Control system and control method thereof

Abstract

The application relates to a control system and a control method thereof. A converter provides an output voltage for a load. The converter has a low load gain curve, a high load gain curve, a preset low load operating frequency and a preset high load operating frequency according to a characteristic. A detection module samples the output voltage of the converter and a first electric signal. The first electric signal is a sampling signal reflecting an actual load value of the load. A control module adjusts the output voltage of the converter according to the first electric signal and a gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter, so that the difference between the full load operating frequency and the no-load operating frequency of the converter is less than a first preset frequency difference. The gain change coefficient is determined according to the low load gain curve, the high load gain curve, the preset low load operating frequency and the preset high load operating frequency.

Description

Technical Field

[0001] This case involves the field of power electronics, specifically a control system and its control method. Background Technology

[0002] Currently, power supply systems are developing towards modularity, high frequency, and digitalization. LLC circuits in power supply systems can achieve zero-voltage conduction across the entire load range and offer advantages such as low switching losses, high efficiency, and small size, leading to their widespread application. However, LLC circuits utilize digital signal processing for control and have a wide gain range. This results in significant frequency variations during switching between no-load and full-load conditions, causing instability in the converter's operation within the power supply system. Furthermore, the converter's control via digital signal processing suffers from loop delays such as sampling delays, causing a slow frequency change during dynamic load variations, resulting in poor dynamic response. To address these issues, traditional power supply systems incorporate the converter's operating current into the control loop to adjust the converter's gain. This reduces the frequency variation range of the LLC circuit during no-load and full-load switching, while simultaneously improving the converter's response speed during dynamic load changes.

[0003] Currently, converters have two operating frequency regulation methods. The first method is direct modulation, which, during load switching, obtains the periodic change value by looking up a table or calculating the output current before and after the load switch, and then superimposes it onto the linear controller to achieve rapid adjustment of the operating frequency. However, the above method requires accurate modeling of the converter and calculation of the switching period, which places high demands on the controller. Furthermore, if the operating frequency variation range is wide, it is prone to output voltage overshoot due to excessively rapid frequency switching.

[0004] The second adjustment method is the gradual adjustment method. When load changes cause output voltage fluctuations, the output voltage is sampled and compared with the set value to obtain the deviation. When the deviation exceeds the allowable value, the operating frequency is adjusted. Through gradual adjustment over multiple switching cycles, the switching frequency for stable converter operation is achieved. Furthermore, the output voltage is PI-regulated within each switching cycle to ensure stability. However, this method suffers from slow dynamic response speed due to sampling delays or program calculation delays, and the converter is unstable during frequency switching.

[0005] Therefore, it is necessary to develop a control system and its control method to solve the problems faced by previous technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a control system and its control method, which utilizes a detection module to adjust the output voltage of a converter based on a first electrical signal and a gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter, so that the difference between the full-load operating frequency and the no-load operating frequency of the converter is less than a first preset frequency difference. In other words, the control system of this invention achieves the wide gain requirement of the converter under load by adjusting the output voltage, so that the operating frequency can be switched when the change between the full-load operating frequency and the no-load operating frequency is small, thereby improving the speed of dynamic response and reducing the risk of output voltage overshoot, and further improving the adaptive capability, achieving the advantages of simple control, reduced cost and improved algorithm.

[0007] To achieve the above objectives, this invention provides a control system comprising a load, a converter, a detection module, and a control module. The converter provides an output voltage to the load and, based on its characteristics, has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency, and a preset high-load operating frequency. The first load value corresponding to the low-load gain curve is less than the second load value corresponding to the high-load gain curve. The detection module samples the converter's output voltage and a first electrical signal, where the first electrical signal is a sampled signal reflecting the actual load value of the load. The control module adjusts the converter's output voltage based on the first electrical signal and a gain variation coefficient, and outputs a control signal to adjust the converter's operating frequency, ensuring that the difference between the converter's full-load operating frequency and its no-load operating frequency is less than a first preset frequency difference. The gain variation coefficient is determined based on the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency.

