Charging protection circuit of rechargeable lithium battery terminal equipment and charging device thereof

Abstract

The utility model discloses a charging protection circuit of rechargeable lithium battery terminal equipment and a charging device thereof. The charging protection circuit comprises a voltage signal input circuit, an overvoltage and overcurrent protection circuit, an anti-reverse connection circuit, a surge protection circuit, a surge secondary protection circuit and a voltage signal output circuit. The output end of the voltage signal input circuit is electrically connected with the input end of the anti-reverse connection circuit and the input end of the surge protection circuit, the output end of the anti-reverse connection circuit is electrically connected with the input end of the overvoltage and overcurrent protection circuit, and the output end of the overvoltage and overcurrent protection circuit is electrically connected with the input end of the surge secondary protection circuit. And the output end of the overvoltage and overcurrent protection circuit is also electrically connected with the charging circuit through the voltage signal output circuit. According to the utility model, comprehensive protection can be carried out on the charging process of the rechargeable lithium battery terminal equipment from multiple angles, the protection is diversified, the synergism is good, charging faults can be effectively avoided, the service life of the equipment is prolonged, the use efficiency of the equipment is improved, and the use experience of the equipment is further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of charging of rechargeable lithium battery terminal equipment, in particular to a charging protection circuit and a charging device of the rechargeable lithium battery terminal equipment. Background Art

[0002] With the advancement of technology, various portable electronic devices such as mobile phones, smartwatches, and personal locator cards have become an integral part of people's daily lives and work. These devices are typically equipped with rechargeable lithium batteries to meet the needs of long-term use. However, if the charging port of these devices is not properly protected during charging, there may be safety risks. For example, the charger may be damaged by excessive voltage, current, or temperature, and may even burn out the device's internal circuitry.

[0003] Currently, device charging port protection is primarily achieved through hardware design. For example, adding components like fuses and voltage-stabilizing diodes can protect against overvoltage and overcurrent. Adding a temperature sensor can monitor the device's internal temperature to prevent overheating.

[0004] However, this type of protection design has several drawbacks: First, the protection designs are often independent and lack effective coordination, thus limiting their effectiveness. Second, they often only address a single failure mode, lacking comprehensive protection capabilities for multiple failure modes. Furthermore, this type of protection design often fails to effectively address abnormal charging port conditions, such as excessive charger output voltage or current. These issues can affect the normal use of rechargeable lithium battery terminal devices and may even cause damage. Utility Model Content

[0005] In view of this, the utility model provides a charging protection circuit and a charging device for a rechargeable lithium battery terminal device to solve the problem that the current protection design mode of rechargeable lithium battery terminal devices is single, has poor coordination, and is unable to cope with abnormal conditions of the charging port, resulting in the rechargeable lithium battery terminal device being unable to be used normally or being damaged.

[0006] The utility model provides a charging protection circuit for a rechargeable lithium battery terminal device, wherein the rechargeable lithium battery terminal device is equipped with a charging circuit, and the charging protection circuit of the rechargeable lithium battery terminal device includes a voltage signal input circuit, an overvoltage and overcurrent protection circuit, an anti-reverse connection circuit, a surge protection circuit, a surge secondary protection circuit and a voltage signal output circuit;

[0007] The output end of the voltage signal input circuit is electrically connected to the input end of the anti-reverse connection circuit and the input end of the surge protection circuit. The output end of the anti-reverse connection circuit is electrically connected to the input end of the overvoltage and overcurrent protection circuit. The output end of the overvoltage and overcurrent protection circuit is electrically connected to the input end of the surge secondary protection circuit. The output end of the overvoltage and overcurrent protection circuit is also electrically connected to the charging circuit through the voltage signal output circuit.

