Pre-charge circuit, electric vehicle

Abstract

The utility model discloses an embodiment of a pre-charging circuit and an electric automobile. The pre-charging circuit comprises a pre-charging switch, a choke element and a freewheeling element. The pre-charging switch and the choke element are connected in series between the first end of a battery and the first end of a bus capacitor. The freewheeling element is connected in parallel with the choke element and the bus capacitor. The utility model can reduce the size, cost and heat generation of the pre-charging circuit, and prolong the service life.

Description

Technical Field

[0001] This utility model relates to the field of battery charging technology, and in particular to a pre-charging circuit and an electric vehicle. Background Technology

[0002] With the widespread application of new energy vehicles, the requirements for power batteries, which are an important power source for these vehicles, are becoming increasingly stringent. Power batteries require pre-charging via a pre-charging circuit during charging.

[0003] However, the pre-charging circuits in related technologies all use a combination of relays and pre-charging resistors, which has disadvantages such as large size, serious heat generation, high cost and short life. Utility Model Content

[0004] This utility model provides a pre-charging circuit and an electric vehicle to reduce the size, cost, and heat generation of the pre-charging circuit, and extend its service life.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This utility model embodiment provides a pre-charging circuit, which includes: a pre-charging switch, a choke element, and a freewheeling element;

[0007] The precharge switch and the choke element are connected in series between the first end of the battery and the first end of the bus capacitor.

[0008] The freewheeling element is connected in parallel with the choke element and the bus capacitor.

[0009] Optionally, the choke element includes a choke inductor;

[0010] The first end of the precharge switch is electrically connected to the first end of the battery, the second end of the precharge switch is electrically connected to the first end of the choke element, and the second end of the choke element is used to electrically connect to the first end of the bus capacitor.

[0011] Optionally, the freewheeling element includes a first diode, the anode of which is electrically connected to the second terminal of the bus capacitor, and the cathode of which is electrically connected to the first terminal of the choke element.

[0012] Optionally, the pre-charge circuit further includes a unidirectional conducting element, which is connected in series with the pre-charge switch and the choke element between the first terminal and the second terminal of the battery; wherein the second terminal of the battery is electrically connected to the second terminal of the bus capacitor.

[0013] Optionally, the first end of the unidirectional conducting element is electrically connected to the first end of the battery, and the second end of the unidirectional conducting element is electrically connected to the first end of the precharge switch.

[0014] Optionally, the unidirectional conducting element includes a second diode, the anode of which is connected to the first terminal of the battery, and the cathode of which is connected to the second terminal of the battery.

[0015] Optionally, the freewheeling element is connected in parallel with a series structure including the choke element and the bus capacitor, the series structure further comprising:

[0016] A current sampling element is connected in series with the choke element and the bus capacitor.

[0017] Optionally, the current sampling element is connected between the second terminal of the battery and the second terminal of the bus capacitor.

[0018] Optionally, the pre-charging circuit further includes a main negative switch, and the current sampling element is connected in series with the main negative switch between the second terminal of the battery and the second terminal of the bus capacitor.

[0019] Optionally, the pre-charging circuit further includes a battery management system, which is electrically connected to the control terminal of the pre-charging switch.

[0020] Optionally, the precharge switch is an electronic switch.

[0021] Optionally, the precharge switch includes a field-effect transistor or an insulated-gate bipolar transistor.

[0022] According to another aspect of the present invention, an electric vehicle is provided, the electric vehicle including the pre-charging circuit as described above.

[0023] The technical solution provided in this embodiment of the invention employs a pre-charging circuit including a pre-charging switch, a choke element, and a freewheeling element. The pre-charging switch and the choke element are connected in series between the first terminal of the battery and the first terminal of the bus capacitor. The freewheeling element is connected in parallel with the choke element and the bus capacitor. By utilizing the freewheeling element, the pre-charging switch, and the choke element to form the pre-charging circuit, the choke element can suppress sudden current changes, while the freewheeling element can provide freewheeling current, ensuring continuous charging of the bus capacitor. Furthermore, the choke element generates less heat during operation, allowing for a smaller size, and can initiate pre-charging multiple times consecutively in a short period, thereby extending its service life. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of this utility model and these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a pre-charging circuit provided for an embodiment of this utility model;

