Direct current converter control method

Abstract

The application belongs to the field of automobile electric control, and discloses a DC converter control method. When the DC converter is abnormal, the control unit adjusts the duty cycle instruction input to the DC converter, obtains the adjusted duty cycle instruction, and then controls at least one upper switch tube of the DC converter to be turned on through the adjusted duty cycle instruction, and all lower switch tubes are kept off, so as to keep the energy on both sides of the DC converter to flow bidirectionally. Compared with the existing method of directly turning off the DC converter or directly passing through the upper bridge, the above-mentioned method can control at least one upper switch tube of the DC converter to be turned on through adjusting the duty cycle instruction input to the DC converter, all lower switch tubes are kept off, and the energy on both sides of the DC converter is kept to flow bidirectionally, so that the DC converter can be smoothly switched to the pass-through limp state, thereby ensuring that the electric control system has the limp ability, and avoiding LC oscillation.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic control technology, and in particular to a DC-DC converter control method. Background Technology

[0002] With the continuous expansion of the new energy vehicle market, high power density, low cost, and long driving range are the major trends in automotive development. To improve motor efficiency and driving capability, and to fully utilize battery voltage, a DC-DC converter is added between the power battery and the motor drive inverter in the electronic control system. When the battery voltage is low, the DC-DC converter can stably control the output voltage, keeping the system in optimal operating condition, and the motor can effectively utilize the bus voltage to achieve maximum capacity at any time. When the DC-DC converter experiences a boost failure that prevents closed-loop control of the bus voltage, the controller will generally shut down the DC-DC converter directly or initiate a limp state by directly switching it off. If the DC-DC converter is shut down directly, the bus voltage will become overvoltaged when the electronic control system feeds back energy, causing the electronic control system to malfunction and potentially damaging components. If the DC-DC converter is directly initiated by directly switching it off, a large difference between the battery voltage and the bus voltage will cause LC oscillations in the input capacitor, inductor, and output capacitor, potentially leading to overvoltage in the input or output capacitor, overcurrent in the inductor, or instability in the subsequent electronic control system. Therefore, how to control the DC-DC converter so that the electronic control system has both limp-out capability and avoids LC oscillation has become an urgent problem to be solved.

[0003] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The main objective of this invention is to provide a DC-DC converter control method, which aims to solve the technical problem of controlling a DC-DC converter so that the electronic control system has both limp-out capability and avoids LC oscillation.

[0005] To achieve the above objectives, the present invention provides a DC-DC converter control method, which includes the following steps:

[0006] When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter to obtain an adjusted duty cycle command.

[0007] The adjusted duty cycle command controls at least one upper switch of the DC converter to be turned on while all lower switches remain off, thus maintaining bidirectional energy flow between the two sides of the DC converter.

[0008] Optionally, the step of adjusting the duty cycle command input to the DC converter to obtain an adjusted duty cycle command when the DC converter malfunctions specifically includes:

[0009] When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter through open-loop control of the bus voltage to obtain the adjusted duty cycle command.

[0010] Optionally, the step of adjusting the duty cycle command input to the DC converter through open-loop control of the bus voltage when the DC converter malfunctions, to obtain the adjusted duty cycle command, specifically includes:

[0011] When a DC-DC converter malfunctions, the control unit controls the bus voltage command value of the DC-DC converter to be reduced to the input power supply voltage of the DC-DC converter, so as to adjust the duty cycle command input to the DC-DC converter and obtain the adjusted duty cycle command.

[0012] Optionally, the step of adjusting the duty cycle command input to the DC converter through open-loop control of the bus voltage when the DC converter malfunctions, to obtain the adjusted duty cycle command, specifically includes:

[0013] When a DC-DC converter malfunctions, the control unit controls the bus voltage command value of the DC-DC converter to be reduced to the input power supply voltage of the DC-DC converter by a preset voltage drop gradient, so as to adjust the duty cycle command input to the DC-DC converter and obtain the adjusted duty cycle command.