[0008] To achieve the above objectives, this invention provides a control method applied to a control system. The control system includes a load, a converter, a detection module, and a control module. The converter provides an output voltage to the load. The control method includes the following steps: First, the converter has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency, and a preset high-load operating frequency based on its characteristics. The first load value corresponding to the low-load gain curve is less than the second load value corresponding to the high-load gain curve. Next, the detection module samples the converter's output voltage and a first electrical signal, where the first electrical signal is a sampled signal reflecting the actual load value of the load. Then, the control module adjusts the converter's output voltage based on the first electrical signal and a gain variation coefficient, and outputs a control signal to adjust the converter's operating frequency, making the difference between the converter's full-load operating frequency and its no-load operating frequency less than a first preset frequency difference. The gain variation coefficient is determined based on the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency. Attached Figure Description

[0009] Figure 1This is a block topology diagram of the first embodiment of the control system in this case;

[0010] Figure 2 for Figure 1 The gain curve of the converter in the control system is shown.

[0011] Figure 3 for Figure 1 The detailed circuit topology diagram of the control system shown is as follows;

[0012] Figure 4 for Figure 1 The voltage and current timing diagram of the control system shown is as follows;

[0013] Figure 5 This is a detailed circuit topology diagram of the second embodiment of the control system in this case;

[0014] Figure 6 This is a detailed circuit topology diagram of the third embodiment of the control system in this case; and

[0015] Figure 7 This is a flowchart of the control method for the control system in this case.

[0016] The reference numerals in the attached figures are explained as follows:

[0017] 1, 1a, 1b: Control System

[0018] 2: Load

[0019] 3: Converter

[0020] Cin: Input capacitance

[0021] Q1, Q2: Switching transistors

[0022] Cr: Resonant capacitor

[0023] Lr: Resonant inductance

[0024] Lm: Magnetizing inductance

[0025] 31: Transformer

[0026] 32: Primary winding

[0027] 33: Secondary winding

[0028] D1: First diode

[0029] D2: Second diode

[0030] Co: Output capacitor

[0031] Ro: Output resistance

[0032] A: Connection point

[0033] 4: Detection Module

[0034] R1: First resistor

[0035] R2: Second resistor

[0036] Rsense: Sampling resistor

[0037] R3: First filter resistor

[0038] R4: Second filter resistor

[0039] R5: Third filter resistor

[0040] R6: Fourth filter resistor

[0041] 41: Amplifier

[0042] C1: First capacitor

[0043] C2: Second capacitor

[0044] 5: Control Module

[0045] 51: Signal Processing Module

[0046] Rgain: Gain coefficient resistor

[0047] R7: First voltage divider resistor

[0048] R8: Second voltage divider resistor

[0049] 52: Microcontroller

[0050] 53: Driver Module

[0051] S1-S3: Steps Detailed Implementation

[0052] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different forms, all of which do not depart from the scope of this invention, and the descriptions and drawings therein are for illustrative purposes only and not for limiting this invention.

[0053] Please see Figure 1 and Figure 2 ,in Figure 1 This is a block topology diagram of the first embodiment of the control system in this case. Figure 2 for Figure 1 The gain curve of the converter in the control system is shown. Figure 1As shown, the control system 1 of this case includes a load 2, a converter 3, a detection module 4, and a control module 5. The converter 3 can be, but is not limited to, a resonant converter, and is connected to the load 2. The converter 3 receives and converts the input voltage into an output voltage and an output current, and provides the output voltage and output current to the load 2. The converter 3 has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency, and a preset high-load operating frequency according to its own characteristics.

[0054] like Figure 2 As shown, the low-load gain curve and the high-load gain curve are the gain curves formed by the gain and operating frequency of converter 3 at two different load values ​​of load 2, respectively. The load value of load 2 corresponding to the low-load gain curve is less than the load value of load 2 corresponding to the high-load gain curve. The gain curve represents the functional relationship between gain and operating frequency. In some embodiments, the low-load gain curve can be the gain curve of converter 3 when the load value of load 2 is unloaded, and the high-load gain curve can be the gain curve of converter 3 when the load value of load 2 is full load. In one embodiment, the gain variation range of converter 3 is less than or equal to 1, and the low-load gain curve and the high-load gain curve can be obtained by converter 3 according to the fundamental frequency analysis method. The low-load gain curve and the high-load gain curve can be calculated by the following formula (1).

[0055]

[0056] Where fn is the normalized frequency, Q is the quality factor, and λ is the inductance coefficient in converter 3.

