Zero-voltage conversion Buck converter soft switching control system and method

Abstract

The invention discloses a zero-voltage conversion Buck converter soft switching control system and method, and belongs to the technical field of power electronic high-frequency DC-DC conversion. According to the system, on the basis of a main Buck circuit, a ZVT branch composed of a resonant inductor, an auxiliary switch tube, a buffer capacitor and a voltage dividing capacitor is connected in parallel, and diodes are connected to the two ends in an anti-parallel mode so as to provide a lossless charge discharge channel; through a soft switching control module, based on a ZVT branch, the advanced opening time of an auxiliary switching tube and the turn-off time of the auxiliary switching tube are accurately calculated, the duty ratio control quantity of the auxiliary switching tube is obtained, then a control feedback loop for achieving soft switching is obtained, and all-around soft switching of opening and closing of a main switching tube and the auxiliary switching tube is achieved; the converter is more stable and efficient, and the control method is simple and easy to implement.

Description

Technical Field

[0001] This invention relates to the field of power electronics high-frequency DC-DC conversion technology, and in particular to a soft-switching control system and method for a zero-voltage conversion Buck converter. Background Technology

[0002] In the field of power electronics, DC-DC converters are widely used in various power management systems. Among them, the Buck converter, as a basic step-down converter, has attracted much attention due to its simple structure and high efficiency. However, with the development of power electronic equipment towards higher frequencies, higher efficiency, and smaller size, traditional hard-switching Buck converters face problems such as large switching losses, severe electromagnetic interference (EMI), and decreased efficiency under high-voltage and high-frequency operating conditions. These limiting factors seriously affect the performance and reliability of the converter. To overcome the shortcomings of hard switching, soft-switching technology has emerged. Zero-voltage switching (ZVT) technology is a common soft-switching method that significantly reduces switching losses and EMI by making the voltage across the switching transistor zero when it is turned on or off.

[0003] Existing ZVT (Zero-Voltage Transformer) technologies typically achieve soft switching by adding an auxiliary resonant network. However, most solutions suffer from complex control and the auxiliary switching transistor itself cannot achieve soft switching, making them difficult to implement in practical applications. Therefore, there is an urgent need in the field for a ZVT Buck converter that is simple to control and can achieve omnidirectional soft switching of both the main and auxiliary switching transistors to improve the converter's efficiency and stability. Summary of the Invention

[0004] To address the problems of high switching losses, complex control, and limited soft-switching range in existing technologies, this invention proposes a soft-switching control system and method for a zero-voltage conversion Buck converter. By connecting a ZVT auxiliary branch in parallel with the main Buck circuit and designing a precise soft-switching control method, zero-voltage turn-on and turn-off of the main and auxiliary switching transistors can be achieved, thereby significantly improving the efficiency and reliability of the converter.

[0005] The present invention adopts the following technical solution: a soft-switching control system for a zero-voltage conversion Buck converter, comprising: a main Buck circuit, a ZVT auxiliary branch, and a soft-switching control module.

[0006] The main Buck circuit includes at least a main switching transistor. Main freewheeling diode Filter inductor and filter capacitors ;

[0007] The ZVT auxiliary branch is connected to the main switch transistor in the main Buck circuit. Parallel connection, including: resonant inductors Auxiliary switching transistor Buffer capacitor And voltage divider capacitors;

[0008] The voltage divider capacitor is connected between the positive and negative terminals of the input voltage, including a first voltage divider capacitor connected in series. Second voltage divider capacitor The resonant inductor The left side is connected to a voltage divider capacitor. , Point B in the middle is connected to the auxiliary switch tube on the right. Drain, auxiliary switching transistor Source connected to main switch transistor The source; the first voltage divider capacitor A diode is also connected in anti-parallel at both ends to provide a lossless charge discharge path. ;

[0009] The soft-switching control module includes: a voltage regulator module, Duty cycle calculation module and drive circuit;

[0010] The voltage regulation module samples the input voltage after voltage division and compares it with a set reference value, then sends the sample to the voltage loop regulator. The voltage loop regulator uses PID control and outputs a modulation signal as the main switch. The duty cycle control value is compared with the triangular wave signal to obtain the value of the main switch transistor. The required PWM duty cycle signal is supplied to the main circuit switching transistor. ;

