Charging protection circuit and charging device

Abstract

The utility model relates to the technical field of charging protection, and relates to a charging protection circuit and a charging device. The circuit comprises a power supply input end, a power supply output end, a first MOS tube, a second MOS tube, a first triode, a second triode, a first driving circuit unit and a second driving circuit unit, the source electrode of the first MOS tube is connected with the source electrode of the second MOS tube, the drain electrode of the first MOS tube is connected with the negative electrode of the power supply input end, the drain electrode of the second MOS tube is connected with the negative electrode of the power supply output end, and the first driving circuit unit is connected with the second driving circuit unit. A base electrode of the first triode is connected with a power input end through the first driving circuit unit, a collector electrode of the first triode is connected with a grid electrode of the first MOS tube and a grid electrode of the second MOS tube, an emitting electrode of the first triode is connected with a collector electrode of the second triode, and a base electrode of the second triode is connected with a power output end through the second driving circuit unit. The emitter of the second triode is connected with the anode of the power input end and the anode of the power output end. The system is low in loss, does not need to be controlled by a single-chip microcomputer chip, and is low in cost.

Description

TECHNICAL FIELD

[0001] The utility model relates to charging protection technical field, especially a kind of charging protection circuit and charging device. BACKGROUND

[0002] With the development of electronic equipment, electronic equipment has been popularized into people's daily life, with the popularization of electronic equipment, the application of various charging products for supplying power to electronic equipment is also more and more widely.In the charging product, especially in the high-power charging charging product, a charging protection circuit is usually set to ensure charging safety.

[0003] In the related art, a diode is added between the power input end and the power output end in the charging protection circuit, when the power input end is reversed, the diode is reverse blocked to prevent reverse connection effect;When the power input end is powered off, the voltage of the power output end is higher than that of the power input end, the diode is reverse blocked to prevent reverse flow effect.

[0004] However, the above-mentioned use of diode to realize reverse connection protection and prevent reverse flow mode has large loss of diode. INVENTION CONTENTS

[0005] The technical problem to be solved by the embodiment of the utility model is to provide a charging protection circuit and a charging device to solve the problem of large loss of reverse connection protection mode of charging protection circuit in the prior art.

[0006] The utility model discloses a kind of charging protection circuit, it is characterized by, including: power input end, power output end, first MOS tube, second MOS tube, first triode, second triode, first drive circuit unit and second drive circuit unit, the source of the first MOS tube is connected with the source of the second MOS tube, the drain of the first MOS tube is connected with the negative pole of the power input end, the drain of the second MOS tube is connected with the negative pole of the power output end, the base of the first triode is connected with the power input end by the first drive circuit unit, the collector of the first triode is connected with the gate of the first MOS tube and the gate of the second MOS tube, the emitter of the first triode is connected with the collector of the second triode, the base of the second triode is connected with the power output end by the second drive circuit unit, the emitter of the second triode is connected with the positive pole of the power input end and the positive pole of power output end.

[0007] Optionally, the first driving circuit unit comprises a first pull-up resistor and a first pull-down resistor connected in series, a base of the first transistor is connected to a node of the first pull-up resistor and the first pull-down resistor connected in series, another end of the first pull-up resistor is connected to a positive pole of the power input end and a positive pole of the power output end, and another end of the first pull-down resistor is connected to a negative pole of the power input end.

[0008] Optionally, the first driving circuit unit further comprises a first current-limiting resistor, a first end of the first current-limiting resistor is connected to the node of the first pull-up resistor and the first pull-down resistor connected in series, and a second end of the first current-limiting resistor is connected to the base of the first transistor.

[0009] Optionally, the second driving circuit unit comprises a second pull-up resistor and a second pull-down resistor connected in series, a base of the second transistor is connected to a node of the second pull-up resistor and the second pull-down resistor connected in series, another end of the second pull-up resistor is connected to an emitter of the second transistor, the power input end and a positive pole of the power output end, and another end of the second pull-down resistor is connected to a negative pole of the power output end.

