CN111614237A

CN111614237A - Pre-charging circuit, power distribution device and electric automobile

Info

Publication number: CN111614237A
Application number: CN202010553371.8A
Authority: CN
Inventors: 杨龙博; 熊江; 黄照昆
Original assignee: Dongfeng Motor Co Ltd
Current assignee: Dongfeng Motor Co Ltd
Priority date: 2020-06-17
Filing date: 2020-06-17
Publication date: 2020-09-01
Anticipated expiration: 2040-06-17
Also published as: CN111614237B

Abstract

The application discloses pre-charge circuit, distribution device and electric automobile, it includes: a first transistor switch and a drive circuit, the first transistor switch having a first electrode, a second electrode, a third electrode; the drive circuit is provided with a positive electrode signal receiving end, a negative electrode signal receiving end, a first output end and a second output end, wherein the positive electrode signal receiving end and the negative electrode signal receiving end are used for receiving control signals, the first electrode is connected with the first output end, the third electrode is connected with the second output end, the second electrode and the third electrode are used for being connected with a main positive relay of a BDU main loop in parallel, and the drive circuit controls the on-off of the first transistor switch according to the control signals. The utilization of the pre-charging circuit can avoid the phenomena of burning-free arc adhesion and the like, the service life of the switch device is prolonged, the cost of the switch device in the pre-charging circuit is reduced, the structure is simple, the quality and the occupied volume of the switch device in the pre-charging circuit can be reduced, and the pre-charging circuit is convenient to install and maintain.

Description

Pre-charging circuit, power distribution device and electric automobile

Technical Field

The application relates to the technical field of automobiles, in particular to a pre-charging circuit, a power distribution device and an electric automobile.

Background

A Battery Disconnection Unit (BDU) is a high-voltage safety device for power disconnection and connection of a Battery pack of an electric vehicle, and is a key component in the Battery pack. In order to protect the load of the high-voltage loop from being influenced by impact current, the high-voltage load is pre-charged by the pre-charging circuit before the BDU main loop passes through working current, and the main loop is switched on after the current value is reduced to the normal working current of the high-voltage relay.

At present, the existing BDU includes a pre-charge relay, a main negative relay, and a main positive relay, where the main negative relay and the main positive relay are connected in series to form a main loop, and the pre-charge relay is connected in parallel to the main positive relay to form a pre-charge loop. The pre-charging relay 1 adopts a mechanical relay, generally comprises a shell, a low-voltage coil, a high-voltage contact, a high-voltage pin, a low-voltage pin and the like, and has the switching function that the low-voltage coil is electrified, and then the high-voltage contact is kept to be connected through magnetic force so as to realize high-voltage conduction; after the low-voltage coil is powered off, the high-voltage contact is disconnected through the elasticity of the reset spring, and therefore the disconnection of the high-voltage electric loop is tested. The inventor is realizing the in-process discovery of this application, the preliminary filling relay adopts mechanical relay structure complicacy, the cost is higher, high pressure contact needs sufficient magnetic force adsorption motion just can realize switching on, switch response speed is slow, and when mechanical relay area load was cut off, take place easily and draw the arc phenomenon, burn inside sound contact, especially when the electric current is great, arcing and adhesion phenomenon can take place, the day and month of arcing phenomenon still can increase high pressure contact's contact resistance, lead to mechanical relay's temperature rise performance to worsen with higher speed, and working life shortens, and the cost is improved.

Disclosure of Invention

In view of the above, the present application provides a pre-charging circuit, a power distribution device and an electric vehicle to solve the above technical problems.

The present application provides a pre-charge circuit, which includes: a first transistor switch and a drive circuit, the first transistor switch having a first electrode, a second electrode, a third electrode; the drive circuit is provided with a positive electrode signal receiving end, a negative electrode signal receiving end, a first output end and a second output end, wherein the positive electrode signal receiving end and the negative electrode signal receiving end are used for receiving control signals, the first electrode is connected with the first output end, the third electrode is connected with the second output end, the second electrode and the third electrode are used for being connected with a main positive relay of a BDU main loop in parallel, and the drive circuit controls the on-off of the first transistor switch according to the control signals.

