WO2021056652A1

WO2021056652A1 - Gain frequency modulation method and related apparatus

Info

Publication number: WO2021056652A1
Application number: PCT/CN2019/112906
Authority: WO
Inventors: 周峰武; 张小勇; 饶沛南; 张庆; 曹金洲; 罗盼
Original assignee: 株洲中车时代电气股份有限公司
Priority date: 2019-09-29
Filing date: 2019-10-24
Publication date: 2021-04-01
Also published as: CN111884510B; CN111884510A

Abstract

Provided in embodiments of the present invention are a gain frequency modulation method applied to a flying capacitance half-bridge three-level LLC resonant converter and a related apparatus. The method comprises: according to different input and output voltages, controlling a flying capacitance half-bridge three-level LLC resonant converter to switch between a high gain frequency modulation mode and a low gain frequency modulation mode. When there is a high input voltage and a low output voltage, work is carried out in the low gain frequency modulation mode. For the same input voltage, a peak-to-peak value of LLC resonant cavity input voltage of the flying capacitance half-bridge three-level LLC resonant converter in the low gain frequency modulation mode is less than a peak-to-peak value of the LLC resonant cavity input voltage in the high gain frequency modulation mode, thereby reducing the gain of a circuit. By means of changing the frequency modulation mode, the gain range of the flying capacitance half-bridge three-level LLC resonant converter is expanded.

Description

Gain frequency modulation method and related device

This application claims the priority of a domestic application filed with the Chinese Patent Office on September 29, 2019, the application number is 201910932862.0, and the invention title is "Gain Frequency Modulation Method and Related Device", the entire content of which is incorporated into this application by reference.

Technical field

The present invention relates to the technical field of three-level LLC topologies, and more specifically, to a gain frequency modulation method and related devices of a flying capacitor type half-bridge three-level LLC resonant converter.

Background technique

In high-voltage applications, a three-level LLC topology can be used to reduce the voltage stress of the switch tube. The flying capacitor type three-level LLC topology uses a small number of clamping components and has a strong automatic voltage equalization capability. It does not require additional voltage equalization control. It has very good application value in high-voltage and wide-gain ranges. Flying capacitor half-bridge three-level LLC resonant converter, composed of input voltage dividing capacitors C _d1 and C _d2 , flying capacitor C _k , switching tubes Q ₁ ～Q ₄ , transformer T, magnetizing inductance L _m , and resonant inductance L _s , resonant capacitor C _s , rectifier diode D ₁ ~ D ₄ and output capacitor C _o , as shown in Figure 1.

After the resonant parameters of the flying capacitor half-bridge three-level LLC resonant converter are fixed and the gain frequency modulation mode is unchanged, the gain curve of the flying capacitor half-bridge three-level LLC resonant converter under different loads is shown in Figure 2. As shown, the ordinate represents the gain G, the abscissa represents the normalized frequency k _f , k _f = f _s /f _r , f _s represents the switching frequency, f _r represents the resonant frequency, and Q represents the quality factor of the circuit, which is proportional to the load , Q=0 at no load, Q=Q _{max at} full load. The gain curve of a specific load has a maximum gain frequency point. On the right side of the maximum gain frequency point, the gain is inversely proportional to the frequency. For a specific load, when the frequency range is (k _{f_min} , k _{f_max} ), the minimum frequency point k _{f_min} corresponds to the maximum gain G _max , and the maximum frequency point k _{f_max} corresponds to the minimum gain G _min , so the flying capacitor type half bridge The gain range of the three-level LLC resonant converter is (G _min , G _max ). After the output voltage V _o is determined, the larger the input voltage V _in, the smaller the required gain. For wide voltage range applications, when the required gain of the _{circuit's maximum input voltage V in_max} _{is less than G min} , the flying capacitor half-bridge three-level LLC resonant converter cannot output the required voltage value.

Summary of the invention

In view of this, the present invention proposes a gain frequency modulation method and related devices, which intend to expand the gain range of a flying capacitor half-bridge three-level LLC resonant converter without increasing the cost and without increasing the circuit volume. , In order to be suitable for the purpose of wide voltage range.