[0010] Optionally, the second driving circuit unit further comprises a second current-limiting resistor, a first end of the second current-limiting resistor is connected to the node of the second pull-up resistor and the second pull-down resistor connected in series, and a second end of the second current-limiting resistor is connected to the base of the second transistor.

[0011] Optionally, the charging protection circuit further comprises an overvoltage protection circuit unit, the overvoltage protection circuit unit is configured to turn off the second transistor when a voltage input by the power input end exceeds a preset voltage.

[0012] Optionally, the overvoltage protection circuit unit comprises a third transistor, a third pull-up resistor, a controllable voltage source and a reference voltage subunit, the third pull-up resistor and the controllable voltage source are connected in series, a base of the third transistor is connected to a node of the third pull-up resistor and the controllable voltage source connected in series, an emitter of the third transistor is connected to the emitter of the second transistor, another end of the third pull-up resistor, a positive pole of the power input end and a positive pole of the power output end, a collector of the third transistor is connected to the base of the second transistor, an anode of the controllable voltage source is connected to a negative pole of the power output end, a reference end of the controllable voltage source is connected to the reference voltage subunit, and the reference voltage subunit is connected between the positive pole of the power output end and a ground end.

[0013] Optionally, the reference voltage subunit comprises a fourth pull-up resistor and a fourth pull-down resistor connected in series, a node of the fourth pull-up resistor and the fourth pull-down resistor is connected to the reference end of the controllable voltage regulator, the other end of the fourth pull-up resistor is connected to the emitter of the third transistor, the positive pole of the power input end and the positive pole of the power output end, and the other end of the fourth pull-down resistor is connected to the negative pole of the power output end.

[0014] Optionally, the fourth pull-down resistor is a rheostat.

[0015] The utility model discloses still a kind of charging device, including the charging protection circuit as described above.

[0016] Compared with prior art, the charging protection circuit provided by the utility model embodiment has the beneficial effects that: the charging protection circuit of the utility model is provided with first MOS tube and second MOS tube on the charging loop of power input end and power output end, and the on and off of first MOS tube and second MOS tube are driven and controlled by the switching state of first transistor and second transistor, wherein first transistor and second transistor are driven by corresponding drive circuit under the correct connection of power input end and power output end, to realize reverse connection protection and anti-backflow, reduce the probability of damage of applied charging device, reduce maintenance cost, improve the reliability of applied charging device, enhance the user experience, wherein, due to the smaller voltage drop in on state of first MOS tube and second MOS tube compared with existing diode in high-power charging, the loss is smaller, and the two MOS tubes are driven by hardware circuit, without single-chip microcomputer chip control, with lower cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] The technical scheme of the utility model will be further explained in detail below with reference to the drawings and embodiments, and the drawings are as follows:

[0018] Figure 1 It is the structure diagram of charging protection circuit provided by the utility model embodiment;

[0019] Figure 2 It is the circuit schematic diagram of charging protection circuit provided by the utility model embodiment.

[0020] Reference signs in the drawings are as follows:

[0021] 110, first drive circuit unit;120, second drive circuit unit;130, overvoltage protection circuit unit;131, reference voltage subunit;

[0022] Q1, First MOSFET; Q2, Second MOSFET; Q3, First transistor; Q4, Second transistor; Q5, Third transistor; R1, First pull-up resistor; R2, First pull-down resistor; R3, First current-limiting resistor; R4, Second pull-up resistor; R5, Second pull-down resistor; R6, Second current-limiting resistor; R7, Third pull-up resistor; R8, Fourth pull-up resistor; R9, Fourth pull-down resistor; R10, Second current-limiting resistor; C1, First filter capacitor; C2, Second filter capacitor; U1, Controllable voltage regulator. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0024] This utility model provides a charging protection circuit that can be used in charging devices, such as car chargers, power banks, and energy storage power supplies, to achieve charging protection for the charging device.