Optionally, the drive circuit includes first resistance, second resistance, left diode, triode, third resistance and first electric capacity, the positive pole and the positive pole signal receiving terminal of left diode are connected, first electric capacity is connected between negative pole signal receiving terminal and the negative pole of left diode, the triode has base, projecting pole and collecting electrode, the projecting pole is connected with the negative pole of left diode, first resistance is connected between left diode negative pole and base, second resistance is connected between collecting electrode and first output, third resistance is connected between first output and second output, base, second output all are connected with negative pole signal receiving terminal.

Optionally, still include control circuit, it includes power supply, fourth resistance, second electric capacity, right diode and second transistor switch, second transistor switch has fourth pole, fifth pole and sixth pole, and the sixth pole is used for receiving control signal, power supply's positive pole is connected with anodal signal receiving terminal and fourth pole respectively, and the fifth pole is connected with the negative pole and the negative pole signal receiving terminal of right diode respectively, and the positive pole of right diode is connected with power supply's negative pole, second electric capacity, fourth resistance all connect in parallel with right diode, power supply's negative pole, fourth resistance, second electric capacity, right diode all are connected with automobile body earthing terminal.

Optionally, the over-temperature protection circuit comprises a first driving power supply, a second driving power supply, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a thermistor, a comparator and a first processor, the comparator is provided with a first input end, a second input end and a third output end, the thermistor is connected with the first driving power supply, the fifth resistor is connected between the thermistor and the ground end of the vehicle body, the sixth resistor is connected between the thermistor and the first input end, the seventh resistor is connected with the second driving power supply, the eighth resistor is connected between the seventh resistor and the ground end of the vehicle body, the seventh resistor is connected with the second input end, the third output end and the positive pole of the power supply both input signals to the first processor, the first processor obtains a processing signal according to the input signal and sends the processing signal to the positive electrode signal receiving end.

Optionally, the first transistor switch and the second transistor switch are both MOS transistors or IGBTs.

Optionally, the BDU further comprises a second processor and a current detector for monitoring current or energization time, the current detector is connected in series between the third electrode and the BDU main loop, the current detector sends the monitored current or energization time to the second processor, the positive pole of the power supply sends a control signal to the second processor, and the second processor obtains a processing signal according to the current or energization time and the control signal and sends the processing signal to the positive pole signal receiving end.

Optionally, the BDU further comprises a pre-charging resistor for limiting current, and the pre-charging resistor is connected between the third electrode and the BDU main loop in series.

The application also provides a power distribution device, which comprises a main positive relay and the pre-charging circuit, wherein the first transistor switch of the pre-charging circuit is connected with the main positive relay in parallel through a second electrode and a third electrode.

Optionally, the system further comprises a main negative relay, a direct current positive bus, a direct current negative bus, an external direct current charging port, and at least one output port; the external charging port is coupled to the direct current positive bus and the direct current negative bus through the main positive relay and the main negative relay; the at least one output port is coupled with the direct current positive bus and the direct current negative bus; the second electrode is connected between the main positive relay and the external charging port, and the third electrode is connected between the main negative relay and the at least one output port.

The application also provides an electric automobile which comprises the power distribution device.

The utility model provides a precharge circuit, distribution device and electric automobile are through setting up drive circuit and first transistor switch, break-make through the first transistor switch of drive circuit control, first transistor switch is the voltage drive type device, give a suitable voltage between grid and source electrode, just can form the route between source electrode and drain electrode, compare with mechanical relay, whole break-make process does not have mechanical action, on-load cutting-off ability and switch response speed are fast, can avoid phenomenons such as burning-free arc adhesion, promote switching element's life, reduce the cost of switching element in the precharge circuit, and simple structure, can reduce the quality and the shared volume of switching element in the precharge circuit, easy to assemble and maintenance.

Drawings

Fig. 1 is a circuit diagram of a precharge circuit according to the present application.