[0011] The The duty cycle calculation module includes: Duty cycle control quantity D_rise operation submodule The duty cycle control quantity D_rise calculation submodule and the asymmetric PWM submodule are used to calculate the auxiliary switching transistor. The control values ​​at the rising and falling edges of the duty cycle are used to generate the auxiliary switching transistor. The PWM duty cycle signal is input to the drive circuit;

[0012] The driving circuit is used to switch the main switch and auxiliary switching transistors The PWM duty cycle signal is converted into a gate drive signal output to drive the main switch. and auxiliary switching transistors To achieve zero-voltage start-up of the main switch transistor and zero-voltage turn-off auxiliary switch .

[0013] Preferably, in the main Buck circuit, the positive terminal of the input voltage is connected to the main switching transistor. The drain of the main switch transistor Source connection filter inductor Left side; filter capacitor Connection and filter inductor Between the right side and ground; main switch tube A buffer capacitor is connected in parallel with the parasitic diode. ;

[0014] The negative terminal of the input voltage is connected to the main freewheeling diode. anode, main freewheeling diode Cathode connected to main switch tube With filter inductor Point A between them, the main freewheeling diode capacitor connected in parallel It is its parasitic capacitance.

[0015] Preferably, the The duty cycle control quantity D_rise calculation submodule, through Computing unit calculates auxiliary switching transistor Leading main switch transistor Time The method is as follows:

[0016] Auxiliary switching transistor Turn on, main switch tube Not turned on, resonant inductor and buffer capacitor Resonance begins, causing the voltage at point A to rise and the current to increase. From the resonant inductor Flow in from the left and out from the right. The voltage at point A increases from zero to its maximum value and then decreases. hour, Input voltage, main switching transistor The parasitic diode is turned on, and this moment is denoted as _____. .

[0017] Preferably, the The duty cycle control quantity D_fall operation submodule, through Computing unit calculates auxiliary switching transistor shutdown time The method is as follows:

[0018] main switch transistor The parasitic diode is turned on, achieving... Soft switch activation conditions From the resonant inductor The current flows in from the left and out from the right, and the current relationship is as follows: ;in, Main switch transistor The current of the parasitic diode, For filter inductors The current;

[0019] Open tube, resonant inductor and buffer capacitor Resonance ends, main switch transistor Auxiliary switching transistor When both are on, the current relationship is as follows: ;in, Main switch transistor The current;

[0020] getting bigger and bigger Gradually decrease until reverse, from the resonant inductor The current flows in from the right and out from the left, and the current relationship is as follows: ;

[0021] Through auxiliary switching transistor Provide voltage divider capacitors Charging, from the resonant inductor The flow from the right side to the left side causes the voltage at point B to... Rise to ,and When the diodes connected in parallel conduct, this moment is denoted as .

[0022] Preferably, the In the duty cycle control quantity D_rise operation submodule, the auxiliary switching transistor Leading main switch transistor The time is greater than At that time, the main switch transistor is satisfied. Zero-voltage turn-on;

[0023] The result The input is fed into the first multiplier, multiplied by the peak value H of the triangular wave in the asymmetric PWM submodule, and then passed through the first divider, divided by the period of the triangular wave. ,get Corresponding to The duty cycle control amount, plus The duty cycle control value is obtained. Duty cycle control quantity D_rise.

[0024] Preferably, the In the duty cycle control quantity D_fall operation submodule, Auxiliary switching transistor The activation time is zero, in the auxiliary switching tube After activation, it is greater than Time to turn off auxiliary switch tube To meet the requirements of auxiliary switching transistors Zero-voltage shutdown.

[0025] The result The signal is fed into the second multiplier and multiplied by twice the peak value H of the triangular wave in the asymmetric PWM submodule. Then, it is passed through the second divider and divided by the period of the triangular wave. ,generate Duty cycle control variable D_fall.

[0026] Preferably, the asymmetric PWM module uses a triangular wave signal, and sets comparison values ​​for the falling and rising phases of the triangular wave respectively;

[0027] Auxiliary switching transistor The PWM duty cycle signal is jointly determined by D_rise and D_fall: D_rise serves as the comparison value during the falling phase of the triangular wave and determines the rising edge of the PWM signal; D_fall serves as the comparison value during the rising phase of the triangular wave and determines the falling edge of the PWM signal.