[0025] like Figure 1 As shown, the charging protection circuit includes a power input terminal VIN, a power output terminal VOUT, a first MOSFET Q1, a second MOSFET Q2, a first transistor Q3, a second transistor Q4, a first driving circuit unit 110, and a second driving circuit unit 120. The source of the first MOSFET Q1 is connected to the source of the second MOSFET Q2, and the drain of the first MOSFET Q1 is connected to the negative terminal of the power input terminal VIN. The drain of the second MOSFET Q2 is connected to the negative terminal of the power output terminal VOUT. The base of the first transistor Q3 is connected to the power input terminal VIN through the first driving circuit unit 110. The collector of the first transistor Q3 is connected to the gate of the first MOSFET Q1 and the gate of the second MOSFET Q2. The emitter of the first transistor Q3 is connected to the collector of the second transistor Q4. The base of the second transistor Q4 is connected to the power output terminal VOUT through the second driving circuit unit 120. The emitter of the second transistor Q4 is connected to the positive terminal of the power input terminal VIN and the positive terminal of the power output terminal VOUT.

[0026] The charging protection circuit of the embodiment of the utility model through setting first MOS Q1 and second MOS Q2 on the charging loop of power input terminal VIN and power output terminal VOUT, and using the switch state of first triode Q3 and second triode Q4 to drive and control the conduction and disconnection of first MOS Q1 and second MOS Q2, wherein first triode Q3 and second triode Q4 are driven to work under the correct connection of power input terminal VIN and power output terminal VOUT through the corresponding drive circuit respectively, so as to realize reverse connection protection and anti backflow, reduce the probability of damage of the applied charging device, reduce the maintenance cost, improve the reliability of the applied charging device, enhance the user experience, wherein, due to the fact that the first MOS Q1 and the second MOS Q2 have smaller voltage drop in the conduction state compared with the existing diode under the condition of high-power charging, the loss is smaller, and the two MOS tubes are driven by hardware circuit without the need of single-chip microcomputer chip control, so the cost is lower.

[0027] Specifically, when one of the first triode Q3 and the second triode Q4 is disconnected, or both triodes are disconnected, the gate of the first MOS Q1 and the second MOS Q2 is in the cut-off state, the charging loop of the power input terminal VIN and the power output terminal VOUT is disconnected, the first triode Q3 is only turned on under the condition that the power input terminal VIN is correctly connected to the external input source, and the second triode Q4 is only turned on under the condition that the power output terminal VOUT is correctly connected to the external battery, therefore, the charging protection circuit of the embodiment of the utility model can realize reverse connection protection and anti backflow.

[0028] In specific implementation, the first MOS Q1 and the second MOS Q2 are both NMOS tubes, and the first triode Q3 and the second triode Q4 are both PNP triodes.

[0029] In the prior art, diodes are used to realize reverse connection protection and anti backflow, and the forward voltage drop is about 0.3V, if the charging current of the external battery is 10A, the loss of the diode is 3W, which is relatively large and the temperature is relatively high. The first MOS Q1 and the second MOS Q2 are used in combination with the first triode Q3 and the second triode Q4 to realize reverse connection protection and anti backflow, if the charging current of the external battery is 10A, the loss of the first MOS Q1 and the second MOS Q2 is about 0.2W, which is much smaller than the loss of the prior art.

[0030] Reference Figure 1 And Figure 2In the alternative embodiment of the present application, the first driving circuit unit 110 includes the first pull-up resistor R1 and the first pull-down resistor R2 connected in series, the base of the first transistor Q3 is connected to the series node of the first pull-up resistor R1 and the first pull-down resistor R2, the other end of the first pull-up resistor R1 is connected to the positive pole of the power input terminal VIN and the positive pole of the power output terminal VOUT, and the other end of the first pull-down resistor R2 is connected to the negative pole of the power input terminal VIN.

[0031] By connecting the series node of the first pull-up resistor R1 and the first pull-down resistor R2 to the base of the first transistor Q3, the first pull-down resistor R2 pulls down the voltage to drive the first transistor Q3 to turn on.