[0008] Optionally, the overvoltage and overcurrent protection circuit includes an overload protection chip U1, a first resistor R2, and a second resistor R3;

[0009] The signal input pin IN of the overload protection chip U1 is electrically connected to the output end of the voltage signal input circuit through the anti-reverse connection circuit; the overvoltage lock pin OVLO of the overload protection chip U1 is grounded through the first resistor R2, the current limiting pin ILIM of the overload protection chip U1 is grounded through the second resistor R3, the first ground pin GND and the second ground pin EPAD of the overload protection chip U1 are both grounded, and the output pin OUT of the overload protection chip U1 is electrically connected to the input end of the voltage signal output circuit and the input end of the surge secondary protection circuit.

[0010] Optionally, the overload protection chip U1 is specifically a P14C3ND overvoltage and overcurrent protection chip.

[0011] Optionally, the secondary surge protection circuit includes a first capacitor C1 and a first unidirectional TVS diode D2;

[0012] The first end of the first capacitor C1 and the cathode of the first unidirectional TVS diode D2 are both electrically connected to the 5V power supply end, the output pin OUT of the overload protection chip U1 is connected to the common connection end between the first end of the first capacitor C1 and the 5V power supply end, and the second end of the first capacitor C1 and the anode of the first unidirectional TVS diode D2 are both grounded.

[0013] Optionally, the voltage signal output circuit includes a connector J1 having 8 pins;

[0014] The eight pins of the connector J1 are all electrically connected to the charging circuit; pins 1, 2, and 3 of the connector J1 are all connected together and grounded, and pins 7 and 8 of the connector J1 are all connected together and grounded; pins 4, 5, and 6 of the connector J1 are all connected together and connected to the common connection terminal between the output pin OUT of the overload protection chip U1 and the 5V power supply terminal.

[0015] Optionally, the anti-reverse connection circuit includes a first fuse F1, a MOS tube Q1, a second capacitor C2, a third resistor R1, a fourth resistor R4 and a second unidirectional TVS tube D3;

[0016] A first end of the first fuse F1 is electrically connected to the output end of the voltage signal input circuit, and a second end of the first fuse F1 is electrically connected to the signal input pin IN of the overload protection chip U1. The gate of the MOS transistor Q1 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1 through the third resistor R1. A first end of the fourth resistor R4 and a cathode of the second unidirectional TVS transistor D3 are both connected to the common connection end between the gate of the MOS transistor Q1 and the third resistor R1. A second end of the fourth resistor R4 and an anode of the second unidirectional TVS transistor D3 are both connected to the source of the MOS transistor Q1 and grounded. A first end of the second capacitor C2 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1. A second end of the second capacitor C2 is connected to the drain of the MOS transistor Q1 and grounded.

[0017] Optionally, the surge protection circuit includes a bidirectional TVS diode D1;

[0018] A first end of the bidirectional TVS tube D1 is connected to a common connection end between the first fuse F1 and the output end of the voltage signal input circuit, and a second end of the bidirectional TVS tube D1 is grounded.

[0019] Optionally, the surge protection circuit further includes a second fuse F2;

[0020] The first end of the bidirectional TVS tube D1 is connected to the common connection end between the first fuse F1 and the output end of the voltage signal input circuit through the second fuse F2.

[0021] In addition, the utility model also provides a charging device for a rechargeable lithium battery terminal device, comprising a charging circuit and the aforementioned charging protection circuit for the rechargeable lithium battery terminal device;

[0022] The input end of the charging circuit is electrically connected to the output end of the charging protection circuit of the rechargeable lithium battery terminal device, and the output end of the charging circuit is electrically connected to the rechargeable lithium battery terminal device.

