Overcurrent protection circuit and charging equipment

Abstract

The utility model discloses an overcurrent protection circuit and charging equipment, and relates to the field of protection circuits. The overcurrent protection circuit collects a first differential signal and a second differential signal at the two ends of the overcurrent protection circuit through a sampling resistor; and the differential circuit is used for receiving the differential signals and transmitting the corresponding differential signals to the comparator circuit, so that the comparator circuit obtains a reverse over-current signal and a forward over-current signal, and the reverse over-current signal and the forward over-current signal are input to the driving circuit to determine a driving signal, so that the working state of the load is controlled according to the driving signal. Therefore, the differential signal acquired by the sampling resistor is transmitted to the comparator circuit, so that the forward current and the reverse current can be subjected to overcurrent protection at the same time, and the safety of the circuit is improved.

Description

Technical Field

[0001] The utility model relates to the field of protection circuits, in particular to an overcurrent protection circuit and a charging device. Background Art

[0002] With the rapid development of chargers, existing on-board chargers used in new energy vehicles generally implement overcurrent protection for on-board chargers by setting fuses or relay accessories. When the charging current exceeds the current value in the current loop, the fuse is disconnected or the contacts in the control relay accessories are actuated. However, on-board chargers can simultaneously realize both charging and discharging functions, and the currents flowing in their current loops correspond to forward current and reverse current, respectively. At this time, only the set fuses or relay accessories can only realize overcurrent protection for one of the forward current or reverse current, and cannot simultaneously realize overcurrent protection for both the forward current and the reverse current.

[0003] In view of the above-mentioned prior art, finding out how to simultaneously perform overcurrent protection on both forward current and reverse current is an urgent problem to be solved by those skilled in the art. Utility Model Content

[0004] The utility model aims to provide an overcurrent protection circuit and a charging device, which are used to solve the problem that overcurrent protection cannot be performed on both forward current and reverse current at the same time.

[0005] In order to solve the above technical problems, the utility model provides an overcurrent protection circuit, including: a sampling resistor, a comparator circuit, and a drive circuit; the comparator circuit includes a first comparator and a second comparator;

[0006] The first end of the sampling resistor is connected to a common end formed by an inverting input end of the first comparator and a non-inverting input end of the second comparator, and is used to collect the first differential signal;

[0007] The second end of the sampling resistor is connected to a common end formed by the non-inverting input end of the first comparator and the inverting input end of the second comparator, and is used to collect the second differential signal;

[0008] The output terminal of the first comparator is connected to the first input terminal of the driving circuit, and is used to determine the reverse overcurrent signal according to the first differential signal and the second differential signal;

[0009] The output terminal of the second comparator is connected to the second input terminal of the driving circuit, and is used to determine the forward overcurrent signal according to the first differential signal and the second differential signal;

[0010] The output end of the driving circuit is connected to the load and is used to determine the driving signal according to the reverse overcurrent signal and the forward overcurrent signal.

[0011] On the other hand, the driving circuit includes: an AND gate chip, a latch chip, and a driver;

[0012] The first end of the AND gate chip serves as the first input end of the driving circuit, the second end of the AND gate chip serves as the second input end of the driving circuit, the output end of the AND gate chip serves as the output end of the driving circuit and is connected to the input end of the latch chip, the output end of the latch chip is connected to the input end of the driver, and the output end of the driver is connected to the load.

[0013] On the other hand, it also includes: a synchronous rectification circuit;

[0014] The synchronous rectification circuit includes: a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube;

[0015] The gate of the first switch tube, the gate of the second switch tube, the gate of the third switch tube, and the gate of the fourth switch tube are used to receive control signals for controlling the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube;

[0016] The drain of the first switch tube is connected to the drain of the third switch tube, the source of the first switch tube is connected to the drain of the second switch tube, the source of the third switch tube is connected to the drain of the fourth switch tube, the source of the second switch tube is connected to the source of the fourth switch tube, and the common end formed by the source of the second switch tube and the source of the fourth switch tube is connected to the first end of the sampling resistor.