[0057] The preset low-load operating frequency and the preset high-load operating frequency are the expected operating frequencies of converter 3 for two different load values ​​of load 2, respectively. The load value of load 2 corresponding to the preset low-load operating frequency is less than the load value of load 2 corresponding to the preset high-load operating frequency. In some embodiments, the preset low-load operating frequency can be the expected operating frequency of converter 3 when the load value of load 2 is unloaded, i.e., the unloaded operating frequency; the preset high-load operating frequency can be the expected operating frequency of converter 3 when the load value of load 2 is fully loaded, i.e., the full-load operating frequency, but it is not limited to these.

[0058] In this embodiment, the converter 3 determines the gain variation coefficient based on the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency. The unit of the gain variation coefficient is volts per ampere (V / A), and the gain variation coefficient is positively correlated with the difference between the first gain and the second gain. In other embodiments, the gain variation coefficient can be obtained by multiplying the difference between the first gain and the second gain by a correction factor; this application is not limited to this. The first gain is determined based on the low-load gain curve and the preset low-load operating frequency. For example, the first gain can be the gain corresponding to a preset low-load operating frequency on the low-load gain curve when the load 2 is unloaded. The second gain is determined based on the high-load gain curve and the preset high-load operating frequency. For example, the second gain can be the gain corresponding to a preset high-load operating frequency on the high-load gain curve when the load 2 is fully loaded. Depending on the application scenario, the preset low-load operating frequency and the preset high-load operating frequency can be the same or different. For example, when the control system 1 has only a single operating frequency requirement, the preset low-load operating frequency and the preset high-load operating frequency are the same; when the control system 1 has two different operating frequency requirements, the preset low-load operating frequency and the preset high-load operating frequency are different and differ by a second preset frequency difference, where the second preset frequency difference can be, but is not limited to, 10KHz.

[0059] Please refer to the previous document. Figure 1 The detection module 4 is connected to the converter 3 and samples the output voltage of the converter 3 and the first electrical signal of the load 2. The first electrical signal is a sampling signal that reflects the actual load value of the load 2. The first electrical signal can be the current signal of the converter 3, and the unit is amperes. For example, it can be the output current or input current of the converter 3. In other words, the detection module 4 can confirm the load value of the load 2 based on the output current or input current of the converter 3.

[0060] The control module 5 is connected to the detection module 4 and the converter 3. Based on the first electrical signal provided by the detection module 4 and the gain change coefficient of the converter 3, the control module 5 controls the converter 3 to adjust its output voltage and outputs a control signal to adjust the operating frequency of the converter 3, making the difference between the full-load operating frequency and the no-load operating frequency of the converter 3 less than a first preset frequency difference, which can be, but is not limited to, 20kHz. Specifically, the operating frequency of the converter 3 under high load conditions is lower than its operating frequency under low load conditions. Therefore, the output voltage can be reduced, thereby increasing the operating frequency under high load conditions and making it closer to the operating frequency under low load conditions. In this embodiment, the control module 5 adjusts the original output voltage by subtracting the product of the gain change coefficient and the first electrical signal from the original output voltage in each adjustment, reducing the output voltage so that the full-load operating frequency is close to the no-load operating frequency, and thus reducing the difference between the full-load operating frequency and the no-load operating frequency to less than the first preset frequency difference.

[0061] As can be seen from the above, the control system 1 of this case uses the detection module 4 to adjust the output voltage of the converter 3 according to the first electrical signal and the gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter 3, so that the difference between the full-load operating frequency and the no-load operating frequency of the converter is less than the first preset frequency difference. In other words, the control system 1 of this case achieves the wide gain requirement of the converter under load by adjusting the output voltage, so that the output voltage can switch the operating frequency when the change between the full-load operating frequency and the no-load operating frequency is small, thereby improving the speed of dynamic response and reducing the risk of output voltage overshoot, and further improving the adaptive capability, achieving the advantages of simple control, reduced cost and improved algorithm.

