DCDC conversion circuit and vehicle

Abstract

The utility model discloses a DCDC conversion circuit and a vehicle, and belongs to the technical field of new energy vehicles. The DCDC conversion circuit includes: a conversion circuit having a high voltage side and a low voltage side; and the first end of the step-down circuit is electrically connected with the low-voltage side of the conversion circuit, and the step-down circuit is configured to step down the input voltage accessed by the second end of the step-down circuit and transmit the voltage after step-down to the low-voltage side of the conversion circuit for voltage conversion. According to the DCDC conversion circuit, when reverse pre-charging is carried out, the output voltage of the storage battery is firstly reduced, and the direct current bus is pre-charged, so that the current and voltage of a low-voltage side switching tube of the conversion circuit can be reduced, and the overvoltage and overcurrent risk of the low-voltage side switching tube can be reduced; and after the direct-current bus is charged for a period of time to reach a certain voltage, the output voltage of the storage battery is boosted, and pre-charging of the direct-current bus is completed.

Description

Technical Field

[0001] The present application belongs to the technical field of new energy vehicles, and in particular, relates to a DCDC conversion circuit and a vehicle. Background Art

[0002] The electrical system architecture of new energy vehicles includes high-voltage systems and low-voltage systems. The high-voltage system usually includes high-voltage power batteries, relays, inverters, air conditioners, bus capacitors, DCDC conversion circuits, PTC (heater) and other high-voltage accessories; the low-voltage system includes batteries, BMS (Battery Management System) and VCU (Vehicle Control Unit) and other modules.

[0003] In order to prevent the instantaneous surge current when the relay is closed from damaging the wiring harness, relay and other accessories, there is usually a pre-charging resistor and a pre-charging relay between the power battery and the high-voltage accessories. The main relay is closed only when the voltage difference between the power battery and the high-voltage bus capacitor is small.

[0004] At present, the DCDC conversion circuit has a reverse pre-charging function, that is, it can convert low voltage electricity into high voltage for pre-charging the bus capacitor, which can eliminate the pre-charging relay and pre-charging resistor, saving system costs. However, the current DCDC conversion circuit is prone to failure when working in reverse. Utility Model Content

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a DCDC conversion circuit and a vehicle to reduce the current and voltage of the low-voltage side switch tube of the conversion circuit and reduce the risk of overvoltage and overcurrent of the low-voltage side switch tube.

[0006] In a first aspect, the present application provides a DCDC conversion circuit, comprising:

[0007] A conversion circuit having a high voltage side and a low voltage side, wherein the high voltage side is used to connect to a DC bus;

[0008] A step-down circuit, wherein the first end of the step-down circuit is electrically connected to the low-voltage side of the conversion circuit, and the step-down circuit is configured to step down the input voltage connected to the second end of the step-down circuit, and transmit the stepped-down voltage to the low-voltage side of the conversion circuit for voltage conversion.

[0009] According to the DCDC conversion circuit of the present application, when reverse pre-charging is performed, the output voltage of the battery is stepped down and the DC bus is pre-charged, so that the current and voltage of the low-voltage side switch tube of the conversion circuit can be reduced, and the risk of overvoltage and overcurrent of the low-voltage side switch tube can be reduced; after the DC bus is charged to a certain voltage, the output voltage of the battery is boosted to complete the pre-charging of the DC bus.

[0010] According to one embodiment of the present application, a step-down circuit includes:

[0011] An inductor, a first end of the inductor being electrically connected to the low voltage side of the conversion circuit;

[0012] A first switch element, wherein a first end of the first switch element is electrically connected to a second end of the inductor, and a second end of the first switch element is used to access an input voltage;

[0013] The second switch element has a first end electrically connected to a connection node between the inductor and the first switch element, and a second end electrically connected to a ground node.

[0014] According to an embodiment of the present application, the second switch element is a diode, a cathode of the diode is electrically connected to a connection node between the inductor and the first switch element, and an anode of the diode is electrically connected to a ground node.

