Soft switching control method and Buck converter

Abstract

The invention discloses a soft switching control method and a Buck converter. The method comprises the following steps: respectively calculating the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in a first mode, the real-time state of a switching tube stray capacitor C1 and the real-time state of a follow current switching stray capacitor C2; generating a control signal according to the duration of each mode and the current corresponding to the energy storage inductor; monitoring a current iLr corresponding to the energy storage inductor; when it is monitored that the current iLr corresponding to the energy storage inductor reaches a first current value In1, the Buck converter is controlled to be switched from the first mode to other modes in sequence according to the control signal, so that soft switching control over the Buck converter is achieved. According to the invention, a wider zero-voltage turn-on range can be provided, so that the adaptability and the stability of the system are improved; and the MCU sampling rate limitation can be broken through, so that the input signal can be responded and processed more quickly, and the real-time performance and the accuracy of the system are improved.

Description

Technical Field

[0001] This application relates to the technical field of inverter control, and particularly to a soft-switching control method and a Buck converter. Background Art

[0002] Due to its advantages such as simple structure, low cost, and easy control, the Buck circuit is widely used in photovoltaic power generation, hybrid vehicles, and energy storage systems. To meet the design requirements of high power, high efficiency, and small volume, increasing the switching frequency is a direct method. However, high-frequency operation will bring greater switching losses and electromagnetic interference problems. Soft-switching technology improves the feasibility of high-frequency operation by reducing switching losses and electromagnetic interference. Traditional soft-switching uses an auxiliary network to achieve zero-voltage or zero-current switching, but it increases circuit complexity, volume, and cost. Soft-switching technology without an auxiliary network has become a research hotspot. Among them, TCM (Transition Conduction Mode, continuous conduction mode) control is a common method, and soft-switching is achieved through the resonance of the inductor reverse current.

[0003] However, the existing converters based on TCM control have problems such as limited zero-voltage turn-on range and difficulty in breaking through the existing MCU sampling rate limit for the switching frequency. Summary of the Invention

[0004] An object of an embodiment of this application is to provide a soft-switching control method and a Buck converter to solve the technical problems that the current soft-switching control strategy has a limited zero-voltage turn-on range and difficulty in breaking through the existing MCU sampling rate limit for the switching frequency.

[0005] To solve the above technical problems, a technical solution adopted in an embodiment of this application is: to provide a soft-switching control method applied to a Buck converter. The Buck converter includes an input circuit module, a main power switch module, an energy storage and transmission module, a freewheeling loop module, and an output filtering module. The input circuit module includes an input power supply. The main power switch module includes a power switch tube Q 1 , a parasitic capacitance C of the switch tube 1 and a body diode D 1 . The energy storage and transmission module includes a storage inductor. The freewheeling loop module includes a freewheeling switch tube Q 2 , a parasitic capacitance C of the freewheeling switch 2 and a freewheeling body diode D 2 . The output filtering module includes a storage filtering capacitor EC 2 and a load resistor R L . The positive pole of the input power supply is connected to the drain of the power switch tube Q 1 . One end of the storage inductor is connected to the power switch tube Q 1between the source electrode of 2 and the drain electrode of the freewheeling switching transistor Q 2 , the other end of the energy storage inductor is connected to the source electrode of the freewheeling switching transistor Q through the output filtering module 2 , the energy storage filtering capacitor EC L and the load resistor R 1 are connected in parallel to smooth the output voltage and supply it to the load. The Buck converter further includes a control module, and the control module is used to connect the power switching transistor Q 2 and the freewheeling switching transistor Q 1 to the gate electrodes. The method includes: the control module calculates the duration of each mode and the current corresponding to the energy storage inductor respectively according to the state of the current of the energy storage inductor, the real-time state of the parasitic capacitance C 2 of the switching transistor and the real-time state of the parasitic capacitance C 1 of the freewheeling switching transistor in the first mode. Wherein, in the first mode, the power switching transistor Q 2 and the freewheeling switching transistor Q Lr are in the initialization state; generate a control signal according to the duration of each mode and the current corresponding to the energy storage inductor; monitor the current i Lr corresponding to the energy storage inductor; when it is monitored that the current i n1 corresponding to the energy storage inductor reaches a preset first current value I n1 , the control module controls the Buck converter to sequentially switch from the first mode to other modes according to the control signal to realize the soft switching control of the Buck converter; wherein, the first current value I 1 satisfies a first preset condition, and the first preset condition is set according to the input voltage corresponding to the input power supply, the parasitic capacitance C

[0006] of the switching transistor and the energy storage inductor. n1 Optionally, the first current value I 1 satisfies a first preset condition, and the first preset condition is set according to the input voltage corresponding to the input power supply, the parasitic capacitance C

[0007]

[0008] including: determining the first preset condition according to the following formula, and the formula is: in where V oss is the input voltage corresponding to the input power supply, C 1 is the capacitance value of the parasitic capacitance C r of the switching transistor, and L

[0009] Optionally, the start time of the first mode is t 0 , and the end time is t 1 . In the first mode, the switching period control of the power switch tube Q 1 and the freewheeling switch tube Q 2 includes: at time t 0 , i Lr decreases to zero, and the terminal voltage V 2 of the output energy storage filter capacitor EC 0 charges the energy storage inductor reversely, and i Lr starts to increase linearly in the negative direction. At time t 1 , when i Lr increases negatively to a preset first current value I n1 , the freewheeling switch tube Q 2 is turned off.

[0010] Optionally, in the first mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor, the real-time state of the parasitic capacitance C 1 of the switch tube, and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including: calculating the current i Lr (t) corresponding to the energy storage inductor of the first mode according to the following formula (1), and calculating the duration Δt 1 of the first mode according to the following formula (2);

[0011] The formula (1) is:

[0012]

[0013] The formula (2) is:

[0014]

[0015] where L r is the inductance value corresponding to the energy storage inductor.

