Referring to Figure 2 , the battery secondary protection circuit 1 includes a power pin PIN1, a sense pin PIN2, a mode switching circuit 10, and a protection circuit 12. The power pin PIN1 is connected in series with a resistor RDD. The sense pin PIN2 is connected in series with a resistor R1. One end of a capacitor CDD is coupled between the power pin PIN1 and the resistor RDD, and the other end of the capacitor CDD is coupled between the sense pin PIN2 and the resistor R1. During testing, a positive terminal + and a negative terminal - of an external power supply PS are coupled to the resistor RDD and the resistor R1, respectively, to generate a voltage difference VTM between the power pin PIN1 and the sense pin PIN2.

[0072] The resistors RDD, R1, and the capacitor CDD constitute a filter circuit disposed outside the battery secondary protection circuit 1. The battery secondary protection circuit 1 can include one or more sense pins, but is not limited thereto.

[0073] As shown in Figure 2 , the power pin PIN1 is coupled to the mode switching circuit 10. The sense pin PIN2 is coupled to the mode switching circuit 10 and the protection circuit 12, respectively. The mode switching circuit 10 is coupled to the power pin PIN1, the sense pin PIN2, and the protection circuit 12, respectively.

[0074] The mode switching circuit 10 selectively provides the first time signal DLS1 or the second time signal DLS2 to the protection circuit 12 according to the voltage difference VTM between the power pin PIN1 and the sense pin PIN2. If the voltages of the power pin PIN1 and the sense pin PIN2 are VDD and VC1 respectively, the voltage difference VTM between the power pin PIN1 and the sense pin PIN2 is (VDD-VC1).

[0075] In an embodiment, the mode switching circuit 10 can determine to provide the first time signal DLS1 or the second time signal DLS2 to the protection circuit 12 according to whether the voltage difference VTM between the power pin PIN1 and the sense pin PIN2 is greater than a preset voltage.

[0076] For example, when the voltage difference VTM between the power pin PIN1 and the sense pin PIN2 is less than the preset voltage (e.g. 4 volts), the mode switching circuit 10 provides the first time signal DLS1 to the protection circuit 12. When the voltage difference VTM between the power pin PIN1 and the sense pin PIN2 is greater than the preset voltage (e.g. 4 volts), the mode switching circuit 10 provides the second time signal DLS2 to the protection circuit 12.

[0077] When the protection circuit 12 receives the first time signal DLS1 or the second time signal DLS2, the protection circuit 12 performs a circuit protection operation according to the first time signal DLS1 or the second time signal DLS2.

[0078] In an embodiment, the protection circuit 12 includes a delay circuit 120 and an overvoltage protection circuit 122. The delay circuit 120 is coupled to the sense pin PIN2, the mode switching circuit 10 and the overvoltage protection circuit 122 respectively. The overvoltage protection circuit 122 is coupled to the delay circuit 120.

[0079] The delay circuit 120 is used to receive the sense signal VC1 from the sense pin PIN2 and selectively delay the filtered sense signal VC1” for a first preset time or a second preset time according to the first time signal DLS1 or the second time signal DLS2 provided by the mode switching circuit 10, and then output the filtered sense signal VC1” to the overvoltage protection circuit 122. When the overvoltage protection circuit 122 receives the filtered sense signal VC1”, the overvoltage protection circuit 122 outputs an overvoltage protection signal OVP to start an overvoltage protection operation.

[0080] In practical applications, the first preset time corresponding to the first time signal DLS1 can be more than 100 times greater than the second preset time corresponding to the second time signal DLS2, for example, if the first preset time corresponding to the first time signal DLS1 is 60 seconds and the second preset time corresponding to the second time signal DLS2 is 4 milliseconds, the former is 15000 times the latter, but the application is not limited thereto.

[0081] like Figure 2 As shown, the delay circuit 120 may include a filter circuit DB and a logic circuit LG. The filter circuit DB is coupled to the sensing pin PIN2 to receive the sensing signal VC1 and output the filtered sensing signal VC1' to the logic circuit LG after a preset time. The logic circuit LG is coupled to the mode switching circuit 10, the filter circuit DB, and the overvoltage protection circuit 122, respectively, to selectively delay the filtered sensing signal VC1' to the overvoltage protection circuit 122 after a first preset time or a second preset time according to the first time signal DLS1 or the second time signal DLS2. In this embodiment, the filter circuit may be a debouncer, a timer, a filter, and a signal masking circuit or a combination thereof, and the logic circuit LG may be an AND gate, but is not limited thereto.