In order to achieve the above-mentioned purpose, the proposed scheme is as follows:

In the first aspect, an embodiment of the present invention provides a gain frequency modulation method, which is applied to a flying capacitor half-bridge three-level LLC resonant converter, and the method includes:

In the high-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is judged whether the current demand gain is less than the preset first gain threshold, if so, switch to the low-gain frequency modulation mode to adjust the switching frequency , To obtain the target output voltage, if not, adjust the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage;

In the low-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is determined whether the current demand gain is greater than the preset second gain threshold, and the second gain threshold is greater than the first gain Threshold, if yes, switch to the high-gain frequency modulation mode to perform switching frequency adjustment to obtain the target output voltage, if not, adjust the switching frequency in the low-gain frequency modulation mode to obtain the target output voltage;

For the same input voltage, the peak-to-peak value of the LLC resonant input voltage of the flying capacitor half-bridge three-level LLC resonant converter in the low-gain frequency modulation mode is smaller than that in the high-gain frequency modulation mode The peak-to-peak value of the input voltage of the LLC resonant cavity of the capacitive half-bridge three-level LLC resonant converter.

Optionally, the low-gain frequency modulation mode specifically includes:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 3/4 of the switching cycle time and turning off 1/4 of the switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/4 switching cycle time and turning off 3/4 switching cycle time;

Controlling the fourth switching tube to be turned on while controlling the first switching tube to be turned off;

Controlling the third switching tube to be turned on while controlling the second switching tube to be turned off;

After the first switching tube is controlled to be turned on for 1/4 of the switching cycle time, the second switching tube is controlled to be turned off.

Optionally, the high-gain frequency modulation mode specifically includes:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

While controlling the third switching tube and the fourth switching tube to be turned off at the same time, controlling the first switching tube and the second switching tube to be turned on at the same time;

While the first switching tube and the second switching tube are controlled to be turned off at the same time, the third switching tube and the fourth switching tube are controlled to be turned on at the same time.

Optionally, the process of calculating the current demand gain includes:

Divide the product of the target output voltage and the transformer ratio by the input voltage to get the current demand gain.

In a second aspect, an embodiment of the present invention provides a gain frequency modulation device, which is applied to a flying capacitor half-bridge three-level LLC resonant converter, and the device includes:

The first adjustment unit is used to calculate the current demand gain if the input voltage changes in the high-gain frequency modulation mode, and determine whether the current demand gain is less than the preset first gain threshold, and if so, switch to low gain Adjust the switching frequency in the frequency modulation mode to obtain the target output voltage, if not, adjust the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage;

The second adjustment unit is configured to calculate the current demand gain if the input voltage changes in the low-gain frequency modulation mode, and determine whether the current demand gain is greater than the preset second gain threshold, the second gain The threshold is greater than the first gain threshold. If yes, switch to the high-gain frequency modulation mode for switching frequency adjustment to obtain the target output voltage; if not, adjust the switching frequency in the low-gain frequency modulation mode to Obtain the target output voltage. For the same input voltage, the peak-to-peak input voltage of the LLC resonant cavity of the flying capacitor half-bridge three-level LLC resonant converter in the low-gain frequency modulation mode is less than that at the high-gain frequency The peak-to-peak value of the input voltage of the LLC resonant cavity of the flying capacitor half-bridge three-level LLC resonant converter in the modulation mode.

Optionally, the low-gain frequency modulation mode specifically includes:

Optionally, the high-gain frequency modulation mode specifically includes:

Optionally, the process of calculating the current demand gain includes:

In a third aspect, an embodiment of the present invention provides a readable storage medium on which a program is stored, and when the program is executed by a processor, it realizes a flying capacitor type half-bridge three-level LLC resonant converter The gain frequency modulation method includes:

Optionally, the low-gain frequency modulation mode specifically includes:

Optionally, the high-gain frequency modulation mode specifically includes:

Optionally, the process of calculating the current demand gain includes:

In a fourth aspect, an embodiment of the present invention provides a controller, including a memory and a processor, the memory is used to store a program, and the processor is used to execute the program to implement a flying capacitor type The gain frequency modulation method of half-bridge three-level LLC resonant converter, the method includes:

Optionally, the low-gain frequency modulation mode specifically includes:

Optionally, the high-gain frequency modulation mode specifically includes:

Optionally, the process of calculating the current demand gain includes:

Compared with the prior art, the technical solution of the present invention has the following advantages:

The above technical solution provides a gain frequency modulation method applied to flying capacitor half-bridge three-level LLC resonant converters. According to different input and output voltages, the flying capacitor half-bridge three-level LLC resonant converter is controlled Switch between high-gain frequency modulation mode and low-gain frequency modulation mode. At high input voltage and low output voltage, it works in low gain frequency modulation mode. For the same input voltage, the peak-to-peak value of the LLC resonant input voltage of the flying capacitor half-bridge three-level LLC resonant converter in the low-gain frequency modulation mode is smaller than the LLC resonant input voltage in the high-gain frequency modulation mode The peak-to-peak value, thereby reducing the gain of the circuit. By changing the frequency modulation mode, the gain range of the flying capacitor half-bridge three-level LLC resonant converter is expanded.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Figure 1 is a schematic circuit diagram of a flying capacitor type half-bridge three-level LLC resonant converter;

Figure 2 shows the gain curve of a flying capacitor half-bridge three-level LLC resonant converter under different loads;

FIG. 3 is a flowchart of a gain frequency modulation method applied to a flying capacitor half-bridge three-level LLC resonant converter according to an embodiment of the present invention;

4 is a schematic diagram of a high-gain frequency modulation mode provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of a low-gain frequency modulation mode provided by an embodiment of the present invention;

6 is a schematic logical structure diagram of a schematic diagram of a gain frequency modulation device applied to a flying capacitor type half-bridge three-level LLC resonant converter according to an embodiment of the present invention;

Fig. 7 is a schematic structural diagram of a controller provided by an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Increasing the gain range by changing the hardware parameters of the flying capacitor type half-bridge three-level LLC resonant converter will increase the hardware cost, but also increase the loss and reduce the circuit efficiency. The core idea of the present invention is to expand the gain range of the circuit by switching the frequency modulation mode. For different input and output voltages, the circuit switches between high-gain frequency modulation mode and low-gain frequency modulation mode. When the working condition is high input and low output voltage, the circuit works in low gain frequency modulation mode.

Refer to FIG. 3, which is a flowchart of a gain frequency modulation method applied to a flying capacitor half-bridge three-level LLC resonant converter according to an embodiment of the present invention. The method may include the steps:

S31: Determine whether the current mode is a high-gain frequency modulation mode, if yes, execute step S32, if not, execute step S36.

In this embodiment, the flying capacitor half-bridge three-level LLC resonant converter is in two modes, one is a high-gain frequency modulation mode, and the other is a low-gain frequency modulation mode. Through step S31, it is determined whether the current mode of the flying capacitor half-bridge three-level LLC resonant converter is the high-gain frequency modulation mode or the low-gain frequency modulation mode.

_{For the same input voltage, the peak-to-peak value of the LLC resonant input voltage V AB} of the flying capacitor type half-bridge three-level LLC resonant converter in the low gain frequency modulation mode is smaller than that of the flying capacitor type in the high gain frequency modulation mode The peak-to-peak value of the _{input voltage V AB} of the LLC resonant cavity of the half-bridge three-level LLC resonant converter. The LLC resonant cavity input voltage V _AB is the voltage between point A and point B in Fig. 1. LLC resonant cavity input voltage peak value of V _AB LLC resonant cavity difference between the input signal maximum and minimum values in one cycle of the voltage V _AB.

S32: After the input voltage changes, calculate the current demand gain.

The gain formula of the circuit is G=(N×V _o )/V _in , where N represents the transformation ratio of the transformer, V _o represents the output voltage of the flying capacitor half-bridge three-level LLC resonant converter, and V _in represents the flying span The input voltage of the capacitive half-bridge three-level LLC resonant converter, and G represents the gain of the flying capacitor half-bridge three-level LLC resonant converter. Therefore, by dividing the product of the target output voltage and the transformer ratio by the changed input voltage, the current demand gain can be obtained.

S33: Determine whether the current demand gain is less than the preset first gain threshold, if yes, execute step S34, if not, execute step S35.

S34: Switch to the low-gain frequency modulation mode and adjust the switching frequency to obtain the target output voltage.

S35: Adjust the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage.

In a specific embodiment, the switching frequency is adjusted in a closed loop adjustment manner to obtain the target output voltage.

S36: After the input voltage changes, calculate the current demand gain.

Step S36 is consistent with step S32, and will not be repeated in this embodiment.

S37: Determine whether the current demand gain is greater than the preset second gain threshold, if yes, execute step S38, if not, execute step S39.

The second gain threshold is greater than the first gain threshold. The difference between the second gain threshold and the first gain threshold determines the width of the hysteresis adjustment, which can prevent frequent switching between the two modes caused by small voltage jitter.

