Resonant converter and control method thereof

Abstract

The invention provides a resonant converter and a control method thereof, the resonant converter comprises an input circuit, a resonant circuit, a transformer and an output circuit which are connected in sequence, the resonant converter further comprises a controller, and the controller is used for receiving a target signal of the resonant converter in a current control period, a controller output value is determined at least according to the target signal and a reference signal of the resonant converter, when the controller output value is larger than the maximum frequency value, the duty ratio of the enable signal is determined according to the controller output value, the maximum frequency value and a set constant, and a driving signal is generated according to the enable signal and the pulse signal; the driving signal is used for controlling the resonant converter to work in the current control period. According to the invention, the output signal ripples during light load can be improved to the required frequency and the stability of the frequency can be maintained without being limited by the frequency controlled by a loop, so that the output signal ripples can be well filtered.

Description

TECHNICAL FIELD

[0001] The present application relates to the power electronics technology, and particularly to a resonant converter and a control method thereof. BACKGROUND

[0002] As one of the resonant converters, the LLC resonant converter usually adopts a pulse frequency modulation (PFM) control mode.

[0003] In order to ensure the stability of the LLC resonant converter output, the output signal needs to be controlled to control the output power. For example, by controlling the output current of the LLC resonant converter to ensure the stability of the output voltage. However, due to the limitation of the gain of the control chip, when the frequency of the control signal output by the control chip reaches the highest (i.e. the lowest gain), a relatively high power will still be output. Therefore, in the light load condition, the LLC resonant converter needs to adopt a burst mode.

[0004] However, the conventional burst mode control will cause a large ripple in the output signal, which may not meet the user's requirements. In order to reduce the ripple, it is considered to use the circuit equivalent between the LLC resonant converter and the electrical equipment as a low-pass filter to filter the output signal. Generally speaking, the higher the output signal ripple frequency, the better the filtering effect of the equivalent circuit.

[0005] However, the control frequency of the conventional LLC resonant converter is difficult to be improved to a very high frequency due to the limitation of the performance of the control chip, so that the highest frequency of the output signal ripple frequency in the burst mode can reach about 1 / 10 of the control frequency of the LLC resonant converter. In addition, the stability of the output signal ripple frequency in the burst mode cannot be guaranteed. SUMMARY

[0006] The present application provides a resonant converter and a control method thereof, which can improve the output signal ripple in the light load condition to the required frequency and maintain the stability of the frequency, which is not limited by the frequency of the loop control, so that the output signal ripple can be filtered out better.

[0007] Some embodiments of the present application provide a resonant converter, comprising an input circuit, a resonant circuit, a transformer and an output circuit connected in sequence:

[0008] The output end of the input circuit is connected to the input end of the resonant circuit, the output end of the resonant circuit is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the input end of the output circuit;

[0009] The resonant converter further comprises a controller, and the controller is configured to:

[0010] receiving a target signal of the resonant converter in a current control period, and determining a controller output value according to at least the target signal and a reference signal of the resonant converter;

[0011] when the controller output value is greater than the maximum frequency value, determining a duty cycle of the enable signal according to the controller output value, the maximum frequency value and a setting constant;

[0012] generating a driving signal according to the enable signal and the pulse signal, the driving signal being used to control the resonant converter in the current control period.

[0013] In some embodiments, when the controller output value is less than or equal to the maximum frequency value, the duty cycle of the enable signal is determined as 1.

[0014] In some embodiments, an input terminal of the controller is connected with an output terminal of an output circuit, the target signal is an output of the output circuit, and an output terminal of the controller is connected with a control terminal of the resonant converter.

[0015] In some embodiments, the controller is specifically used for:

[0016] when the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is calculated according to a formula, the formula specifically comprising:

[0017]

[0018] wherein k is a setting constant and k>0, f1 is the controller output value, f max is the maximum frequency value, and D is the duty cycle.

[0019] In some embodiments, the controller is further used for:

[0020] when the setting constant is less than or equal to a difference between the controller output value and the maximum frequency value, the duty cycle of the enable signal is determined as 0.

[0021] In some embodiments, the controller is further used for:

[0022] when the controller output value is less than or equal to the maximum frequency value, a frequency value of the driving signal is determined as the controller output value; and when the controller output value is greater than the maximum frequency value, the frequency value of the pulse signal and the frequency value of the driving signal are determined as the maximum frequency value.

