Control method of resonant converter and resonant conversion device

Abstract

This application proposes a control method and device for a resonant converter. A controller is used to control the resonant converter to operate in either a frequency control phase or a hiccup mode. During the ripple generation phase of the hiccup mode, the controller generates a cluster of drive signals within a portion of its control cycle. The duration of each cluster of drive signals is equal to the control cycle of the controller. Conversely, the controller does not generate any drive signals during a portion of its control cycle. This reduces the ripple of the resonant converter's output voltage.

Description

Technical Field

[0001] This application relates to the field of power supply, and in particular to control methods and devices for resonant converters. Background Technology

[0002] The resonant converter is a highly attractive isolated DC-DC converter. Because it can achieve soft switching across the entire load range, it can reduce switching losses, improve converter efficiency, reduce size, and increase power density, thus being widely used in various fields.

[0003] With the development of technology and market demand, electric vehicles are becoming increasingly popular. Resonant converters are commonly used in electric vehicles, such as in their on-board chargers, to improve the efficiency of power conversion within the electric vehicle and reduce the size of the power conversion device.

[0004] The hiccup control strategy of the resonant converter is to avoid extremely high switching frequencies under light loads, as excessively high switching frequencies place stringent demands on the drive power. Specifically, when the drive frequency output by the resonant circuit loop exceeds a certain value, the resonant converter enters hiccup control mode. Please refer to [link to relevant documentation]. Figure 1 The diagram shown illustrates the operating waveforms of a prior art resonant converter in hiccup mode. The existing hiccup control mode includes a blocking phase t1 and a transmitting phase t2. During the blocking phase t1, the drive signals for the switching transistors within the resonant converter are blocked, meaning all the transistors in the resonant converter are turned off. When certain conditions are met, such as loop parameters or output voltage conditions, the drive signals for the resonant converter are turned on, i.e., the transmitting phase t2 begins. The resonant converter then receives the drive signal and enters a high-frequency switching state. This alternating operation of the blocking and transmitting phases constitutes the hiccup control mode.

[0005] As can be seen, in the aforementioned existing technology, entering the blocking phase t1 or the transmission phase t2 is determined by the sampling signal output by the sampling circuit, and the controller decides whether to operate in the blocking phase t1 or the transmission phase t2 based on the sampling signal. We know that the sampling circuit has a sampling period, and the controller has a control period. For example, the controller's control period is determined by its timer. Assuming the controller's control period is 20µs, this corresponds to a control frequency of approximately 50kHz, meaning that a sampling signal is obtained and a control command is output every 20µs. In other words, the controller can only respond to changes in the output signal every 20µs.

[0006] We know that the driving frequency of the driving circuit is relatively high. For resonant converters, the driving frequency is usually several hundred kilohertz, such as 300 kHz. That is, the driving circuit sends a driving signal to the switching transistor at a frequency of 300 kHz.

[0007] It is evident that the driving frequency is much higher than the controller's control frequency. This causes the resonant converter to remain in the wave-sealing phase t1, even though it should have transitioned from the wave-sealing phase t1 to the wave-generating phase t2. Because the controller's control frequency is low and the control commands are delayed, the resonant converter continues to operate in the wave-sealing phase t1. During this period, the output voltage Vo of the resonant converter will continuously decrease. (See reference...) Figure 1 As shown. Similarly, the waveform should transition from the waveform generation stage t2 to the waveform blocking stage t1. However, due to the low control frequency of the controller and the lag in the control commands, the resonant converter remains in the waveform generation stage t2. During this period, the output voltage Vo of the resonant converter will continuously rise. (See reference...) Figure 1 As shown, this results in a large output voltage ripple ΔV for Vo, which is undesirable for a resonant converter. Summary of the Invention

[0008] According to one embodiment, this application provides a control method for a resonant converter, comprising:

[0009] S1: Determine whether the driving frequency of the resonant converter is greater than the maximum frequency setting value. If not, proceed to step S5; if yes, proceed to step S2.

[0010] S2: Determine whether the output voltage of the resonant converter is less than the voltage setting value. If not, proceed to step S3; if yes, proceed to step S4.

[0011] S3: Enter the wave blocking stage of hiccup mode, and then proceed to step S1;

[0012] S4: Enter the wave generation stage of hiccup mode. In the wave generation stage of hiccup mode, the flag value is calculated based on the control frequency of the controller. If the flag value is the first value, the controller sends a cluster of drive signals. If the flag value is the second value, the controller does not send drive signals and then proceeds to step S1.