[0062] Please see Figure 3 and cooperate Figure 1 ,in Figure 3 for Figure 1 The diagram shows the detailed circuit topology of the control system. As shown, in this embodiment, the converter 3 includes an input capacitor Cin, two switching transistors Q1 and Q2, a resonant capacitor Cr, a resonant inductor Lr, a magnetizing inductor Lm, a transformer 31, a first diode D1, a second diode D2, an output capacitor Co, and an output resistor Ro. The input capacitor Cin receives the input voltage Vin. The two switching transistors Q1 and Q2 are connected in series and in parallel with the input capacitor Cin; the connection point between the two switching transistors Q1 and Q2 forms connection point A. The resonant capacitor Cr, the resonant inductor Lr, and the magnetizing inductor Lm are connected in series between connection point A and one end of the switching transistor Q2. The transformer 31 includes a primary winding 32 and a secondary winding 33; the primary winding 32 is connected in parallel with the magnetizing inductor Lm. The anode of the first diode D1 is connected to one end of the secondary winding 33, and the anode of the second diode D2 is connected to the other end of the secondary winding 33. The detection module 4 is connected between the midpoint of the secondary winding 33 and the output capacitor Co. The output resistor Ro is connected in parallel to the output capacitor Co. In this embodiment, the converter 3 is a resonant converter, and the resonant capacitor Cr and the resonant inductor Lr in the converter 3 constitute the resonant cavity of the converter 3. The first electrical signal sampled by the detection module 4 is the current of the resonant cavity. In other words, the detection module 4 can also determine the load value of the load 2 based on the current of the resonant cavity.

[0063] The detection module 4 may include, but is not limited to, circuits such as sampling circuits and operational amplifiers. For example... Figure 3As shown, the detection module 4 further includes a first resistor R1, a second resistor R2, a sampling resistor Rsense, a first filter resistor R3, a second filter resistor R4, a third filter resistor R5, a fourth filter resistor R6, an amplifier 41, a first capacitor C1, and a second capacitor C2. The first resistor R1 and the second resistor R2 are connected in series and in parallel with the output resistor Ro. The midpoint between the first resistor R1 and the second resistor R2 forms the output voltage sampling point and is connected to the control module 5. The sampling resistor Rsense is connected between the midpoint of the secondary winding 33 and one end of the output resistor Ro, using the sampled output current as the first electrical signal. The first filter resistor R3 and the third filter resistor R5 are connected in series between the first end of the sampling resistor Rsense and the first end of the amplifier 41. The second filter resistor R4 and the fourth filter resistor R6 are connected in series between the second end of the sampling resistor Rsense and the second end of the amplifier 41. One end of the first capacitor C1 is connected between the first filter resistor R3 and the third filter resistor R5, and the other end of the first capacitor C1 is connected between the second filter resistor R4 and the fourth filter resistor R6. The second capacitor C2 is connected between the first and third terminals of amplifier 41. The third terminal of amplifier 41 is connected to the control module 5. Amplifier 41 converts the output current sampled by sampling resistor Rsense into an output voltage signal, wherein the output voltage signal is proportional to the output current.

[0064] In this embodiment, as Figure 1 and 3 As shown, the control module 5 may further include a signal processing module 51, a microcontroller 52, and a drive module 53. The signal processing module 51 is connected between the detection module 4 and the microcontroller 52, and is used to receive and process the output voltage of the converter 3 and the first electrical signal of the load 2 sampled by the detection module 4, so as to transmit the sampling result to the microcontroller 52. In this embodiment, the signal processing module 51 further includes a gain coefficient resistor Rgain, a first voltage divider resistor R7, and a second voltage divider resistor R8. The gain coefficient resistor Rgain is connected between the third terminal of the amplifier 41 and the microcontroller 52. One end of the first voltage divider resistor R7 is connected to the midpoint between the first resistor R1 and the second resistor R2, and the other end of the first voltage divider resistor R7 is connected to the microcontroller 52. One end of the second voltage divider resistor R8 is grounded, and the other end of the second voltage divider resistor R8 is connected to the microcontroller 52. The microcontroller 52 is connected between the signal processing module 51 and the drive module 53. Based on the sampling results provided by the signal processing module 51, it controls the drive module 53 to output corresponding drive signals to control the operation of the switching transistors Q1 and Q2 of the converter 3, thereby controlling the output voltage of the converter 3. Please refer to [link to relevant documentation]. Figure 4 and cooperate Figures 1 to 3 ,in Figure 4 for Figure 1 The voltage and current timing diagram of the control system is shown. Figure 4 The following figures show the timing diagrams of the output voltage, the voltage across the gain coefficient resistor Rgain, and the output current, respectively. Figure 4 It can be seen that the electrical signal corresponding to the output voltage of converter 3 sampled by detection module 4 is divided by the first voltage divider resistor R7 and the second voltage divider resistor R8, while the electrical signal corresponding to the output current sampled by sampling resistor Rsense is divided by the gain coefficient resistor Rgain and the second voltage divider resistor R8. The reference voltage in control module 5 can control the voltage on the second voltage divider resistor R8 to remain constant. When the first electrical signal of load 2 reflects an increase in the load value of load 2, the current on load 2 increases, such as... Figure 4 As shown at time t1, the electrical signal corresponding to the output current sampled by the sampling resistor Rsense also increases. The electrical signal corresponding to the output voltage of converter 3 sampled by detection module 4 increases in voltage division across the second voltage divider resistor R8. Since the reference voltage remains constant, the voltage division across the second voltage divider resistor R8 decreases due to the electrical signal corresponding to the output current sampled by the sampling resistor Rsense. This results in a decrease in output voltage when the load 2 increases, making the gain of converter 3 under load close to the gain required for stable operation of converter 3. Similarly, at... Figure 4 At time t2, load 2 decreases, the current in load 2 decreases from high to low, the output voltage increases, the voltage across the gain coefficient resistor Rgain decreases, and the reference voltage remains unchanged. From this, it can be seen that when converter 3 is in a stable operating state, changes in load 2 will cause changes in the output voltage and switching frequency. Since different gains in converter 3 correspond to different switching frequencies, to ensure the stable operation of converter 3, after directly adjusting the gain, the switching frequency needs further adjustment.