[0082] Please refer to Figure 3 In one embodiment, the mode switching circuit 10 may include a comparison circuit 100, a first timing circuit 102, a second timing circuit 104, and a switching circuit SW. The two input terminals + and - of the comparison circuit 100 are respectively coupled to a power supply pin PIN1 and a sensing pin PIN2, for receiving the voltage VDD of the power supply pin PIN1 and the voltage VC1 of the sensing pin PIN2, and generating a voltage difference VTM based on the voltage VDD of the power supply pin PIN1 and the voltage VC1 of the sensing pin PIN2, which is then output to the switching circuit SW. The first timing circuit 102 generates a first timing signal DLS1. The second timing circuit 104 generates a second timing signal DLS2. The switching circuit SW selectively couples to either the first timing circuit 102 or the second timing circuit 104 based on the voltage difference VTM, to selectively provide either the first timing signal DLS1 or the second timing signal DLS2.

[0083] Please refer to Figure 4 , Figure 4 This diagram illustrates how the battery secondary protection circuit IC2 and the battery primary protection circuit IC1 are connected in series and operate in the third mode (working mode) to provide battery overvoltage protection.

[0084] like Figure 4 As shown, the battery secondary protection circuit IC2 includes a power pin PIN1, sensing pins PIN2-PIN4, a mode switching circuit 10, and a protection circuit 12. The power pin PIN1 and sensing pin PIN2 are short-circuited. The battery primary protection circuit IC1 includes pins PIN5-PIN9.

[0085] In the battery secondary protection circuit IC2, the protection circuit 12 includes a delay circuit 120 and an over-voltage protection circuit 122. The power pin PIN1 is coupled to the mode switching circuit 10 and the fuse FS, respectively. The sense pin PIN2 is coupled to the mode switching circuit 10, the delay circuit 120 and the high voltage terminal + of the battery cell B1, and is shorted to the power pin PIN1. The sense pin PIN3 is coupled to the low voltage terminal - of the battery cell B1 and the high voltage terminal + of the battery cell B2. The sense pin PIN4 is coupled to the low voltage terminal - of the battery cell B2. The mode switching circuit 10 is coupled to the power pin PIN1, the sense pin PIN2 and the delay circuit 120, respectively. The delay circuit 120 is coupled to the mode switching circuit 10, the sense pin PIN2 and the over-voltage protection circuit 122, respectively. The over-voltage protection circuit 122 is coupled to the delay circuit 120 and the fuse FS, respectively.

[0086] In the battery primary protection circuit IC1, the pins PIN5-PIN7 are coupled to the high voltage terminal + and the low voltage terminal - of the battery cells B1 and B2, respectively. The pins PIN8-PIN9 are coupled to the control terminals of the protection switches M1-M2, respectively. The protection switches M1 and M2 are connected in series to the negative terminal - of the battery B2. The battery cells B1 and B2 are connected in series to each other. The positive terminal + of the battery cell B1 is coupled to the fuse FS.

[0087] When the voltage VDD of the pin PIN1 of the battery secondary protection circuit IC2 starts to rise from 0V, which indicates the first power-up, the voltage difference (VDD-VC1) between the power pin PIN1 and the sense pin PIN2 is less than a preset voltage (e.g. 4V). At this time, the mode switching circuit 10 provides a first time signal DLS1 to the delay circuit 120 of the protection circuit 12 according to the voltage difference (VDD-VC1), so that the battery secondary protection circuit IC2 operates in the sleep mode first. The delay circuit 120 filters the sense signal VC1 received from the sense pin PIN2, and outputs the filtered sense signal VC1" to the over-voltage protection circuit 122 after a first preset time according to the first time signal DLS1. When the over-voltage protection circuit 122 receives the filtered sense signal VC1", the over-voltage protection circuit 122 outputs an over-voltage protection signal OVP to blow the fuse FS arranged in the power supply path of the batteries B1-B2, so as to provide the one-time over-voltage protection.

[0088] Please refer to Figure 5 , Figure 5 The figure is a schematic diagram of the pin coupling state of the battery secondary protection circuit IC2 in the test mode.