[0013] S5: Enter the frequency control stage, and then proceed to step S1.

[0014] Furthermore, the drive frequency is much higher than the controller's control frequency.

[0015] Furthermore, the duration of each cluster of drive signals is equal to the control cycle of the controller.

[0016] Furthermore, the number of switching cycles for each cluster of drive signals is the same.

[0017] Furthermore, the first value is 1; the second value is 0.

[0018] Furthermore, step S4, which calculates the flag value using the controller's control frequency, includes:

[0019] S41: Set the initial value of the count value cnt and set the pulse density value D;

[0020] S42: Determine whether the count value cnt is less than or equal to 0.5. If yes, proceed to step S43; otherwise, proceed to step S44.

[0021] S43: Update the count value according to the first formula based on the count value cnt and the pulse density value D, and then proceed to S45;

[0022] S44: Update the count value according to the second formula based on the count value cnt and the pulse density value D, and proceed to S45;

[0023] S45: Determine whether the updated count value cnt is less than or equal to 0.5. If yes, proceed to step S46; otherwise, proceed to step S47.

[0024] S46: Assign the first value to the flag value and proceed to step S48;

[0025] S47: Assign the flag value to the second value and proceed to step S48;

[0026] S48: Output the flag value and output the updated count value cnt to step S42.

[0027] Furthermore, the first formula is cnt = cnt + 1 - D; the second formula is cnt = cnt - D.

[0028] Furthermore, in step S5, the frequency control stage involves controlling the driving frequency of the resonant converter based on the sampled signal obtained from the resonant converter.

[0029] This application also provides a resonant converter, comprising:

[0030] Resonant converter, including:

[0031] A first switching unit, wherein a first terminal of the first switching unit is connected to a first voltage source terminal;

[0032] The transformer includes a first winding and a second winding, wherein the first winding is connected to the second end of the first switching unit;

[0033] The second switching unit has a first end connected to the second winding and a second end connected to the second voltage source.

[0034] The controller executes the control method for the resonant converter described above.

[0035] Furthermore, the first switching unit is configured as a full-bridge topology, and the second switching unit is configured as any one of a half-bridge topology, a full-bridge topology, or a rectifier unit.

[0036] Furthermore, the first switching unit is configured as a half-bridge topology, and the second switching unit is configured as any one of a half-bridge topology, a full-bridge topology, or a rectifier unit.

[0037] Furthermore, the resonant unit is connected between the first switching unit and the first winding, or between the second winding and the second switching unit.

[0038] This application also provides a resonant converter, comprising:

[0039] A resonant converter, including at least one switching transistor;

[0040] A controller is used to control the resonant converter to operate in the frequency control phase or the hiccup mode. During the emitting phase of the hiccup mode of the resonant converter, the controller emits a cluster of drive signals within a portion of the controller's control cycle. The duration of each cluster of drive signals is equal to the controller's control cycle. The controller does not emit drive signals during the portion of the controller's control cycle.

[0041] Furthermore, the driving frequency of each cluster of driving signals is much greater than the control frequency of the controller.

[0042] Furthermore, the controller calculates a flag value in each control cycle. If the flag value is 1, the controller sends a cluster of drive signals in that control cycle. If the flag value is 0, the controller does not send any drive signals in that control cycle.

[0043] The features and technical advantages of this disclosure have been outlined quite extensively above to facilitate a better understanding of the detailed description that follows. Additional features and advantages of this disclosure, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying or designing other structures or processes to achieve the same purpose as this disclosure. Those skilled in the art will also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0044] To gain a more complete understanding of this disclosure and its advantages, the following description is given in conjunction with the accompanying drawings, wherein:

[0045] Figure 1 A schematic diagram of the operating waveforms of a prior art resonant converter when it is operating in hiccup mode;

[0046] Figure 2 A control flowchart of a resonant converter according to an embodiment of this application is shown;

[0047] Figure 3A schematic diagram of the operating waveform of a resonant converter according to an embodiment of this application when it is operating in the wave generation phase of hiccup mode is shown.

[0048] Figure 4 A flowchart illustrating the calculation of a flag value according to an embodiment of this application is shown;

[0049] Figure 5 A schematic diagram of a resonant converter according to an embodiment of this application is shown;

[0050] Figure 6 A schematic block diagram of a resonant converter circuit according to an embodiment of this application is shown;

[0051] Figure 7 A schematic block diagram of a resonant converter circuit according to another embodiment of this application is shown.