[0016] Optionally, the other modes include the second mode, the third mode, the fourth mode, the fifth mode, the sixth mode, the seventh mode, and the eighth mode. In each of the other modes, the switching period control of the power switch tube Q 1 and the freewheeling switch tube Q 2 includes: the start time of the second mode is t 1 , and the end time is t 2 . After time t 1 , the inductor L r is connected to the parasitic capacitance C 1 of the switch tube and the parasitic capacitance C 2Start resonating, the current i of the energy storage inductor Lr Continues to increase negatively, the parasitic capacitance C 1 The voltage of starts to decrease positively from V in The voltage of the freewheeling switch parasitic capacitance C 2 Starts to increase positively from zero, the voltage of the freewheeling switch parasitic capacitance C 2 The voltage of increases positively to V pm The current i of the energy storage inductor Lr Increases negatively to I n2 The second mode ends; the start time of the third mode is t 2 The end time is t 3 t 2 After the moment, V pm And the voltage V on the energy storage and filtering capacitor EC 2 The difference charges the inductor L 0 Positively, the freewheeling switch parasitic capacitance C r Discharges, the terminal voltage of the switch parasitic capacitance C 2 Is clamped to negative V 1 By the body diode D 1 At the moment of t F The current i of the energy storage inductor 3 Decreases to equal I Lr The third mode ends; the start time of the fourth mode is t n1 The end time is t 3 At the moment of t 4 The terminal voltage of the switch parasitic capacitance C 3 Is clamped to negative V 1 By the body diode D 1 At the moment of t F The input voltage V in And the output voltage V 0 The difference charges the inductor L r Positively, the current i of the energy storage inductor Lr Continues to decrease linearly negatively, at the moment of t 4 The current i of the energy storage inductor Lr Decreases to zero, the fourth mode ends; the start time of the fifth mode is t 4 The end time is t 5 At the moment after t 4 The input voltage V in And the output voltage V 0 The difference continues to charge the inductor L r Positively, the current i of the energy storage inductor Lr Starts to increase linearly positively from zero, at the moment of t 5 The current i of the energy storage inductor Lr Increases to the positive maximum value I pm, the fifth mode ends; the start time of the sixth mode is t 5 , the end time is t 6 , at t 5 , turn off the power switch Q 1 , L r and the parasitic capacitance C of the switch 1 , the parasitic capacitance C of the freewheeling switch 2 start to resonate, and the parasitic capacitance C of the switch 1 is charged, and its terminal voltage u C1 gradually increases from zero, and the parasitic capacitance C of the freewheeling switch 2 discharges, and its terminal voltage u C2 gradually decreases from V in , at t 6 , u C1 increases to V pm , u C2 decreases to equal negative V F , the sixth mode ends; the start time of the seventh mode is t 6 , the end time is t 7 , t 6 , after time t Lr , the current i of the energy storage inductor 2 forms a freewheeling loop through the body diode D 7 , to supply power to the load, at t 2 , turn on the freewheeling switch Q 7 , the seventh mode ends; the start time of the eighth mode is t 8 , the end time is t 7 , after time t Lr , the current i of the energy storage inductor 2 forms a freewheeling loop through the freewheeling switch Q Lr to supply power to the load, and the current i of the energy storage inductor 8 continues to decrease linearly in the positive direction, at t Lr , i

[0017] Optionally, in the second mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C of the switch 1 and the real-time state of the parasitic capacitance C of the freewheeling switch 2 , including:

[0018] Calculate the current i Lr (t) corresponding to the energy storage inductor in the second mode according to the following formula (3), and calculate the duration Δt of the second mode according to the following formula (4) 2 ;

[0019] The formula (3) is as follows:

[0020]

[0021] The formula (4) is as follows:

[0022]

[0023] Wherein,

[0024] Optionally, in the third mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C 1 of the switching tube and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including:

[0025] Calculate the current i Lr (t) corresponding to the energy storage inductor in the third mode according to the following formula (5), and calculate the duration Δt of the third mode according to the following formula (6) 3 ;

[0026] The formula (5) is as follows:

[0027]

[0028] The formula (6) is as follows:

[0029]

[0030] Optionally, in the fourth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode r , the real-time state of the parasitic capacitance C 1 of the switching tube and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including:

[0031] Calculate the current i Lr (t) corresponding to the energy storage inductor in the fourth mode according to the following formula (7), and calculate the duration Δt of the fourth mode according to the following formula (8) 4 ;

[0032] The formula (7) is as follows:

[0033]

[0034] The formula (8) is as follows:

[0035]

[0036] Optionally, in the fifth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C 1 of the switching transistor and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including:

[0037] Calculate the current i Lr (t) corresponding to the energy storage inductor in the fifth mode according to the following formula (9), and calculate the duration Δt 5 ;

[0038] The formula (9) is:

[0039]

[0040] The formula (10) is:

[0041]

[0042] Optionally, in the sixth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode r , the real-time state of the parasitic capacitance C 1 of the switching transistor and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including:

[0043] Calculate the current i Lr (t) corresponding to the energy storage inductor in the sixth mode according to the following formula (11), and calculate the duration Δt 6 ;

[0044] The formula (11) is:

[0045]

[0046] The formula (12) is:

[0047]

[0048] Optionally, in the seventh mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C 1 of the switching transistor and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including:

[0049] Calculate the current i corresponding to the energy storage inductor of the seventh mode according to the following formula (13), and calculate the duration Δt of the seventh mode according to the following formula (14). Lr (t), and calculate the duration Δt of the seventh mode according to the following formula (14). 7 ;

[0050] The formula (13) is as follows:

[0051]

[0052] The formula (14) is as follows:

[0053] Δt 7 = t 7 - t 6 = nΔt 6 ;

[0054] Wherein,

[0055] Optionally, in the eighth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C of the switching transistor 1 and the real-time state of the parasitic capacitance C of the freewheeling switch, including: 2 Calculate the current i corresponding to the energy storage inductor of the eighth mode according to the following formula (15), and calculate the duration Δt of the eighth mode according to the following formula (16).

[0056] Calculate the current i corresponding to the energy storage inductor of the eighth mode according to the following formula (15). Lr (t), and calculate the duration Δt of the eighth mode according to the following formula (16). 8 ;

[0057] The formula (15) is as follows:

[0058]

[0059] The formula (16) is as follows:

[0060]

[0061] Wherein,

[0062] To solve the above technical problems, a technical solution adopted in the embodiments of the present application is: to provide a Buck converter, the Buck converter includes an input circuit module, a main power switch module, an energy storage and transmission module, a freewheeling circuit module, and an output filter module. The input circuit module includes an input power supply, and the main power switch module includes a power switching transistor Q 1 , the parasitic capacitance C of the switching transistor 1 and the body diode D1 , the energy storage and transmission module includes an energy storage inductor, and the freewheeling loop module includes a freewheeling switch tube Q 2 , a freewheeling switch parasitic capacitor C 2 and a freewheeling body diode D 2 , the output filtering module includes an energy storage filtering capacitor EC 2 and a load resistor R L , the positive pole of the input power supply is connected to the drain of the power switch tube Q 1 , one end of the energy storage inductor is connected between the source of the power switch tube Q 1 and the drain of the freewheeling switch tube Q 2 , the other end of the energy storage inductor is connected to the source of the freewheeling switch tube Q 2 through the output filtering module, the energy storage filtering capacitor EC 2 and the load resistor R L are in parallel, used to smooth the output voltage and supply it to the load. The Buck converter further includes a control module, and the control module is used to connect the power switch tube Q 1 and the gate of the freewheeling switch tube Q 2 . The control module is used to: calculate the duration of each mode and the current corresponding to the energy storage inductor respectively according to the state of the current of the energy storage inductor, the real-time state of the switch tube parasitic capacitor C 1 and the real-time state of the freewheeling switch parasitic capacitor C 2 in the first mode. Wherein, in the first mode, the power switch tube Q 1 and the freewheeling switch tube Q 2 are in the initialization state; generate a control signal according to the duration of each mode and the current corresponding to the energy storage inductor; monitor the current i Lr corresponding to the energy storage inductor; when it is monitored that the current i Lr corresponding to the energy storage inductor reaches a preset first current value I n1 , control the Buck converter to sequentially switch from the first mode to other modes according to the control signal to realize the soft-switching control of the Buck converter; wherein, the first current value I n1 satisfies a first preset condition, and the first preset condition is set according to the input voltage corresponding to the input power supply, the switch tube parasitic capacitor C 1 and the energy storage inductor.