[0023] The beneficial effects of the present invention are as follows: since the output end of the voltage signal input circuit is electrically connected to the input end of the overvoltage and overcurrent protection circuit through the anti-reverse connection circuit, the voltage signal input circuit can input voltage to the overvoltage and overcurrent protection circuit, and first utilize the anti-reverse connection circuit to play an anti-reverse connection role, thereby preventing the input voltage from being mistakenly reversely connected, thereby protecting the rechargeable lithium battery terminal device and its charging circuit from damage; then utilizing the overvoltage and overcurrent protection circuit can play an overvoltage protection and overcurrent protection role, thereby preventing the rechargeable lithium battery terminal device from excessive voltage and excessive current during the charging process; since the output end of the voltage signal input circuit is also electrically connected to the input end of the surge protection circuit, the voltage can also be input to the surge protection circuit, and then utilizing the surge protection circuit can play a surge protection role, thereby enabling the charging circuit to have a higher surge tolerance; at the output end of the overvoltage and overcurrent protection circuit, on the one hand, a surge secondary protection circuit is connected to play a secondary surge protection role, and on the other hand, a voltage signal output circuit is connected to output the signal output by the overvoltage and overcurrent protection circuit to the charging circuit through the voltage signal output circuit, thereby realizing charging protection of the rechargeable lithium battery terminal device;

[0024] The charging protection circuit and charging device of the rechargeable lithium battery terminal equipment of the present invention can protect the charging circuit of the rechargeable lithium battery terminal equipment from multiple angles such as overcurrent protection, overvoltage protection, surge protection and reverse connection protection, avoiding overcurrent, overvoltage, excessive surge and reverse connection at the charging port. The protection design mode is diversified and has good coordination. It can comprehensively protect the charging process of the rechargeable lithium battery terminal equipment, ensure that the rechargeable lithium battery terminal equipment can be charged normally, effectively avoid charging failures, extend the service life of the equipment, improve the use efficiency of the equipment, and thus enhance the user experience of the rechargeable lithium battery terminal equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0026] Figure 1 The following is a structural diagram of a charging protection circuit of a rechargeable lithium battery terminal device in the first embodiment of the present invention;

[0027] Figure 2 The specific design diagram of the overvoltage and overcurrent protection circuit, the anti-reverse connection circuit, the surge protection circuit and the secondary surge protection circuit in the first embodiment of the present utility model is shown;

[0028] Figure 3 The specific design diagram of the voltage signal output circuit in the first embodiment of the present utility model is shown;

[0029] Figure 4The figure shows a structural diagram of a charging device for a rechargeable lithium battery terminal device in the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 1 As shown, a charging protection circuit for a rechargeable lithium battery terminal device is provided. The rechargeable lithium battery terminal device is equipped with a charging circuit. The charging protection circuit for the rechargeable lithium battery terminal device includes a voltage signal input circuit, an overvoltage and overcurrent protection circuit, an anti-reverse connection circuit, a surge protection circuit, a surge secondary protection circuit, and a voltage signal output circuit.

[0033] The output end of the voltage signal input circuit is electrically connected to the input end of the anti-reverse connection circuit and the input end of the surge protection circuit. The output end of the anti-reverse connection circuit is electrically connected to the input end of the overvoltage and overcurrent protection circuit. The output end of the overvoltage and overcurrent protection circuit is electrically connected to the input end of the surge secondary protection circuit. The output end of the overvoltage and overcurrent protection circuit is also electrically connected to the charging circuit through the voltage signal output circuit.

[0034] In this embodiment, since the output end of the voltage signal input circuit is electrically connected to the input end of the overvoltage and overcurrent protection circuit via the anti-reverse connection circuit, the voltage signal input circuit can input a voltage to the overvoltage and overcurrent protection circuit. The anti-reverse connection circuit is first used to prevent reverse connection and prevent the input voltage from being erroneously reversely connected, thereby protecting the rechargeable lithium battery terminal device and its charging circuit from damage. The overvoltage and overcurrent protection circuit can then be used to provide overvoltage and overcurrent protection, preventing the rechargeable lithium battery terminal device from excessive voltage and excessive current during the charging process. Since the output end of the voltage signal input circuit is also electrically connected to the input end of the surge protection circuit, the voltage can also be input to the surge protection circuit, which can then be used to provide surge protection, thereby enabling the charging circuit to have a higher surge withstand capability. The output end of the overvoltage and overcurrent protection circuit is connected to a secondary surge protection circuit on the one hand, which can provide secondary surge protection, and is also connected to a voltage signal output circuit on the other hand. The signal output by the overvoltage and overcurrent protection circuit is output to the charging circuit configured for the rechargeable lithium battery terminal device via the voltage signal output circuit, thereby implementing charging protection for the rechargeable lithium battery terminal device.