[0028] The present invention also provides: a soft-switching control method for a zero-voltage conversion Buck converter, used for soft-switching control of the aforementioned zero-voltage conversion Buck converter, comprising the following steps:

[0029] Step 1: Construct the ZVT auxiliary branch based on the main Buck circuit; the main Buck circuit includes at least the main switching transistor. Main freewheeling diode Filter inductor and filter capacitors The ZVT auxiliary branch is connected to the main switching transistor in the main Buck circuit. Parallel connection, including: resonant inductors Auxiliary switching transistor Buffer capacitor And voltage divider capacitors;

[0030] Step 2: The input voltage is regulated by a voltage regulator module. After voltage division sampling, the result is compared with a set reference value and sent to the voltage loop regulator to obtain the main switching transistor. The required PWM duty cycle signal is supplied to the main switch transistor. Control the output voltage;

[0031] Step 3: Model the turn-on stage of the auxiliary switch, through... The duty cycle control quantity D_rise calculation submodule calculates the auxiliary switching transistor. Leading main switch transistor Time ,get Duty cycle control quantity D_rise;

[0032] Step 4: Model the turn-on phase of the main switch transistor, through... The duty cycle control quantity D_fall operation submodule calculates the auxiliary switching transistor. shutdown time ,get Duty cycle control value D_fall;

[0033] Step 5: Using the asymmetric PWM submodule, set the comparison values ​​for the falling and rising phases of the triangular wave, and generate the auxiliary switching transistor based on D_rise and D_fall. The PWM duty cycle signal;

[0034] Step 6: Activate the main switch via the drive circuit. and auxiliary switching transistors The PWM duty cycle signal is converted into a gate drive signal output to achieve zero-voltage turn-on of the main switch. Turn off the auxiliary switch tube .

[0035] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0036] 1. This invention models the turn-on phase of the auxiliary switch to accurately calculate the time when the auxiliary switch leads the main switch. Used to be greater than The auxiliary switch is turned on in advance to achieve zero-voltage start-up of the main switch.

[0037] 2. This invention models the turn-on phase of the main switch transistor to accurately calculate the turn-off time of the auxiliary switch transistor. Used to be greater than The auxiliary switch is turned off at a specific time to achieve zero-voltage turn-off of the auxiliary switch.

[0038] 3. This invention achieves its goals through precise calculations. and It achieves comprehensive soft-switching operation, avoiding the high switching losses caused by high frequency; the asymmetric PWM submodule design is simple and easy to implement. Attached Figure Description

[0039] Figure 1 This is the main circuit topology of the zero-voltage conversion Buck converter of this invention;

[0040] Figure 2 This is a block diagram of the soft-switching control system for the zero-voltage conversion Buck converter of the present invention;

[0041] Figure 3 This is the mode conversion diagram of the zero-voltage conversion Buck converter of the present invention;

[0042] Figure 4 This is a schematic diagram of the asymmetric PWM submodule of the present invention;

[0043] Figure 5 This is a schematic diagram of the working waveform of the zero-voltage conversion Buck converter of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0045] In one embodiment of the present invention, a soft-switching control system for a zero-voltage conversion Buck converter is provided, comprising: a main Buck circuit, a ZVT auxiliary branch, and a soft-switching control module. The main circuit topology of this embodiment is as follows: Figure 1 As shown, the system control flow is as follows: Figure 2 As shown.

[0046] The main Buck circuit includes the main switching transistor. Main freewheeling diode Filter inductor and filter capacitors ;in, For load, This represents the filter inductor current. This indicates the output voltage.

[0047] ZVT auxiliary branch and main switch transistor of main Buck circuit Parallel connection, by resonant inductor Auxiliary switching transistor Buffer capacitor and the first voltage divider capacitor connected in series. Second voltage divider capacitor Composition; among which, A diode connected in anti-parallel at both ends provides a lossless charge discharge path. .

[0048] The soft-switching control module includes: a voltage regulator module, The duty cycle calculation module and drive circuit perform soft-switching control on the main Buck circuit and ZVT auxiliary branch through the soft-switching control module.