[0032] When the power input terminal VIN is correctly connected to the external input source, the first transistor Q3 turns on. When the power input terminal VIN is reversely connected to the external input source or is not connected to the external input source, the first transistor Q3 turns off.

[0033] Optionally, the first driving circuit unit 110 further includes the first current-limiting resistor R3, the first end of the first current-limiting resistor R3 is connected to the series node of the first pull-up resistor R1 and the first pull-down resistor R2, and the second end of the first current-limiting resistor R3 is connected to the base of the first transistor Q3.

[0034] By arranging the first current-limiting resistor R3 at the base of the first transistor Q3, the function of current limiting is achieved, which avoids the damage of the first transistor Q3 caused by the excessively high current and ensures the stability and safety of the circuit.

[0035] Optionally, the first driving circuit unit 110 further includes the first filter capacitor C1, which is connected in parallel with the first pull-up resistor R1. The first filter capacitor C1 can absorb and store charges. When voltage fluctuation occurs in the circuit, the voltage signal can be smoothed by releasing or absorbing the charges, the fluctuation amplitude of the voltage is reduced, and the circuit can be kept stable.

[0036] In the embodiment of the present application, the driving of the first MOS transistor Q1 is realized by pure hardware circuit without the need of single-chip microcomputer chip control, and the cost is low.

[0037] Reference Figure 1 and Figure 2 In the alternative embodiment of the present application, the second driving circuit unit 120 includes the second pull-up resistor R4 and the second pull-down resistor R5 connected in series, the base of the second transistor Q4 is connected to the series node of the second pull-up resistor R4 and the second pull-down resistor R5, the other end of the second pull-up resistor R4 is connected to the emitter of the second transistor Q4, the positive pole of the power input terminal VIN and the positive pole of the power output terminal VOUT, and the other end of the second pull-down resistor R5 is connected to the negative pole of the power output terminal VOUT.

[0038] The second pull-down resistor R5 pulls down the voltage to turn on the second triode Q4 by connecting the base of the second triode Q4 to the series node of the second pull-up resistor R4 and the second pull-down resistor R5.

[0039] When the power output terminal VOUT is correctly connected to the external battery, the second triode Q4 is turned on. When the power output terminal VOUT is reversely connected to the external battery or is not connected to the external battery, the second triode Q4 is turned off.

[0040] Optionally, the second driving circuit unit 120 further comprises a second current-limiting resistor R6, a first end of the second current-limiting resistor R6 being connected to the series node of the second pull-up resistor R4 and the second pull-down resistor R5, and a second end of the second current-limiting resistor R6 being connected to the base of the second triode Q4.

[0041] By arranging the second current-limiting resistor R6 at the base of the second triode Q4, the function of current limiting is achieved, which avoids damage to the second triode Q4 caused by excessively high current and ensures the stability and safety of the circuit.

[0042] Optionally, the second driving circuit unit 120 further comprises a second filter capacitor C2, the second filter capacitor C2 being connected in parallel to the second pull-up resistor R4. The second filter capacitor C2 can absorb and store charges, and when voltage fluctuation occurs in the circuit, the voltage signal can be smoothed by releasing or absorbing charges, the fluctuation amplitude of the voltage is reduced, and the circuit can be kept stable.

[0043] In the embodiment of the application, the driving of the second MOS tube Q2 is realized by a pure hardware circuit, without the need for a single-chip microcomputer chip control, and the cost is low.

[0044] Reference Figure 1 and Figure 2 In the optional embodiment of the application, the charging protection circuit further comprises an overvoltage protection circuit unit 130, the overvoltage protection circuit unit 130 being configured to turn off the second triode Q4 when the voltage input by the power input terminal VIN exceeds a preset voltage.