[0089] As Figure 5As shown, the power supply pin PIN1 and sensing pin PIN2 of the battery secondary protection circuit IC2 are coupled to the positive (+) and negative (-) terminals of the power supply PS, respectively. In other words, the voltage difference VTM between the power supply pin PIN1 and the sensing pin PIN2 is the voltage provided by the power supply PS.

[0090] In test mode, the voltage supplied by power supply PS is greater than a preset voltage (e.g., 4 volts), causing mode switching circuit 10 to provide a second time signal DLS2 to delay circuit 120 of protection circuit 12 based on the voltage difference VTM. Delay circuit 120 filters the sensing signal VC1 received from self-sensing pin PIN2, and delays it for a second preset time (e.g., 4 milliseconds) based on the second time signal DLS2 before outputting the filtered sensing signal VC1” to overvoltage protection circuit 122. When overvoltage protection circuit 122 receives the filtered sensing signal VC1”, overvoltage protection circuit 122 outputs overvoltage protection signal OVP.

[0091] Please refer to Figure 6A , 6B and 6C, Figure 6A , 6B 6C and 6C are the waveform timing diagrams of the battery secondary protection circuit in sleep mode, test mode and working mode, respectively.

[0092] like Figure 4 and Figure 6A As shown, at time t0, due to the short circuit between power supply pin PIN1 and sensing pin PIN2, the voltage difference VTM is less than the preset voltage (e.g., 4 volts). Therefore, Figure 3 The comparison circuit 100 outputs a switching signal TM that remains at a low level, causing the switching circuit SW to turn on the first time circuit 102, thereby providing a first time signal DLS1 (with a preset time of 60 seconds) to the delay circuit 120 in the protection circuit 12, so that it can operate in sleep mode to meet assembly requirements.

[0093] During this preset time period, the delay circuit 120 will not output the filtered sensing signal VC1”, so its waveform remains at a low level. Similarly, during this preset time period, since the overvoltage protection circuit 122 has not yet received the filtered sensing signal VC1”, the overvoltage protection circuit 122 will not output the overvoltage protection signal OVP, so its waveform remains at a low level.

[0094] like Figure 5 and Figure 6B As shown, at time t0, because the voltage difference VTM between the power supply pin PIN1 and the sensing pin PIN2 is greater than the preset voltage (e.g., 4 volts), therefore, Figure 3The comparison circuit 100 in the battery secondary protection circuit outputs a switching signal TM maintained at a high level, causing the switching circuit SW and the second time circuit 104 to be turned on to provide a second time signal DLS2 (with a preset time of 4 milliseconds) from the second time circuit to the delay circuit 120 in the protection circuit 12, so as to operate in a test mode that meets the test requirements.

[0095] During the preset time (from time t0 to t3), the delay circuit 120 does not output the filtered sensing signal VC1", so its waveform is maintained at a low level until time t3 when the filtered sensing signal VC1" is output to make its waveform become a high level. Similarly, during the preset time (from time t0 to t3), since the overvoltage protection circuit 122 has not received the filtered sensing signal VC1", the overvoltage protection circuit 122 also does not output the overvoltage protection signal OVP, so its waveform is maintained at a low level until time t3 when the overvoltage protection circuit 122 receives the filtered sensing signal VC1" to output the overvoltage protection signal OVP, making its waveform become a high level.

[0096] It should be noted that in the production of the battery secondary protection circuit, the first time signal DLS1 (with a preset time of 60 seconds) generated by the first time circuit 102 or the second time signal DLS2 (with a preset time of 4 milliseconds) generated by the second time circuit 104 can be set as a preset signal source by laser trimming technology to meet different customer requirements, but not limited thereto.