[0052] Unless otherwise stated, correspondences and symbols in the different figures generally refer to corresponding parts. These figures are drawn to clearly illustrate relevant aspects of the various embodiments and are not necessarily drawn to scale. Detailed Implementation

[0053] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] This application provides a control method for a resonant converter according to one embodiment. See also... Figure 2 The control flowchart of a resonant converter according to an embodiment of this application shown includes:

[0055] S1: Determine whether the driving frequency fs of the resonant converter is greater than the maximum frequency setting value ft. If not, proceed to step S5; if yes, proceed to step S2.

[0056] S2: Determine whether the output voltage Vo of the resonant converter is less than the voltage setting value Vt. If no, proceed to step S3; if yes, proceed to step S4.

[0057] S3: Enter the wave blocking stage of hiccup mode, and then proceed to step S1;

[0058] S4: Enter the wave generation stage of hiccup mode. In the wave generation stage of hiccup mode, the flag value Flag is calculated based on the control frequency of the controller. If the flag value Flag is the first value F1, the controller sends a cluster of drive signals. If the flag value Flag is the second value F2, the controller does not send drive signals and then proceeds to step S1.

[0059] S5: Enter the frequency control stage, and then proceed to step S1.

[0060] See also Figure 3 The diagram shown illustrates the waveform of a resonant converter according to an embodiment of this application during the emitting phase of the hiccup mode. During the emitting phase of the hiccup mode, a flag value (Flag) is calculated using the controller's control frequency; that is, the flag value (Flag) is calculated once per control cycle. Figure 3 As shown, each control cycle has a flag value (Flag). And as... Figure 3 As shown, if the flag value is 1, the controller sends a cluster of drive signals within that control cycle; if the flag value is 0, the controller does not send any drive signals within that control cycle. That is, during the wave generation phase of the hiccup mode, wave generation is not continuous, nor is it determined by the output voltage or loop parameters. Instead, it is determined by the flag value calculated internally by the controller, thus distributing the drive pulses during the wave generation phase of the hiccup mode across multiple control cycles. For example... Figure 3 As shown, the output voltage Vo rises during a set of drive signals and falls during periods without drive signals. This is unlike... Figure 1 The existing technology shown continuously sends a drive signal during the wave generation phase of the hiccup mode, resulting in a very high output voltage, which is then dropped very low during the wave blocking phase. In contrast, this application distributes the drive pulses across multiple control cycles during the wave generation phase of the hiccup mode, preventing the output voltage from being raised or dropped too low, thus resulting in a smaller output voltage Vo ripple ΔV.

[0061] For resonant converters of the same voltage level, such as using Figure 1 The hiccup pattern shown in the prior art has an output voltage ripple of approximately 7.2V. (See reference...) Figure 1 If the hiccup mode of this application is used, the output voltage ripple is approximately 2.8V, as can be found in [reference needed]. Figure 3 Therefore, it can be seen that the hiccup mode of this application can result in a smaller output voltage Vo ripple ΔV.

[0062] More specifically, such as Figure 3 As shown, the driving frequency is much higher than the controller's control frequency. For example, if the control frequency is approximately 50 kHz and the driving frequency is 300 kHz, then using the existing hiccup control mode, as described in the prior art, would result in a large output voltage Vo ripple. However, using the method of this application, because the driving pulse is distributed across multiple control cycles during the ripple generation phase of the hiccup mode, the output voltage Vo ripple is smaller.

[0063] More specifically, such as Figure 3 As shown, the duration of each cluster of drive signals is equal to the controller's control cycle. For example... Figure 3 As shown, in the first control cycle td1, if the calculated flag value Flag is 1, a cluster of drive signals is output. At the end of the first control cycle td1, the transmission of drive pulses stops. At this time, regardless of the output voltage of the resonant converter, the transmission of drive pulses stops, thus preventing the output voltage Vo from being raised too high and entering the falling phase. In the following second control cycle td2, if the calculated flag value Flag is 0, the controller does not send drive signals, and the output voltage Vo decreases. In the following third control cycle td3, if the calculated flag value Flag is 1, the controller sends another cluster of drive signals, and the output voltage Vo rises. At the end of the third control cycle td3, the transmission of drive signals stops, and the output voltage Vo begins to fall. This process continues, calculating the flag value Flag for each control cycle. Based on the real-time flag value Flag within each control cycle, it is determined whether to send a cluster of drive signals, ensuring that the output voltage is neither raised too high nor dropped too low, thus minimizing the output voltage Vo ripple.