Fig. 2 is a circuit connection diagram of the control circuit of the present application.

Fig. 3 is a circuit connection diagram of the overheat protection circuit of the present application and the first transistor switch.

Fig. 4 is a circuit connection diagram of the current detector and the first transistor switch of the present application.

Detailed Description

The technical solutions of the present application are described in detail below with reference to the accompanying drawings and specific embodiments. In which like parts are designated by like reference numerals. It should be noted that the terms "front," "back," "left," "right," "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component.

Fig. 1 shows a circuit connection diagram of a precharge circuit of the present application, and as shown in fig. 1, the present application provides a precharge circuit including: a first transistor switch 10 and a drive circuit.

The first transistor switch 10 has a first electrode, a second electrode, and a third electrode; the driving circuit has a positive signal receiving terminal 11, a negative signal receiving terminal 12, a first output terminal 13 and a second output terminal 14.

The positive electrode signal receiving end 11 and the negative electrode signal receiving end 12 are used for receiving control signals, the first electrode is connected with the first output end 13, and the third electrode is connected with the second output end 14.

The first transistor switch 10 is connected with the main positive relay 3 of the BDU main loop in parallel through a second electrode and a third electrode, and the driving circuit controls the on-off of the first transistor switch 10 according to a control signal.

In one embodiment, the first Transistor switch 10 may be a MOS Transistor (Metal-Oxide-Semiconductor Field Effect Transistor, MOSFET) or an IGBT (Insulated Gate Bipolar Transistor).

Preferably, the MOS tube is an N-MOSFET tube, and the first electrode, the second electrode and the third electrode are a grid (G pole), a drain (D pole) and a source (S pole) in sequence; the IGBT is of an N-IGBT type, and the first electrode, the second electrode and the third electrode are a gate electrode, a collector electrode and an emitter electrode of the IGBT in sequence.

Now, taking an N-MOSFET tube as an example to explain the working principle of the precharge circuit of the present application, the details are as follows:

in a steady state, when the main negative relay 2 is closed and the G pole is not conducted, a leakage current (about 100uA) exists between the D pole and the S pole, the potential of the S pole is 0V, and the pre-charging circuit is in an off state at this time.

When the G pole is connected with the DC voltage (about 12V), the D pole is connected with the S pole, and the pre-charging circuit is in a conducting state.

In a dynamic state, at the moment when the G pole is electrified, the resistance between the D pole and the S pole is stable, the charging current in the pre-charging loop gradually decreases along with the increase of the charging percentage of the load capacitor 6 of the whole vehicle, and the voltage between the D pole and the S pole gradually decreases. The N-MOSFET tube works in the variable resistance interval, and the pre-charging route is switched from off to on.

The current of the pre-charging circuit is gradually reduced along with the charging of the load capacitor 6 of the whole vehicle, the main positive relay 3 is closed to short-circuit the pre-charging circuit, and meanwhile, the G-pole voltage of the pre-charging circuit is disconnected, so that high impedance is presented between a D pole and an S pole, and the current of the pre-charging circuit is blocked.

Meanwhile, if the pre-charging circuit is electrified for a long time (when the pre-charging circuit is short-circuited), the G pole voltage of the N-MOSFET is cut off, so that high impedance is presented between the D pole and the S pole of the N-MOSFET, the high-voltage circuit current can still be cut off, and the pre-charging circuit is switched from on to off.

When the pre-charging circuit works, as shown in fig. 1, after receiving a power-on operation signal of a user, a vehicle control unit (VCM)5 sends a control signal to a positive electrode signal receiving terminal 11 and a negative electrode signal receiving terminal 12, closes a first transistor switch 10, sends a control signal to a main negative relay 2, and closes the main negative relay 2.

When the charging of the load capacitor 6 of the whole vehicle reaches a preset proportion (for example, 98%), the main positive relay 3 is closed to short-circuit the pre-charging circuit, the high-voltage circuit is conducted, the first transistor switch 10 is disconnected to disconnect the pre-charging circuit, and then the charging of the load capacitor 6 of the whole vehicle can be completed.