[0097] In the use of the battery secondary protection circuit, the power pin PIN1 and the sensing pin PIN2 are short-circuited, so that the mode switching circuit 10 is always in a preset state and is started only once each time the battery secondary protection circuit is powered on for the first time (such as replacing the battery), and then is in a working mode when continuously powered on, as shown in Figure 6C The time signal DLS output by the mode switching circuit 10 is continuously maintained at a low level, so the filtering time of the sensing signal VC1 by the delay circuit 120 is the continuous filtering time of the stabilizing circuit DB itself, and the continuous filtering time is not extended, but not limited thereto. During time t0 to t2, the stabilizing circuit DB continuously filters, and the delay circuit 120 does not output the filtered sensing signal VC1", so its waveform is maintained at a low level until time t2 when the filtered sensing signal VC1" is output to make its waveform become a high level. Similarly, during time t0 to t2, since the overvoltage protection circuit 122 has not received the filtered sensing signal VC1", the overvoltage protection circuit 122 also does not output the overvoltage protection signal OVP, so its waveform is maintained at a low level until time t2 when the overvoltage protection circuit 122 receives the filtered sensing signal VC1" to output the overvoltage protection signal OVP, making its waveform become a high level.

[0098] Another embodiment of the present application is a mode switching method for a battery secondary protection circuit. In this embodiment, the battery secondary protection circuit is connected in series with a battery primary protection circuit and has a power pin and a sensing pin, but is not limited thereto.

[0099] Please refer to Figure 7 , Figure 7 a flowchart of the mode switching method for the battery secondary protection circuit in this embodiment.

[0100] As shown in Figure 7 , the mode switching method in this embodiment includes the following steps:

[0101] Step S10: determining whether the battery secondary protection circuit is powered on for the first time;

[0102] If the result of step S10 is yes, step S11 is performed to determine whether the voltage difference between the power pin and the sensing pin is greater than a preset value;

[0103] If the result of step S10 is no, step S12 is performed to switch the battery secondary protection circuit to a third mode;

[0104] If the result of step S11 is yes, step S13 is performed to switch the battery secondary protection circuit to a second mode; and

[0105] If the result of step S11 is no, step S14 is performed to switch the battery secondary protection circuit to a first mode.

[0106] In practical applications, step S10 can determine whether the battery secondary protection circuit is powered on for the first time according to the voltage value of the power pin, but is not limited thereto.

[0107] When step S14 switches the battery secondary protection circuit to the first mode (sleep mode), the battery secondary protection circuit will delay a first preset time before transmitting the sensing signal to the overvoltage protection circuit; when step S13 switches the battery secondary protection circuit to the second mode (test mode), the battery secondary protection circuit will delay a second preset time before transmitting the sensing signal to the overvoltage protection circuit.

[0108] It should be noted that the first preset time of the battery secondary protection circuit in the first mode (sleep mode) is longer than the second preset time in the second mode (test mode), and preferably, the first preset time is more than 100 times the second preset time, for example, when the first preset time is 60 seconds and the second preset time is 4 milliseconds, the first preset time is 15000 times the second preset time, but is not limited thereto.

[0109] In one embodiment, when the battery secondary protection circuit is switched to the third mode (working mode) in step S12, the preset time of the battery secondary protection circuit in the third mode (working mode) is shorter than the second preset time (e.g. 1 ms), and of course much shorter than the first preset time, but the present application is not limited thereto. In another embodiment, the battery secondary protection circuit in the third mode (working mode) can also not be delayed, but the present application is not limited thereto.

[0110] Compared with the prior art, the battery secondary protection circuit and the mode switching method thereof can switch the mode according to different requirements of assembly and testing to provide preset times (e.g. 60 seconds and 4 ms) required for assembly and testing, respectively, so that the assembly noise can be effectively prevented from mistakenly starting the overvoltage protection function, the testing time can be greatly shortened, and the testing efficiency can be improved.

Claims

1. A mode switching method of a battery secondary protection circuit, characterized by, The battery secondary protection circuit is connected in series with the battery primary protection circuit and has a power pin and a sensing pin. The mode switching method includes the following steps: (S1) determining whether a voltage difference between the power pin and a sensing signal of the sensing pin is greater than a preset value; and (S2) selectively switching the battery secondary protection circuit to a first mode or a second mode according to a result of step (S1), wherein the battery secondary protection circuit delays for a first preset time and a second preset time respectively in the first mode and the second mode before performing a circuit protection operation, and the first preset time is longer than the second preset time, and the mode switching method further includes: receiving the sensing signal from the sensing pin and filtering the sensing signal to generate a filtered sensing signal; and outputting the filtered sensing signal after selectively delaying for the first preset time or the second preset time according to the result of step (S1).

2. The mode switching method of claim 1, wherein, The first preset time is greater than the second preset time by more than 100 times.