[0045] By arranging the overvoltage protection circuit unit 130, the second triode Q4 is turned off when the voltage input by the power input terminal VIN exceeds a preset voltage, and then the first MOS tube Q1 and the second MOS tube Q2 are turned off, so that the charging circuit is disconnected when overvoltage occurs. In addition to the functions of reverse connection protection and anti-backflow protection, the charging protection circuit also has the function of overvoltage protection, which prevents the charging device or the charged device from being damaged.

[0046] Reference Figure 1 and Figure 2Optionally, the overvoltage protection circuit unit 130 comprises a third transistor Q5, a third pull-up resistor R7, a controllable voltage source U1 and a reference voltage subunit 131, the third pull-up resistor R7 is connected with the controllable voltage source U1 in series, the base of the third transistor Q5 is connected with the series connection node of the third pull-up resistor R7 and the controllable voltage source U1, the emitter of the third transistor Q5 is connected with the emitter of the first transistor Q3, the other end of the third pull-up resistor R7, the positive pole of the power input terminal VIN and the positive pole of the power output terminal VOUT, the collector of the third transistor Q5 is connected with the base of the first transistor Q3, the anode of the controllable voltage source U1 is connected with the negative pole of the power output terminal VOUT, the reference end is connected with the reference voltage subunit 131, and the reference voltage subunit 131 is connected between the positive pole of the power output terminal VOUT and the ground terminal.

[0047] The controllable voltage source U1 is an electronic component, which mainly provides a stable output voltage in a circuit. Specifically, the controllable voltage source U1 can automatically adjust the output voltage according to the change of the input voltage, so as to keep the output voltage within a preset stable value range. The controllable voltage source U1 can adopt a TL431 type voltage source.

[0048] By connecting the controllable voltage source U1 and the third pull-up resistor R7 in series, that is, connecting the cathode of the controllable voltage source U1 with the third pull-up resistor R7, connecting the anode with the negative pole of the power output terminal VOUT, connecting the reference end with the reference voltage subunit 131, and the reference voltage subunit 131 providing a stable reference voltage for the controllable voltage source U1, the controllable voltage source U1 clamps the base voltage of the third transistor Q5 at a preset voltage. When the voltage difference between the base and the emitter of the third transistor Q5 is less than-0.5V, the third transistor Q5 is turned on, the base and the emitter of the first transistor Q3 are pulled to the same potential, the second transistor Q4 is turned off, and the gate of the first MOS Q1 and the gate of the second MOS Q2 are pulled low, so that the first MOS Q1 and the second MOS Q2 are both in the off state, the charging circuit is disconnected, and the overvoltage protection function is realized.

[0049] Optionally, the reference Figure 2 voltage subunit 131 comprises a fourth pull-up resistor R8 and a fourth pull-down resistor R9 connected in series, the series connection node of the fourth pull-up resistor R8 and the fourth pull-down resistor R9 is connected with the reference end of the controllable voltage source U1, the other end of the fourth pull-up resistor R8 is connected with the emitter of the third transistor Q5, the positive pole of the power input terminal VIN and the positive pole of the power output terminal VOUT, and the other end of the fourth pull-down resistor R9 is connected with the negative pole of the power output terminal VOUT.

[0050] By connecting the series node of the fourth pull-up resistor R8 and the fourth pull-down resistor R9 to the reference end of the controllable voltage regulator U1, the fourth pull-down resistor R9 provides a reference voltage for the controllable voltage regulator U1, and the size of the reference voltage depends on the voltage of the power input end VIN, the resistance value of the fourth pull-up resistor R8 and the resistance value of the fourth pull-down resistor R9.

[0051] Optionally, the fourth pull-down resistor R9 is a variable resistor. The variable resistor is an electronic element that can adjust the resistance value. By adjusting the resistance value of the variable resistor, the size of the reference voltage of the controllable voltage regulator U1 can be adjusted, so that different overvoltage protection points can be set, and charging devices of different voltage segments can be adapted.

[0052] In a specific implementation, the variable resistor can be an electronic element with adjustable resistance value, such as a knob potentiometer, a linear potentiometer, a multi-turn potentiometer, etc.