When the voltage difference between the positive electrode and the negative electrode of the finished automobile load capacitor 6 reaches a certain value, the finished automobile controller 5 controls the main negative relay 2 and the main positive relay 3 to be switched off in sequence, and the first transistor switch 10 does not participate in the work in the power-off process.

The utility model provides a pre-charging circuit is through setting up drive circuit and first transistor switch, break-make through the first transistor switch of drive circuit control, first transistor switch is the voltage drive type device, as long as give an appropriate voltage between grid and source electrode, just can form the route between source electrode and drain electrode, compare with mechanical type relay, whole break-make process does not have mechanical action, the on-load cutting-off ability and switch response speed are fast, can avoid phenomenons such as burning arc adhesion, promote the working life of switching device, reduce the cost of switching device in the pre-charging circuit, and simple structure, can reduce the quality and the shared volume of switching device in the pre-charging circuit, easy to assemble and maintenance.

This application adopts first transistor switch 10, compares with mechanical type relay, and the volume of pre-charge circuit can reduce 80%, and the quality reduces 80%, and the cost reduces 10 yuan per car. The service life of the mechanical relay with load is 7.5 ten thousand times, the service life of the first transistor switch 10 with load is more than 10 ten thousand times, and the service life with load is greatly prolonged.

Further, the driving circuit may employ a filter isolation circuit. In the embodiment of fig. 1, the driving circuit includes a first resistor R1, a second resistor R2, a left diode D1, a triode, a third resistor R3, and a first capacitor C1.

The anode of the left diode D1 is connected to the anode signal receiving terminal 11, and the first capacitor C1 is connected between the cathode signal receiving terminal 12 and the cathode of the left diode D1.

The triode is provided with a base electrode, an emitting electrode and a collector electrode, the emitting electrode is connected with the negative electrode of the left diode D1, the first resistor R1 is connected between the negative electrode and the base electrode of the left diode D1, the second resistor R2 is connected between the collector electrode and the first output end 13, the third resistor R3 is connected between the first output end 13 and the second output end 14, and the base electrode and the second output end 14 are both connected with the negative electrode signal receiving end 12.

The driving circuit is provided with the first resistor R1, the second resistor R2, the left diode D1, the triode, the third resistor R3 and the first capacitor C1, so that the structure of the driving circuit can be simplified, and the cost is reduced to a greater extent.

Preferably, as shown in fig. 2, the pre-charging circuit further includes a control circuit including a power supply U1, a fourth resistor R4, a second capacitor C2, a right diode D2, and a second transistor switch Q.

The second transistor switch Q has a fourth pole, a fifth pole and a sixth pole. The sixth pole is used for receiving a control signal, such as a power-on operation signal of a user. The control signal may be applied to the sixth pole in the form of a voltage.

In a specific embodiment, the second transistor switch Q may also be of the N-MOSFET transistor or N-IGBT type.

Preferably, the MOS tube is an N-MOSFET tube, and the fourth pole, the fifth pole and the sixth pole are a drain electrode, a source electrode and a grid electrode in sequence; the IGBT is of an N-IGBT type, and the fourth pole, the fifth pole and the sixth pole are sequentially a collector, an emitter and a gate.

The anode of the power supply U1 is connected with the anode signal receiving terminal 11 and the fourth electrode, and the fifth electrode is connected with the cathode of the right diode D2 and the cathode signal receiving terminal 12.

The anode of the right diode D2 is connected with the cathode of the power supply U1, and the second capacitor C2 and the fourth resistor R4 are both connected in parallel with the right diode D2.

And the negative electrode of the power supply U1, the fourth resistor R4, the second capacitor C2 and the right diode D2 are all connected with the ground end of the vehicle body.

The control circuit is arranged so as to better control the on-off of the pre-charging circuit. In this embodiment, the control circuit may be built in the vehicle control unit 5.

Further, as shown in fig. 3, the pre-charge circuit further includes an over-temperature protection circuit, which includes a first driving power source U2, a second driving power source U3, a fifth resistor R6, a sixth resistor R7, a seventh resistor R8, an eighth resistor R9, a thermistor R5, a comparator 8, and the first processor 6.