[0035] The charging protection circuit of the rechargeable lithium battery terminal device of this embodiment can protect the charging circuit of the rechargeable lithium battery terminal device from multiple angles such as overcurrent protection, overvoltage protection, surge protection and reverse connection protection, avoiding overcurrent, overvoltage, excessive surge and reverse connection. The protection design mode is diversified and has good coordination. It can comprehensively protect the charging process of the rechargeable lithium battery terminal device, ensure that the rechargeable lithium battery terminal device can be charged normally, effectively avoid charging failures, extend the service life of the device, improve the use efficiency of the device, and thereby enhance the user experience of the rechargeable lithium battery terminal device.

[0036] It should be understood that this embodiment only designs and improves the hardware circuit structure of the charging protection circuit of the rechargeable lithium battery terminal device to achieve more comprehensive protection during the charging process of the rechargeable lithium battery terminal device, and does not involve computer-level improvements. The computer programs involved are all conventional computer programs in the field.

[0037] Specifically, the voltage signal input circuit of this embodiment refers to the power input circuit input to the charging protection circuit input end of the entire rechargeable lithium battery terminal device. In this embodiment, it is specifically a 5V power input circuit. Its specific circuit design adopts a conventional design and is not limited here. Figure 2 In the figure, the INPUT_5V port is the output end of the 5V power input circuit, which inputs 5V voltage to the charging protection circuit input end of the entire rechargeable lithium battery terminal device.

[0038] In this embodiment, the rechargeable lithium battery terminal device includes but is not limited to a mobile phone, a smart watch, a personnel positioning card, etc.

[0039] Preferably, if Figure 2 As shown, the overvoltage and overcurrent protection circuit includes an overload protection chip U1, a first resistor R2, a second resistor R3 and a first fuse F1;

[0040] The signal input pin IN of the overload protection chip U1 is electrically connected to the output end of the voltage signal input circuit through the anti-reverse connection circuit; the overvoltage lock pin OVLO of the overload protection chip U1 is grounded through the first resistor R2, the current limiting pin ILIM of the overload protection chip U1 is grounded through the second resistor R3, the first ground pin GND and the second ground pin EPAD of the overload protection chip U1 are both grounded, and the output pin OUT of the overload protection chip U1 is electrically connected to the input end of the voltage signal output circuit and the input end of the surge secondary protection circuit.

[0041] In the overvoltage and overcurrent protection circuit of the above structure, the overload protection chip U1 can realize the configuration of the overvoltage protection threshold through the pull-down resistor R2 (i.e., the first resistor R2), and can realize the configuration of the overcurrent protection threshold through the pull-down resistor R3 (i.e., the second resistor R3). The voltage and current in the subsequent circuit of the overload protection chip (i.e., the voltage output circuit and the charging circuit) can be compared with the configured overvoltage protection threshold and overcurrent protection threshold, respectively; when an overload phenomenon such as a short circuit occurs in the subsequent circuit of the overload protection chip (i.e., the voltage exceeds the overvoltage protection threshold and / or the current exceeds the overcurrent protection threshold), overload protection is performed, including overcurrent protection and / or overvoltage protection. Specifically, a fault signal is generated through the fault pin of the overload protection chip U1 to an external controller such as an MCU to realize alarm and signal reporting, and then the MCU is used to control the circuit to be cut off, thereby protecting the subsequent circuit and equipment from damage, improving the safety of the equipment, and extending the service life of the equipment.