[0063] For the soft-switching control method and Buck converter provided by the embodiments of the present application, the control module can, according to the state of the current of the energy storage inductor in the first mode and the parasitic capacitors C 1 of the switch tube and the freewheeling switch parasitic capacitor C 2characteristics, dynamically adjust the switching mode to optimize the switching process and ensure switching operation near zero voltage. Additionally, based on the real-time state of current i Lr and the parasitic capacitance, the control module can accurately calculate the duration of each mode. This precise timing control can optimize the switching process and reduce switching losses; according to the calculated duration and current value of each mode, the control module generates corresponding control signals, which are used to precisely control the switching behavior of the power switch and the freewheeling switch, ensuring turn-on under zero voltage conditions and reducing switching losses; moreover, the set first current value meets specific preset conditions, which are set based on the voltage of the input power supply, parasitic capacitance, and energy storage inductor, enabling the system to maintain soft-switching operation under different input conditions. This adaptability allows the Buck converter to break through the sampling rate limitations of traditional MCUs, operate stably in a wider working environment, achieve a higher switching frequency, and thus the system can respond and process input signals faster, improving the real-time performance and accuracy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0065] Figure 1 is the circuit diagram of a Buck converter provided by an embodiment of the present application;

[0066] Figure 2 is the flowchart of a soft-switching control method provided by an embodiment of the present application;

[0067] Figure 3 is the working waveform diagram corresponding to the Buck converter executing the soft-switching control method provided by an embodiment of the present application;

[0068] Figures 4a to 4h are respectively the schematic diagrams of the circuit modes corresponding to the operation of eight modes (i.e., the first mode to the eighth mode) provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] In order to make the objectives, technical solutions, and advantages of the present application clearer, the following further details the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0070] It should be noted that if there is no conflict, the various features in the embodiments of the present application can be combined with each other, and all are within the protection scope of the present application. In addition, although the functional modules are divided in the device schematic diagram and the logical sequence is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the module division in the device or the flowchart. Furthermore, the terms "first", "second", "third", etc. adopted in the present application do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects.

[0071] Due to its simple structure, low cost, easy control and high reliability, the Buck circuit topology has become the most commonly used topology in non-isolated DC / DC buck converters and is widely used in fields such as photovoltaic power generation, hybrid vehicles and energy storage systems. To meet the requirements of engineering applications for high power, high efficiency, high integration, small size and light weight, increasing the switching frequency is the most direct method. However, a higher switching frequency also brings greater switching losses and more serious electromagnetic interference problems.

[0072] For this reason, soft-switching technology has emerged, which can effectively reduce switching losses and electromagnetic interference while increasing the switching frequency. Traditional soft-switching technology usually realizes zero-voltage or zero-current switching of high-frequency switching tubes by introducing an auxiliary network. Although this method improves the switching performance, the additional auxiliary network circuit also brings some problems, such as increasing the complexity, cost and volume of the circuit. Therefore, soft-switching technology without an auxiliary network has gradually become a research hotspot, and with the advantages of low cost, small size, high stability and easy implementation, it has become an important direction for the development of soft-switching technology.

[0073] In soft-switching technology without an auxiliary network, BCM (Boundary Conduction Mode) control and TCM (Transition Conduction Mode) control are the most commonly used implementation methods. This method controls the reverse current of the inductor to make the inductor resonate with the parasitic capacitance of the switching tube, thereby realizing soft-switching actions and reducing switching losses. Currently, Buck converters using BCM or TCM control usually adopt a variable-frequency control strategy, that is: operating at a high switching frequency under light load to optimize the soft-switching effect; operating at a low switching frequency under heavy load to reduce losses and stress.

[0074] Although the Buck converter based on BCM or TCM control can achieve soft-switching within a certain range, there are still some problems in its actual application, mainly including the problem that zero-voltage turn-on is difficult to cover the full range and the switching frequency is limited.

[0075] Among them, for a Buck converter adopting the traditional BCM control strategy, due to the large output parasitic capacitance of the high-power MOS tube, it is difficult for the Buck tube to achieve zero-voltage turn-on within the full voltage and full power range in the scenarios of wide input voltage and wide power variation; especially under high-frequency operating conditions, the charging and discharging time of the parasitic capacitance is insufficient, resulting in the switch tube being unable to maintain zero-voltage turn-on, increasing the switching loss and electromagnetic interference.

[0076] Among them, for a Buck converter adopting the TCM control strategy, in order to achieve variable-frequency control, it usually relies on the sampling rate of the MCU to achieve peak current detection. However, limited by the processing power of the existing MCU, the sampling rate is difficult to support high-frequency (such as exceeding 150 kHz) operation, which restricts the increase of the switching frequency, thus affecting the soft-switching performance and variable-frequency range of the converter under wide voltage input conditions and making it difficult to meet the engineering requirements for high-efficiency and high-frequency operation.

[0077] Therefore, the current soft-switching control strategy has problems of limited zero-voltage turn-on range and difficulty in breaking through the sampling rate limitation of the existing MCU for the switching frequency.

[0078] To solve the above problems, the embodiment of the present application provides a soft-switching control method. This method divides the PWM period into multiple precisely controlled modes, and through the real-time detection and control of the inductor current and voltage states, realizes the seamless connection of each mode; through the resonance process between modes, completes the natural charging and discharging of the parasitic capacitance of the switch tube, thereby realizing zero-voltage switching.

[0079] This method can accurately adjust the duration and current of each working mode according to dynamic parameters such as the input voltage and parasitic capacitance by monitoring the current i corresponding to the energy storage inductor Lr and calculating the duration and current in the mode, ensuring that zero-voltage switching can be achieved even within a wide input voltage and output power range, thus overcoming the limitations of the traditional control strategy.

[0080] By pre-calculating the duration of each mode and the inductor current, and using these pre-calculation results to generate control signals, it no longer depends on the real-time sampling of the MCU, avoiding the problem that high-frequency soft-switching control cannot be achieved due to the sampling rate limitation.

[0081] The control module can also calculate the duration of each mode according to the state of the real-time current and parasitic capacitance, and switch the working modes in sequence, which provides an accurate switching control signal for the Buck converter, ensuring its efficient operation and improving the overall control accuracy.