[0017] On the other hand, it also includes: a resonant circuit;

[0018] The resonant circuit includes: inductance and capacitance;

[0019] The first end of the inductor serves as the first input end of the resonant circuit, and the first end of the capacitor serves as the second input end of the resonant circuit; the second end of the inductor serves as the first output end of the resonant circuit, and is connected to the common end formed by the source of the first switching tube and the drain of the second switching tube; the second end of the capacitor serves as the second output end of the resonant circuit, and is connected to the common end formed by the source of the third switching tube and the drain of the fourth switching tube.

[0020] On the other hand, it also includes: transformer;

[0021] The primary side of the transformer is connected to the voltage conversion circuit, the first end of the secondary side of the transformer is connected to the first input end of the resonant circuit, and the second end of the secondary side of the transformer is connected to the second input end of the resonant circuit.

[0022] On the other hand, it also includes: filters;

[0023] The first input end of the filter is connected to the common end formed by the drain of the first switching tube and the drain of the third switching tube; the second input end of the filter is connected to the common end formed by the source of the second switching tube and the source of the fourth switching tube, so as to obtain a filtered signal at the output end of the above-mentioned filter after filtering the synchronous rectification signal output by the synchronous rectification circuit.

[0024] On the other hand, it also includes: a battery; the input end of the battery is connected to the output end of the filter, the maximum voltage value of the battery is 500V, and the minimum voltage value of the battery is 0V.

[0025] On the other hand, it also includes: a prompting device; the prompting device is connected to the output end of the driving circuit.

[0026] In order to solve the above technical problems, the utility model also provides a charging device including all the overcurrent protection circuits mentioned above.

[0027] On the other hand, it also includes: a charger; the charger is connected to the overcurrent protection circuit.

[0028] The utility model provides an overcurrent protection circuit, which collects the first differential signal and the second differential signal at both ends of the sampling resistor; and transmits the corresponding differential signal to the comparator circuit, so that the comparator circuit obtains the reverse overcurrent signal and the forward overcurrent signal, and inputs the reverse overcurrent signal and the forward overcurrent signal to the drive circuit to determine the drive signal, so as to control the working state of the load according to the drive signal. It can be seen that the differential signal collected by the sampling resistor is transmitted to the comparator circuit to simultaneously perform overcurrent protection on the forward current and the reverse current, thereby improving the safety of the circuit.

[0029] The utility model also provides a charging device with the same effect as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present utility model, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A circuit diagram of an overcurrent protection circuit provided by the utility model;

[0032] Figure 2 The present invention is a schematic structural diagram of a charging device provided by the utility model.

[0033] Among them, 1 is an overcurrent protection circuit, 2 is a comparator circuit, 3 is a drive circuit, 4 is a synchronous rectification circuit, 5 is a resonant circuit, 6 is an AND gate chip, 7 is a latch chip, 8 is a driver, 9 is a filter, 10 is a battery, 11 is a voltage conversion circuit, and 12 is a charger. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0035] The core of the utility model is to provide an overcurrent protection circuit and a charging device, which are used to simultaneously perform overcurrent protection on forward current and reverse current to improve the safety of the circuit.

[0036] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0037] Figure 1 A circuit diagram of an overcurrent protection circuit provided by the utility model is shown as follows: Figure 1 As shown, the overcurrent protection circuit 1 includes: a sampling resistor Rt, a comparator circuit 2, and a drive circuit 3; wherein the comparator circuit 2 includes a first comparator U1 and a second comparator U2;

[0038] The first end of the sampling resistor is connected to a common end formed by an inverting input end of the first comparator and a non-inverting input end of the second comparator, and is used to collect the first differential signal;

[0039] The second end of the sampling resistor is connected to a common end formed by the non-inverting input end of the first comparator and the inverting input end of the second comparator, and is used to collect the second differential signal;

[0040] The output terminal of the first comparator is connected to the first input terminal of the driving circuit, and is used to determine the reverse overcurrent signal according to the first differential signal and the second differential signal;

[0041] The output terminal of the second comparator is connected to the second input terminal of the driving circuit, and is used to determine the forward overcurrent signal according to the first differential signal and the second differential signal;

[0042] The output end of the driving circuit is connected to the load and is used to determine the driving signal according to the reverse overcurrent signal and the forward overcurrent signal.