[0026] Figure 2 A schematic diagram of another pre-charging circuit provided in an embodiment of this utility model;

[0027] Figure 3 A schematic diagram of another pre-charging circuit provided in an embodiment of this utility model;

[0028] Figure 4 This is a schematic diagram of the current curve during a pre-charging process, provided as an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] A1 - Battery terminal 1, A2 - Battery terminal 2, C - Bus capacitor, Q1 - Precharge switch, 11 - Choke element, 12 - Freewheeling element, 31 - Series structure, 21 - Battery, L - Choke inductor, D1 - First diode, 13 - Unidirectional conduction element, D2 - Second diode, 14 - Current sampling element, K2 - Main negative switch, K1 - Main positive switch, R1 - Sampling resistor. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The pre-charging circuits in related technologies suffer from problems such as large size, high cost, severe heat generation, and short lifespan. After careful research, the applicant discovered that the cause of these technical problems lies in the fact that the pre-charging circuits in these technologies use a combination of relays and pre-charging resistors. During pre-charging, the pre-charging resistors lose energy, requiring a large size to meet heat dissipation requirements, thus increasing the overall size of the pre-charging circuit and affecting the energy density of the battery pack. Furthermore, because the pre-charging resistors generate significant heat during pre-charging, multiple consecutive pre-charging cycles cannot be performed in a short period to prevent damage from overheating, which limits the flexibility of high-voltage connection in the vehicle.

[0034] Based on the above-mentioned technical problems, this embodiment proposes the following solutions:

[0035] Example 1

[0036] Figure 1 A circuit structure diagram of a pre-charging circuit provided for an embodiment of this utility model is shown below. Figure 1 The pre-charge circuit includes: a pre-charge switch Q1, a choke element 11, and a freewheeling element 12; the pre-charge switch Q1 and the choke element 11 are connected in series between the first terminal A1 of the battery and the first terminal of the bus capacitor C; the freewheeling element 12 is connected in parallel with the choke element 11 and the bus capacitor C.

[0037] Specifically, the pre-charging circuit is used to pre-charge the battery 21, which is, for example, a power battery used in new energy vehicles. The battery 21 comprises multiple battery cells, which are connected in series and / or parallel to form the battery 21. Each battery cell can be a lithium-ion battery, such as a lithium iron phosphate battery or a ternary lithium battery, etc., and this embodiment does not specifically limit this. The pre-charging circuit includes a first terminal A1 and a second terminal A2, wherein the first terminal A1 is electrically connected to the first terminal of the battery 21, and the second terminal A2 is electrically connected to the second terminal of the battery 21.

[0038] The bus capacitance C is the equivalent capacitance of all capacitors connected across the high-voltage bus. In new energy vehicles, components such as the motor controller, air conditioning compressor, front and rear electric drives, OBC (On-Board Charger), and DC-DC converter all contain large capacitors connected in parallel across the bus. The bus capacitance C is the equivalent capacitance of all these capacitors combined.

[0039] After the car is completely turned off, the main positive and negative relays inside the car will disconnect, thus isolating battery 21 from bus capacitor C. Bus capacitor C will slowly release energy, causing the voltage across bus capacitor C to eventually reach 0 volts or close to 0 volts. When the car is powered on, if the main positive and negative relays are directly closed, the high voltage on battery 21 will momentarily surge through bus capacitor C. This instantaneous high current may damage the relays and devices connected to the high-voltage bus. Therefore, when the car is started, that is, before the vehicle is connected to high voltage, pre-charging is required. The pre-charging circuit pre-charges the voltage of bus capacitor C to the corresponding threshold to avoid excessive current damaging the high-voltage circuit devices when high voltage is applied. This threshold is the same as or close to the voltage across battery 21. The threshold may vary for different cars, and this embodiment does not specify a particular threshold.