The comparator 8 has a first input terminal, a second input terminal and a third output terminal, and the voltage value is input to the first input terminal and the second input terminal. The comparator 8 calculates a voltage difference value according to the voltage value input by the first and second input terminals, and outputs a signal according to the voltage difference value.

For example, the off signal is output when the voltage difference is greater than a predetermined difference, and the on signal is output when the voltage difference is less than the predetermined difference.

The thermistor R5 is connected to the first drive power source U2, the fifth resistor R6 is connected between the thermistor R5 and the vehicle body ground, and the sixth resistor R7 is connected between the thermistor R5 and the first input terminal.

The seventh resistor R8 is connected with the second driving power supply U3, the eighth resistor R9 is connected between the seventh resistor R8 and the ground end of the vehicle body, and the seventh resistor R8 is connected with the second input end.

The third output end and the positive electrode of the power supply U1 both input signals to the first processor 6, and the first processor 6 obtains a processed signal according to the input signal and sends the processed signal to the positive electrode signal receiving end 11.

When the signal sent by the over-temperature protection circuit is a connection signal and the signal sent by the control circuit is also a connection signal, the first processor 6 sends the connection signal to the positive electrode signal receiving end 11, otherwise, the first processor 6 sends a disconnection signal to the positive electrode signal receiving end 11.

Through the over-temperature protection circuit, the pre-charging circuit can be disconnected when the temperature exceeds a first preset temperature (for example, 80 ℃), and the pre-charging circuit can be automatically closed when the temperature is lower than a second preset temperature (for example, 70 ℃), so that the pre-charging circuit can be prevented from being damaged due to impact and overheating of an electrical load, and the pre-charging circuit can be timely disconnected to guarantee safety under the condition that the pre-charging circuit is short-circuited.

In the embodiment of fig. 3, the comparator 8 is connected in series between the third drive power supply U4 and the vehicle body ground. The power supply U1, the first driving power U2, the second driving power U3 and the third driving power U4 can all adopt 12V direct current power supplies.

Preferably, as shown in fig. 1, the pre-charge circuit further includes a pre-charge resistor R0 for limiting current, and the pre-charge resistor R0 is connected in series between the third electrode and the BDU main circuit. That is, the precharge resistor R0 is connected in series with the first transistor switch 10 and then connected in parallel with the main positive relay 3.

By arranging the pre-charging resistor R0, the current during pre-charging can be limited, and the load capacitor 6 of the whole vehicle is prevented from being damaged due to current impact.

Preferably, as shown in fig. 4, the pre-charging circuit further includes a second processor 16 and a current detector 15 for monitoring current or power-on time, wherein the current detector 15 is connected in series between the third electrode and the BDU main circuit, i.e. the current detector 15 is connected in parallel with the main positive relay 3 after being connected in parallel with the first transistor switch 10.

The current detector 15 sends the monitored current or the energization time to the second processor 16, and the positive pole of the power supply U1 sends a control signal to the second processor 16.

The second processor 16 obtains a processing signal according to the current and the control signal or the power-on time and the control signal, and sends the processing signal to the positive electrode signal receiving end 11.

When the current is less than the predetermined current and the positive electrode of the power supply U1 sends the control signal to the second processor 16 as the on signal, or the power-on time is less than the predetermined time and the positive electrode of the power supply U1 sends the control signal to the second processor 16 as the on signal, the second processor 16 sends the on instruction to the positive electrode signal receiving end 11 of the driving circuit, and the first transistor switch 10 is controlled to be closed. In other cases, the instructions issued by the second processor 16 are all disconnect instructions.

By arranging the current detector 15, the pre-charging circuit is subjected to overcurrent protection, so that the first transistor switch 10 is prevented from being damaged due to overlarge current, short circuit can be prevented, and the normal work of the pre-charging circuit is protected.