[0049] The voltage regulator module processes the following: output voltage After voltage division sampling, compare with the set reference value The signal is compared and fed into the voltage loop regulator, which uses PID control. The modulation signal of the voltage loop is... The duty cycle control value is compared with the triangular wave signal to obtain the required PWM duty cycle, which is then supplied to the main circuit switching transistor. This allows for the control of the output voltage.

[0050] The duty cycle calculation module includes: Duty cycle control quantity D_rise (used for) (Control quantity of rising edge of duty cycle) calculation submodule Duty cycle control value D_fall (used for) The submodule for calculating the control quantity of the falling edge of the duty cycle is used to generate... An asymmetric PWM submodule for controlling the PWM duty cycle signal.

[0051] The duty cycle control quantity D_rise operation submodule is used through Time calculated by the computing unit Then, after passing through the first multiplier, the first divider, and the adder, it generates... Duty cycle control quantity D_rise.

[0052] The duty cycle control quantity D_fall operation submodule is used through Time calculated by the computing unit Then, after passing through the second multiplier and the second divider, it generates... Duty cycle control variable D_fall.

[0053] The asymmetric PWM submodule uses a triangular wave signal, and sets the comparison values ​​for the falling and rising phases of the triangular wave respectively.

[0054] Auxiliary switching transistor The PWM duty cycle signal is jointly determined by D_rise and D_fall: D_rise serves as the comparison value during the falling phase of the triangular wave and determines the rising edge of the PWM signal; D_fall serves as the comparison value during the rising phase of the triangular wave and determines the falling edge of the PWM signal.

[0055] The drive circuit is used to convert the PWM duty cycle signal into a gate drive signal.

[0056] To better understand the analysis process of this invention, before describing the specific implementation steps of each control module in the system, a comprehensive analysis of the circuit mode conversion is first performed, such as... Figure 3 As shown.

[0057] Mode 1: Diode freewheeling state: This mode is the main switching transistor. Auxiliary switching transistor All closed.

[0058] Mode 2: Auxiliary switch Open, due to Auxiliary switching transistor exists. The activation itself satisfies the soft-switching condition; at this time, the main switch transistor... Not yet open. and The initiation of resonance causes the voltage at point A to rise. from Flow in from the left and out from the right. The value increases from zero to its maximum value, then decreases; the nodes of change are: ,until , The parasitic diode of the tube conducts, and the resonance ends; this moment is denoted as . .

[0059] Next, we enter Mode 3: Main Switch Transistor The body diode is turned on, which is the main switching transistor. Soft switching provides the conditions at this time ;

[0060] in, Main switch transistor The current of the parasitic diode, For filter inductors The current.

[0061] Next, the main switch transistor Turn on, enter mode 4: the main switch transistor in this mode Auxiliary switching transistor When all are turned on, the current relationship is as follows: ,and getting bigger and bigger Gradually decrease until it becomes zero. Reverse; among which, Main switch transistor The current.

[0062] Entering Mode 5: Reverse from The current flows in from the right and out from the left. The current relationship at this time is: ; pass pipe to Charging enables Rise to ,and When the parallel diodes are turned on, at this time When the voltage across the tube is the same, the condition for zero-voltage turn-off is met; this moment is denoted as _____. .

[0063] Entering Mode 6: The parallel diodes are turned on, and the auxiliary switching transistor is activated. To achieve soft switching conditions, the auxiliary switching transistor... closure.

[0064] Entering Mode 7: Auxiliary Switch closure, Through auxiliary switching transistor The body diode flows through, waiting for the main switching transistor. When the drive signal ends, the main switch transistor... closure.

[0065] Entering mode 8: due to the buffer capacitor The presence of the main switch transistor Closing also satisfies the soft-switching conditions, thus ending the entire cycle mode.

[0066] The following is a detailed description of each control module in the system.

[0067] First, to ensure stable output voltage, the voltage regulator module in this embodiment adopts the following... Figure 2 The circuit shown controls the main switching transistor. ;in, The output voltage is sampled after voltage division and compared with the set reference value. The data is compared and fed into the voltage loop regulator, which uses PID control.

[0068] The modulation signal of the voltage loop is... The duty cycle control value is compared with the triangular wave signal to obtain the required PWM duty cycle, which is then supplied to the main circuit switching transistor. This allows for the control of the output voltage.