[0064] More specifically, such as Figure 3 As shown, each cluster of drive signals has the same number of switching cycles. That is, when the calculated flag value is 1, the controller sends a cluster of drive signals with the same switching cycle, which can further reduce the output voltage ripple.

[0065] For more details, please refer to Figure 4 , Figure 4 This is a flowchart illustrating the calculation of a flag value according to an embodiment of this application. Step S4, which calculates the flag value using the controller's control frequency as the frequency, includes:

[0066] S41: Set the initial value of the count value cnt and set the pulse density value D;

[0067] S42: Determine whether the count value cnt is less than or equal to 0.5. If yes, proceed to step S43; otherwise, proceed to step S44.

[0068] S43: Update the count value cnt according to the first formula based on the count value cnt and the pulse density value D, and then proceed to S45;

[0069] S44: Update the count value cnt according to the second formula based on the count value cnt and the pulse density value D, and then proceed to S45;

[0070] S45: Determine whether the updated count value cnt is less than or equal to 0.5. If yes, proceed to step S46; otherwise, proceed to step S47.

[0071] S46: Assign the flag value Flag to the first value F1, and proceed to step S48;

[0072] S47: Assign the flag value Flag to the second value F2, and proceed to step S48;

[0073] S48: Output the flag value Flag and output the updated count value cnt to step S42.

[0074] The flag value (Flag) is calculated in real time for each control cycle, and the count value (cnt) is updated accordingly.

[0075] In one specific embodiment, the first formula is cnt = cnt + 1 - D; the second formula is cnt = cnt - D.

[0076] In one specific embodiment, the initial value of the count value cnt is set to 0, and the pulse density value D is set to 0.6. In step S42, if the count value cnt is determined to be less than 0.5, then in step S43, the updated count value is calculated to be 0.4 according to the first formula cnt = cnt + 1 - D. Then, in step S45, if the count value cnt is determined to be less than 0.5, then in step S46, the flag value Flag is assigned the first value, i.e., 1. A cluster of drive signals is then issued within this control cycle. Figure 3 The first control cycle td1 is shown. At this time, the updated count value cnt is 0.4. In step S42, it is determined that the count value cnt is less than 0.5. Then, in step S43, the updated count value is calculated according to the first formula cnt = cnt + 1 - D, which is 0.8. Then, in step S45, it is determined that the count value cnt is greater than 0.5. Then, in step S47, the flag value Flag is assigned the second value, which is 0. Therefore, no cluster of drive signals is issued during this control cycle. Figure 3 The second control cycle td2 is shown. At this time, the updated count value cnt is 0.8. In step S42, if the count value cnt is greater than 0.5, then in step S44, the updated count value is calculated according to the second formula cnt = cnt - D, which is 0.2. Then, in step S45, if the count value cnt is less than 0.5, then in step S46, the flag value Flag is assigned the first value, i.e., 1. A cluster of drive signals is then issued within this control cycle, such as... Figure 3 The third control cycle, td3, is shown. The flag value (Flag) is calculated sequentially for each control cycle to determine whether a cluster of drive signals should be issued, and the count value is updated accordingly.

[0077] Calculate in this manner, such as Figure 3 As shown, within ten control cycles, a cluster of drive signals is generated in six of them, meaning a cluster of drive signals is generated in a portion of the control cycles; in the other four control cycles, no drive signals are generated, meaning no drive signals are generated in a portion of the control cycles. This disperses the drive pulses during the ripple generation phase of the hiccup mode, thereby reducing the output voltage ripple.

[0078] In one specific embodiment, the frequency control stage in step S5 is as follows: the driving frequency of the resonant converter is controlled according to the sampling signal obtained from the resonant converter. This is a conventional frequency control mode, that is, the driving frequency of the resonant converter is controlled according to the sampling signal obtained from the resonant converter to control the target value within the desired range, such as the output voltage within the desired voltage range. During this period, the driving frequency of the resonant converter is less than the maximum frequency setting value ft, and it is continuously judged whether the driving frequency of the resonant converter is greater than the maximum frequency setting value ft. If it is, the hiccup mode is entered, and the control is performed according to the above steps S2 to S4 to determine whether to operate in the blocking stage or the emitting stage of the hiccup mode, and whether to emit a cluster of driving pulses in each control cycle within the emitting stage of the hiccup mode.