[0053] Optionally, the overvoltage protection unit further comprises a third current-limiting resistor R10, one end of the third current-limiting resistor R10 is connected to the base of the third NPN transistor Q5, and the other end of the third current-limiting resistor R10 is connected to the series node of the third pull-up resistor R7 and the controllable voltage regulator U1. The third current-limiting resistor R10 functions as a current limiter to prevent the current from being too high to damage the third NPN transistor Q5, and to ensure the stability and safety of the circuit.

[0054] In combination Figure 1 and Figure 2 The specific working principle of the charging protection circuit of the embodiment of the present application is described as follows:

[0055] When the power input terminal VIN is connected to an external input source correctly and the power output terminal VOUT is not connected, the first triode Q3 is turned on, the second triode Q4 is turned off, the gate of the first MOS Q1 and the gate of the second MOS Q2 are both low, the two MOS are in the off state, the charging circuit between the power input terminal VIN and the power output terminal VOUT is disconnected, and the power output terminal VOUT has no output. When the power input terminal VIN is connected to an external input source correctly and the power output terminal VOUT is connected to an external battery correctly, the first triode Q3 and the second triode Q4 are both turned on, the gate of the first MOS Q1 and the gate of the second MOS Q2 are both high, the two MOS are in the on state, the charging circuit between the power input terminal VIN and the power output terminal VOUT is connected, and the output of the power output terminal VOUT is equal to the input of the power input terminal VIN, which charges the external battery. When the power input terminal VIN is connected to an external input source reversely and the power output terminal VOUT is connected to an external battery correctly, the second triode Q4 is turned on, the first triode Q3 is turned off, the gate of the first MOS Q1 and the gate of the second MOS Q2 are both low, the two MOS are in the off state, the charging circuit between the power input terminal VIN and the power output terminal VOUT is disconnected, and the power output terminal VOUT has no output, which plays a reverse connection protection function. When the external input source is suddenly cut off during normal operation, the power input terminal VIN drops from a normal voltage to 0V instantaneously, at this time, the first triode Q3 is turned off, the second triode Q4 is turned on, the gate of the first MOS Q1 and the gate of the second MOS Q2 are both low, the two MOS are in the off state, the power circuit is disconnected, the reverse flow of electric charge is prevented, and a reverse flow protection function is played. When the voltage of the external input source is too high, the base potential of the third triode Q5 is clamped at a preset voltage by the controllable voltage source U1, when the voltage difference between the base and the emitter of the third triode Q5 is less than-0.5V, the third triode Q5 is turned on, the base and the emitter potential of the second triode Q4 are pulled down, so that the second triode Q4 is turned off, at this time, the gate of the first MOS Q1 and the gate of the second MOS Q2 are both low, the two MOS are in the off state, the charging circuit is disconnected, and the power output terminal VOUT outputs 0V, which plays an overvoltage protection function.

[0056] The embodiment of the application also provides a charging device comprising the charging protection circuit.

[0057] The charging protection circuit in the charging device of the embodiment of the application is configured by arranging the first MOS tube Q1 and the second MOS tube Q2 on the charging loop between the power input end VIN and the power output end VOUT, and the on and off of the first MOS tube Q1 and the second MOS tube Q2 are driven and controlled by the switching state of the first triode Q3 and the second triode Q4, wherein the first triode Q3 and the second triode Q4 are driven to work by the corresponding driving circuit under the correct connection of the power input end VIN and the power output end VOUT, thereby realizing reverse connection protection and anti-backflow, reducing the probability of damage of the charging device, reducing the maintenance cost, improving the reliability of the use of the charging device, and enhancing the use experience of the user, wherein, due to the smaller voltage drop in the on state of the first MOS tube Q1 and the second MOS tube Q2 compared with the existing diode in the case of high-power charging, the loss is smaller, and the two MOS tubes are driven by the hardware circuit without the need for single-chip microcomputer chip control, and the cost is lower.