[0040] In this embodiment, the pre-charge circuit includes a pre-charge switch Q1 connected in series with a choke element 11, and a freewheeling element 12. The choke element 11 can suppress sudden changes in current, allowing the current to change linearly and slowly. That is, when the pre-charge switch Q1 is closed, the choke element 11 can prevent a sudden high current from impacting the bus capacitor C, instead controlling the current to rise slowly. When the current reaches the upper limit, the pre-charge switch Q1 is opened. At this time, the freewheeling element 12 can provide a freewheeling path, allowing the choke element 11 to release current. The current of the choke element 11 decreases linearly, and the current released by the choke element 11 can form a loop through the freewheeling element 12. In other words, when the pre-charge switch Q1 is opened, the choke element 11 continues to charge the bus capacitor C, causing the voltage of the bus capacitor C to continue to rise, preventing oscillation between the choke element 11 and the bus capacitor C. When the voltage across the bus capacitor C reaches the aforementioned threshold, the pre-charge ends. After this, when the main positive relay and the main negative relay are closed again, the battery 21 will not generate a sudden large current that impacts the devices connected to the high-voltage bus. The precharge switch Q1 is an electronic switch. Unlike mechanical switches, electronic switches are based on semiconductor devices and have advantages such as fast response speed, low cost, and small size. Understandably, during the precharge process, the precharge switch Q1 needs to be turned on and off at a relatively high frequency, so it can be controlled using PWM (Pulse Width Modulation).

[0041] In this embodiment, since a choke element 11 and a freewheeling element 12 are used for pre-charging the bus capacitor C, and the choke element 11 itself is a reactive element that ideally does not generate heat, with heat mainly coming from parasitic factors, the choke element 11 does not consume energy during pre-charging and generates relatively little heat. Therefore, it can be made smaller in size and can initiate pre-charging multiple times in a short period. Furthermore, the combination of the choke element and the freewheeling element has advantages over a pre-charging resistor in terms of smaller size and lower cost.

[0042] It is understood that although this embodiment uses the operation of the pre-charging circuit during vehicle startup as an example, those skilled in the art will understand that when charging the battery 21, it is also necessary to use the pre-charging circuit for pre-charging. The operation of the pre-charging circuit is similar to that during vehicle startup, both using the battery to charge the bus capacitor, which will not be described in detail here.

[0043] The technical solution of this embodiment employs a pre-charge circuit including a pre-charge switch, a choke element, and a freewheeling element. The pre-charge switch and the choke element are connected in series between the first terminal of the battery and the first terminal of the bus capacitor. The freewheeling element is connected in parallel with the choke element and the bus capacitor. By utilizing the freewheeling element, pre-charge switch, and choke element to form the pre-charge circuit, the choke element can suppress sudden current changes, while the freewheeling element can provide freewheeling current, ensuring continuous charging of the bus capacitor. Furthermore, the choke element generates less heat during operation, allowing for a smaller size, and can initiate pre-charge multiple times consecutively in a short period, thereby extending its service life.

[0044] Example 2

[0045] Optionally, in some implementations, the precharge switch is an electronic switch.

[0046] Specifically, in related technologies, the pre-charging circuit uses a combination of a relay and a pre-charging resistor. The relay is a mechanical switch, and it closes under load every time high voltage is applied, limiting the overall vehicle lifespan. Furthermore, the pre-charging resistor and relay are relatively expensive, especially since a more expensive ceramic-encapsulated relay is required to extend the relay's lifespan. In this embodiment, the pre-charging switch is an electronic switch. Electronic switches not only meet the requirements of PWM high-frequency control but also have advantages such as small size and long service life, significantly extending the overall vehicle lifespan. Compared to the combination of a relay and a pre-charging resistor, the combination of an electronic switch, a choke element, and a freewheeling element offers advantages such as small size and low cost.

[0047] Example 3

[0048] Optionally, in some embodiments, the precharge switch includes a field-effect transistor, such as a metal-oxide-semiconductor field-effect transistor (MOS-FET); or the precharge switch includes an insulated-gate bipolar transistor (IGBT). Field-effect transistors and IGBTs have simple structures and low costs, which helps to further reduce the cost of the precharge circuit. In some embodiments, the precharge switch can also be other types of electronic switches.