[0014] Optionally, the step of adjusting the duty cycle command input to the DC converter to obtain an adjusted duty cycle command when the DC converter malfunctions specifically includes:

[0015] When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter through open-loop duty cycle control to obtain the adjusted duty cycle command.

[0016] Optionally, the step of adjusting the duty cycle command input to the DC converter through open-loop duty cycle control when the DC converter malfunctions, to obtain the adjusted duty cycle command, specifically includes:

[0017] When a DC-DC converter malfunctions, the control unit increases the duty cycle in the current duty cycle command input to the DC-DC converter to adjust the duty cycle command input to the DC-DC converter and obtain an adjusted duty cycle command.

[0018] Optionally, the step of adjusting the duty cycle command input to the DC converter through open-loop duty cycle control when the DC converter malfunctions, to obtain the adjusted duty cycle command, specifically includes:

[0019] When a DC-DC converter malfunctions, the control unit controls the current duty cycle in the current duty cycle command input to the DC-DC converter to increase by a preset duty cycle rise gradient, so as to adjust the duty cycle command input to the DC-DC converter and obtain an adjusted duty cycle command.

[0020] Optionally, the step of controlling at least one upper switch of the DC-DC converter to be turned on while all lower switches remain off, thereby maintaining bidirectional energy flow between the two sides of the DC-DC converter, through the adjusted duty cycle command, specifically includes:

[0021] The adjusted duty cycle command is modulated into a PWM signal using a PWM module.

[0022] The PWM signal controls at least one upper switch of the DC-DC converter to be turned on while all lower switches remain off, thus maintaining bidirectional energy flow between the two sides of the DC-DC converter.

[0023] This invention adjusts the duty cycle command input to the DC-DC converter when an anomaly occurs, obtaining an adjusted duty cycle command. This adjusted duty cycle command then controls at least one upper switch of the DC-DC converter to turn on, while all lower switches remain off, maintaining bidirectional energy flow across the DC-DC converter. Compared to existing methods that directly shut down the DC-DC converter or directly enable the upper bridge, this invention, by adjusting the duty cycle command input to the DC-DC converter, controls at least one upper switch to turn on while all lower switches remain off, maintaining bidirectional energy flow across the DC-DC converter. This allows the DC-DC converter to smoothly switch to a limp-through state, thus ensuring both limp-through capability of the control system and avoiding LC oscillation. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the first embodiment of the DC-DC converter control method of the present invention;

[0025] Figure 2 This is a schematic diagram of an electrical control system with a DC-DC converter according to the present invention;

[0026] Figure 3 and Figure 4 This is a schematic diagram of a DC-DC converter according to the present invention;

[0027] Figure 5 This is the control loop for the DC-DC converter of the present invention during normal operation;

[0028] Figure 6 This is a flowchart illustrating the second embodiment of the DC-DC converter control method of the present invention;

[0029] Figure 7 This is a schematic diagram of the open-loop control of the bus voltage of the present invention;

[0030] Figure 8 This is a schematic diagram of the bus voltage variation in the open-loop control of bus voltage according to the present invention.

[0031] Figure 9 This is a flowchart illustrating the third embodiment of the DC-DC converter control method of the present invention;

[0032] Figure 10 This is a schematic diagram of the duty cycle variation in the open-loop duty cycle control of the present invention.

[0033] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] This invention provides a DC-DC converter control method, referring to... Figure 1 , Figure 1 This is a flowchart illustrating the first embodiment of the DC-DC converter control method of the present invention.

[0036] In this embodiment, the DC-DC converter control method includes the following steps:

[0037] Step S10: When the DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC converter to obtain the adjusted duty cycle command;

[0038] It should be noted that the execution subject in this embodiment can be a control unit, such as a CPU or MCU, and this embodiment does not impose any specific restrictions on it.