[0023] In some embodiments, the frequency of the enable signal is the same as a ripple frequency of the target signal.

[0024] In some embodiments, the controller is specifically used for:

[0025] determining the controller output value according to a target signal and a reference signal of the resonant converter using a PI control model.

[0026] In some embodiments, the input circuit comprises an inverter circuit, and the output circuit comprises a rectifier circuit.

[0027] Some embodiments of the present application provide a control method of a resonant converter, the resonant converter comprising an input circuit, a resonant circuit, a transformer, an output circuit and a controller, the control method comprising:

[0028] receiving a target signal of the resonant converter in a current control period, and determining a controller output value according to at least the target signal and a reference signal of the resonant converter;

[0029] when the controller output value is greater than a maximum frequency value, determining a duty cycle of an enable signal according to the controller output value, the maximum frequency value and a setting constant;

[0030] generating a driving signal according to the enable signal and a pulse signal, the driving signal being used to control the resonant converter to operate in the current control period.

[0031] In some embodiments, when the controller output value is less than or equal to the maximum frequency value, the duty cycle of the enable signal is determined to be 1.

[0032] In some embodiments, when the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value and a setting constant, specifically comprising:

[0033] when the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is calculated according to a formula, the formula specifically comprising:

[0034]

[0035] wherein k is the setting constant and k>0, f1 is the controller output value, f max is the maximum frequency value, and D is the duty cycle.

[0036] In some embodiments, when the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value and a setting constant, further comprising:

[0037] when the setting constant is less than or equal to the difference between the controller output value and the maximum frequency value, the duty cycle of the enable signal is determined to be zero.

[0038] In some embodiments, the method further comprises:

[0039] when the controller output value is less than or equal to the maximum frequency value, the frequency value of the driving signal is determined to be the controller output value; and when the controller output value is greater than the maximum frequency value, the frequency value of the pulse signal and the frequency value of the driving signal are determined to be the maximum frequency value.

[0040] In some embodiments, the frequency of the enable signal is the same as the ripple frequency of the target signal.

[0041] In some embodiments, the controller output value is determined according to the target signal and a reference signal of the resonant converter, in particular for:

[0042] The controller output value is determined according to the target signal and a reference signal of the resonant converter using a PI control model.

[0043] The resonant converter and the control method thereof provided in the present application, when the controller output value is determined to be greater than the maximum frequency value in the current control period, that is, the controller cannot output the controller output value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value and a set constant, the drive signal is generated according to the enable signal and the pulse signal, the resonant converter is made to work in the intermittent working mode, the output power of the resonant converter is adjusted in the current period, and the output of the resonant converter is stabilized. The output signal ripple of the resonant converter in the intermittent working mode is determined by the drive signal. Since the frequency of the drive signal can be fixed, the output signal ripple frequency of the resonant converter can be stabilized, and the output ripple frequency can be adjusted, so that the subsequent filter circuit can filter out the ripple well. BRIEF DESCRIPTION OF DRAWINGS

[0044] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the specification.

[0045] Figure 1 A topological schematic diagram of a resonant converter provided for some embodiments of the present application;

[0046] Figure 2 A signal timing diagram of a controller provided for some embodiments of the present application;

[0047] Figure 3 A control principle schematic diagram of a controller provided for some embodiments of the present application;

[0048] Figure 4 A control method of a resonant converter provided for some embodiments of the present application.

[0049] REFERENCE NUMERALS:

[0050] 100, resonant converter; 110, input circuit; 120, resonant circuit; 130, transformer; 140, output circuit; 150, controller; Q11, first transistor; Q12, second transistor; Q13, third transistor; Q14, fourth transistor; Lp, resonant inductor; Cp, resonant capacitor; Q15, fifth transistor; Q16, sixth transistor; Q17, seventh transistor; Q18, eighth transistor; Cout, output capacitor; Vbat, target voltage signal; Vbat', processed target voltage signal; Ibat, target current signal; Ibat', processed target current signal; VbatRefCom, reference voltage signal; IbatRefCom, reference current signal; IbatRef, selected reference current; f1, controller output value; f max , maximum frequency value; D, duty cycle; k, set constant; PWM, driving signal.