S38: Switch to the high-gain frequency modulation mode and adjust the switching frequency to obtain the target output voltage.

S39: Adjust the switching frequency in the low gain frequency modulation mode to obtain the target output voltage.

In a specific embodiment, adjusting the switching frequency specifically refers to adjusting the switching frequency in a closed loop adjustment manner to obtain the target output voltage.

4, Ts represents the switching cycle time, V _C1 represents the voltage across the capacitor C ₁ of the first switching tube Q ₁ _{, V C2} represents the voltage across the capacitor C ₂ of the second switching tube Q ₂ , and V _C3 represents the The voltage across the capacitor C ₃ of the three-switch tube Q ₃ _{, V C4} represents the voltage across the capacitor C ₄ of the fourth switching tube Q ₄ _{, i Ls} represents the current through the resonant inductor L _s , and i _Lm represents the magnetizing inductance L _m of current. The driving pulses of Q ₁ ˜Q ₄ are high level, which means that the corresponding switching tubes are turned on, and _{the driving pulses of Q 1} ˜Q ₄ are low level, which means that the corresponding switching tubes are turned off. The high-gain frequency modulation modes specifically include:

Q ₁ and Q _{2 are} controlled to work periodically by turning on Ts/2 and turning off Ts/2.

Q ₃ and Q _{4 are} controlled to work periodically in a manner of turning on Ts/2 and turning off Ts/2.

While controlling Q ₃ and Q ₄ to turn off at the same time, control Q ₁ and Q ₂ to turn on at the same time.

While controlling Q ₁ and Q ₂ to turn off at the same time, control Q ₃ and Q ₄ to turn on at the same time.

In the high-gain frequency modulation mode, the drive pulses of _{Q 1} and Q ₂ _{are always synchronized, and the drive pulses of Q 3} and Q ₄ are always synchronized, and the duty cycle is maintained at 50%. When Q1 and Q2 are turned on at the same time, V _AB =V _in /2; when Q3 and Q4 are turned on at the same time, V _AB =-V _in /2. In this way, the _{duty cycle of V AB is} fixed at 50%, and the peak-to-peak value of _{V AB} _{is the input voltage V in} . Therefore, the output voltage V _o =M1*V _in /(2*N), M1 is the gain in high-gain frequency modulation mode . The frequency of the LLC resonant cavity input voltage V _AB is equal to the switching frequency f _s .

Referring to Figure 5, the low-gain frequency modulation mode specifically includes:

Q ₁ and Q _{2 are} controlled to work periodically by turning on 3Ts/4 and turning off Ts/4.

Q ₃ and Q _{4 are} controlled to work periodically in a manner of turning on Ts/4 and turning off 3Ts/4.

While controlling Q _{1 to turn} off, control Q _{4 to} turn on. While controlling Q _{2 to turn} off, control Q _{3 to} turn on. After the time that the control Q _{1 is} turned on reaches Ts/4, the control Q _{2 is} turned off.

When Q1 and Q2 are simultaneously turned on, V _AB, V _C3 and V _C4 are V _in / 2.

When Q1 and Q3 are turned on at the same time, V _AB is zero, V _C2 and V _C4 are both V _in /2, i _Ls is negative, and the flying capacitor C _k is discharged.

When Q2 and Q4 are turned on at the same time, V _AB is zero, V _C1 and V _C3 are both V _in /2, i _Ls is negative, and the flying capacitor C _k is charged.

When modulating according to the above process, the duty ratio of the driving pulses of _{Q 1} and Q ₂ _{is 75%, and the driving pulses of Q 3} and Q ₄ are 25%, so that the peak-to-peak value of V _AB _{is V in} /2. Therefore, the output voltage V _o =M2*V _in /(4*N), M2 is the gain in the low-gain frequency modulation mode. The frequency of V _AB _{becomes twice that of f s} . According to the gain curve shown in Fig. 2, under the same resonant cavity parameters and load conditions, M2<M1. For the same input voltage, in the low gain frequency modulation mode, the output voltage of the flying capacitor half-bridge three-level LLC resonant converter is lower than half of the high gain frequency modulation mode, which means that the flying capacitor half bridge The gain of the three-level LLC resonant converter is lower than half of the high-gain frequency modulation.

For the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described sequence of actions, because according to the present invention, Some steps can be performed in other order or at the same time.