[0069] It is particularly important to note that, in order to prevent the output duty cycle from being too large, a limiting circuit is added after the PID output in this embodiment.

[0070] Then, to The specific control steps of the duty cycle control quantity D_rise operation submodule are as follows:

[0071] (1) Through Computing unit calculation Advanced time :

[0072] according to Figure 3 From mode 2 in the text, we can derive that for , , , have:

[0073] ;

[0074] ;

[0075] ;

[0076] ;

[0077] in, Indicates the input voltage. express time; , , , Indicates capacitance , , , The current.

[0078] right have:

[0079] ;

[0080] in, Let be the voltage from point B to point A.

[0081] The following conditions must be met between the currents:

[0082] ;

[0083] ;

[0084] At this stage, the following conditions must be met:

[0085] M ;

[0086] in, , .

[0087] At this stage, the following conditions must be met:

[0088] ;

[0089] At this stage, the following conditions must be met:

[0090] ;

[0091] ;

[0092] make = The unique unknown of the equation can be obtained. Since this equation is a transcendental equation, it can be solved by numerical substitution. It can be obtained simultaneously ( ), ( ), in calculation It will be used at that time.

[0093] (2) In obtaining Advanced time After that, the result will be The first multiplier is fed into H, where H is the peak value of the triangular wave in the asymmetric PWM module. Then, the first divider is fed into H, which is divided by the period of the triangular wave. The purpose is to obtain Corresponding to The duty cycle control amount, plus The duty cycle control value is obtained. Duty cycle control quantity D_rise.

[0094] Due to the auxiliary switching transistor Turn off the main switch tube The time must be greater than Only then can it be satisfied The tube turns on at zero voltage, therefore The duty cycle control value D_rise can only be rounded up.

[0095] Furthermore, on The specific control steps of the duty cycle control quantity D_fall operation submodule are as follows:

[0096] (1) Through Computing unit calculates auxiliary switching transistor shutdown time ,according to Figure 3 From mode 5, we can derive:

[0097]

[0098] right , have:

[0099] ;

[0100] ;

[0101] right have:

[0102] ;

[0103] The relationships between the currents are as follows:

[0104] ;

[0105] The relationship that satisfies this is:

[0106] ;

[0107] for , Available Time corresponding ( ), ( )(exist (The calculation unit has been determined) , Numerical solution; let = Similarly, the numerical substitution method can be used to calculate... .

[0108] (2) After calculating The conduction time of the parasitic diode of the tube After that, the result will be The second multiplier is fed in, multiplying by 2H, followed by the second divider, dividing by... ,get Corresponding to Duty cycle control quantity D_fall, due to It is relative to The corresponding time when the tube is activated is zero. After the pipe is turned on, it is greater than Time off Only through management can satisfaction be achieved. The tube is turned off at zero voltage, therefore, The duty cycle control value D_fall can only be rounded up.

[0109] Furthermore, the specific implementation steps for the asymmetric PWM module are as follows:

[0110] like Figure 4 As shown, the asymmetric PWM module internally uses a triangular wave signal, and the comparison values ​​for the falling and rising phases of the triangular wave can be set separately as D_rise and D_fall. The PWM duty cycle signal of the transistor is determined by D_rise and D_fall. The part of the triangular wave signal that is larger than the comparison value is an invalid signal, and the part of the triangular wave signal that is smaller than the comparison value is an valid signal.

[0111] D_rise, as the comparison value during the falling phase of the triangular wave, determines the rising edge of the PWM signal; D_fall, as the comparison value during the rising phase of the triangular wave, determines the falling edge of the PWM signal.

[0112] This embodiment illustrates the operating waveforms of the zero-voltage conversion Buck converter, as shown below. Figure 5 As shown.

[0113] As described above, the zero-voltage conversion Buck converter soft-switching control system of the present invention, due to the topology itself, allows the auxiliary switching transistor... When turned on, It has a built-in soft-switch effect when turned off, and further, through the control method of this invention, it can achieve... When turned on, The soft-switching effect during shutdown ultimately achieves a comprehensive soft-switching effect. This significantly optimizes system efficiency, simplifies the control method, and makes it easy to implement.