[0082] Therefore, this soft-switching control method realizes high-frequency, wide-range, and high-efficiency soft-switching control as a whole, breaks through the limitations of the traditional method, and can meet the application requirements of higher frequency and higher efficiency.

[0083] The soft-switching control method provided by the embodiments of the present application will be described below through specific embodiments.

[0084] See Figure 1 , Figure 1 is the circuit diagram of a Buck converter provided by the embodiments of the present application. The Buck converter includes an input circuit module, a main power switch module, an energy storage and transmission module, a freewheeling loop module, and an output filtering module. Among them, the input circuit module includes an input power supply V in , the main power switch module includes a power switch tube Q 1 , the parasitic capacitance C of the switch tube 1 , and the body diode D 1 , the energy storage and transmission module includes an energy storage inductor L r , the freewheeling loop module includes a freewheeling switch tube Q 2 , the parasitic capacitance C of the freewheeling switch 2 , and the freewheeling body diode D 2 , the output filtering module includes an energy storage filtering capacitor EC 2 , and a load resistor R L . Among them, the positive pole of the input power supply V in is connected to the drain of the power switch tube Q 1 , one end of the energy storage inductor L r is connected between the source of the power switch tube Q 1 and the drain of the freewheeling switch tube Q 2 , the other end of the energy storage inductor L r is connected to the source of the freewheeling switch tube Q 2 through the output filtering module, and the energy storage filtering capacitor EC 2 and the load resistor R L are connected in parallel to smooth the output voltage and supply it to the load. Among them, Figure 1 The arrow direction in is the reference positive direction of the physical quantity.

[0085] This Buck converter is a step-down DC-DC converter, and its working principle is based on the characteristics of energy storage and release of the inductor. Its working process mainly includes the following stages: First, the switch-on stage. When the power switch tube Q 1 is turned on, the voltage of the input power supply is applied to the energy storage inductor through Q 1 , and the energy storage inductor L r starts to charge and store energy, and the current gradually increases. At the same time, the energy storage filtering capacitor EC 2 will supply power to the load resistor R L . Then, the switch-off stage. When Q 1 is turned off, the current in the energy storage inductor L r does not immediately interrupt, forming a freewheeling current; the freewheeling switch tube Q 2Conduct, and the current of the energy storage inductor L r flows through Q 2 to the output filter module; the energy storage inductor releases the stored energy and continues to supply power to the load. Finally, in the output smoothing stage, the energy storage filter capacitor EC 2 smooths the output voltage to reduce fluctuations and enables the load to obtain a stable voltage.

[0086] In the embodiment of the present application, the Buck converter further includes a control module, which is used to connect the power switch Q 1 and the freewheeling switch Q 2 to their gates. The control module realizes precise regulation of the states of the power switch Q 1 and the freewheeling switch Q 2 , ensuring that the energy conversion process is more efficient and stable. The control module is used to execute the soft-switching control method of the embodiment of the present application. This method divides each PWM cycle into multiple precisely controlled modes. Through real-time detection of the current and voltage states of the energy storage inductor and the resonance process between the modes, natural charging and discharging of the parasitic capacitance of the switch tube are achieved, thereby achieving the effect of zero-voltage switching.

[0087] Specifically, referring to Figure 2 , Figure 2 is a flowchart of a soft-switching control method provided by the embodiment of the present application.

[0088] S11. The control module calculates the duration of each mode and the current corresponding to the energy storage inductor respectively according to the current state of the energy storage inductor, the real-time state of the parasitic capacitance C 1 of the switch tube, and the real-time state of the parasitic capacitance C 2 of the freewheeling switch. Among them, in the first mode, the states of the power switch Q 1 and the freewheeling switch Q 2 are in the initialization state.

[0089] S12. Generate a control signal according to the duration of each mode and the current corresponding to the energy storage inductor.

[0090] S13. Monitor the current i Lr corresponding to the energy storage inductor.

[0091] S14. When it is monitored that the current i Lr corresponding to the energy storage inductor reaches the preset first current value I n1 , the control module controls the Buck converter to sequentially switch from the first mode to other modes according to the control signal to realize the soft-switching control of the Buck converter; among them, the first current value I n1 satisfies the first preset condition, and the first preset condition is based on the input voltage corresponding to the input power supply, the parasitic capacitance C 1Set the energy storage inductor.

[0092] See Figure 3 , the first mode is from t 0 - t 1 moment. The start moment of the first mode is t 0 , and the end moment is t 1 . In the first mode, the switching period control of the power switch tube Q 1 and the freewheeling switch tube Q 2 includes: at t 0 moment, i Lr decreases to zero, and the terminal voltage V 2 of the output energy storage filter capacitor EC 0 charges the energy storage inductor reversely, and i Lr starts to increase linearly in the negative direction. At t 1 moment, i Lr increases negatively to the preset first current value I n1 , then turn off the freewheeling switch tube Q 2 , and the first mode is completed. Among them, before t 0 moment, the power switch tube Q 1 is in the off state, the freewheeling switch tube Q 2 is in the on state, the freewheeling switch tube Q 2 provides a freewheeling path for the energy storage inductor, and the current i Lr corresponding to the energy storage inductor decreases linearly in the positive direction.

[0093] This first mode realizes the release and reverse energy storage of the energy storage inductor, providing a basis for energy conversion in subsequent modes.

[0094] The above step S13 monitors the current i Lr corresponding to the energy storage inductor, and the purpose is to obtain the current value of i Lr for triggering mode switching or judging whether the control conditions are met. This monitoring process is real-time and runs through the entire control process.

[0095] The above steps S11 and S12 can be pre-calculated and generated parts. According to the state of the current of the energy storage inductor in the first mode and the real-time states of the parasitic capacitors C 1 and C 2 , the control module can calculate the duration of each mode and the current of the energy storage inductor in each mode. The current of the energy storage inductor in each mode changes dynamically with time. According to the control logic of the inverter, the duration of the mode and the current determine the switching timing and energy transfer efficiency. These calculations can be completed through preset parameters before the system runs and adjusted dynamically during operation. Based on the calculation results of step S11, specific control signals are generated to drive the power switch tube Q 1 and the freewheeling switch tube Q2 The above-mentioned step S11 can be completed during system initialization as initialization data, and step S12 can be performed during real-time application to adapt to the dynamic changes of the circuit state.

[0096] Among them, in the first mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor, the real-time state of the parasitic capacitance C of the switching transistor, and the real-time state of the parasitic capacitance C of the freewheeling switch, including: 1 of the switching transistor and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, respectively calculating the duration of each mode and the current corresponding to the energy storage inductor, including:

[0097] Calculating the current i Lr (t) corresponding to the energy storage inductor in the first mode according to the following formula (1), and calculating the duration Δt of the first mode according to the following formula (2) 1 ;

[0098] Formula (1) is:

[0099]

[0100] Formula (2) is:

[0101]

[0102] Among them, L r is the inductance value corresponding to the energy storage inductor. I n1 is the current value corresponding to the energy storage inductor, which satisfies the first preset condition. The first preset condition can be determined according to the following formula, and the formula is:

[0103]

[0104] Among them, V in is the input voltage corresponding to the input power supply, C oss is the capacitance value of the parasitic capacitance C of the switching transistor, L 1 of the switching transistor, and L r is the inductance value corresponding to the energy storage inductor.