[0058] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them, and the technical solutions recorded in the above embodiments can be modified by those skilled in the art, or some technical features can be replaced by equivalents; all these modifications and replacements shall belong to the protection scope of the claims of the present application.

Claims

1. A charging protection circuit, characterized by, The charging protection circuit comprises a power input end, a power output end, a first MOS tube, a second MOS tube, a first triode, a second triode, a first driving circuit unit and a second driving circuit unit, the source of the first MOS tube is connected to the source of the second MOS tube, the drain of the first MOS tube is connected to the negative pole of the power input end, the drain of the second MOS tube is connected to the negative pole of the power output end, the base of the first triode is connected to the power input end through the first driving circuit unit, the collector of the first triode is connected to the gate of the first MOS tube and the gate of the second MOS tube, the emitter of the first triode is connected to the collector of the second triode, the base of the second triode is connected to the power output end through the second driving circuit unit, and the emitter of the second triode is connected to the positive pole of the power input end and the positive pole of the power output end. The first driving circuit unit comprises a first pull-up resistor and a first pull-down resistor connected in series, the base of the first triode is connected to the series connection node of the first pull-up resistor and the first pull-down resistor, the other end of the first pull-up resistor is connected to the positive pole of the power input end and the positive pole of the power output end, and the other end of the first pull-down resistor is connected to the negative pole of the power input end.

2. The charge protection circuit of claim 1, wherein, The first driving circuit unit further comprises a first current-limiting resistor, the first end of the first current-limiting resistor is connected to the series connection node of the first pull-up resistor and the first pull-down resistor, and the second end of the first current-limiting resistor is connected to the base of the first triode.

3. The charge protection circuit of claim 2, wherein, The second driving circuit unit comprises a second pull-up resistor and a second pull-down resistor connected in series, the base of the second triode is connected to the series connection node of the second pull-up resistor and the second pull-down resistor, the other end of the second pull-up resistor is connected to the emitter of the second triode, the positive pole of the power input end and the positive pole of the power output end, and the other end of the second pull-down resistor is connected to the negative pole of the power output end.

4. The charge protection circuit of claim 1, wherein, The second driving circuit unit further comprises a second current-limiting resistor, the first end of the second current-limiting resistor is connected to the series connection node of the second pull-up resistor and the second pull-down resistor, and the second end of the second current-limiting resistor is connected to the base of the second triode.

5. The charge protection circuit of claim 4, wherein, The charging protection circuit further comprises an overvoltage protection circuit unit, which is used to turn off the second triode when the voltage input by the power input end exceeds a preset voltage.

6. The charge protection circuit of any one of claims 1-5, wherein, The overvoltage protection circuit unit comprises a third triode, a third pull-up resistor, a controllable voltage source and a reference voltage subunit, the third pull-up resistor is connected in series with the controllable voltage source, the base of the third triode is connected to the series connection node of the third pull-up resistor and the controllable voltage source, the emitter of the third triode is connected to the emitter of the second triode, the other end of the third pull-up resistor, the positive pole of the power input end and the positive pole of the power output end, the collector of the third triode is connected to the base of the second triode, the anode of the controllable voltage source is connected to the negative pole of the power output end, the reference end is connected to the reference voltage subunit, and the reference voltage subunit is connected between the positive pole of the power output end and the ground end.

7. The charge protection circuit of claim 6, wherein, ​ 8. The charge protection circuit of claim 7, wherein, The reference voltage subunit comprises a fourth pull-up resistor and a fourth pull-down resistor connected in series, a series node of the fourth pull-up resistor and the fourth pull-down resistor being connected to a reference end of the controllable voltage regulator, the other end of the fourth pull-up resistor being connected to an emitter of the third transistor, a positive pole of the power input end and a positive pole of the power output end, and the other end of the fourth pull-down resistor being connected to a negative pole of the power output end.

9. The charge protection circuit of claim 8, wherein, The fourth pull-down resistor is a rheostat.

10. A charging device, characterized by A charging protection circuit comprising the charging protection circuit according to any one of claims 1-9.

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