The present application further provides a power distribution apparatus, which includes a main positive relay 3 and the pre-charging circuit as described above, wherein the first transistor switch 10 of the pre-charging circuit is connected in parallel with the main positive relay 3 through the second electrode and the third electrode.

The utility model provides a distribution device is through setting up drive circuit and first transistor switch, break-make through the first transistor switch of drive circuit control, first transistor switch is the voltage drive type device, as long as give an appropriate voltage between grid and source electrode, just can form the route between source electrode and drain electrode, compare with mechanical type relay, whole break-make process does not have mechanical action, the on-load cutting-off ability and switch response speed are fast, can avoid phenomenons such as burning arc adhesion, promote the working life of switching device, reduce the cost of switching device in the pre-charging circuit, and simple structure, can reduce the quality and the shared volume of switching device in the pre-charging circuit, easy to assemble and maintenance.

Further, the power distribution device further comprises a main negative relay 2, a direct current positive bus 1, a direct current negative bus 4, an external direct current charging port and at least one output port.

The external charging port is coupled to the direct current positive bus 1 and the direct current negative bus 4 through the main positive relay 3 and the main negative relay 2. The main positive relay 3 and the main negative relay 2 are connected in series.

The at least one output port is coupled with the direct current positive bus 1 and the direct current negative bus 4; the second electrode is connected between the main positive relay 3 and the external charging port, and the third electrode is connected between the main positive relay 3 and the at least one output port.

As shown in fig. 1, a PDU (Power Distribution Unit) may be connected to the output port, so as to distribute Power to the in-vehicle device.

Further, the power distribution device further comprises a current detection unit 9, wherein the current detection unit 9 is connected with the main positive relay 3 or the main negative relay 2 in series to acquire current data in the circuit. In the present embodiment, the current detection unit 9 and the current detector 15 may be current sensors.

The application also provides an electric automobile which comprises the power distribution device. The electric automobile also comprises a battery pack, a vehicle controller 5 and a vehicle load capacitor 6.

The battery pack is connected to an external DC charging port of the power distribution device to supply power to vehicle-mounted devices (e.g., PTC (positive temperature Coefficient thermal) air conditioner heating, a/C electric air conditioner compressor, DC/DC converter, OBC vehicle-mounted charger, etc., INV motor).

The whole vehicle load capacitor 6 is connected between the direct current positive bus and the direct current negative bus and is connected with the main positive relay 3 and the main negative relay 2 in series. The main positive relay 3 and the main negative relay 2 are respectively driven and controlled by the vehicle control unit 5.

A positive signal receiving end 11 and a negative signal receiving end 12 of the driving circuit are respectively connected with the vehicle control unit and receive an output signal of the vehicle control unit 5.

The vehicle control unit 5 controls signals output to the positive signal receiving end 11, the negative signal receiving end 12, the main positive relay 3 and the main negative relay 2 to control on and off of the first transistor switch 10, the main positive relay 3 and the main negative relay 2, and further controls charging and discharging of the vehicle load capacitor 6.

The utility model provides an electric automobile is through setting up drive circuit and first transistor switch, break-make through the first transistor switch of drive circuit control, first transistor switch is the voltage drive type device, as long as give an appropriate voltage between grid and source electrode, just can form the route between source electrode and drain electrode, compare with mechanical type relay, whole break-make process does not have mechanical action, the on-load cutting-off ability and switch response speed are fast, can avoid phenomenons such as burning arc adhesion, promote the working life of switching device, reduce the cost of switching device in the pre-charging circuit, and simple structure, can reduce the quality and the shared volume of switching device in the pre-charging circuit, easy to assemble and maintenance.

The technical solutions of the present application are described in detail with reference to specific embodiments, which are used to help understand the ideas of the present application. The derivation and modification made by the person skilled in the art on the basis of the specific embodiment of the present application also belong to the protection scope of the present application.