[0105] When the current of the energy storage inductor is the above I n1 , mode switching is performed. The above conditions are imposed on I n1 to ensure that the voltage or current on the parasitic capacitance reaches an appropriate level, thereby reducing switching losses and electromagnetic interference. I n1 is related to the input voltage V inIt is directly related to parasitic parameters. Such a setting ensures that the system can dynamically adapt to changes in the input power supply and circuit parameters, avoiding the operating state deviating from the design target. Moreover, the current condition limitation ensures that the circuit state meets the design requirements during mode switching, avoiding system oscillation or instability caused by discontinuous changes in current or voltage. And the preset condition of the current is based on the system design parameters and can dynamically adapt to load changes, thereby improving the stability of the system in different working environments. Therefore, the setting of the above first preset condition reduces switching losses, reduces overshoot and harmonic interference, improves system reliability, and achieves smooth operation in a dynamic environment.

[0106] See Figure 4a , Figure 4a is the equivalent circuit corresponding to the above first mode, where the arrow indicates the actual direction of the current during the operation of the inverter. In addition to the above first mode, the embodiments of the present application also provide other modes, and the other modes include a second mode, a third mode, a fourth mode, a fifth mode, a sixth mode, a seventh mode, and an eighth mode, corresponding respectively Figures 4b to 4h , where the arrow indicates the actual direction of the current during the operation of the inverter.

[0107] See Figure 3 and Figure 4b , the second mode is at t 1 -t 2 moment, the start time of the second mode is t 1 , and the end time is t 2 , after the t 1 moment, the inductor L r and the parasitic capacitance C 1 of the switching tube, and the parasitic capacitance C 2 of the freewheeling switch start to resonate. The current i Lr of the energy storage inductor continues to increase negatively. The voltage of the parasitic capacitance C 1 starts to decrease positively from V in . The voltage of the parasitic capacitance C 2 of the freewheeling switch starts to increase positively from zero. The voltage of the parasitic capacitance C 2 of the freewheeling switch increases positively to V pm . The current i Lr of the energy storage inductor increases negatively to I n2 , and the second mode ends. In the second mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor respectively according to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitance C 1 of the switching tube, and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including: calculating the current i Lr (t) corresponding to the energy storage inductor in the second mode according to the following formula (3), and calculating the duration Δt of the second mode according to the following formula2 。

[0108] Formula (3) is:

[0109]

[0110] Formula (4) is:

[0111]

[0112] Wherein,

[0113] Wherein, at time t 2 , the negative current of the energy storage inductor is I n2 , and its corresponding calculation formula is:

[0114]

[0115] At time t 2 , the maximum positive voltage of u c2 is V pm , which is: V pm = V in + V F . Wherein, V F is very small and can be ignored.

[0116] Wherein, the duration of t 1 - t 2 is mainly determined by the driving power switch tube Q 1 and the conduction voltage of its corresponding body diode. The voltage on the parasitic capacitance of the driving power switch tube Q 1 is -V F . At this time, the body diode of the driving power switch tube Q 1 conducts, and V F is the voltage required for the body diode to conduct.

[0117] Wherein, in the second mode, the voltages of C 1 and C 2 are calculated according to the following formula:

[0118]

[0119] The above-mentioned second mode completes the resonance of the energy storage inductor, the parasitic capacitance C 1 of the switch tube, and the parasitic capacitance C 2 of the freewheeling switch, and realizes the energy storage inductor current and the parasitic capacitance voltages u C1 , u C2The adjustment lays the foundation for the smooth switching of subsequent modes and soft-switching control. In this second mode, zero-voltage switching is achieved, reducing the switching loss; the second mode utilizes the resonance mechanism to efficiently transfer energy between the energy storage inductor and the parasitic capacitance, reducing the waste of inductor energy and maximizing the energy utilization rate; during the mode switching process, the resonance is used to achieve the smooth change of current and voltage, avoiding the impact of high voltage and high current on the devices.

[0120] See Figure 3 and Figure 4c For the third mode, at time t 2 −t 3 The start time of the third mode is t 2 and the end time is t 3 t 2 After time t 2 the voltage V pm at the terminal of the freewheeling switch parasitic capacitance C 2 minus the voltage V 0 on the energy storage and filtering capacitance EC r charges the inductor L 2 forward, the freewheeling switch parasitic capacitance C 1 discharges, and the voltage at the terminal of the switch parasitic capacitance C 1 is clamped to negative V F At time t 3 the current i Lr of the energy storage inductor decreases to equal I n1 and the third mode ends.

[0121] In the third mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor described in the first mode, the real-time state of the switch parasitic capacitance C 1 and the real-time state of the freewheeling switch parasitic capacitance C 2 , including: calculating the current i Lr (t) corresponding to the energy storage inductor in the third mode according to the following formula (5), and calculating the duration Δt 3 of the third mode according to the following formula (6);

[0122] Formula (5) is:

[0123]

[0124] Formula (6) is:

[0125]

[0126] In the third mode, through the discharge of the freewheeling switch parasitic capacitance C 2 and the forward charging of the energy storage inductor, the inductor current i is gradually adjustedLr And the related voltage provide support for subsequent operations and the stable operation of the system. Through this third mode, through the energy transfer and clamping of the energy storage inductor and parasitic capacitance, an ideal current and voltage state are established for subsequent operations, while achieving efficient soft-switching control.

[0127] See Figure 3 and Figure 4d , the fourth mode is from t 3 –t 4 moment. The start moment of the fourth mode is t 3 , and the end moment is t 4 . At the moment of t 3 , the voltage at the parasitic capacitance C 1 of the switching transistor is clamped to a negative V 1 by the body diode D F . The difference between the input voltage V in and the output voltage V 0 charges the inductor L r positively. The current i Lr of the energy storage inductor continues to decrease linearly in the negative direction. At the moment of t 4 , the current i Lr of the energy storage inductor decreases to zero, and the fourth mode ends. In the fourth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor described in the first mode, the real-time state of the parasitic capacitance C 1 of the switching transistor, and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including: calculating the current i Lr (t) corresponding to the energy storage inductor in the fourth mode according to the following formula (7), and calculating the duration Δt 4 of the fourth mode according to the following formula (8);

[0128] Formula (7) is:

[0129]

[0130] Formula (8) is:

[0131]

[0132] The fourth mode is the energy transfer and regulation stage. It mainly provides an ideal starting point for the energy control in the next stage through the positive charging of the energy storage inductor and the state regulation of the parasitic capacitance. In this fourth mode, the positive reduction of the current of the energy storage inductor is achieved, so that the current of the energy storage inductor meets the initial conditions of the next mode, and at the same time, partial release or storage of the energy of the energy storage inductor is realized. The voltage of the parasitic capacitance C 1 of the switching transistor is clamped to a negative V F , and the driving of the power switching transistor Q is achieved1 The zero-voltage turn-off condition, thus reducing the power loss during the switching process. The input voltage V in and the output voltage V 0 The difference charges the inductor L r Forward, adjusting the energy distribution of the system to ensure that the system energy is reasonably distributed at each stage and avoiding the situation of excessive or insufficient energy. At t 4 moment, the current i Lr of the energy storage inductor decreases to zero, providing a stable initial current condition for the next mode switch. This process can achieve smooth mode switching and reduce system oscillations caused by current mutations.