[0042] Preferably, if Figure 2 As shown, the surge secondary protection circuit includes a first capacitor C1 and a first unidirectional TVS diode D2;

[0043] The first end of the first capacitor C1 and the cathode of the first unidirectional TVS diode D2 are both electrically connected to the 5V power supply end, the output pin OUT of the overload protection chip U1 is connected to the common connection end between the first end of the first capacitor C1 and the 5V power supply end, and the second end of the first capacitor C1 and the anode of the first unidirectional TVS diode D2 are both grounded.

[0044] Connecting the first capacitor C1 to the output end of the overload protection chip U1 can achieve a filtering effect and make the output voltage more stable. Because some residual voltage of the overload protection chip U1 will be given to the subsequent circuit before the protection is triggered, connecting the first unidirectional TVS tube D2 to the output end of the overload protection chip U1 can achieve surge residual voltage protection for the subsequent load, playing a role of secondary surge protection for the entire charging process, and preventing the residual voltage from damaging the subsequent circuit.

[0045] Preferably, if Figure 3 As shown, the voltage signal output circuit includes a connector J1 with 8 pins;

[0046] The eight pins of the connector J1 are all electrically connected to the charging circuit; pins 1, 2, and 3 of the connector J1 are all connected together and grounded, and pins 7 and 8 of the connector J1 are all connected together and grounded; pins 4, 5, and 6 of the connector J1 are all connected together and connected to the common connection terminal between the output pin OUT of the overload protection chip U1 and the 5V power supply terminal.

[0047] Through the voltage signal output circuit, the voltage signal can be output safely and stably to the subsequent charging circuit.

[0048] Preferably, if Figure 2 As shown, the anti-reverse connection circuit includes a first fuse F1, a MOS tube Q1, a second capacitor C2, a third resistor R1, a fourth resistor R4 and a second unidirectional TVS tube D3;

[0049] A first end of the first fuse F1 is electrically connected to the output end of the voltage signal input circuit, and a second end of the first fuse F1 is electrically connected to the signal input pin IN of the overload protection chip U1. The gate of the MOS transistor Q1 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1 through the third resistor R1. A first end of the fourth resistor R4 and a cathode of the second unidirectional TVS transistor D3 are both connected to the common connection end between the gate of the MOS transistor Q1 and the third resistor R1. A second end of the fourth resistor R4 and an anode of the second unidirectional TVS transistor D3 are both connected to the source of the MOS transistor Q1 and grounded. A first end of the second capacitor C2 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1. A second end of the second capacitor C2 is connected to the drain of the MOS transistor Q1 and grounded.

[0050] Because the reverse withstand voltage of overload protection chip U1 is typically low, a reverse polarity protection circuit is designed using MOS transistor Q1. This circuit is located at the negative terminal of overload protection chip U1. This allows the MOS transistor to quickly disconnect the circuit if the voltage output from the preceding voltage signal input circuit is mistakenly connected in reverse, preventing the reverse voltage from directly applying to the overload protection chip and protecting it from damage. Furthermore, a first fuse F1 is connected between the output end of the voltage signal input circuit and the third resistor R1. This means that the voltage signal is connected via first fuse F1. When excessive current flows through the preceding stage of the overload protection chip, the first fuse F1 can be used to disconnect the input, further implementing overcurrent protection and safeguarding the charging process of the rechargeable lithium battery terminal device.

[0051] Preferably, if Figure 2 As shown, the surge protection circuit includes a bidirectional TVS tube D1;

[0052] A first end of the bidirectional TVS tube D1 is connected to a common connection end between the first fuse F1 and the output end of the voltage signal input circuit, and a second end of the bidirectional TVS tube D1 is grounded.