3. The mode switching method of claim 1, wherein, Before step (S1), the switching method further includes the following step: (S0) determining whether the battery secondary protection circuit is powered on for the first time.

4. The mode switching method of claim 3, wherein, Step (S0) determines whether the battery secondary protection circuit is powered on for the first time according to a voltage value of the power pin.

5. The mode switching method of claim 3, wherein, If the result of step (S0) is yes, step (S1) is performed; if the result of step (S0) is no, the battery secondary protection circuit is switched to a third mode.

6. The mode switching method of claim 1, wherein, If the result of step (S1) is yes, step (S2) switches the battery secondary protection circuit to the second mode; if the result of step (S1) is no, step (S2) switches the battery secondary protection circuit to the first mode.

7. A battery secondary protection circuit, characterized by comprising: The battery secondary protection circuit includes: a power pin; a sensing pin for receiving a sensing signal; a mode switching circuit coupled to the power pin and the sensing pin, and determining whether a voltage difference between the power pin and the sensing signal is greater than a preset value to selectively provide a first time signal or a second time signal to switch the battery secondary protection circuit to a first mode or a second mode; and a protection circuit coupled to the mode switching circuit, delaying for a first preset time and a second preset time respectively in the first mode and the second mode before performing a circuit protection operation, and the first preset time is longer than the second preset time, the protection circuit includes a delay circuit, and the delay circuit includes: a filtering circuit coupled to the sensing pin, receiving the sensing signal from the sensing pin and filtering the sensing signal to output a filtered sensing signal; and a logic circuit coupled to the mode switching circuit and the filtering circuit, receiving the filtered sensing signal and outputting the filtered sensing signal after selectively delaying for the first preset time or the second preset time according to the first time signal or the second time signal.

8. The battery secondary protection circuit according to claim 7, characterized by The first preset time is greater than the second preset time by more than 100 times. Before step (S1), the switching method further includes the following step: (S0) determining whether the battery secondary protection circuit is powered on for the first time. Step (S0) determines whether the battery secondary protection circuit is powered on for the first time according to a voltage value of the power pin. If the result of step (S0) is yes, step (S1) is performed; if the result of step (S0) is no, the battery secondary protection circuit is switched to a third mode. If the result of step (S1) is yes, step (S2) switches the battery secondary protection circuit to the second mode; if the result of step (S1) is no, step (S2) switches the battery secondary protection circuit to the first mode. The battery secondary protection circuit includes: a power pin; a sensing pin for receiving a sensing signal; a mode switching circuit coupled to the power pin and the sensing pin, and determining whether a voltage difference between the power pin and the sensing signal is greater than a preset value to selectively provide a first time signal or a second time signal to switch the battery secondary protection circuit to a first mode or a second mode; and a protection circuit coupled to the mode switching circuit, delaying for a first preset time and a second preset time respectively in the first mode and the second mode before performing a circuit protection operation, and the first preset time is longer than the second preset time, the protection circuit includes a delay circuit, and the delay circuit includes: a filtering circuit coupled to the sensing pin, receiving the sensing signal from the sensing pin and filtering the sensing signal to output a filtered sensing signal; and a logic circuit coupled to the mode switching circuit and the filtering circuit, receiving the filtered sensing signal and outputting the filtered sensing signal after selectively delaying for the first preset time or the second preset time according to the first time signal or the second time signal. The first preset time is greater than the second preset time by more than 100 times.

9. The battery secondary protection circuit according to claim 7, characterized by The mode switching circuit provides the second time signal when the voltage difference is greater than a preset voltage.

10. The battery secondary protection circuit according to claim 7, characterized by The mode switching circuit provides the first time signal when the voltage difference is less than the preset voltage.

11. The battery secondary protection circuit according to claim 7, characterized by The first time signal corresponds to the first mode and the second time signal corresponds to the second mode.

12. The battery secondary protection circuit according to claim 7, wherein The mode switching circuit includes: a comparison circuit coupled to the power pin and the sense pin, respectively, and configured to obtain the voltage difference based on a voltage of the power pin and a voltage of the sense pin; a first time circuit configured to provide the first time signal; a second time circuit configured to provide the second time signal; and a switching circuit configured to selectively turn on the first time circuit or the second time circuit based on the voltage difference, so as to selectively provide the first time signal or the second time signal.

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