[0133] See Figure 3 and Figure 4e , the fifth mode is from t 4 -t 5 moment. The start moment of the fifth mode is t 4 , and the end moment is t 5 . After the t 4 moment, the difference between the input voltage V in and the output voltage V 0 continues to charge the inductor L r forward. The current i Lr of the energy storage inductor linearly increases forward from zero. At the t 5 moment, the current i Lr of the energy storage inductor increases to the positive maximum value I pm , and the fifth mode ends. In the fifth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor described in the first mode, the real-time state of the parasitic capacitance C 1 of the switching transistor, and the real-time state of the parasitic capacitance C 2 of the freewheeling switch, including: calculating the current i Lr (t) corresponding to the energy storage inductor in the fifth mode according to the following formula (9), and calculating the duration Δt 5 of the fifth mode according to the following formula (10);

[0134] Formula (9) is:

[0135]

[0136] Formula (10) is:

[0137]

[0138] The fifth mode mainly replenishes energy to the energy storage inductor, making its current linearly increase forward from zero, providing ideal conditions for the subsequent mode switch. This fifth mode realizes a smooth transition from the zero-current state to the maximum positive current state, improving the dynamic performance of the system.

[0139] See Figure 3 and Figure 4f ; the sixth mode is t 5 -t 6 At this moment, the start time of the sixth mode is t 5 , and the end time is t 6 , at t 5 Turn off the power switch Q 1 , L r Resonates with the parasitic capacitance C of the switch 1 , the parasitic capacitance C of the freewheeling switch 2 Starts to resonate, and the parasitic capacitance C of the switch 1 Is charged, and its terminal voltage u C1 Gradually increases from zero, and the parasitic capacitance C of the freewheeling switch 2 Is discharged, and its terminal voltage u C2 Gradually decreases from V in , at t 6 moment, u C1 Increases to V pm , u C2 Decreases to equal negative V F , and the sixth mode ends. In the sixth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor, the real-time state of the parasitic capacitance C of the switch 1 And the real-time state of the parasitic capacitance C of the freewheeling switch 2 , including: calculating the current i Lr (t) corresponding to the energy storage inductor in the sixth mode according to the following formula (11), and calculating the duration Δt of the sixth mode according to the following formula (12) 6 ;

[0140] Formula (11) is:[[]]

[0141]

[0142] Formula (12) is:[[]]

[0143]

[0144] Among them, in the sixth mode, the voltages of C 1 And C 2 Are calculated according to the following formula:[[]]

[0145]

[0146] Among them, at t 6 moment, the negative current of the energy storage inductor is I p1 , and its corresponding calculation formula is as follows:[[]]

[0147]

[0148] Among them,

[0149] In the sixth mode, the resonant dynamics of the energy storage inductor, the parasitic capacitance C of the switching transistor 1 and the parasitic capacitance C of the freewheeling switch 2 ensure the soft-switching condition of the power switch and provide a starting point for the energy management in the next cycle. Among them, the parasitic capacitance C of the switching transistor 1 and the parasitic capacitance C of the freewheeling switch 2 complete the voltage adjustment through resonance with the energy storage inductor, adjust the voltage of the parasitic capacitance, and create conditions for realizing the zero-voltage switching operation of the power switching transistor. Then, the resonant dynamics between the energy storage inductor and the parasitic capacitance cause the current of the energy storage inductor to linearly change negatively from the positive maximum value I pm and finally reach the negative value I p1 , which provides the necessary initial conditions for the mode switching in the next cycle. At the moment of t 6 , u C1 increases to V pm , u C2 decreases to equal negative V F . At this time, the body diodes of the power switch and the freewheeling switch are turned on, which reduces the turn-on and turn-off losses during the switching process and improves the efficiency of the switching device. During the resonant dynamic process corresponding to this mode, the energy exchange between the energy storage inductor and the parasitic capacitance realizes the optimal distribution of the system energy.

[0150] See Figure 3 and Figure 4g , the seventh mode is from the moment of t 6 to t 7 . The start moment of the seventh mode is t 6 , and the end moment is t 7 . After the moment of t 6 , the current i Lr of the energy storage inductor forms a freewheeling loop through the body diode D 2 to supply power to the load. At the moment of t 7 , the freewheeling switch Q 2 is turned on, and the seventh mode ends. In the seventh mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor described in the first mode, the real-time states of the parasitic capacitance C of the switching transistor 1 and the parasitic capacitance C of the freewheeling switch 2 , including: calculating the current i Lr (t) corresponding to the energy storage inductor in the seventh mode according to the following formula (13), and calculating the duration Δt 7 of the seventh mode according to the following formula (14);

[0151] Equation (13) is:

[0152]

[0153] Equation (14) is:

[0154] Δt 7 = t 7 - t 6 = nΔt 6 ;

[0155] Wherein, I p1 refers to the above-mentioned sixth mode.

[0156] Wherein, at time t 7 , the negative current of the energy storage inductor is I p2 , and its corresponding calculation formula is:

[0157]

[0158] Wherein, n is a constant, and the value of n can be set according to actual requirements.

[0159] The seventh mode is an important stage in which the energy storage inductor forms a freewheeling loop through the body diode to supply power to the load. In this mode, the current of the energy storage inductor gradually decreases, providing ideal conditions for the turn-on of the freewheeling switch tube Q 2 . This mode improves the continuity and reliability of the load power supply, especially when the load changes dynamically; it also reduces the switching loss, decreases the heat generation of the switching device, prolongs the service life of the switching device, provides a smooth mode switching, and enhances the system adaptability.