[0049] Example 4

[0050] Optionally, Figure 2 This is a schematic diagram of another pre-charging circuit provided in an embodiment of the present invention, with reference to... Figure 2 The choke element 11 includes a choke inductor L; the first terminal of the precharge switch Q1 is electrically connected to the first terminal A1 of the battery, the second terminal of the precharge switch Q1 is electrically connected to the first terminal of the choke element 11, and the second terminal of the choke element 11 is used to be electrically connected to the first terminal of the bus capacitor C.

[0051] Specifically, when the pre-charge switch Q1 is closed, the battery 21, the choke inductor L, and the bus capacitor C form a charging circuit. At this time, the battery 21 outputs energy to the choke inductor L, which stores energy, causing the current in the charging circuit to rise slowly and linearly, and the voltage across the bus capacitor C to gradually increase. During this stage, the freewheeling element 12 is in the off state. When the pre-charge switch Q1 is turned off, the freewheeling element 12 is turned on, and the choke inductor L, the bus capacitor C, and the freewheeling element 12 form a charging circuit. The energy stored in the choke inductor L is released to the bus capacitor C, causing the voltage across the bus capacitor C to continue to rise. In this embodiment, the function of the choke element 11 can be achieved using the choke inductor L. The circuit structure is simple, low-cost, and easy to implement. Of course, in other embodiments, some circuit structures that can be equivalent to a choke inductor can also be used as the choke element.

[0052] Example 5

[0053] Optionally, refer to Figure 2 The freewheeling element 12 includes a first diode D1, the anode of the first diode D1 is electrically connected to the second terminal of the bus capacitor C, and the cathode of the first diode D1 is electrically connected to the first terminal of the choke element 11.

[0054] Specifically, the first terminal A1 of the battery is connected to the positive terminal of battery 21, and the second terminal A2 is connected to the negative terminal of battery 21. When the pre-charge switch Q1 is turned on, the anode of the first diode D1 is connected to the negative terminal of battery 21, and the cathode of the first diode D1 is connected to the positive terminal of battery 21. At this time, the first diode D1 is in the off state, and battery 21, choke inductor L, and bus capacitor C form a charging circuit. When the pre-charge switch Q1 is turned off, the cathode of the first diode D1 is connected to the potential of the first terminal of choke inductor L, and the anode of the first diode D1 is connected to the potential of the second terminal of bus capacitor C. Since the potential of the second terminal of bus capacitor C is higher than the potential of the first terminal of choke inductor L, the first diode D1 is turned on, providing a path for energy release on choke inductor L. In this embodiment, the first diode D1 is used to realize the function of a freewheeling element, which has a simple circuit structure, small size, and low cost.

[0055] Example 6

[0056] Optionally, refer to Figure 1 and Figure 2 The pre-charging circuit also includes a unidirectional conducting element 13, which is connected in series with the pre-charge switch Q1 and the choke element 11 between the first terminal A1 and the second terminal A2 of the battery; wherein the second terminal A2 of the battery is electrically connected to the second terminal of the bus capacitor C. The unidirectional conducting element 13 is used to conduct when the voltage at the first terminal of the unidirectional conducting element is higher than the voltage at the second terminal of the unidirectional conducting element; that is, the unidirectional conducting element 13 conducts unidirectionally when the voltage at the end connected to the first terminal A1 of the battery is higher than the voltage at the end connected to the second terminal A2 of the battery.

[0057] Specifically, the precharge switch Q1 is an electronic switch, which may contain a body diode. When the precharge switch Q1 is off, if the positive and negative terminals of battery 21 are reverse-connected to high-voltage devices (such as the precharge circuit), the body diode of the precharge switch Q1 may provide a current path, causing the high-voltage devices to burn out. In this embodiment, by setting a unidirectional conducting element 13, the unidirectional conducting element can only conduct when battery 21 is connected in the correct direction; when battery 21 is connected in the reverse direction, the unidirectional conducting element 13 is always in the off state, preventing the high-voltage devices from burning out. In addition, the unidirectional conducting element 13 can also prevent energy from the high-voltage load terminal from being recharged back to battery 21.