[0039] It should be understood that, referring to Figure 2 , Figure 2 This is a schematic diagram of an electrical control system with a DC-DC converter according to the present invention. Figure 2 As shown, Ubat is the voltage of battery BAT, C1 is the first capacitor, L1 is the inductor, IL is the current of inductor L1, Q1 is the first switching transistor, Q2 is the second switching transistor, D1 is the first diode, D2 is the second diode, C2 is the second capacitor, Udc is the bus voltage, and MG represents the motor. Figure 3The first capacitor C1, inductor L1, first switch Q1, first diode D1, second switch Q2, second diode D2, and second capacitor C2 constitute a DC-DC converter. Specifically, the first diode D1 is the body diode built into the first switch Q1, and the second diode D2 is the body diode built into the second switch Q2.

[0040] Additionally, refer to Figure 3 and Figure 4 , Figure 3 and Figure 4 This is a schematic diagram of a DC-DC converter according to the present invention. Figure 2 Part of Figure 3 as well as Figure 4 These are schematic diagrams of DC-DC converters. As can be seen from the diagrams... Figure 3 Compare Figure 2 The DC-DC converter has an additional inductor L2 and two switching transistors Q3 and Q4. Figure 4 Also than Figure 2 There are two more switching transistors, Q3 and Q4, and one more capacitor, C3.

[0041] Understandably, a DC-DC converter can boost the voltage of a DC power source (such as a battery, solar cell, or fuel cell) from a low voltage to a high voltage. Then, an inverter converts the DC voltage back to AC voltage to drive the motor.

[0042] In practical implementation, a DC-DC converter malfunction refers to a failure in the DC-DC converter that prevents it from continuing to boost voltage, or a DC-DC converter malfunction that prevents it from continuing to boost voltage. A boost voltage failure can be defined as a fault that prevents the DC-DC converter from performing normal boost voltage control.

[0043] Furthermore, referring to Figure 5 , Figure 5 This is the control loop during normal operation of the DC-DC converter of this invention. For example... Figure 5 As shown, the external voltage loop controls the bus voltage Udc to approach the voltage command Uset, and the internal current loop controls the inductor current IL to approach the current command Iset. Finally, the duty cycle command Dset is generated to control the circuit. Figure 2 The switching status of the first switch Q1 and the second switch Q2 in the circuit. Figure 4 This is the control loop for the DC-DC converter during normal operation. The specific calculation of current command and duty cycle command can be referred to the PID algorithm in the prior art. This embodiment will not elaborate on this further.

[0044] Step S20: Control at least one upper switch of the DC converter to turn on and all lower switches to remain off by means of the adjusted duty cycle command, so as to maintain bidirectional energy flow on both sides of the DC converter.

[0045] Understandably, this embodiment can control at least one upper switch of the DC-DC converter to turn on while keeping all lower switches off via an adjusted duty cycle command. Specifically, Figure 2 Q1 is on and Q2 is off. Figure 3 In this configuration, either Q1 or Q2 is turned on, or both Q1 and Q2 are turned on, while Q3 and Q4 are turned off. Figure 4 In this configuration, either Q1 or Q2 is turned on, or both Q1 and Q2 are turned on, while both Q3 and Q4 are turned off.

[0046] It should be understood that after at least one upper switch of the DC-DC converter is turned on and all lower switches are kept off, energy can flow bidirectionally between the two sides of the DC-DC converter, and the DC-DC converter will smoothly switch from the current operating state to the shoot-through limp state. Smooth switching means switching over a certain period of time, rather than switching immediately.

[0047] In the specific implementation, Figure 2 Taking the DC-DC converter as an example, if the DC-DC converter does not switch smoothly, the DC-DC converter will directly connect to the bridge. When the battery voltage Ubat and the bus voltage Udc differ greatly, the first capacitor C1 (input capacitor), inductor L1, and second capacitor C2 (output capacitor) will experience LC oscillation, which may lead to overvoltage of the input capacitor and output capacitor, overcurrent of the inductor current, or instability of the downstream electronic control system.