[0160] See Figure 3 and Figure 4h , the eighth mode is at time t 7 - t 8 . The start time of the eighth mode is t 7 , and the end time is t 8 . After time t 7 , the current i Lr of the energy storage inductor forms a freewheeling loop through the freewheeling switch tube Q 2 to supply power to the load. The current i Lr of the energy storage inductor continues to decrease linearly in the positive direction. At time t 8 , i Lr decreases to zero, and the eighth mode ends. In the eighth mode, the control module is based on the state of the current of the energy storage inductor described in the first mode, the real-time state of the parasitic capacitance C 1 of the switch tube, and the parasitic capacitance C 2For the real-time status, calculate the duration of each mode and the current corresponding to the energy storage inductor respectively, including: calculate the current i Lr (t) corresponding to the energy storage inductor in the eighth mode according to the following formula (15), and calculate the duration Δt of the eighth mode according to the following formula (16) 8 ;

[0161] Formula (15) is:[[]]

[0162]

[0163] Formula (16) is:[[]]

[0164]

[0165] Wherein, I p2 is the negative current of the energy storage inductor, and its calculation formula refers to the above seventh mode.

[0166] The current decay process of the energy storage inductor in the eighth mode realizes continuous power supply to the load, and at the same time lays a foundation for the reset and stable operation of the circuit mode. The end of the eighth mode marks the end of a complete control PWM control cycle, provides an ideal initial state condition for entering a new cycle, and plays a key role in the efficient and stable operation of the system.

[0167] The division of the above eight working modes can achieve precise control of the inductor current and the charging and discharging process of the parasitic capacitance of the switching tube, ensuring the realization of zero-voltage switching at a specific moment. In some embodiments, the mode division can also be reduced or increased, and the specific division can be flexibly adjusted according to actual application requirements.

[0168] The soft-switching control method provided by the embodiments of the present application firstly achieves a wider zero-voltage switching. By setting the initial negative resonant current of the inductor, the energy stored in the resonant inductor is precisely controlled, enabling the BUCK transistor to achieve ideal zero-voltage switching under a wider range of input voltages and output voltages, a larger range of output powers, and higher MOS transistor output parasitic capacitance conditions. Moreover, the control precision and switching frequency are improved. Among the eight operating modes of the Buck converter, the duration of each mode and the inductor current can be accurately calculated based on relevant parameters, thereby accurately calculating the switching period. This advantage enables the MCU to be no longer limited by the sampling rate and supports higher-frequency soft-switching control. For example, when specifically applied to a Buck converter product with an output of 500W, its highest switching frequency reaches 300kHz, demonstrating excellent control performance. Finally, the conversion efficiency is improved. By implementing the control strategy proposed in this embodiment in a Buck converter with an output of 500W, the conversion efficiency of this converter under full-load conditions reaches 97.8%. Compared with a Buck converter operating in the traditional fixed-frequency CCM mode, the full-load conversion efficiency is increased by nearly 2%, significantly optimizing the energy utilization rate of the system.

[0169] The Buck converter provided by the embodiments of the present application can be used to execute the above soft-switching control method. By precisely controlling the dynamic process of the inductor current and the parasitic capacitance of the switching transistor, high-frequency soft-switching operation is achieved on the premise of ensuring efficiency and stability, and it has the same beneficial effects as the embodiments of the soft-switching control method. Through the above soft-switching control method, the Buck converter can operate efficiently and stably under complex working conditions, is particularly suitable for application scenarios with wide input and output ranges and high power densities, and demonstrates significant advantages in aspects such as energy utilization, control precision, and system reliability, having important practical value.

[0170] The above-disclosed are only the preferred embodiments of the present application. Of course, the scope of the rights of the present application cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.

Claims

1. A soft switch control method, applied to a Buck converter, wherein the Buck converter includes an input circuit module, a main power switch module, an energy storage and transmission module, a freewheeling loop module and an output filter module, wherein the input circuit module includes an input power supply, the main power switch module includes a power switch tube Q1, a switch tube parasitic capacitor C1 and a body diode D1, the energy storage and transmission module includes an energy storage inductor, the freewheeling loop module includes a freewheeling switch tube Q2, a freewheeling switch parasitic capacitor C2 and a freewheeling body diode D2, and the output filter module includes an energy storage filter capacitor EC2 and a load resistor R L The positive electrode of the input power supply is connected to the drain of the power switch tube Q1, one end of the energy storage inductor is connected between the source of the power switch tube Q1 and the drain of the freewheeling switch tube Q2, the other end of the energy storage inductor is connected to the source of the freewheeling switch tube Q2 through the output filter module, the energy storage filter capacitor EC2 and the load resistor R L Connected in parallel to smooth the output voltage and provide it to the load. It is characterized in that The Buck converter further includes a control module, which is used to connect the gates of the power switch tube Q1 and the freewheeling switch tube Q2. The method includes: The control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor, the real-time state of the switch tube parasitic capacitor C1 and the real-time state of the freewheeling switch parasitic capacitor C2 in the first mode, wherein in the first mode, the states of the power switch tube Q1 and the freewheeling switch tube Q2 are in the initialization state; generating a control signal according to the duration of each mode and the current corresponding to the energy storage inductor; Monitor the current i corresponding to the energy storage inductor Lr ; When the current i corresponding to the energy storage inductor is monitored Lr Reaching the preset first current value I n1 , the control module controls the Buck converter to switch from the first mode to other modes in sequence according to the control signal to achieve soft switching control of the Buck converter; wherein the first current value I n1 A first preset condition is met, and the first preset condition is set according to the input voltage corresponding to the input power supply, the parasitic capacitance C1 of the switch tube, and the energy storage inductor.

2. The method according to claim 1, characterized in that The first current value I n1 A first preset condition is satisfied, and the first preset condition is set according to the input voltage corresponding to the input power supply, the parasitic capacitance C1 of the switch tube, and the energy storage inductor, including: The first preset condition is determined according to the following formula: Among them, V in is the input voltage corresponding to the input power supply, C oss is the capacitance value of the parasitic capacitance C1 of the switch tube, L r is the inductance value corresponding to the energy storage inductor.

3. The method according to claim 1, characterized in that The first mode starts at t0 and ends at t1. In the first mode, the switching cycle control of the power switch tube Q1 and the freewheeling switch tube Q2 includes: At time t0, i Lr The terminal voltage V0 of the output energy storage filter capacitor EC2 reversely charges the energy storage inductor. Lr It starts to increase linearly in a negative direction. At time t1, i Lr The negative current increases to the preset first current value I n1 When the freewheeling switch tube Q2 is turned off.

4. The method according to claim 3, characterized in that In the first mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor, the real-time state of the switch tube parasitic capacitor C1 and the real-time state of the freewheeling switch parasitic capacitor C2 in the first mode, including: The current i corresponding to the energy storage inductor in the first mode is calculated according to the following formula (1): Lr (t), and calculate the duration Δt1 of the first mode according to the following formula (2); The formula (1) is: The formula (2) is: Among them, L r is the inductance value corresponding to the energy storage inductor.