[0058] A unidirectional conducting element 13, a pre-charge switch Q1, and a choke element 11 are connected in series between the first terminal A1 and the second terminal A2 of the battery. The position of the unidirectional conducting element 13 can be arbitrary. For example, the unidirectional conducting element 13 can be placed between the first terminal A1 and the pre-charge switch Q1, between the pre-charge switch Q1 and the choke element 11, between the choke element 11 and the bus capacitor C, or between the bus capacitor C and the second terminal A2 of the battery, etc. It should be noted that the end of the unidirectional conducting element 13 connected to the first terminal A1 of the battery can be directly connected to the first terminal A1 or indirectly connected to the first terminal A1 of the battery. Similarly, the end of the unidirectional conducting element 13 connected to the second terminal A2 of the battery can be directly connected to the second terminal A2 of the battery or indirectly connected to the second terminal A2 of the battery.

[0059] Example 7

[0060] Alternatively, in some implementations, such as Figure 1 and Figure 2 As shown, the first end of the unidirectional conducting element 13 is electrically connected to the first end A1 of the battery, and the second end of the unidirectional conducting element 13 is electrically connected to the first end of the pre-charge switch Q1. That is, the unidirectional conducting element 13 is connected between the first end A1 of the battery and the pre-charge switch Q1. If the battery 21 is reverse-connected, the unidirectional conducting element 13 can protect all devices downstream of the current outflow terminal (i.e., the positive terminal) of the battery 21. In other words, the configuration of this embodiment enables the unidirectional conducting element 13 to provide more effective protection for high-voltage devices.

[0061] Example 8

[0062] Optionally, refer to Figure 2 The unidirectional conducting element 13 includes a second diode D2; the anode of the second diode D2 is connected to the first terminal A1 of the battery, and the cathode of the second diode D2 is connected to the second terminal A2 of the battery. When the positive and negative terminals of the battery are reversed, the negative terminal of the battery 21 is electrically connected to the anode of the second diode, and the second diode D2 is in a cut-off state, preventing high-voltage devices from burning out due to the reverse polarity of the battery. It is understood that the reverse polarity of the battery may occur during the assembly process of the battery pack manufacturing stage or during the maintenance stage, etc., and this embodiment does not limit this. In addition, the function of the unidirectional conducting element 13 can be realized using only a second diode D2, the circuit structure is simple, and it is beneficial to further reduce the cost of the pre-charging circuit.

[0063] Example 9

[0064] Optionally, continue to refer to Figure 1 and Figure 2The freewheeling element is connected in parallel with the series structure 31, which includes the choke element and the bus capacitor; the series structure 31 also includes a current sampling element 14, which is connected in series with the choke element 11 and the bus capacitor C.

[0065] Specifically, the current sampling element 14 can sample the current flowing through the series structure 31 to determine whether the current flowing through the series structure 31 has reached its upper or lower limit. When the pre-charge switch Q1 is turned on, the current in the series structure 31 increases. At this time, the current sampling element 14 can detect whether the current in the series structure 31 has reached its upper limit. If it has, the pre-charge switch Q1 is turned off. Conversely, when the current in the series structure 31 decreases, the current sampling element 14 can detect whether the current in the series structure 31 has reached its lower limit. If it has, the pre-charge switch Q1 is turned on. It should be noted that pre-charging ends when the voltage across the bus capacitor C reaches the corresponding threshold.

[0066] The current sampling element 14 is connected in series in the series structure 31. Its position is not limited. For example, it can be connected between the first end of the freewheeling element 12 and the first end of the choke element 11, between the choke element 11 and the bus capacitor C, or between the second end of the bus capacitor C and the second end of the freewheeling element 11, etc.

[0067] Example 10

[0068] Optionally, such as Figure 1 As shown, the current sampling element 14 is connected between the second terminal A2 of the battery and the second terminal of the bus capacitor C. Furthermore, the pre-charging circuit also includes a main negative switch K2, with the current sampling element 14 and the main negative switch K2 connected in series between the second terminal A2 of the battery and the second terminal of the bus capacitor C. Specifically, the main negative switch K2 is also a main negative relay, and the current sampling element 14 is connected between the main negative relay and the negative terminal of the battery 21. The current sampling unit 14 can be reused with the element that samples the current of the battery 21 during operation, eliminating the need for an additional current sampling element and further reducing the cost of the pre-charging circuit.