[0043] It should be noted that in this embodiment, the drive signal can be used to control the working state of the load, wherein the working state of the load is divided into a working state and a stopped state. It can be understood that when a reverse overcurrent signal or / and a forward overcurrent signal appears, it indicates that the current in the current circuit is in an overcurrent situation. At this time, the load needs to be changed from the working state to the stopped state; when no reverse overcurrent signal or / and a forward overcurrent signal appears, it indicates that the current in the current circuit is in a normal working condition. At this time, if the load is in a stopped state, the load needs to be changed to a working state, and if the load is in a working state, the working state continues to be maintained.

[0044] In this embodiment, the first differential signal and the second differential signal are collected at both ends of the sampling resistor; and the corresponding differential signal is transmitted to the comparator circuit, so that the comparator circuit obtains the reverse overcurrent signal and the forward overcurrent signal, and the reverse overcurrent signal and the forward overcurrent signal are input to the drive circuit to determine the drive signal, so as to control the working state of the load according to the drive signal. It can be seen that the differential signal collected by the sampling resistor is transmitted to the comparator circuit, which can simultaneously protect the forward current and the reverse current from overcurrent, thereby improving the safety of the circuit.

[0045] In addition, two comparators are provided in the comparator circuit, and it can be divided into two comparator paths, wherein the comparator path corresponding to the first comparator can set the overcurrent limit value of the forward current corresponding to the forward current, and a forward overcurrent signal is obtained at the output end of the first comparator; wherein the comparator path corresponding to the second comparator can set the overcurrent limit value of the reverse current corresponding to the reverse current, and a reverse overcurrent signal is obtained at the output end of the second comparator; at this time, overcurrent protection can be performed on the forward current and the reverse current at the same time, thereby improving the safety of the circuit.

[0046] On the basis of the above embodiments, in some embodiments, the driving circuit 3 includes: an AND gate chip 6, a latch chip 7, and a driver 8; the first end of the AND gate chip serves as the first input end of the driving circuit, the second end of the AND gate chip serves as the second input end of the driving circuit, the output end of the AND gate chip serves as the output end of the driving circuit and is connected to the input end of the latch chip, the output end of the latch chip is connected to the input end of the driver, and the output end of the driver is connected to the load.

[0047] In this embodiment, the AND gate chip can perform AND logic operations on the forward overcurrent signal and the reverse overcurrent signal, so as to transmit the signal after the AND logic operation to the latch chip, wherein it should be noted that when the forward overcurrent signal and / or the reverse overcurrent signal appear, it indicates that the current in the current needs to be protected from overcurrent. At this time, the latch circuit will generate a long-term level signal according to the forward overcurrent signal and / or the reverse overcurrent signal. It is known that the latch circuit can convert the microsecond signal into a long-term millisecond signal, so as to act on the driver according to the millisecond signal. At this time, the driver performs a level flip after receiving the long-term millisecond signal, so that the driver stops working.

[0048] In addition, based on the above embodiment, it further includes: a synchronous rectification circuit 4;

[0049] The synchronous rectification circuit includes: a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, and a fourth switch tube Q4; the gates of the first switch tube, the gates of the second switch tube, the gates of the third switch tube, and the gates of the fourth switch tube are used to receive control signals for controlling the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube; the drain of the first switch tube is connected to the drain of the third switch tube, the source of the first switch tube is connected to the drain of the second switch tube, the source of the third switch tube is connected to the drain of the fourth switch tube, the source of the second switch tube is connected to the source of the fourth switch tube, and the common end formed by the source of the second switch tube and the source of the fourth switch tube is connected to the first end of the sampling resistor.

[0050] It should be noted that the control signal received by the gate of the first switch tube, the gate of the second switch tube, the gate of the third switch tube, and the gate of the fourth switch tube can be a pulse signal or a square wave signal, as long as it can be used to control the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube to be in a working state. In addition, the first end of the sampling resistor is arranged on the synchronous rectification side of the synchronous rectification circuit.