[0051] The specific embodiments of the application have been shown and described in the above drawings and text. These drawings and text are not meant to limit the scope of the inventive concept in any way but are merely meant to illustrate the inventive concept to one of ordinary skill in the art by reference to a particular embodiment. DETAILED DESCRIPTION

[0052] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The description of the exemplary embodiments is intended to apply to all alternative embodiments, as would be understood by one skilled in the art. The following exemplary embodiments are described herein with reference to specific embodiments thereof, but those skilled in the art will recognize that the application is not limited thereto. Thus, embodiments showing a lesser number of elements are to be understood as not excluding additional elements not shown. In addition to the exemplary embodiments shown and described herein, equivalents and modifications are intended to be within the scope of the application. For example, it will be readily apparent to one of ordinary skill in the art that known methods can be adapted for use with the application described herein without undue experimentation, and that art-recognized changes can be made to the embodiments described herein without undue experimentation. Therefore, the described embodiments are merely exemplary and are not intended to limit the scope of the application, as claimed.

[0053] A resonant converter is a type of converter that achieves high efficiency and high power density by introducing resonance in the power conversion stage. Its working principle is based on resonant oscillation, by controlling the switching time and frequency of the switching tube, so that the inductance, capacitance and other elements in the resonant circuit produce resonant oscillation, thereby realizing efficient conversion of energy.

[0054] As a type of resonant converter, the LLC resonant converter usually adopts a pulse frequency modulation control method, that is, by adjusting the pulse frequency to adjust the output power of the LLC resonant converter.

[0055] To ensure stable output of the LLC resonant converter, the output signal needs to be controlled to control the output power. For example, the output voltage can be stabilized by controlling the output current of the LLC resonant converter. However, due to the gain limitation of the control chip, when the frequency of the control signal output by the control chip reaches its maximum (i.e., the minimum gain), it will still output high power. Therefore, under light load conditions, the LLC resonant converter needs to adopt an intermittent operating mode.

[0056] Intermittent operation mode refers to the process of periodically turning the power switch on and off, allowing the LLC resonant converter to operate for a period within a cycle and then stop operating for a period. However, conventional intermittent operation mode control can generate significant ripple in the output signal, which may not meet the user's requirements.

[0057] To reduce ripple, we consider using the equivalent circuit between the LLC resonant converter and the power supply as a low-pass filter to filter the output signal. Generally, the higher the output signal ripple frequency, the better the filtering effect of the equivalent circuit.

[0058] However, the control frequency of conventional LLC resonant converters is difficult to increase to a very high level due to the limitations of the control chip performance. As a result, the highest frequency that the output signal ripple frequency can reach in intermittent operation mode is about 1 / 10 of the control frequency of the LLC resonant converter. In addition, the stability of the output signal ripple frequency in intermittent operation mode cannot be guaranteed.

[0059] In view of the above problems, some embodiments of this application provide a resonant converter and control method that can boost the output signal ripple of an LLC under light load to the required frequency and maintain frequency stability, without being limited by the frequency of the loop control, thereby enabling better filtering of the output signal ripple. In some embodiments of this application, the output signal ripple refers to the output current ripple or the output voltage ripple.

[0060] like Figure 1 The diagram shown is a topology schematic of a resonant converter provided in some embodiments of this application. The resonant converter 100 includes an input circuit 110, a resonant circuit 120, a transformer 130, and an output circuit 140 connected in sequence.

[0061] The input terminal of the input circuit 110 is used to receive external power signals. The output terminal of the input circuit 110 is connected to the input terminal of the resonant circuit 120. The output terminal of the resonant circuit 120 is connected to the primary side of the transformer 130. The secondary side of the transformer 130 is connected to the input terminal of the output circuit 140.

[0062] The external power signal is transmitted to the output circuit 140 after being converted by the input circuit 110, the resonant circuit 120 and the transformer 130. The output circuit 140 is used to supply power to the load.