[0069] Example 11

[0070] Optionally, refer to Figure 2 The current sampling element 14 includes a sampling resistor R1. The first terminal of the sampling resistor R1 is electrically connected to the second terminal A2 of the battery, and the second terminal of the sampling resistor R1 is electrically connected to the main negative relay K2. The resistance value of the sampling resistor R1 is known. When sampling the current in the series structure 31, it is only necessary to detect the voltage across the sampling resistor R1 to calculate the current flowing through the series structure 31.

[0071] Example 12

[0072] Optionally, continue to refer to Figure 1 and Figure 2 The pre-charge circuit also includes a main positive switch K1, which is also a main positive relay, connected between the positive terminal of battery 21 and the positive terminal of bus capacitor C. In this embodiment, the pre-charge switch Q1 and the main positive switch K1 are connected in parallel. In some other embodiments, the pre-charge switch Q1 and the main positive switch K1 can also be connected in series.

[0073] Example 13

[0074] Optionally, Figure 3 This is a schematic diagram of another pre-charging circuit provided in an embodiment of the present invention, with reference to... Figure 3 The pre-charge circuit also includes a battery management system (BMS) 15, which is electrically connected to the control terminal of the pre-charge switch Q1.

[0075] Specifically, during the pre-charging process, the battery management system 15 can detect the voltage across the current sampling element 14 and automatically calculate the current flowing through the series structure 31, thereby automatically determining whether the pre-charging switch Q1 needs to be turned on or off. It is understood that the battery management system 15 can be electrically connected to the control terminal of the pre-charging switch Q1 through a corresponding drive circuit, thereby driving the pre-charging switch Q1 to turn on and off. Alternatively, the battery management system 15 can also be electrically connected to the current sampling element 14 through a structure such as a voltage detection element; this embodiment does not specifically limit this. It is also understood that the battery management system 15 can monitor the vehicle current, battery voltage, and the voltage across the bus capacitor.

[0076] For example, such as Figure 4 As shown, Figure 4 A schematic diagram of the current curve during the pre-charging process is provided for an embodiment of this utility model, with reference to... Figure 4After the battery management system (BMS) is initialized, it enters the pre-charge command monitoring state. Upon receiving a pre-charge command, the BMS first closes the main negative switch K2, then checks whether the voltage across the bus capacitor C and the voltage across battery 21 are equal (i.e., the threshold value corresponding to the bus capacitor is equal to the voltage across the battery). If they are equal, pre-charging is complete; otherwise, the pre-charge switch Q1 is closed. After the pre-charge switch Q1 is closed, the current in the series structure increases, and the voltage across the bus capacitor C rises slowly. At this time, the system continuously monitors whether the voltage across the bus capacitor C is equal to the voltage across battery 21, and continuously monitors whether the current in the series structure 31 reaches its upper limit. If the voltage across the bus capacitor C is less than the voltage across battery 21, and the current reaches its upper limit, the pre-charge switch Q1 is turned off. At this time, the current in the series structure 31 decreases. Due to the freewheeling effect of the freewheeling element, the choke element continues to charge the bus capacitor C, and the voltage across the bus capacitor C continues to rise. After the pre-charge switch is turned off, the voltage across the bus capacitor C is continuously monitored to ensure it is equal to the voltage across battery 21, and the current in the series structure 31 is continuously monitored to ensure it reaches the lower limit. If the voltage across the bus capacitor C is equal to the voltage across the battery, pre-charging ends. If the voltage across the bus capacitor C is still lower than the voltage across the battery, and the current in the series structure reaches the lower limit, the pre-charge switch Q1 is turned on. This cycle repeats until the voltage across the bus capacitor C is equal to the voltage across battery 21, at which point pre-charging ends. After pre-charging is complete, the pre-charge switch Q1 is turned off. It is understandable that... Figure 4 The average pre-charge current can be calculated based on the upper and lower current limits.

[0077] Example 14

[0078] Based on the same inventive concept, this utility model also provides an electric vehicle, which includes the pre-charging circuit provided in any embodiment of this utility model. The electric vehicle can be a pure electric vehicle, a range-extended electric vehicle, or a plug-in hybrid electric vehicle, etc. Since the electric vehicle provided in this utility model embodiment includes the pre-charging circuit provided in this utility model embodiment, it also has the same beneficial effects, which will not be elaborated further here.