[0015] According to an embodiment of the present application, the first switch element is a MOS tube, the source of the MOS tube is electrically connected to the second end of the inductor, and the drain of the MOS tube is used to connect to the battery.

[0016] According to one embodiment of the present application, the DCDC conversion circuit further includes:

[0017] The controller is electrically connected to the gate of the first switch element and is configured to transmit a first switch signal to the first switch element, wherein the duty cycle of the first switch signal is greater than 0 and less than 100%, so that the buck circuit performs voltage reduction.

[0018] According to an embodiment of the present application, the controller is further configured to transmit a second switching signal to the first switching element, and the duty cycle of the second switching signal is equal to 100%, so that the buck circuit is directly turned on.

[0019] According to one embodiment of the present application, the conversion circuit includes a transformer and a secondary switch circuit electrically connected to the secondary winding of the transformer, the controller is electrically connected to the secondary switch circuit, and is configured to transmit a first drive signal and a second drive signal to a first switch loop and a second switch loop connected in parallel in the secondary switch circuit, respectively, or transmit a third drive signal and a fourth drive signal to the first switch loop and the second switch loop, respectively;

[0020] The first driving signal and the second driving signal are complementary, and the duty cycles of the third driving signal and the fourth driving signal are both greater than 50%.

[0021] According to an embodiment of the present application, the secondary side switch circuit and the inductor constitute a secondary side rectifier circuit.

[0022] According to one embodiment of the present application, the secondary rectifier circuit is a half-bridge rectifier circuit, a current doubler rectifier circuit or a full-bridge rectifier circuit.

[0023] In a second aspect, the present application provides a vehicle, comprising a DCDC conversion circuit according to the foregoing, wherein the high voltage side of the DCDC conversion circuit is electrically connected to the vehicle's high voltage bus, and the low voltage side of the DCDC conversion circuit is electrically connected to the vehicle's low voltage battery.

[0024] According to the vehicle of the present application, when the DCDC conversion circuit is performing reverse pre-charging, the current and voltage of the low-voltage side switch tube of the conversion circuit are low, thereby reducing the risk of overvoltage and overcurrent and ensuring vehicle safety.

[0025] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 It is one of the circuit topology diagrams of the DCDC conversion circuit provided in the embodiment of the present application;

[0028] Figure 2 This is the second circuit topology diagram of the DCDC conversion circuit provided in the embodiment of the present application;

[0029] Figure 3 This is the third circuit topology diagram of the DCDC conversion circuit provided in the embodiment of the present application;

[0030] Figure 4 This is the fourth circuit topology diagram of the DCDC conversion circuit provided in the embodiment of the present application.

[0031] Reference numerals:

[0032] Conversion circuit 100, step-down circuit 200, battery 300, transformer T1, first to ninth MOS tubes M1-M9, DC bus capacitor Cbus, inductors Lo, Lo1, Lo2, and diode D1. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0034] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0035] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0036] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0037] Reference Figure 1 , Figure 1 The circuit structure of a DCDC conversion circuit is shown, and an embodiment of the present application provides a DCD conversion circuit. In this embodiment, the DCDC conversion circuit includes a conversion circuit 100 and a buck circuit 200, and the conversion circuit 100 has a high voltage side and a low voltage side; the first end of the buck circuit 200 is electrically connected to the low voltage side of the conversion circuit 100, and the buck circuit 200 is configured to buck the input voltage connected to the second end of the buck circuit 200, and transmit the bucked voltage to the low voltage side of the conversion circuit 100 for voltage conversion.

[0038] It should be noted that the high-voltage side of the conversion circuit 100 refers to the side with a higher voltage, which is usually used to connect the DC bus; the low-voltage side refers to the side with a lower voltage. Taking the vehicle system as an example, the high-voltage side of the conversion circuit 100 is usually connected to the DC bus, and the second end of the step-down circuit 200 is usually connected to the battery 300. The DC bus HVDC+ and HVDC- are usually electrically connected to the in-vehicle power battery, and the voltage can reach 200-500VDC or 300-800VDC. The battery 300 can be an in-vehicle battery, and its voltage is usually 9-16V. The second end of the step-down circuit 200 can be connected to the LVDC+ end to power the low-voltage components.