[0048] Furthermore, in this embodiment, step S20 includes: modulating the adjusted duty cycle command into a PWM signal through a PWM module; controlling at least one upper switch of the DC converter to be turned on according to the PWM signal, while keeping all lower switches off, so as to maintain bidirectional energy flow between the two sides of the DC converter.

[0049] In the specific implementation, the adjusted duty cycle obtained by software calculation needs to be modulated into a PWM signal by the PWM module. The PWM signal can then directly control the switching state of Q1 and Q2 in the DC converter through the drive circuit, that is, control at least one upper switch of the DC converter to be turned on, while keeping all lower switches off. The PWM module can be software or hardware within the control unit, or it can be an external circuit.

[0050] In this embodiment, when a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter to obtain an adjusted duty cycle command. Then, the adjusted duty cycle command controls at least one upper switch of the DC-DC converter to turn on, while all lower switches remain off, maintaining bidirectional energy flow between the two sides of the DC-DC converter. Compared to existing methods that directly shut down the DC-DC converter or directly enable the upper bridge, this embodiment, by adjusting the duty cycle command input to the DC-DC converter, controls at least one upper switch of the DC-DC converter to turn on while all lower switches remain off, maintaining bidirectional energy flow between the two sides of the DC-DC converter. This allows the DC-DC converter to smoothly switch to a shoot-through limp-out state, thus ensuring both limp-out capability of the electronic control system and avoiding LC oscillation.

[0051] refer to Figure 6 , Figure 6 This is a flowchart illustrating the second embodiment of the DC-DC converter control method of the present invention.

[0052] Based on the first embodiment described above, in this embodiment, step S10 includes:

[0053] Step S101: When the DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC converter through open-loop control of the bus voltage to obtain the adjusted duty cycle command.

[0054] It should be understood that open-loop control of bus voltage refers to open-loop control of the bus voltage Udc of the DC converter.

[0055] Furthermore, in order to achieve open-loop control of the bus voltage, in this embodiment, step S101 includes: when the DC converter malfunctions, the control unit controls the bus voltage command value of the DC converter to be reduced to the input power supply voltage of the DC converter, so as to adjust the duty cycle command input to the DC converter and obtain the adjusted duty cycle command.

[0056] Understandably, the bus voltage open-loop control in this embodiment can be implemented by controlling the bus voltage command value of the open-loop control to decrease from the current bus voltage to the current input power supply voltage, thereby obtaining the duty cycle command of the bus voltage open-loop control output. Ultimately, it is desired that the actual bus voltage value decreases from the initial bus voltage value Udc to the input power supply voltage value Ubat. Furthermore, it is not necessary for the bus voltage value Udc to completely decrease to the power supply voltage value Ubat; it is sufficient to reduce the bus voltage value Udc to a sufficiently low voltage value so that the oscillation generated when switching to upper bridge direct limp-out is sufficiently small. Specifically, the bus voltage Udc can decrease at any decreasing slope, that is, the decreasing trajectory of the bus voltage Udc can be a curve of any shape.

[0057] It should be understood that during the decrease of the bus voltage Udc, the sudden change needs to be small, so small that the input power supply voltage Ubat will not oscillate overvoltage, the inductor current IL will not oscillate overcurrent, and the bus voltage Udc will not oscillate overvoltage. As long as the above conditions are met during the decrease process, the bus voltage Udc can be decreased in any manner.

[0058] In the specific implementation, when the bus voltage Udc of the DC-DC converter drops to the input power supply voltage Ubat of the DC-DC converter, the duty cycle corresponding to the DC-DC converter in the adjusted duty cycle command is 1.

[0059] Furthermore, in order to achieve open-loop control of the bus voltage and make the electrical control system more stable, in this embodiment, step S101 includes: when the DC converter malfunctions, the control unit controls the bus voltage command value of the DC converter to be reduced to the input power supply voltage of the DC converter by a preset voltage drop gradient, so as to adjust the duty cycle command input to the DC converter and obtain the adjusted duty cycle command.