[0079] It should be noted that the pre-charging circuit involved in the above embodiments may include at least one of Embodiments 1 to 13. For example, Embodiment 1 can be implemented as an independent embodiment, Embodiment 1+2 can be implemented as an independent embodiment, Embodiment 1+2+3 can be implemented as an independent embodiment, Embodiment 1+2+4 can be implemented as an independent embodiment, Embodiment 1+2+3+4 can be implemented as an independent embodiment, Embodiment 1+2+4+5 can be implemented as an independent embodiment, Embodiment 1+2+3+4+5 can be implemented as an independent embodiment, Embodiment 1+2+4+6 can be implemented as an independent embodiment, Embodiment 1+2+3+4+6 can be implemented as an independent embodiment, Embodiment 1+2+4+5+6 can be implemented as an independent embodiment, and Embodiment 1+2+3+4+5+6 can be implemented as an independent embodiment. Examples of embodiments 1 and 2 can be implemented as independent embodiments, as can examples 1, 2, 3, 4, 5, 6, 6, 7, 8, 9, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9 ...12, 3, 4, 5, 6, 7, 8, 9, 11, 12, 3, 4, 5, 6, 7, 8, 9, 9, 11, 12, 3, 4, 5, 6, 7, 8, 9, 9, 11, 12, 3, 4, 5, 6, 7, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,

[0080] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A pre-charging circuit, characterized in that, The pre-charge circuit includes: a pre-charge switch, a choke element, and a freewheeling element; The precharge switch and the choke element are connected in series between the first end of the battery and the first end of the bus capacitor. The freewheeling element is connected in parallel with the choke element and the bus capacitor.

2. The pre-charging circuit according to claim 1, characterized in that, The choke element includes a choke inductor; The first end of the precharge switch is electrically connected to the first end of the battery, the second end of the precharge switch is electrically connected to the first end of the choke element, and the second end of the choke element is used to electrically connect to the first end of the bus capacitor.

3. The pre-charging circuit according to claim 1 or 2, characterized in that, The freewheeling element includes a first diode, the anode of which is electrically connected to the second terminal of the bus capacitor, and the cathode of which is electrically connected to the first terminal of the choke element.

4. The pre-charging circuit according to any one of claims 1-3, characterized in that, The pre-charging circuit further includes a unidirectional conducting element, which is connected in series with the pre-charging switch and the choke element between the first terminal and the second terminal of the battery; wherein the second terminal of the battery is electrically connected to the second terminal of the bus capacitor.

5. The pre-charging circuit according to claim 4, characterized in that, The first end of the unidirectional conducting element is electrically connected to the first end of the battery, and the second end of the unidirectional conducting element is electrically connected to the first end of the precharge switch.

6. The pre-charging circuit according to claim 4 or 5, characterized in that, The unidirectional conducting element includes a second diode, the anode of which is connected to the first terminal of the battery, and the cathode of which is connected to the second terminal of the battery.

7. The pre-charging circuit according to any one of claims 1-6, characterized in that, The freewheeling element is connected in parallel with a series structure including the choke element and the bus capacitor, and the series structure further includes: A current sampling element is connected in series with the choke element and the bus capacitor.

8. The pre-charging circuit according to claim 7, characterized in that, The pre-charging circuit also includes a main negative switch, and the current sampling element is connected in series with the main negative switch between the second terminal of the battery and the second terminal of the bus capacitor.

9. The pre-charging circuit according to any one of claims 1-8, characterized in that, The pre-charging circuit also includes a battery management system, which is electrically connected to the control terminal of the pre-charging switch.

10. The pre-charging circuit according to any one of claims 1-9, characterized in that, The precharge switch is an electronic switch.

11. The pre-charging circuit according to any one of claims 1-10, characterized in that, The precharge switch includes a field-effect transistor or an insulated-gate bipolar transistor.

12. An electric vehicle, characterized in that, The electric vehicle includes the pre-charging circuit as described in any one of claims 1-11.

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