[0065] Please see Figure 5 This is a detailed circuit topology diagram of the second embodiment of the control system in this case. As shown in the figure, the control module 5 of the control system 1a in this embodiment only includes a microcontroller 52 and a drive module 53, and does not include a signal processing module. The microcontroller 52 is directly connected to the midpoint between the first resistor R1 and the second resistor R2 to directly sample the voltage.

[0066] In some embodiments, the control module of the control system may include only a signal processing module and a microcontroller, without a drive module, so that the microcontroller directly controls the operation of the switching transistors Q1 and Q2.

[0067] Please see Figure 6 This is a detailed circuit topology diagram of the third embodiment of the control system in this case. The control system 1b of this embodiment is similar to... Figure 3 The control system shown is, compared to Figure 3The sampling resistor Rsense of the detection module 4 of the control system 1 is connected between the midpoint of the secondary winding 33 and one end of the output resistor Ro, and the sampling output current is used as the first electrical signal. In this embodiment, the sampling resistor Rsense of the detection module 4 of the control system 1b is connected between one end of the input capacitor Cin and one end of the switching transistor Q1, and the sampling input current is used as the first electrical signal.

[0068] Of course, the control system in this case is not limited to sampling the current with a resistor, and the sampled current can be the winding current of the transformer, in addition to the input current, output current and resonant cavity current.

[0069] Please see Figure 7 This is a flowchart of the control method of the control system in this case. As shown in the figure, firstly, step S1 is executed. The converter has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency, and a preset high-load operating frequency according to its characteristics. The load value corresponding to the low-load gain curve is less than the load value corresponding to the high-load gain curve. Next, step S2 is executed. The detection module samples the output voltage of the converter and a first electrical signal, where the first electrical signal is a sampled signal reflecting the load value. Next, step S3 is executed. The control module adjusts the output voltage of the converter according to the first electrical signal and the gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter, so that the difference between the full-load operating frequency and the no-load operating frequency of the converter is less than a first preset frequency difference. The gain change coefficient is determined according to the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency.

[0070] In summary, the control system of this invention utilizes a detection module to adjust the converter's output voltage based on a first electrical signal and a gain change coefficient, and outputs a control signal to adjust the converter's operating frequency, ensuring that the difference between the converter's full-load operating frequency and its no-load operating frequency is less than a first preset frequency difference. In other words, the control system of this invention achieves the wide gain requirement of the converter under load by adjusting the output voltage, allowing the operating frequency to switch when the change between the full-load and no-load operating frequencies is small. This improves the speed of dynamic response, reduces the risk of output voltage overshoot, and enhances adaptive capability, achieving advantages such as simplified control, reduced costs, and improved algorithms.