[0039] The DCDC conversion circuit can operate in a forward state and a reverse pre-charge state. In the forward state, the DCDC conversion circuit converts the electric energy on the DC bus to power the battery 300 and the LVDC+ terminal. In the reverse pre-charge state, the DCDC conversion circuit converts the electric energy of the battery 300 to charge the DC bus.

[0040] It is understandable that when the DCDC conversion circuit is running in the forward direction, it is usually necessary to pre-charge the DC bus to prevent the surge current when the power battery is closed from damaging the wiring harness, relays and other accessories. In this embodiment, the pre-charging is achieved by the DCDC conversion circuit through reverse pre-charging.

[0041] Generally, since the voltage of the storage battery 300 is much lower than the voltage of the power battery, when the voltage of the high-voltage side bus capacitor is small, the energy of the inductive element on the low-voltage side of the conversion circuit 100 cannot be discharged, so the conversion circuit 100 is easily damaged.

[0042] The buck circuit 200 operates in a buck state, which means that the output voltage of the battery 300 is bucked, and electric energy with a voltage lower than the output voltage of the battery 300 is provided to the low-voltage side of the conversion circuit 100. The buck circuit 200 operates in a freewheeling state, which means that the output voltage of the battery 300 is not processed, and electric energy with a voltage equal to the output voltage of the battery 300 is provided to the low-voltage side of the conversion circuit 100. The buck circuit has a mature technology, and this embodiment will not be described in detail here.

[0043] In this embodiment, a step-down circuit 200 is provided on the low-voltage side of the conversion circuit 100. When the reverse pre-charging of the DCDC conversion circuit starts, the step-down circuit 200 is controlled to operate in a step-down state, thereby reducing the energy of the inductive elements on the low-voltage side of the conversion circuit 100 and reducing the risk of overvoltage and overcurrent. After the bus capacitor voltage is relatively large, the step-down circuit 200 is controlled to operate in a freewheeling state, and the conversion circuit 100 can be controlled to achieve boosting to complete pre-charging.

[0044] According to the DCDC conversion circuit of the present application, when reverse pre-charging is performed, the output voltage of the battery 300 is stepped down and the DC bus is pre-charged, so that the current and voltage of the low-voltage side switch tube of the conversion circuit 100 can be reduced, and the risk of overvoltage and overcurrent of the low-voltage side switch tube can be reduced; after the DC bus is charged to a certain voltage, the output voltage of the battery 300 is boosted to complete the pre-charging of the DC bus.

[0045] Reference Figure 2 , Figure 2 The circuit structure of a DCDC conversion circuit is shown. In some embodiments, the conversion circuit 100 may include a transformer T1, a primary switch circuit electrically connected to the primary winding of the transformer T1, and a secondary switch circuit connected to the secondary winding circuit of the transformer T1. The primary switch circuit includes a full-bridge circuit composed of a first MOS tube M1, a second MOS tube M2, a third MOS tube M3, and a fourth MOS tube M4. The primary switch circuit is connected to the DC bus HVDC+ and HVDC-, and a DC bus capacitor Cbus is provided between the DC bus HVDC+ and HVDC-. The secondary switch circuit includes a half-bridge circuit composed of a fifth MOS tube M5 and a sixth MOS tube M6.

[0046] In some embodiments, the step-down circuit 200 includes an inductor Lo, a first switch element, and a second switch element. The first end of the inductor Lo is electrically connected to the low-voltage side of the conversion circuit 100; the first end of the first switch element is electrically connected to the second end of the inductor Lo, and the second end of the first switch element is used to connect to the battery 300; the first end of the second switch element is electrically connected to the connection node between the inductor Lo and the first switch element, and the second end of the second switch element is electrically connected to the ground node.