[0053] The bidirectional TVS diode D1 is connected between the first fuse F1 and the output terminal of the voltage signal input circuit, which is equivalent to connecting the bidirectional TVS diode D1 in parallel to the circuit. When the circuit is operating normally, the TVS diode is in a high-impedance state and does not affect the normal operation of the circuit. However, when a surge voltage (transient overvoltage) appears in the circuit, the voltage across the TVS diode rises rapidly. Once the voltage exceeds the breakdown voltage (VBR) of the TVS diode, the TVS diode will experience an avalanche effect. At this time, the TVS diode is in a low-impedance state, providing a low-resistance path for the surge current, clamping the surge voltage below a predetermined maximum clamping voltage (VC), thereby protecting the subsequent circuit from damage caused by the surge voltage and achieving surge protection.

[0054] Furthermore, if Figure 2 As shown, the surge protection circuit further includes a second fuse F2;

[0055] The first end of the bidirectional TVS tube D1 is connected to the common connection end between the first fuse F1 and the output end of the voltage signal input circuit through the second fuse F2.

[0056] If the surge intensity and duration exceed the bidirectional TVS diode D1's tolerance, the bidirectional TVS diode D1 may be damaged or even fail. Failure of the bidirectional TVS diode D1 will cause a short circuit, which in turn generates heat. In this embodiment, a second fuse F2 is connected in series with the bidirectional TVS diode D1. This second fuse F2 disconnects the circuit before the bidirectional TVS diode D1 fails, preventing short-circuit heating and providing TVS failure protection.

[0057] Specifically, for this embodiment Figure 2 The first fuse F1 and the second fuse F2 can be glued and coated during circuit design to prevent explosions when the fuses blow and affect the circuit. The glue coating process is a conventional process operation and the specific details are not repeated here.

[0058] Specifically, the overload protection chip U1 in this embodiment is a P14C3ND overvoltage and overcurrent protection chip.

[0059] The above-mentioned overload protection chip has the advantages of high voltage resistance (maximum voltage resistance value is +40V) and overcurrent protection capability, fast response and precise control, small size and easy integration. It can better achieve the purpose of overvoltage and overcurrent protection during the charging process of rechargeable lithium battery terminal equipment.

[0060] Specifically, in this embodiment, the first resistor R2 is a resistor with a specification of 0R / 1%, the second resistor R3 is a resistor with a specification of 3K / 1%, the third resistor R1 is a resistor with a specification of 20K / 1%, the MOS transistor Q1 is specifically an NMOS transistor, the first fuse F1 is specifically a fuse with a specification of 1.5A / 63V, the second fuse F2 is specifically a fuse with a specification of 10A / 32V, the bidirectional TVS transistor D1 is specifically a bidirectional TVS of the SMB10J12CA model, the first unidirectional TVS transistor D2 is specifically a unidirectional TVS of the 5V specification, and the second unidirectional TVS transistor D3 is specifically a unidirectional TVS of the 5.6V specification.

[0061] Based on the first resistor R2, the overvoltage protection threshold VOLO = 6V (i.e., the internal default voltage threshold of the overload protection chip U1). Based on the second resistor R3, the overcurrent protection threshold ILIM = 1.87A. The SMB10J12CA bidirectional TVS diode D1 has a reverse working voltage VRWM of 12V, a maximum clamping voltage VC of 19.9V, and a breakdown voltage VBR of 13.3V. Therefore, the surge protection circuit can withstand ±1200V surges and has a wide input voltage range of -12V to +12V.

[0062] For the short-circuit failure of the bidirectional TVS diode D1, the short-circuit current and I1 are calculated based on the 8 / 20μs current waveform in the IEC61000-4-5 standard and the assumed internal resistance (2Ω). 2 T value, where the short-circuit current I1 is calculated as I1 = (1300-19.9) / 2A = 640.05A. In this calculation formula, 1300V is the voltage difference before and after the assumed TVS failure, 19.9V is the maximum clamping voltage, and the internal resistance of 2Ω is the short-circuit resistance. The obtained 640.05A is an estimated short-circuit current peak value. I1 2 The T value is the product of the square of the short-circuit current and the time during the short-circuit process. It is an important indicator to measure whether the fuse can effectively disconnect the circuit under short-circuit conditions. The calculation process of this value is I1 2 T=640A×640A×20μs=8.192A 2 s. When the second fuse F2 with 10A / 32V specification is selected, its corresponding I1 2 The T value is 10.385A 2 s, which is greater than the I1 of the bidirectional TVS tube D1 when it is short-circuited. 2 T value (8.192A 2 s), so it can withstand sufficient energy under short-circuit conditions and disconnect the circuit before the bidirectional TVS tube D1 fails, thereby protecting subsequent circuits from damage.