[0114] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A soft-switching control system for a zero-voltage conversion Buck converter, characterized in that, include: Main Buck circuit, ZVT auxiliary branch and soft-switching control module; The main Buck circuit includes at least a main switching transistor. Main freewheeling diode Filter inductor and filter capacitors ; The ZVT auxiliary branch is connected to the main switch transistor in the main Buck circuit. Parallel connection, including: resonant inductors Auxiliary switching transistor Buffer capacitor And voltage divider capacitors; The voltage divider capacitor is connected between the positive and negative terminals of the input voltage, including a first voltage divider capacitor connected in series. Second voltage divider capacitor The resonant inductor The left side is connected to a voltage divider capacitor. , Point B in the middle is connected to the auxiliary switch tube on the right. Drain, auxiliary switching transistor Source connected to main switch transistor The source; the first voltage divider capacitor A diode is also connected in anti-parallel at both ends to provide a lossless charge discharge path. ; The soft-switching control module includes: a voltage regulator module, Duty cycle calculation module and drive circuit; The voltage regulation module samples the input voltage after voltage division and compares it with a set reference value, then sends the sample to the voltage loop regulator. The voltage loop regulator uses PID control, and the output modulation signal serves as the main switch. The duty cycle control value is compared with the triangular wave signal to obtain the value of the main switch transistor. The required PWM duty cycle signal is supplied to the main circuit switching transistor. ; The Duty cycle calculation module, including Duty cycle control quantity D_rise operation submodule The duty cycle control quantity D_rise calculation submodule and the asymmetric PWM submodule are used to calculate the auxiliary switching transistor. The control values ​​at the rising and falling edges of the duty cycle are used to generate the auxiliary switching transistor. The PWM duty cycle signal is input to the drive circuit; The driving circuit is used to switch the main switch and auxiliary switching transistors The PWM duty cycle signal is converted into a gate drive signal output to drive the main switch. and auxiliary switching transistors To achieve zero-voltage start-up of the main switch transistor and zero-voltage turn-off auxiliary switch .

2. The zero-voltage conversion Buck converter soft-switching control system according to claim 1, characterized in that, In the main Buck circuit: The positive terminal of the input voltage is connected to the main switching transistor. The drain of the main switch transistor Source connection filter inductor Left side; filter capacitor Connection and filter inductor Between the right side and ground; main switch tube A buffer capacitor is connected in parallel with the parasitic diode. ; The negative terminal of the input voltage is connected to the main freewheeling diode. anode, main freewheeling diode Cathode connected to main switch tube With filter inductor Point A between them, the main freewheeling diode capacitor connected in parallel It is its parasitic capacitance.

3. The zero-voltage conversion Buck converter soft-switching control system according to claim 2, characterized in that, The The duty cycle control quantity D_rise calculation submodule, through Computing unit calculates auxiliary switching transistor Leading main switch transistor time The method is as follows: Auxiliary switching transistor Turn on, main switch tube Not turned on, resonant inductor and buffer capacitor Resonance begins, causing the voltage at point A to rise and the current to increase. From the resonant inductor Flow in from the left and out from the right. The voltage at point A increases from zero to its maximum value and then decreases. hour, Input voltage, main switching transistor The parasitic diode is turned on, and this moment is denoted as _____. .

4. The zero-voltage conversion Buck converter soft-switching control system according to claim 3, characterized in that, The The duty cycle control quantity D_fall operation submodule, through Computing unit calculates auxiliary switching transistor shutdown time The method is as follows: main switch transistor The parasitic diode is turned on, achieving... Soft switch activation conditions From the resonant inductor The current flows in from the left and out from the right, and the current relationship is as follows: ;in, Main switch transistor The current of the parasitic diode, For filter inductors The current; Open tube, resonant inductor and buffer capacitor Resonance ends, main switch transistor Auxiliary switching transistor When both are on, the current relationship is as follows: ;in, Main switch transistor The current; getting bigger and bigger Gradually decrease until reverse, from the resonant inductor The current flows in from the right and out from the left, and the current relationship is as follows: ; Through auxiliary switching transistor Provide voltage divider capacitors Charging, from the resonant inductor The flow from the right side to the left side causes the voltage at point B to... Rise to ,and When the diodes connected in parallel conduct, this moment is denoted as .