[0047] It should be noted that when the buck circuit 200 implements the buck function, the second switch is in a continuously on state. The inductor Lo, the first switch and the second switch form a BUCK circuit, and the buck function is implemented by controlling the switching action of the first switch. When the buck circuit 200 does not need to buck, the second switch is in a continuously off state.

[0048] like Figure 2 As shown, as an example, the first switch is a seventh MOS tube M7, the source of the seventh MOS tube M7 is electrically connected to the second end of the inductor Lo, and the drain of the seventh MOS tube M7 is used to connect to the battery 300. The second switch is a diode D1, the cathode of the diode D1 is electrically connected to the connection node between the inductor Lo and the seventh MOS tube M7, and the anode of the diode D1 is electrically connected to the ground node. Of course, the second switch can also be a MOS tube.

[0049] It can be understood that the DCDC conversion circuit also includes a controller (not shown in the figure), which is electrically connected to the gate of each MOS tube and transmits a switching signal to each MOS tube to control the operation of each circuit part.

[0050] In some embodiments, the controller transmits a first switch signal to the seventh MOS transistor M7, so that the buck circuit 200 operates in a buck state. The duty cycle of the first switch signal is greater than 0 and less than 100%, so that the seventh MOS transistor M7 is intermittently turned on. In the buck state, the duty cycle of the first switch signal can be gradually increased from 0 to 100%.

[0051] When the seventh MOS tube M7 is turned on, the battery 300 charges the inductor Lo through the seventh MOS tube M7; when the seventh MOS tube M7 is turned off, the inductor Lo is freewheeling through the diode D1. The inductor Lo, the diode D1, the seventh MOS tube M7 and the transformer T1 form a step-down circuit to achieve a step-down function.

[0052] When the DCDC conversion circuit works in the first stage, the controller transmits the first drive signal and the second drive signal to the first switch loop and the second switch loop connected in parallel in the secondary switch circuit respectively, and the first drive signal and the second drive signal are complementary. The first switch loop refers to the loop where the fifth MOS tube M5 is located, and the second switch loop refers to the loop where the sixth MOS tube M6 is located.

[0053] The duty cycle of the first driving signal and the second driving signal may both be 50%, which are complementary signals, so that the fifth MOS transistor M5 and the sixth MOS transistor M6 are alternately turned on, and the voltage of the DC bus capacitor Cbus gradually increases.

[0054] It should be noted that the DCDC conversion circuit needs to increase the DC bus capacitor Cbus to a higher voltage when working in the reverse pre-charge state. The DCDC conversion circuit can be divided into a first stage and a second stage when working in the reverse pre-charge state, and the second stage is after the first stage. In the first stage, the buck circuit 200 operates in a buck state and gradually increases the voltage of the DC bus capacitor Cbus; in the first stage, the buck circuit 200 turns off the buck function, and the DCDC conversion circuit enters a boost mode to further increase the voltage of the DC bus capacitor Cbus.

[0055] It is understandable that after the first stage, the voltage of the DC bus capacitor Cbus has risen to a certain value. At this time, after the DCDC conversion circuit enters the boost mode, the risk of damage to the components in the low-voltage side of the conversion circuit 100 is relatively small.

[0056] As an example, when the buck circuit 200 operates in a buck state until the voltage of the DC bus capacitor Cbus is equal to the target voltage, the DCDC conversion circuit enters a boost mode. The target voltage can be equal to the product of the battery voltage and the turns ratio of the transformer, which can usually be 200V. At this time, the fifth MOS tube M5 and the sixth MOS tube M6 are less than the device rated voltage (usually 100V). In addition, the inductor Lo current is also less than the rated current during forward operation, and there is no risk of overvoltage and overcurrent.

[0057] In some embodiments, in the second stage when the DCDC conversion circuit operates in the reverse pre-charge state, the controller transmits a second switch signal to the seventh MOS transistor M7. The duty cycle of the second switch signal is equal to 100%, so that the seventh MOS transistor M7 is normally closed, and the fifth MOS transistor M5 and the sixth MOS transistor M6 connected to the secondary side of the transformer T1 and the inductor Lo form a boost circuit.