[0079] In practical implementation, the number of control cycles in which a cluster of drive pulses is emitted within 10 control cycles can be controlled by setting different pulse density values ​​D. As mentioned above, if the pulse density value D is 0.6, then a cluster of drive signals will be emitted in six out of the ten control cycles. If the pulse density value D is 0.5, then according to... Figure 4 The method shown calculates that a cluster of drive signals is generated in five out of ten control cycles. In practical applications, the pulse density value D can be determined based on the voltage level of the resonant converter. Specifically, when the voltage level is high, the pulse density value D can be set to be high, meaning that a cluster of drive signals is generated in more out of ten control cycles. Conversely, when the voltage level is low, the pulse density value D can be set to be low, meaning that a cluster of drive signals is generated in more out of ten control cycles. This ensures that the output voltage ripple remains within an acceptable range.

[0080] In actual implementation, the initial value of the count value cnt in step S41 can be set to 0. Of course, it can also be other values, and this application does not limit it.

[0081] In practice, the maximum frequency setting value ft mentioned above is usually the maximum driving frequency that the controller can provide, such as 300KHZ.

[0082] In practical implementation, the aforementioned voltage setting value Vt is typically the maximum acceptable output voltage. In existing technology, when operating in hiccup mode, the output voltage reaches this voltage setting value Vt, triggering the hiccup mode's blocking phase. Using the control method of this application, since the output voltage is neither excessively high nor excessively low (i.e., the ripple is smaller), ideally, the output voltage will not reach the voltage setting value Vt. Therefore, in hiccup mode, the blocking phase will not be triggered, and the system will operate within the hiccup mode. Figure 3The ripple of the output voltage is further reduced by the dispersed ripple stage of the hiccup pattern shown.

[0083] In one embodiment, this application also provides a resonant converter, which can be referred to in [reference]. Figure 5 The diagram shows a resonant converter. Figure 5 As shown, the resonant converter includes a resonant converter 100 and a controller 200, wherein the controller 200 is used to execute the control method of the resonant converter described above, so that the output voltage ripple of the resonant converter is small.

[0084] Resonant converters are typically isolated resonant converters, such as... Figure 5 As shown, the resonant converter includes: a first switching unit 110, the first end of which is connected to a first voltage source terminal V1; a transformer 130, including a first winding Lp and a second winding Ls, the first winding Lp being connected to the second end of the first switching unit 110; and a second switching unit 120, the first end of which is connected to the second winding Ls, and the second end of which is connected to a second voltage source terminal V2.

[0085] More specifically, such as Figure 5 As shown, the resonant unit 140 is connected between the first switching unit 110 and the first winding Lp. In actual implementation, the resonant unit 140 can also be connected between the second winding Ls and the second switching unit 120.

[0086] In actual implementation, the resonant unit 140 can be implemented as an LC resonant unit or an LLC resonant unit.

[0087] In one specific embodiment, such as Figure 6 The schematic diagram of a resonant converter circuit according to an embodiment of this application shows that the first switching unit 110 is configured as a half-bridge topology and the second switching unit 120 is configured as a full-bridge topology, which can realize the conversion of the voltage of the first voltage source terminal V1 to the voltage of the second voltage source terminal V2, and thus implement a unidirectional converter.

[0088] In practical applications, Figure 6 The second switching unit 120 can also be configured as a half-bridge topology or a rectifier unit, etc.

[0089] In one specific embodiment, such as Figure 7 The schematic diagram of the resonant converter circuit according to another embodiment of this application shows that the first switching unit 110 is configured as a full-bridge topology and the second switching unit 120 is configured as a full-bridge topology, which can realize the conversion of the voltage of the first voltage source terminal V1 to the voltage of the second voltage source terminal V2, or the conversion of the voltage of the second voltage source terminal V2 to the voltage of the first voltage source terminal V1, thus implementing a bidirectional converter.

[0090] In practical applications, Figure 7 The second switching unit 120 can also be configured as a half-bridge topology or a rectifier unit, etc.

[0091] In practical applications, the topology of the resonant converter can be selected according to the voltage level or the required power flow direction.

[0092] This application also provides a resonant converter device, which can be found in [reference]. Figure 5 The resonant converter includes a resonant converter 100 and a controller 200. The resonant converter 100 can also be implemented as... Figure 6 and Figure 7 The structure shown.

[0093] The controller 200 controls the resonant converter to operate in either the frequency control phase or the hiccup mode. During the emitting phase of the hiccup mode, the controller emits a cluster of drive signals within a portion of its control cycle. The duration of each cluster of drive signals is equal to the control cycle of the controller. The controller does not emit any drive signals during the remaining portion of its control cycle. (See reference...) Figure 3 As shown.