[0060] It should be understood that, reference Figure 7 , Figure 7 This is a schematic diagram of the open-loop control of the bus voltage according to the present invention. Figure 7 In this context, Uset represents the voltage command, Ubat represents the input power supply voltage, and Dset represents the adjusted duty cycle command. In this embodiment, Dset can be obtained by processing Uset and Ubat.

[0061] Understandably, reference Figure 8 , Figure 8 This is a schematic diagram illustrating the bus voltage variation in the open-loop control of bus voltage according to the present invention. Figure 8 As shown, Figure 8 The horizontal axis represents time, and the vertical axis represents voltage.

[0062] In the specific implementation, Figure 8In the equation, t1 is the moment when the DC-DC converter experiences a boost fault, and t2 is the moment when the DC-DC converter's bus voltage Udc equals the DC-DC converter's input power supply voltage Ubat. Figure 8 The bus voltage Udc of the DC-DC converter in the embodiment decreases to the input power supply voltage Ubat of the DC-DC converter according to a preset voltage descent gradient. That is, the bus voltage Udc decreases at a fixed slope, which is a preferred scheme. In this embodiment, the bus voltage Udc cannot immediately decrease to the input power supply voltage Ubat at time t1, but must decrease within a certain period of time, otherwise it will cause LC oscillation in the electronic control system.

[0063] In this embodiment, when a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter via open-loop control of the bus voltage to obtain an adjusted duty cycle command. This adjustment ensures that the first switch Q1 in the DC-DC converter is closed and the second switch Q2 is turned off, maintaining bidirectional energy flow across the DC-DC converter. This allows for a smooth switch to a shoot-through limp-out state, thus guaranteeing the limp-out capability of the control system while preventing LC oscillation.

[0064] refer to Figure 9 , Figure 9 This is a flowchart illustrating the third embodiment of the DC-DC converter control method of the present invention.

[0065] Based on the above embodiments, in this embodiment, step S10 includes:

[0066] Step S101': When the DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC converter through open-loop duty cycle control to obtain the adjusted duty cycle command.

[0067] It should be understood that duty cycle open-loop control refers to controlling the duty cycle command Dset input to the DC-DC converter.

[0068] Furthermore, in order to achieve open-loop duty cycle control, in this embodiment, step S101' includes: when the DC converter malfunctions, the control unit controls the duty cycle in the current duty cycle command input to the DC converter to increase when the DC converter experiences a boost fault, so as to adjust the duty cycle command input to the DC converter and obtain the adjusted duty cycle command.

[0069] It is understood that the duty cycle open-loop control in this embodiment can be implemented by increasing the duty cycle Dpre to 1. The duty cycle Dpre can be increased by any upward slope, that is, the upward trajectory of the duty cycle Dpre can be a curve of any shape.

[0070] Furthermore, in order to achieve open-loop duty cycle control and make the electronic control system more stable, in this embodiment, step S101' includes: when the DC converter malfunctions, the control unit controls the duty cycle in the current duty cycle command input to the DC converter to be increased by a preset duty cycle rise gradient, so as to adjust the duty cycle command input to the DC converter and obtain the adjusted duty cycle command.

[0071] Understandably, reference Figure 10 , Figure 10 This is a schematic diagram illustrating the duty cycle variation in the open-loop duty cycle control of the present invention. Figure 10 As shown, Figure 10 The horizontal axis represents time, and the vertical axis represents the duty cycle.

[0072] In the specific implementation, Figure 10 In the equation, t1 is the moment when the DC-DC converter experiences a boost fault, and t2 is the moment when the duty cycle Dpre is 1. Figure 10 The duty cycle Dpre in the current duty cycle command input to the DC-DC converter increases with a preset duty cycle gradient, that is, the duty cycle Dpre increases with a fixed slope, which is a preferred scheme. In this embodiment, the duty cycle Dpre cannot immediately rise to 1 at time t1, but must rise within a certain period of time, otherwise it will cause LC oscillation in the electronic control system.