[0058] When the DCDC conversion circuit works in the second stage, the controller transmits the third drive signal and the fourth drive signal to the first switch loop and the second switch loop respectively, and the duty ratios of the third drive signal and the fourth drive signal are both greater than 50%. Among them, the first switch loop refers to the loop where the fifth MOS tube M5 is located, and the second switch loop refers to the loop where the sixth MOS tube M6 is located. Since the duty ratios of the third drive signal and the fourth drive signal are both greater than 50%, the fifth MOS tube M5 and the sixth MOS tube M6 have a certain simultaneous conduction period.

[0059] By controlling the duty cycle of the switch signals of the fifth MOS tube M5 and the sixth MOS tube M6, the DC bus capacitor Cbus is continuously charged so that the voltage of the DC bus capacitor Cbus reaches a specified voltage. The specified voltage is usually equal to the voltage of the power battery. Or slightly less than the voltage of the power battery. Among them, since the fifth MOS tube M5 and the sixth MOS tube M6 have a certain simultaneous conduction period, boosting is achieved. The specific boost control has mature technology, and this embodiment will not be repeated here.

[0060] When the DCDC conversion circuit operates in the forward state, the primary switch circuit of the conversion circuit 100 draws power from the DC bus HVDC+ and HVDC-, and the diode D1 is in reverse cutoff and is actually inoperative. In addition, when the DCDC conversion circuit operates in the forward state, the buck circuit 200 can operate in the boost mode. Among them, the control strategy of the DCDC conversion circuit operating in the forward state has mature technology, and this embodiment will not be repeated here.

[0061] In this embodiment, the secondary-side switch circuit and the inductor Lo form a secondary-side rectifier circuit.

[0062] It can be understood that when the DCDC conversion circuit works in the reverse pre-charge state, the inductor Lo first forms a step-down circuit with the seventh MOS tube M7 and the diode D1, and then forms a boost voltage with the fifth MOS tube M5 and the sixth MOS tube M6. When the DCDC conversion circuit works in the forward state, the inductor Lo forms a half-bridge rectifier circuit with the fifth MOS tube M5 and the sixth MOS tube M6. Therefore, the inductor Lo can be reused for multiple functions, simplifying the circuit structure.

[0063] As an example, assuming that the turns ratio between the primary winding and the secondary winding of the transformer T1 is 15:1, and the voltage of the low-voltage battery is 14V. In the first stage of reverse pre-charging, the duty cycle of the seventh MOS tube M7 can gradually change from 0 to 100%, the voltage of the secondary winding of the transformer T1 gradually rises from 0V to 14V, and the corresponding bus voltage of the primary side of the transformer T1 rises from 0V to 210V; in the second stage, the seventh MOS tube M7 is normally open, the fifth MOS tube M5 and the sixth MOS tube M6 enter the boost mode, the voltage of the secondary winding of the transformer T1 continues to rise from 14V, such as reaching 30V, and the corresponding bus voltage of the primary side of the transformer T1 rises from 210V to 450V.

[0064] Reference Figure 3 , Figure 3 The circuit structure of a DCDC conversion circuit is shown. In this embodiment, the secondary switch circuit and the inductors Lo1 and Lo2 form a current doubler rectifier circuit. The secondary switch circuit includes a half-bridge circuit composed of a fifth MOS tube M5 and a sixth MOS tube M6. The buck circuit 200 includes an inductor Lo1 and an inductor Lo2. Similarly, the inductors Lo1 and Lo2 can form a buck circuit with a diode D1 and a seventh MOS tube M7 to achieve a reverse pre-charge function.

[0065] Reference Figure 4 , Figure 4 The circuit structure of a DCDC conversion circuit is shown. In this embodiment, the secondary switch circuit and the inductor Lo1 form a full-bridge rectifier circuit. The secondary switch circuit includes a full-bridge circuit composed of a fifth MOS tube M5, a sixth MOS tube M6, an eighth MOS tube M8 and a ninth MOS tube M9. The buck circuit 200 includes an inductor Lo1. Similarly, the inductor Lo1 can form a buck circuit with a diode D1 and a seventh MOS tube M7 to realize a reverse pre-charging function.