The following are device embodiments of the present invention, which can be used to implement the method embodiments of the present invention. For details that are not disclosed in the device embodiment of the present invention, please refer to the method embodiment of the present invention.

Refer to FIG. 6, which is a schematic diagram of a gain frequency modulation device applied to a flying capacitor half-bridge three-level LLC resonant converter according to an embodiment of the present invention. The device includes: a first adjustment unit 61 and a second adjustment unit 62.

The first adjustment unit 61 is configured to calculate the current demand gain if the input voltage changes in the high-gain frequency modulation mode, and determine whether the current demand gain is less than the preset first gain threshold, and if so, switch to low Gain frequency modulation mode, if not, adjust the switching frequency in the high gain frequency modulation mode to obtain the target output voltage;

The second adjusting unit 62 is configured to calculate the current gain if the input voltage changes in the low-gain frequency modulation mode, and determine whether the current gain is greater than the preset second gain threshold, and the second gain threshold is greater than the first gain Threshold, if yes, switch to high-gain frequency modulation mode, if not, adjust the switching frequency in low-gain frequency modulation mode to obtain the target output voltage, for the same input voltage, flying capacitor in low-gain frequency modulation mode The peak-to-peak value of the input voltage of the LLC resonant cavity of the half-bridge three-level LLC resonant converter is smaller than the peak-to-peak value of the LLC resonant input voltage of the flying capacitor half-bridge three-level LLC resonant converter in the high-gain frequency modulation mode .

Refer to Fig. 7, which is a schematic diagram of a controller provided by an embodiment of the present invention. The hardware structure of the controller may include: at least one processor 71, at least one communication interface 72, at least one memory 73, and at least one communication bus 74; and the processor 71, the communication interface 72, and the memory 73 communicate with each other through the communication bus 74. Communication.

In some embodiments, the processor 71 may be a CPU (Central Processing Unit, central processing unit), or an ASIC (Application Specific Integrated Circuit, specific integrated circuit), or may be configured to implement one or more of the embodiments of the present invention. Integrated circuits, etc.

The communication interface 72 may include a standard wired interface and a wireless interface (such as a WI-FI interface). It is usually used to establish a communication connection between a data verification device and other electronic devices or systems.

The memory 73 includes at least one type of readable storage medium. The readable storage medium may be NVM (non-volatile memory, non-volatile memory) such as flash memory, hard disk, multimedia card, and card-type memory. The readable storage medium may also be a high-speed RAM (random access memory, random access memory) memory.

The memory 73 stores a computer program, and the processor 71 can call the computer program stored in the memory 73, and the computer program is used for:

In the high-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is determined whether the current demand gain is less than the preset first gain threshold, if so, switch to the low-gain frequency modulation mode, if not, Adjusting the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage;

In the low-gain frequency modulation mode, if the input voltage changes, the current gain is calculated, and it is determined whether the current gain is greater than the preset second gain threshold, and the second gain threshold is greater than the first gain threshold, If yes, switch to the high-gain frequency modulation mode, if not, adjust the switching frequency in the low-gain frequency modulation mode to obtain the target output voltage;

The detailed functions and extended functions of the program can be referred to the above description.

FIG. 7 only shows a controller with components 71 to 74, but it should be understood that it is not required to implement all the illustrated components, and more or fewer components may be implemented instead.

The embodiment of the present invention also provides a readable storage medium, the readable storage medium may store a program suitable for execution by a processor, and the program is used for:

The device embodiments described above are merely illustrative, where the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units. Some or all of the modules can be selected according to actual needs to achieve the objectives of the solutions of the embodiments. Those of ordinary skill in the art can understand and implement it without creative work.

In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such existence between these entities or operations. The actual relationship or order. Moreover, the terms "include", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes those that are not explicitly listed Other elements of, or also include elements inherent to this process, method, article or equipment. If there are no more restrictions, the element defined by the sentence "including a..." does not exclude the existence of other identical elements in the process, method, article, or equipment that includes the element.

The foregoing description of the disclosed embodiments of the present invention enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this document, but should conform to the widest scope consistent with the principles and novel features disclosed in this document.