[0073] In this embodiment, when a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter through open-loop duty cycle control to obtain an adjusted duty cycle command. By adjusting the duty cycle command input to the DC-DC converter through open-loop control when a malfunction occurs, this embodiment enables the first switch Q1 in the DC-DC converter to close and the second switch Q2 to turn off, maintaining bidirectional energy flow across the DC-DC converter. This allows for a smooth switch to a shoot-through limp-out state, thus ensuring both limp-out capability of the electronic control system and preventing LC oscillation.

[0074] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0075] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0076] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as read-only memory / random access memory, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0077] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A DC-DC converter control method, characterized in that, The DC-DC converter control method includes the following steps: When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter to obtain an adjusted duty cycle command. The adjusted duty cycle command controls at least one upper switch of the DC converter to be turned on, while all lower switches remain off, thus maintaining bidirectional energy flow between the two sides of the DC converter. The step of adjusting the duty cycle command input to the DC converter to obtain the adjusted duty cycle command when the DC converter malfunctions specifically includes: When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter through open-loop control of the bus voltage to obtain the adjusted duty cycle command.

2. The DC-DC converter control method as described in claim 1, characterized in that, The step of adjusting the duty cycle command input to the DC converter through open-loop control of the bus voltage when an abnormality occurs, and obtaining the adjusted duty cycle command, specifically includes: When a DC-DC converter malfunctions, the control unit controls the bus voltage command value of the DC-DC converter to be reduced to the input power supply voltage of the DC-DC converter, so as to adjust the duty cycle command input to the DC-DC converter and obtain the adjusted duty cycle command.

3. The DC-DC converter control method as described in claim 1, characterized in that, The step of adjusting the duty cycle command input to the DC converter through open-loop control of the bus voltage when an abnormality occurs, and obtaining the adjusted duty cycle command, specifically includes: When a DC-DC converter malfunctions, the control unit controls the bus voltage command value of the DC-DC converter to be reduced to the input power supply voltage of the DC-DC converter by a preset voltage drop gradient, so as to adjust the duty cycle command input to the DC-DC converter and obtain the adjusted duty cycle command.

4. A DC-DC converter control method, characterized in that, The DC-DC converter control method includes the following steps: When a DC-DC converter malfunctions, the control unit adjusts the duty cycle command input to the DC-DC converter through open-loop duty cycle control to obtain the adjusted duty cycle command. The adjusted duty cycle command controls at least one upper switch of the DC converter to be turned on while all lower switches remain off, thus maintaining bidirectional energy flow between the two sides of the DC converter.

5. The DC-DC converter control method as described in claim 4, characterized in that, The step of adjusting the duty cycle command input to the DC converter through open-loop duty cycle control when the DC converter malfunctions, and obtaining the adjusted duty cycle command, specifically includes: When a DC-DC converter malfunctions, the control unit increases the duty cycle in the current duty cycle command input to the DC-DC converter to adjust the duty cycle command input to the DC-DC converter and obtain an adjusted duty cycle command.

6. The DC-DC converter control method as described in claim 4, characterized in that, The step of adjusting the duty cycle command input to the DC converter through open-loop duty cycle control when the DC converter malfunctions, and obtaining the adjusted duty cycle command, specifically includes: When a DC-DC converter malfunctions, the control unit controls the current duty cycle in the current duty cycle command input to the DC-DC converter to increase by a preset duty cycle rise gradient, so as to adjust the duty cycle command input to the DC-DC converter and obtain an adjusted duty cycle command.

7. The DC-DC converter control method according to any one of claims 1 to 6, characterized in that, The step of controlling at least one upper switch of the DC-DC converter to be turned on while all lower switches remain off, thereby maintaining bidirectional energy flow between the two sides of the DC-DC converter, specifically includes: The adjusted duty cycle command is modulated into a PWM signal using a PWM module. The PWM signal controls at least one upper switch of the DC-DC converter to be turned on while all lower switches remain off, thus maintaining bidirectional energy flow between the two sides of the DC-DC converter.

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