[0066] In a second aspect, the present application provides a vehicle, including the aforementioned DCDC conversion circuit, wherein the high voltage side of the DCDC conversion circuit is electrically connected to the vehicle high voltage bus, and the low voltage side of the DCDC conversion circuit is electrically connected to the vehicle low voltage battery. The specific structure and principle of the DCDC conversion circuit can refer to the aforementioned embodiment, and this embodiment will not be repeated here.

[0067] According to the vehicle of the present application, when the DCDC conversion circuit is performing reverse pre-charging, the current and voltage of the low-voltage side switch tube of the conversion circuit are low, thereby reducing the risk of overvoltage and overcurrent and ensuring vehicle safety.

[0068] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A DCDC conversion circuit, characterized in that: include: A conversion circuit having a high voltage side and a low voltage side; A step-down circuit, wherein the first end of the step-down circuit is electrically connected to the low-voltage side of the conversion circuit, and the step-down circuit is configured to step down the input voltage connected to the second end of the step-down circuit, and transmit the stepped-down voltage to the low-voltage side of the conversion circuit for voltage conversion.

2. The DCDC conversion circuit according to claim 1, characterized in that: The step-down circuit comprises: an inductor, a first end of the inductor being electrically connected to the low voltage side of the conversion circuit; a first switch element, wherein a first end of the first switch element is electrically connected to a second end of the inductor, and a second end of the first switch element is used to access the input voltage; A second switch element, wherein a first end of the second switch element is electrically connected to a connection node between the inductor and the first switch element, and a second end of the second switch element is electrically connected to a ground node.

3. The DCDC conversion circuit according to claim 2, characterized in that: The second switch element is a diode, a cathode of the diode is electrically connected to a connection node between the inductor and the first switch element, and an anode of the diode is electrically connected to a ground node.

4. The DCDC conversion circuit according to claim 2, characterized in that: The first switch element is a MOS tube, a source of the MOS tube is electrically connected to the second end of the inductor, and a drain of the MOS tube is used to connect to a battery.

5. The DCDC conversion circuit according to claim 4, characterized in that: The DCDC conversion circuit also includes: The controller is electrically connected to the gate of the first switch element and is configured to transmit a first switch signal to the first switch element, wherein the duty cycle of the first switch signal is greater than 0 and less than 100%, so that the buck circuit performs voltage reduction.

6. The DCDC conversion circuit according to claim 5, characterized in that: The controller is further configured to transmit a second switching signal to the first switching element, wherein the duty cycle of the second switching signal is equal to 100%, so that the buck circuit is directly turned on.

7. The DCDC conversion circuit according to claim 6, characterized in that: The conversion circuit includes a transformer and a secondary switching circuit electrically connected to the secondary winding of the transformer; The controller is electrically connected to the secondary switch circuit and is configured to transmit a first drive signal and a second drive signal to a first switch loop and a second switch loop connected in parallel in the secondary switch circuit, respectively, or to transmit a third drive signal and a fourth drive signal to the first switch loop and the second switch loop, respectively; The first driving signal and the second driving signal are complementary, and the duty cycles of the third driving signal and the fourth driving signal are both greater than 50%.

8. The DCDC conversion circuit according to claim 7, characterized in that: The secondary side switch circuit and the inductor form a secondary side rectifier circuit.

9. The DCDC conversion circuit according to claim 8, characterized in that: The secondary side rectifier circuit is a half-bridge rectifier circuit, a current doubler rectifier circuit or a full-bridge rectifier circuit.

10. A vehicle, characterized in that: It comprises a DCDC conversion circuit according to any one of claims 1 to 9, wherein the high voltage side of the DCDC conversion circuit is electrically connected to a vehicle high voltage bus, and the low voltage side of the DCDC conversion circuit is electrically connected to a vehicle low voltage battery.

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