Claims

1. A pre-charge circuit, comprising: a first transistor switch and a drive circuit, the first transistor switch having a first electrode, a second electrode, a third electrode; the drive circuit is provided with a positive electrode signal receiving end, a negative electrode signal receiving end, a first output end and a second output end, wherein the positive electrode signal receiving end and the negative electrode signal receiving end are used for receiving control signals, the first electrode is connected with the first output end, the third electrode is connected with the second output end, the second electrode and the third electrode are used for being connected with a main positive relay of a BDU main loop in parallel, and the drive circuit controls the on-off of the first transistor switch according to the control signals.

2. A pre-charge circuit as claimed in claim 1, wherein the driving circuit includes a first resistor, a second resistor, a left diode, a triode, a third resistor and a first capacitor, the anode of the left diode is connected to the anode signal receiving terminal, the first capacitor is connected between the cathode signal receiving terminal and the cathode of the left diode, the triode has a base, an emitter and a collector, the emitter is connected to the cathode of the left diode, the first resistor is connected between the cathode and the base of the left diode, the second resistor is connected between the collector and the first output terminal, the third resistor is connected between the first output terminal and the second output terminal, and the base and the second output terminal are both connected to the cathode signal receiving terminal.

3. A pre-charge circuit according to claim 2, further comprising a control circuit including a power supply, a fourth resistor, a second capacitor, a right diode, and a second transistor switch, wherein the second transistor switch has a fourth pole, a fifth pole, and a sixth pole, the sixth pole is used for receiving a control signal, the positive pole of the power supply is connected to the positive signal receiving terminal and the fourth pole, the fifth pole is connected to the negative signal receiving terminal and the negative signal receiving terminal of the right diode, the positive pole of the right diode is connected to the negative pole of the power supply, the second capacitor and the fourth resistor are connected in parallel to the right diode, and the negative pole of the power supply, the fourth resistor, the second capacitor and the right diode are connected to the ground terminal of the vehicle body.

4. The pre-charge circuit according to claim 3, further comprising an over-temperature protection circuit including a first driving power supply, a second driving power supply, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a thermistor, a comparator and a first processor, wherein the comparator has a first input terminal, a second input terminal and a third output terminal, the thermistor is connected to the first driving power supply, the fifth resistor is connected between the thermistor and the vehicle body ground terminal, the sixth resistor is connected between the thermistor and the first input terminal, the seventh resistor is connected to the second driving power supply, the eighth resistor is connected between the seventh resistor and the vehicle body ground terminal, the seventh resistor is connected to the second input terminal, the third output terminal and the positive terminal of the power supply both input signals to the first processor, the first processor obtains a processed signal according to the input signal, and transmitting the processed signal to the positive signal receiving end.

5. The pre-charge circuit of claim 4, wherein the first transistor switch and the second transistor switch are both MOS transistors or IGBT.

6. A pre-charge circuit as claimed in claim 3, further comprising a second processor and a current detector for monitoring current or power-on time, the current detector being connected in series between the third electrode and the BDU main circuit, the current detector transmitting the monitored current or power-on time to the second processor, the positive electrode of the power supply transmitting a control signal to the second processor, the second processor obtaining a processed signal according to the current or power-on time and the control signal and transmitting the processed signal to the positive electrode signal receiving terminal.

7. A pre-charge circuit as claimed in claim 2, further comprising a pre-charge resistor for limiting current, the pre-charge resistor being connected in series between the third electrode and the BDU primary circuit.

8. An electrical distribution apparatus comprising a main positive relay and a pre-charge circuit as claimed in any of claims 1 to 7, the first transistor switch of the pre-charge circuit being connected in parallel with the main positive relay via the second and third electrodes.

9. The electrical distribution apparatus of claim 8, further comprising a main negative relay, a direct current positive bus, a direct current negative bus, an external direct current charging port, and at least one output port; the external charging port is coupled to the direct current positive bus and the direct current negative bus through the main positive relay and the main negative relay; the at least one output port is coupled with the direct current positive bus and the direct current negative bus; the second electrode is connected between the main positive relay and the external charging port, and the third electrode is connected between the main negative relay and the at least one output port.

10. An electric vehicle, characterized in that it comprises a power distribution device according to any one of claims 8-9.