[0051] Synchronous rectification refers to the process of achieving rectification by fully synchronizing the voltage and frequency on the transmission side with the power supply side through charging equipment. Synchronous rectification can be divided into two types: direct synchronous rectification and indirect synchronous rectification. Direct synchronous rectification means that the power supply side and the transmission side are directly connected, and the electric energy on the power supply side is transferred to the transmission side through equipment such as transformers. Indirect synchronous rectification ensures that the voltage and frequency on the transmission side are synchronized with the power supply side through the operating status of the power grid.

[0052] Synchronous rectification has the following advantages:

[0053] First, high stability: Synchronous rectification can ensure that the voltage and frequency on the transmission side are completely synchronized with the power supply side through the charging equipment to achieve higher stability;

[0054] Second, high efficiency: Synchronous rectification has high efficiency and low transmission loss of electric energy;

[0055] Third, strong controllability: synchronous rectification can accurately control the voltage, frequency and other parameters at the transmission end through charging equipment.

[0056] On the basis of the above embodiment, the present embodiment is further provided with a resonant circuit 5; the resonant circuit includes: an inductor L, a capacitor C; the first end of the inductor is used as the first input end of the resonant circuit, and the first end of the capacitor is used as the second input end of the resonant circuit; the second end of the inductor is used as the first output end of the resonant circuit, and is connected to the common end formed by the source of the first switch tube and the drain of the second switch tube; the second end of the capacitor is used as the second output end of the resonant circuit, and is connected to the common end formed by the source of the third switch tube and the drain of the fourth switch tube. Among them, the primary side of the transformer T provided in addition is connected to the voltage conversion circuit 11, the first end of the secondary side of the transformer is connected to the first input end of the resonant circuit, and the second end of the secondary side of the transformer is connected to the second input end of the resonant circuit. It should be additionally explained that the first end of the primary side of the transformer is connected to the first end of the voltage conversion circuit, and the second end of the primary side of the transformer is connected to the second end of the voltage conversion circuit. At this time, the voltage conversion circuit is used to convert a high voltage DC voltage into a low voltage DC voltage. It should also be noted that the front stage of the voltage conversion circuit is also provided with other circuits, and such circuits can be collectively referred to as the front stage circuit of the charger.

[0057] In addition, the circuit also includes: a filter and a power supply; the first input end of the filter is connected to the common end formed by the drain of the first switch tube and the drain of the third switch tube; the second input end of the filter is connected to the common end formed by the source of the second switch tube and the source of the fourth switch tube, so that the output end of the above filter can obtain a filtered signal after filtering the synchronous rectification signal output by the synchronous rectification circuit. The input end of the battery is connected to the output end of the filter, the maximum voltage value of the battery is 500V, and the minimum voltage value of the battery is 0V.

[0058] It can be known in this embodiment that the additionally arranged battery can determine that the battery can also perform reverse power supply. At this time, the current flowing through the sampling resistor can be divided into forward current and reverse current. Correspondingly, the forward current is transmitted from the first end of the sampling resistor to the second end of the sampling resistor, and the reverse current is transmitted from the second end of the sampling resistor to the first end of the sampling resistor. The reverse current is the current generated on the sampling resistor by the reverse power supply of the power supply.

[0059] Finally, the circuit also includes a prompt device connected to the output end of the driving circuit. The prompt device in this embodiment can output prompt information when the circuit has an overcurrent condition, so as to prompt the staff to repair the circuit. In some embodiments, the prompt device can be set as a buzzer, a prompt light, etc. In this embodiment, the implementation method of the prompt device is not limited, and can be set accordingly according to the specific implementation scenario.

[0060] The above describes in detail the embodiments of the overcurrent protection circuit. The present invention also provides a corresponding embodiment of a charging device.

[0061] The charging device of the utility model includes all the overcurrent protection circuits mentioned above. Figure 2 A schematic diagram of the structure of a charging device provided by the utility model, such as Figure 2 As shown, the charging device also includes a charger connected to the overcurrent protection circuit. The charger is an on-board charger for electric vehicles, and the on-board charger can realize the electric vehicle grid access function (Vehicle to Grid, V2G), vehicle to vehicle charging function (Vehicle to Vehicle, V2V), and vehicle to load function (Vehicle to Load, V2L).