[0063] In addition, when a wide pulse surge occurs due to an abnormal load dump (such as grid instability caused by the moment of motor start-up and stop), both the bidirectional TVS tube D1 and the first unidirectional TVS tube D2 will operate, causing overcurrent, thereby blowing the second fuse F2. Specifically, when a wide pulse surge occurs in the power grid, due to the long duration of the surge, the bidirectional TVS tube D1 and the first unidirectional TVS tube D2 may operate at the same time to limit the voltage rise, which will cause a large current to pass through the TVS tube, which may cause an overcurrent problem. At this time, based on the given voltage (90V), pulse width 100ms, the maximum clamping voltage of the bidirectional TVS tube D1 (19.9V) and the circuit impedance (4Ω), the current I2 is calculated as (90V-19.9V) / 4Ω=17.525A, and the corresponding I2 2 T=17.525A×17.525A×100ms=30.712A 2 s, which is smaller than the second fuse F2 with 10A / 32V specification, and its corresponding I1 2 The T value is 10.385A 2 Therefore, the second fuse F2 will also blow before the bidirectional TVS tube D1 breaks down and short-circuits under the abnormal load dump condition.

[0064] The other electronic components in the charging protection circuit of the rechargeable lithium battery terminal device of this embodiment can select appropriate product models or specifications according to actual conditions. The specific specifications in this embodiment are detailed in Figure 2 As shown, no further listing is given here.

[0065] Example 2

[0066] like Figure 4 As shown, a charging device for a rechargeable lithium battery terminal device includes a charging circuit and a charging protection circuit of the rechargeable lithium battery terminal device of embodiment 1;

[0067] The input end of the charging circuit is electrically connected to the output end of the charging protection circuit of the rechargeable lithium battery terminal device, and the output end of the charging circuit is electrically connected to the rechargeable lithium battery terminal device.

[0068] The above-mentioned charging device can utilize the comprehensive protection of the charging protection circuit of the rechargeable lithium battery terminal device to safely charge the rechargeable lithium battery terminal device, ensure that the rechargeable lithium battery terminal device can be charged normally, effectively avoid charging failures, extend the service life of the device, and improve the use efficiency of the device, thereby enhancing the user experience of the rechargeable lithium battery terminal device.

[0069] The charging circuit in this embodiment may adopt the conventional design of a conventional lithium battery charging circuit, which is not limited here.

[0070] The charging protection circuit of the rechargeable lithium battery terminal device of this embodiment has the same structure as the charging protection circuit of the rechargeable lithium battery terminal device of the first embodiment. Therefore, for details not shown in this embodiment, please refer to the first embodiment and the second embodiment. Figures 1 to 3 The detailed description is omitted here.