5. The zero-voltage conversion Buck converter soft-switching control system according to claim 4, characterized in that, The The calculation unit is for the capacitor. , , , have: ； ； ； ； in, Indicates the input voltage. express time; , , , Indicates capacitance , , , The current; right have: ； in, Let V be the voltage from point B to point A. The following conditions must be met between the currents: ； ； At this stage, the following conditions must be met: ； Among them, parameters , ; At this stage, the following conditions must be met: ； At this stage, the following conditions must be met: ； when = At that time, the numerical substitution method was used to calculate the result. .

6. The zero-voltage conversion Buck converter soft-switching control system according to claim 5, characterized in that, The Computing unit At that time, for capacitor , have: ； ； right have: ； The relationships between the currents are as follows: ； The relationship that satisfies this is: ； Among them, parameters , use The time corresponding ( ), ( ) yields; when = At that time, the numerical substitution method was used to calculate the result. .

7. The zero-voltage conversion Buck converter soft-switching control system according to claim 4, characterized in that, The In the duty cycle control quantity D_rise operation submodule, the auxiliary switching transistor Leading main switch transistor The time is greater than At that time, the main switch transistor is satisfied. Zero-voltage turn-on; The result The input is fed into the first multiplier, multiplied by the peak value H of the triangular wave in the asymmetric PWM submodule, and then passed through the first divider, divided by the period of the triangular wave. ,get Corresponding to The duty cycle control amount, plus The duty cycle control value is obtained. Duty cycle control quantity D_rise.

8. The zero-voltage conversion Buck converter soft-switching control system according to claim 7, characterized in that, The In the duty cycle control quantity D_fall operation submodule, Auxiliary switching transistor The activation time is zero, in the auxiliary switching tube After activation, it is greater than Time to turn off auxiliary switch tube To meet the requirements of auxiliary switching transistors Zero-voltage shutdown; The result The signal is fed into the second multiplier and multiplied by twice the peak value H of the triangular wave in the asymmetric PWM submodule. Then, it is passed through the second divider and divided by the period of the triangular wave. ,generate Duty cycle control variable D_fall.

9. The zero-voltage conversion Buck converter soft-switching control system according to claim 8, characterized in that, The asymmetric PWM submodule uses a triangular wave signal, and sets comparison values ​​for the falling and rising phases of the triangular wave respectively. Auxiliary switching transistor The PWM duty cycle signal is jointly determined by D_rise and D_fall: D_rise serves as the comparison value during the falling phase of the triangular wave and determines the rising edge of the PWM signal; D_fall serves as the comparison value during the rising phase of the triangular wave and determines the falling edge of the PWM signal.

10. A soft-switching control method for a zero-voltage conversion Buck converter, applied to the soft-switching control system of the zero-voltage conversion Buck converter according to any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: Construct the ZVT auxiliary branch based on the main Buck circuit; the main Buck circuit includes at least the main switching transistor. Main freewheeling diode Filter inductor and filter capacitors The ZVT auxiliary branch is connected to the main switching transistor in the main Buck circuit. Parallel connection, including: resonant inductors Auxiliary switching transistor Buffer capacitor And voltage divider capacitors; Step 2: The input voltage is regulated by a voltage regulator module. After voltage division sampling, the result is compared with a set reference value and sent to the voltage loop regulator to obtain the main switching transistor. The required PWM duty cycle signal is supplied to the main switch transistor. Control the output voltage; Step 3: Model the turn-on stage of the auxiliary switch, through... The duty cycle control quantity D_rise calculation submodule calculates the auxiliary switching transistor. Leading main switch transistor time ,get Duty cycle control quantity D_rise; Step 4: Model the turn-on phase of the main switch transistor, through... The duty cycle control quantity D_fall operation submodule calculates the auxiliary switching transistor. shutdown time ,get Duty cycle control value D_fall; Step 5: Using the asymmetric PWM submodule, set the comparison values ​​for the falling and rising phases of the triangular wave, and generate the auxiliary switching transistor based on D_rise and D_fall. The PWM duty cycle signal; Step 6: Activate the main switch via the drive circuit. and auxiliary switching transistors The PWM duty cycle signal is converted into a gate drive signal output to achieve zero-voltage turn-on of the main switch. Turn off the auxiliary switch tube .

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