Claims

1. A control system, comprising: One load; A converter provides an output voltage to the load. The converter has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency and a preset high-load operating frequency according to its characteristics, wherein a first load value of the load corresponding to the low-load gain curve is less than a second load value of the load corresponding to the high-load gain curve. A detection module samples the output voltage of the converter and a first electrical signal, wherein the first electrical signal is a sampled signal reflecting an actual load value of the load; and A control module adjusts the output voltage of the converter according to the first electrical signal and a gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter so that the difference between a full-load operating frequency and an no-load operating frequency of the converter is less than a first preset frequency difference, wherein the gain change coefficient is determined according to the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency.

2. The control system of claim 1, wherein the gain variation coefficient is determined based on a first gain and a second gain, and the gain variation coefficient is positively correlated with the difference between the first gain and the second gain, wherein the first gain is determined based on the low-load gain curve and the preset low-load operating frequency, and the second gain is determined based on the high-load gain curve and the preset high-load operating frequency.

3. The control system as described in claim 1, wherein the first load value of the load corresponding to the low load gain curve is unloaded, and the second load value of the load corresponding to the high load gain curve is fully loaded.

4. The control system as described in claim 1, wherein the preset low-load operating frequency is the same as the preset high-load operating frequency.

5. The control system as described in claim 1, wherein the preset low-load operating frequency differs from the preset high-load operating frequency by a second preset frequency difference.

6. The control system as claimed in claim 1, wherein the control module adjusts the output voltage by subtracting the product of the gain variation coefficient and the first electrical signal from the output voltage, wherein the unit of the gain variation coefficient is volts / amperes, and the first electrical signal is the current signal of the converter, in amperes.

7. The control system of claim 1, wherein the first electrical signal is an output current or an input current of the converter.

8. The control system of claim 1, wherein the converter is a resonant converter and has a resonant cavity, and the first electrical signal is the current of the resonant cavity.

9. The control system as claimed in claim 1, wherein the first preset frequency difference is 20KHz.

10. The control system of claim 1, wherein the gain variation range of the converter is less than or equal to 1.

11. A control method applied to a control system, the control system comprising a load, a converter, a detection module, and a control module, the converter providing an output voltage to the load, wherein the control method comprises: The converter has a low-load gain curve, a high-load gain curve, a preset low-load operating frequency and a preset high-load operating frequency according to its characteristics, wherein a first load value of the load corresponding to the low-load gain curve is less than a second load value of the load corresponding to the high-load gain curve. The detection module samples the output voltage of the converter and a first electrical signal, wherein the first electrical signal is a sampled signal reflecting an actual load value of the load; and The control module adjusts the output voltage of the converter according to the first electrical signal and a gain change coefficient, and outputs a control signal to adjust the operating frequency of the converter so that the difference between a full-load operating frequency and an unloaded operating frequency of the converter is less than a first preset frequency difference. The gain change coefficient is determined according to the low-load gain curve, the high-load gain curve, the preset low-load operating frequency, and the preset high-load operating frequency.

12. The control method of claim 11, wherein the control method further comprises: The gain variation coefficient is determined based on a first gain and a second gain, and the gain variation coefficient is positively correlated with the difference between the first gain and the second gain. The first gain is determined based on the low-load gain curve and the preset low-load operating frequency, and the second gain is determined based on the high-load gain curve and the preset high-load operating frequency.

13. The control method of claim 11, wherein the first load value of the load corresponding to the low load gain curve is unloaded, and the second load value of the load corresponding to the high load gain curve is fully loaded.

14. The control method of claim 11, wherein the control method further comprises: Set the preset low-load operating frequency to be the same as the preset high-load operating frequency.

15. The control method of claim 11, wherein the control method further comprises: The preset low-load operating frequency is set to differ from the preset high-load operating frequency by a second preset frequency difference value.

16. The control method of claim 11, wherein the control method further comprises: The control module adjusts the output voltage by subtracting the product of the gain variation coefficient and the first electrical signal from the output voltage, wherein the unit of the gain variation coefficient is volts / amperes, and the first electrical signal is the current signal of the converter, with the unit of amperes.

17. The control method of claim 11, wherein the first electrical signal is an output current or an input current of the converter.

18. The control method of claim 11, wherein the converter is a resonant converter and has a resonant cavity, and the first electrical signal is the current of the resonant cavity.

19. The control method as described in claim 11, wherein the first preset frequency difference is 20 kHz.

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