[0071] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A charging protection circuit for a rechargeable lithium battery terminal device, characterized in that: The rechargeable lithium battery terminal device is equipped with a charging circuit, and the charging protection circuit of the rechargeable lithium battery terminal device includes a voltage signal input circuit, an overvoltage and overcurrent protection circuit, an anti-reverse connection circuit, a surge protection circuit, a surge secondary protection circuit and a voltage signal output circuit; The output end of the voltage signal input circuit is electrically connected to the input end of the anti-reverse connection circuit and the input end of the surge protection circuit. The output end of the anti-reverse connection circuit is electrically connected to the input end of the overvoltage and overcurrent protection circuit. The output end of the overvoltage and overcurrent protection circuit is electrically connected to the input end of the surge secondary protection circuit. The output end of the overvoltage and overcurrent protection circuit is also electrically connected to the charging circuit through the voltage signal output circuit. The overvoltage and overcurrent protection circuit includes an overload protection chip U1, a first resistor R2, and a second resistor R3; the signal input pin IN of the overload protection chip U1 is electrically connected to the output end of the voltage signal input circuit through the anti-reverse connection circuit; the overvoltage lock pin OVLO of the overload protection chip U1 is grounded through the first resistor R2, the current limit pin ILIM of the overload protection chip U1 is grounded through the second resistor R3, the first ground pin GND and the second ground pin EPAD of the overload protection chip U1 are both grounded, and the output pin OUT of the overload protection chip U1 is electrically connected to the input end of the voltage signal output circuit and the input end of the surge secondary protection circuit; The secondary surge protection circuit includes a first capacitor C1 and a first unidirectional TVS diode D2; the first end of the first capacitor C1 and the cathode of the first unidirectional TVS diode D2 are both electrically connected to the 5V power supply terminal, the output pin OUT of the overload protection chip U1 is connected to the common connection terminal between the first end of the first capacitor C1 and the 5V power supply terminal, and the second end of the first capacitor C1 and the anode of the first unidirectional TVS diode D2 are both grounded; The voltage signal output circuit includes an 8-pin connector J1; the 8 pins of the connector J1 are all electrically connected to the charging circuit; pins 1, 2, and 3 of the connector J1 are all connected together and grounded, and pins 7 and 8 of the connector J1 are all connected together and grounded; pins 4, 5, and 6 of the connector J1 are all connected together and connected to the common connection terminal between the output pin OUT of the overload protection chip U1 and the 5V power supply terminal; The reverse connection prevention circuit includes a first fuse F1, a MOS transistor Q1, a second capacitor C2, a third resistor R1, a fourth resistor R4, and a second unidirectional TVS transistor D3. The first end of the first fuse F1 is electrically connected to the output end of the voltage signal input circuit, and the second end of the first fuse F1 is electrically connected to the signal input pin IN of the overload protection chip U1. The gate of the MOS transistor Q1 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1 through the third resistor R1. The first end of the fourth resistor R4 and the cathode of the second unidirectional TVS transistor D3 are both connected to the common connection end between the gate of the MOS transistor Q1 and the third resistor R1. The second end of the fourth resistor R4 and the anode of the second unidirectional TVS transistor D3 are both connected to the source of the MOS transistor Q1 and grounded. The first end of the second capacitor C2 is connected to the common connection end between the signal input pin IN of the overload protection chip U1 and the first fuse F1. The second end of the second capacitor C2 is connected to the drain of the MOS transistor Q1 and grounded. The surge protection circuit includes a bidirectional TVS tube D1; a first end of the bidirectional TVS tube D1 is connected to a common connection end between the first fuse F1 and the output end of the voltage signal input circuit, and a second end of the bidirectional TVS tube D1 is grounded.

2. The charging protection circuit of the rechargeable lithium battery terminal device according to claim 1, characterized in that: The overload protection chip U1 is specifically a P14C3ND overvoltage and overcurrent protection chip.

3. The charging protection circuit of the rechargeable lithium battery terminal device according to claim 1, characterized in that: The surge protection circuit further includes a second fuse F2; The first end of the bidirectional TVS tube D1 is connected to the common connection end between the first fuse F1 and the output end of the voltage signal input circuit through the second fuse F2.

4. A charging device for a rechargeable lithium battery terminal device, characterized in that: A charging circuit and a charging protection circuit of a rechargeable lithium battery terminal device according to any one of claims 1 to 3; The input end of the charging circuit is electrically connected to the output end of the charging protection circuit of the rechargeable lithium battery terminal device, and the output end of the charging circuit is electrically connected to the rechargeable lithium battery terminal device.

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