[0062] An on-board charger refers to a charger that is fixedly installed on an electric vehicle. It has the ability to safely and automatically charge the electric vehicle's power battery. The charger can dynamically adjust the charging current or voltage parameters based on the data provided by the battery management system, perform corresponding actions, and complete the charging process.

[0063] The on-board charger can be charged in the following ways:

[0064] Different charging methods for the battery of the on-board charger will have different degrees of impact on the battery life. Using an appropriate charging method can extend the battery life.

[0065] Common charging methods for on-board chargers include constant voltage charging, DC charging, staged charging, pulse charging, etc.

[0066] First, constant voltage charging: the charging voltage remains unchanged during the entire charging process, and the charging current gradually decreases as the charging time increases. Charging stops when the charging current is less than a certain value. The energy consumption during the entire charging process is low, which can effectively prevent battery overcharging. The control is simple and easy to operate. However, the initial voltage value of the battery to be charged is often small, resulting in a large charging current at the beginning of charging. On the one hand, excessive current will cause battery polarization and affect the charging speed; on the other hand, it will cause the battery temperature to rise rapidly, which can easily burn the battery and cause an accident in severe cases. Therefore, at the beginning of charging, the charging current value needs to be limited to keep the battery charged within an acceptable current range.

[0067] Second, DC charging: At the beginning, the power battery is charged with a constant current. When it is about to be fully charged, a constant small current is used for floating charge to replenish the remaining power and compensate for the battery self-discharge. When the charging voltage reaches the rated voltage, the charging is stopped. Constant current charging avoids the problem of excessive constant voltage charging current, and the current is always limited to the acceptable range of the battery pack.

[0068] Third, staged charging: It can be divided into two-stage charging or three-stage charging according to the actual application. The first stage is constant current charging, which uses a large current to quickly charge the battery so that the battery voltage reaches a certain voltage value (set according to the voltage of the power battery pack); the second stage is constant voltage charging, which continues to charge the battery with a current smaller than the constant current; the third stage is floating charging, which charges the battery with a trickle current to ensure that the battery can be fully charged. When the charging device detects that the charging current is less than a certain set value, the charging is terminated. Staged charging combines the advantages of constant voltage and constant current charging methods, which is beneficial to reduce battery polarization and avoid overcharging and high current charging shock.

[0069] The charging voltage and current of constant voltage charging, constant current charging and staged charging are continuous, and the battery is not given enough rest time to eliminate polarization. Polarization can cause battery overheating, gassing and other phenomena, limit the charging speed, and seriously affect the battery life. Pulse charging and positive and negative pulse charging use discontinuous charging current, which can effectively reduce or eliminate the occurrence of polarization, speed up the charging speed and prolong the battery life.

[0070] Fourth, pulse charging: Pulse charging is used to provide the battery with sufficient rest time, which is conducive to the full reaction of the active substances inside the battery, effectively reducing and eliminating the occurrence of polarization, and can use a larger current for charging without worrying about battery overheating. It can effectively improve charging efficiency, shorten charging time, and prolong battery life.

[0071] The positive and negative pulse charging method is an improvement on the pulse charging method. The entire charging process includes positive pulse charging, intermittent rest and negative pulse discharge. First, positive pulse charging is performed, and after a period of rest, a short negative pulse discharge is performed. The short negative pulse discharge of the battery can effectively remove the occurrence of polarization, accelerate the electrochemical reaction inside the battery, and reduce the battery temperature. Although some electrical energy is lost, it can enable the battery to be charged at a higher charging current, which can effectively speed up the charging speed and improve the charging efficiency, and prolong the battery life.

[0072] In the overcurrent protection circuit of the present embodiment, by respectively setting the first comparator path and the second comparator path (it can be understood that two comparators are correspondingly set), the current limit values ​​for the forward current and the reverse current can be set at the same time. When the forward current reaches the current limit value set by the first comparator path, the level signal in the drive circuit is flipped, so that the driver stops working; when the reverse current reaches the current limit value set by the second comparator path, the level signal in the drive circuit is flipped, and the driver also stops working.