[0094] Furthermore, the driving frequency of each cluster of driving signals is much greater than the control frequency of the controller.

[0095] Furthermore, the controller calculates a flag value in each control cycle. If the flag value is 1, the controller sends a cluster of drive signals in that control cycle. If the flag value is 0, the controller does not send any drive signals in that control cycle.

[0096] The specific principle is the same as described above, and will not be repeated here.

[0097] In practical implementation, the aforementioned controller is implemented as a digital controller, such as a DSP or MCU. The control cycle is then determined by the digital controller's timer; for example, a control cycle of 20µs corresponds to a control frequency of approximately 50kHz. However, this application does not limit this; the controller's control cycle may also be related to the sampling period of the sampling circuit. For instance, if the sampling period is greater than the control cycle determined by the timer, then the sampling period is used as the controller's control cycle.

[0098] Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

[0099] Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, apparatuses, methods, and steps described in the specification. As will be readily understood by those skilled in the art from the disclosure of this publication, processes, machines, manufactures, compositions of matter, means, methods, or steps that perform substantially the same function, currently exist or will be developed or implemented thereafter, will yield substantially the same results as the corresponding embodiments described herein that are available according to this disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, apparatuses, methods, or steps within their scope.

Claims

1. A control method of a resonant converter, characterized by, include: S1: Determine whether the driving frequency of the resonant converter is greater than the maximum frequency setting value. If not, proceed to step S5; if yes, proceed to step S2. S2: Determine whether the output voltage of the resonant converter is less than the voltage setting value. If not, proceed to step S3; if yes, proceed to step S4. S3: Enter the wave blocking stage of hiccup mode, and then proceed to step S1; S4: Enter the wave generation stage of hiccup mode. In the wave generation stage of hiccup mode, the flag value is calculated based on the control frequency of the controller. If the flag value is the first value, the controller sends a cluster of drive signals, and the duration of each cluster of drive signals is equal to the control cycle of the controller. If the flag value is the second value, the controller does not send drive signals, and then proceeds to step S1. S5: Enter the frequency control stage, then proceed to step S1. Step S4, which calculates the flag value using the controller's control frequency, includes: S41: Set the initial value of the count value cnt and set the pulse density value D; S42: Determine whether the count value cnt is less than or equal to 0.

5. If yes, proceed to step S43; otherwise, proceed to step S44. S43: Update the count value according to the first formula based on the count value cnt and the pulse density value D, and then proceed to S45; S44: Update the count value according to the second formula based on the count value cnt and the pulse density value D, and proceed to S45; S45: Determine whether the updated count value cnt is less than or equal to 0.

5. If yes, proceed to step S46; otherwise, proceed to step S47. S46: Assign the first value to the flag value and proceed to step S48; S47: Assign the flag value to the second value and proceed to step S48; S48: Output the flag value and output the updated count value cnt to step S42, where the first formula is cnt+1-D; the second formula is cnt-D.

2. The control method of the resonant converter according to claim 1, characterized in that, The duration of each cluster of drive signals is equal to the control cycle of the controller.

3. The control method of the resonant converter according to claim 1 or 2, characterized in that, The number of switching cycles for each cluster of drive signals is the same.

4. The control method for the resonant converter according to claim 1, characterized in that, The first value is 1; the second value is 0.

5. The control method for the resonant converter according to claim 1, characterized in that, In step S5, the frequency control stage involves controlling the driving frequency of the resonant converter based on the sampled signal obtained from the resonant converter.

6. A resonant converter, characterized in that, include: Resonant converter, including: A first switching unit, wherein a first terminal of the first switching unit is connected to a first voltage source terminal; The transformer includes a first winding and a second winding, wherein the first winding is connected to the second end of the first switching unit; The second switching unit has a first end connected to the second winding and a second end connected to the second voltage source. The controller executes the control method for the resonant converter as described in claim 1.

7. The resonant converter according to claim 6, characterized in that, The first switching unit is configured as a full-bridge topology, and the second switching unit is configured as any one of a half-bridge topology, a full-bridge topology, or a rectifier unit.

8. The resonant converter according to claim 6, characterized in that, The first switching unit is configured as a half-bridge topology, and the second switching unit is configured as any one of a half-bridge topology, a full-bridge topology, or a rectifier unit.

9. The resonant converter according to claim 6, characterized in that, The resonant unit is connected between the first switching unit and the first winding, or between the second winding and the second switching unit.

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