5. The method according to claim 1, characterized in that The other modes include a second mode, a third mode, a fourth mode, a fifth mode, a sixth mode, a seventh mode and an eighth mode. In each of the other modes, the switching cycle control of the power switch tube Q1 and the freewheeling switch tube Q2 includes: The second mode starts at t1 and ends at t2. After t1, the inductor L r It starts to resonate with the parasitic capacitance C1 of the switch tube and the parasitic capacitance C2 of the freewheeling switch, and the current i Lr Continue to increase negatively, the voltage of parasitic capacitor C1 changes from V in The voltage of the parasitic capacitor C2 of the freewheeling switch increases positively from zero, and the voltage of the parasitic capacitor C2 of the freewheeling switch increases positively to V pm , the current i of the energy storage inductor Lr Negative increase to I n2 , the second mode ends; The start time of the third mode is t2, and the end time is t3. After t2, V pm The difference between the voltage V0 on the energy storage filter capacitor EC2 and the voltage V0 on the inductor L r Positive charging, the freewheeling switch parasitic capacitor C2 discharges, and the voltage at the switch tube parasitic capacitor C1 is clamped to a negative V by the body diode D1. F At time t3, the current i of the energy storage inductor is Lr Reduce to equal I n1 , the third mode ends; The fourth mode starts at time t3 and ends at time t4. At time t3, the voltage at the terminal of the parasitic capacitor C1 of the switch tube is clamped to a negative voltage V by the body diode D1. F , input voltage V in The difference between the output voltage V0 and the inductor L r Forward charging, the current i of the energy storage inductor Lr Continue to decrease linearly in the negative direction. At time t4, the current i Lr Decreases to zero, and the fourth mode ends; The fifth mode starts at time t4 and ends at time t5. After time t4, the input voltage V in The difference between the output voltage V0 and the inductor L r Forward charging, the current i of the energy storage inductor Lr It starts from zero and increases linearly in a positive direction. At time t5, the current i Lr Increase to the positive maximum value I pm , the fifth mode ends; The start time of the sixth mode is t5, and the end time is t6. At t5, the power switch tube Q1 is turned off, and L r It starts to resonate with the parasitic capacitance C1 of the switch tube and the parasitic capacitance C2 of the freewheeling switch. The parasitic capacitance C1 of the switch tube is charged, and its terminal voltage u C1 Starting from zero, it gradually increases, and the parasitic capacitance C2 of the freewheeling switch discharges, and its terminal voltage u C2 From V in begins to decrease gradually. At t6, u C1 Increase to V pm ,u C2 decreases to equal negative V F , the sixth mode ends; The start time of the seventh mode is t6, and the end time is t7. After t6, the current i Lr The body diode D2 forms a freewheeling loop to supply power to the load. At time t7, the freewheeling switch Q2 is turned on, and the seventh mode ends. The eighth mode starts at t7 and ends at t8. After t7, the current i Lr The freewheeling switch tube Q2 forms a freewheeling loop to supply power to the load. The current i Lr Continue to decrease linearly in the positive direction. At time t8, i Lr Decreases to zero and the eighth mode ends.

6. The method according to claim 5, characterized in that In the second mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the second mode is calculated according to the following formula (3): Lr (t), and calculate the duration Δt2 of the second mode according to the following formula (4); The formula (3) is: The formula (4) is: in, 7. The method according to claim 5, characterized in that In the third mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the third mode is calculated according to the following formula (5): Lr (t), and calculate the duration Δt3 of the third mode according to the following formula (6); The formula (5) is: The formula (6) is:

8. The method according to claim 5, characterized in that In the fourth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the fourth mode is calculated according to the following formula (7): Lr (t), and calculate the duration Δt4 of the fourth mode according to the following formula (8); The formula (7) is: The formula (8) is:

9. The method according to claim 5, characterized in that In the fifth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the fifth mode is calculated according to the following formula (9): Lr (t), and calculate the duration Δt5 of the fifth mode according to the following formula (10); The formula (9) is: The formula (10) is:

10. The method according to claim 5, characterized in that In the sixth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the current state of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the sixth mode is calculated according to the following formula (11): Lr (t), and calculate the duration Δt6 of the sixth mode according to the following formula (12); The formula (11) is: The formula (12) is:

11. The method according to claim 5, characterized in that In the seventh mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the seventh mode is calculated according to the following formula (13): Lr (t), and calculate the duration Δt7 of the seventh mode according to the following formula (14); The formula (13) is: The formula (14) is: Δt7=t7-t6=nΔt6; in, 12. The method according to claim 11, characterized in that In the eighth mode, the control module calculates the duration of each mode and the current corresponding to the energy storage inductor according to the state of the current of the energy storage inductor in the first mode, the real-time state of the switch tube parasitic capacitor C1, and the real-time state of the freewheeling switch parasitic capacitor C2, including: The current i corresponding to the energy storage inductor in the eighth mode is calculated according to the following formula (15): Lr (t), and the duration Δt8 of the eighth mode is calculated according to the following formula (16); The formula (15) is: The formula (16) is: in, 13. A Buck converter, comprising an input circuit module, a main power switch module, an energy storage and transmission module, a freewheeling loop module and an output filter module, wherein the input circuit module comprises an input power supply, the main power switch module comprises a power switch tube Q1, a switch tube parasitic capacitor C1 and a body diode D1, the energy storage and transmission module comprises an energy storage inductor, the freewheeling loop module comprises a freewheeling switch tube Q2, a freewheeling switch parasitic capacitor C2 and a freewheeling body diode D2, the output filter module comprises an energy storage filter capacitor EC2 and a load resistor R L The positive electrode of the input power supply is connected to the drain of the power switch tube Q1, one end of the energy storage inductor is connected between the source of the power switch tube Q1 and the drain of the freewheeling switch tube Q2, the other end of the energy storage inductor is connected to the source of the freewheeling switch tube Q2 through the output filter module, the energy storage filter capacitor EC2 and the load resistor R L Connected in parallel to smooth the output voltage and provide it to the load. It is characterized in that The Buck converter further includes a control module, which is used to connect the gates of the power switch tube Q1 and the freewheeling switch tube Q2, and is used to: According to the state of the current of the energy storage inductor in the first mode, the real-time state of the parasitic capacitor C1 of the switch tube, and the real-time state of the parasitic capacitor C2 of the freewheeling switch, respectively calculate the duration of each mode and the current corresponding to the energy storage inductor, wherein in the first mode, the states of the power switch tube Q1 and the freewheeling switch tube Q2 are in the initialization state; generating a control signal according to the duration of each mode and the current corresponding to the energy storage inductor; Monitor the current i corresponding to the energy storage inductor Lr ; When the current i corresponding to the energy storage inductor is monitored Lr Reaching the preset first current value I n1 , according to the control signal, the Buck converter is controlled to switch from the first mode to other modes in sequence to achieve soft switching control of the Buck converter; wherein the first current value I n1 A first preset condition is met, and the first preset condition is set according to the input voltage corresponding to the input power supply, the parasitic capacitance C1 of the switch tube, and the energy storage inductor.

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