[0073] The above is a detailed introduction to an overcurrent protection circuit and charging equipment provided by the utility model. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be referenced to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the utility model.

[0074] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. An overcurrent protection circuit, characterized in that: include: A sampling resistor, a comparator circuit, and a driving circuit; the comparator circuit includes a first comparator and a second comparator; The first end of the sampling resistor is connected to a common end formed by the inverting input end of the first comparator and the non-inverting input end of the second comparator, and is used to collect the first differential signal; The second end of the sampling resistor is connected to a common end formed by the non-inverting input end of the first comparator and the inverting input end of the second comparator, and is used to collect a second differential signal; The output terminal of the first comparator is connected to the first input terminal of the driving circuit, and is used to determine a reverse overcurrent signal according to the first differential signal and the second differential signal; The output terminal of the second comparator is connected to the second input terminal of the driving circuit, and is used to determine the forward overcurrent signal according to the first differential signal and the second differential signal; The output end of the driving circuit is connected to a load and is used to determine a driving signal according to the reverse overcurrent signal and the forward overcurrent signal.

2. The overcurrent protection circuit according to claim 1, characterized in that: The driving circuit comprises: an AND gate chip, a latch chip, and a driver; The first end of the AND gate chip serves as the first input end of the driving circuit, the second end of the AND gate chip serves as the second input end of the driving circuit, the output end of the AND gate chip serves as the output end of the driving circuit and is connected to the input end of the latch chip, the output end of the latch chip is connected to the input end of the driver, and the output end of the driver is connected to the load.

3. The overcurrent protection circuit according to claim 1, characterized in that: Also includes: Synchronous rectification circuit; The synchronous rectification circuit comprises: a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube; The gate of the first switch tube, the gate of the second switch tube, the gate of the third switch tube, and the gate of the fourth switch tube are used to receive a control signal for controlling the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube; The drain of the first switch tube is connected to the drain of the third switch tube, the source of the first switch tube is connected to the drain of the second switch tube, the source of the third switch tube is connected to the drain of the fourth switch tube, the source of the second switch tube is connected to the source of the fourth switch tube, and the common end formed by the source of the second switch tube and the source of the fourth switch tube is connected to the first end of the sampling resistor.

4. The overcurrent protection circuit according to claim 3, characterized in that: Also includes: Resonant circuit; The resonant circuit comprises: an inductor and a capacitor; The first end of the inductor serves as the first input end of the resonant circuit, and the first end of the capacitor serves as the second input end of the resonant circuit; the second end of the inductor serves as the first output end of the resonant circuit, and is connected to the common end formed by the source of the first switching tube and the drain of the second switching tube; the second end of the capacitor serves as the second output end of the resonant circuit, and is connected to the common end formed by the source of the third switching tube and the drain of the fourth switching tube.

5. The overcurrent protection circuit according to claim 4, characterized in that: Also includes: transformer; The primary side of the transformer is connected to the voltage conversion circuit, the first end of the secondary side of the transformer is connected to the first input end of the resonant circuit, and the second end of the secondary side of the transformer is connected to the second input end of the resonant circuit.

6. The overcurrent protection circuit according to claim 5, characterized in that: Also includes: filter; The first input end of the filter is connected to the common end formed by the drain of the first switch tube and the drain of the third switch tube; the second input end of the filter is connected to the common end formed by the source of the second switch tube and the source of the fourth switch tube, so as to obtain a filtered signal at the output end of the above-mentioned filter after filtering the synchronous rectification signal output by the synchronous rectification circuit.

7. The overcurrent protection circuit according to claim 6, characterized in that: Also includes: Battery; The input end of the battery is connected to the output end of the filter, the maximum voltage value of the battery is 500V, and the minimum voltage value of the battery is 0V.

8. The overcurrent protection circuit according to any one of claims 1 to 7, characterized in that: Also includes: Prompt device; The prompting device is connected to the output end of the driving circuit.

9. A charging device, characterized in that: include: An overcurrent protection circuit as claimed in any one of claims 1 to 8.

10. The charging device according to claim 9, characterized in that: Also includes: Battery charger; The charger is connected to the overcurrent protection circuit.

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