Claims

A gain frequency modulation method, characterized in that it is applied to a flying capacitor half-bridge three-level LLC resonant converter, and the method includes:

In the high-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is judged whether the current demand gain is less than the preset first gain threshold, if so, switch to the low-gain frequency modulation mode to adjust the switching frequency , To obtain the target output voltage, if not, adjust the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage;

In the low-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is determined whether the current demand gain is greater than the preset second gain threshold, and the second gain threshold is greater than the first gain Threshold, if yes, switch to the high-gain frequency modulation mode to perform switching frequency adjustment to obtain the target output voltage, if not, adjust the switching frequency in the low-gain frequency modulation mode to obtain the target output voltage;

For the same input voltage, the peak-to-peak value of the LLC resonant input voltage of the flying capacitor half-bridge three-level LLC resonant converter in the low-gain frequency modulation mode is smaller than that in the high-gain frequency modulation mode The peak-to-peak value of the input voltage of the LLC resonant cavity of the capacitive half-bridge three-level LLC resonant converter.
The method according to claim 1, wherein the low-gain frequency modulation mode specifically comprises:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 3/4 of the switching cycle time and turning off 1/4 of the switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/4 switching cycle time and turning off 3/4 switching cycle time;

Controlling the fourth switching tube to be turned on while controlling the first switching tube to be turned off;

Controlling the third switching tube to be turned on while controlling the second switching tube to be turned off;

After the first switching tube is controlled to be turned on for 1/4 of the switching cycle time, the second switching tube is controlled to be turned off.
The method according to claim 1, wherein the high-gain frequency modulation mode specifically comprises:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

While controlling the third switching tube and the fourth switching tube to be turned off at the same time, controlling the first switching tube and the second switching tube to be turned on at the same time;

While the first switching tube and the second switching tube are controlled to be turned off at the same time, the third switching tube and the fourth switching tube are controlled to be turned on at the same time.
The method according to claim 1, wherein the process of calculating the current demand gain comprises:

Divide the product of the target output voltage and the transformer ratio by the input voltage to get the current demand gain.
A controller includes a memory and a processor, the memory is used to store a program, and is characterized in that the processor is used to execute the program to implement a flying capacitor type half-bridge three-level LLC A gain frequency modulation method of a resonant converter, the method includes:

In the high-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is judged whether the current demand gain is less than the preset first gain threshold, if so, switch to the low-gain frequency modulation mode to adjust the switching frequency , To obtain the target output voltage, if not, adjust the switching frequency in the high-gain frequency modulation mode to obtain the target output voltage;

In the low-gain frequency modulation mode, if the input voltage changes, the current demand gain is calculated, and it is determined whether the current demand gain is greater than the preset second gain threshold, and the second gain threshold is greater than the first gain Threshold, if yes, switch to the high-gain frequency modulation mode to perform switching frequency adjustment to obtain the target output voltage, if not, adjust the switching frequency in the low-gain frequency modulation mode to obtain the target output voltage;

For the same input voltage, the peak-to-peak value of the LLC resonant input voltage of the flying capacitor half-bridge three-level LLC resonant converter in the low-gain frequency modulation mode is smaller than that in the high-gain frequency modulation mode The peak-to-peak value of the input voltage of the LLC resonant cavity of the capacitive half-bridge three-level LLC resonant converter.
The controller according to claim 5, wherein the low-gain frequency modulation mode specifically comprises:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 3/4 of the switching cycle time and turning off 1/4 of the switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/4 switching cycle time and turning off 3/4 switching cycle time;

Controlling the fourth switching tube to be turned on while controlling the first switching tube to be turned off;

Controlling the third switching tube to be turned on while controlling the second switching tube to be turned off;

After the first switching tube is controlled to be turned on for 1/4 of the switching cycle time, the second switching tube is controlled to be turned off.
The controller according to claim 5, wherein the high-gain frequency modulation mode specifically comprises:

Controlling the first switching tube and the second switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

Control the third switching tube and the fourth switching tube to periodically work in a manner of turning on 1/2 switching cycle time and turning off 1/2 switching cycle time;

While controlling the third switching tube and the fourth switching tube to be turned off at the same time, controlling the first switching tube and the second switching tube to be turned on at the same time;

While the first switching tube and the second switching tube are controlled to be turned off at the same time, the third switching tube and the fourth switching tube are controlled to be turned on at the same time.
The controller according to claim 5, wherein the process of calculating the current demand gain comprises:

Divide the product of the target output voltage and the transformer ratio by the input voltage to get the current demand gain.
A readable storage medium with a program stored thereon, wherein when the program is executed by a processor, each step of the gain frequency modulation method according to any one of claims 1 to 4 is realized.