[0063] The resonant converter 100 further comprises a controller 150, which is configured to:

[0064] In the current control period, a target signal is received, and a control signal output value is determined according to the target signal and a reference signal of the resonant converter 100. In some embodiments of the present application, an input end of the controller 150 is connected to an output end of the output circuit 140, and an output end of the controller 150 is connected to a control end of the resonant converter 100. The output end of the output circuit 140 is configured to output an output signal, such as an output voltage, an output current, etc., as the target signal. The reference signal can refer to a fixed output value, and an average value of the target signal needs to be adjusted to the fixed output value.

[0065] When the controller output value is greater than a maximum frequency value of the controller 150, a duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value, and a set constant.

[0066] A drive signal is generated according to the enable signal and a pulse signal, and the drive signal is configured to control the resonant converter to work in the current control period. The pulse signal refers to a fixed frequency signal, and the fixed frequency value is the maximum frequency value. The maximum frequency refers to a maximum frequency of the resonant converter 100 when working, such as 300 KHz.

[0067] The controller output value is determined based on the target signal in the current control period and the reference signal of the resonant converter 100, and the controller output value is configured to generate the drive signal for controlling the resonant converter 100 to work. In this way, the resonant converter 100 is adjusted to make the average value of the target signal of the output circuit 140 close to or equal to the average value of the reference signal.

[0068] When the controller output value is greater than the maximum frequency value of the controller 150 in the current control period, that is, the controller 150 cannot output the controller output value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value, and the set constant. The drive signal is generated according to the enable signal and the pulse signal, and the resonant converter 100 is configured to work in an intermittent working mode. The output power of the resonant converter 100 is adjusted in the current period to ensure the stability of the output of the resonant converter 100. The ripple of the output signal of the resonant converter 100 in the intermittent working mode is determined by the drive signal. Since the frequency of the drive signal can be fixed, the frequency of the output signal ripple of the resonant converter can be stabilized, and the size of the output ripple frequency can be adjusted, so that the subsequent filter circuit can filter out the ripple well.

[0069] In some embodiments, the controller 150 is specifically configured to:

[0070] When the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is calculated according to the following formula, which specifically includes:

[0071]

[0072] Where k is a set constant and k > 0, f1 is the controller output value, f max Where is the maximum frequency value, and D is the duty cycle.

[0073] Based on the set constant k, the controller output value f1, and the maximum frequency value f max The difference calculation enables the duty cycle of the signal, which can ensure that when the controller output value f1 is higher, taking the output signal as the output current as an example, that is, when the load is smaller, the duty cycle is smaller, the working time of the resonant converter is smaller, and the output power of the resonant converter is smaller, thus ensuring the output stability of the resonant converter.

[0074] In some embodiments, the controller 150 is further configured to:

[0075] When the set constant k is less than or equal to the controller output value f1 and the maximum frequency value f max When the difference is zero, the duty cycle of the enable signal is determined to be zero.

[0076] In some embodiments, the controller 150 is further configured to:

[0077] When the controller output value f1 is less than or equal to the maximum frequency value f max When the frequency of the drive signal is determined to be the controller output value f1, and when the controller output value f1 is greater than the maximum frequency value f max At that time, the frequency values ​​of the pulse signal and the driving signal are determined to be the maximum frequency value f. max That is, when the controller output value f1 is less than or equal to the maximum frequency value f max When the frequency value is generated as f1, a drive signal with a frequency value of f1 is generated. When the controller output value f1 is greater than the maximum frequency value f max At that time, the generated frequency value is the maximum frequency value f. max The driving signal.

[0078] Figure 2 Signal timing diagrams of controller 150 provided in some embodiments of this application, such as Figure 2 As shown, an AND gate is used to perform AND logic on the enable signal and the pulse signal to output the drive signal. The frequency of the enable signal is the same as the ripple frequency of the target signal, so the ripple frequency of the target signal can be adjusted by adjusting the frequency of the enable signal.

[0079] exist Figure 2In the embodiment, the frequency of the enable signal is 10KHz, and the period is 100us. Furthermore, the ripple frequency of the target signal is also 10KHz, and the period is 100us. In this way, the ripple frequency of the target signal can be maintained stable.

[0080] With reference to the foregoing description Figure 2 In one period of the enable signal, when the enable signal is low, the drive signal is low, and the resonant converter 100 does not work. When the enable signal is high, the drive signal is a pulse signal, and the frequency of the pulse signal is the maximum frequency. For example, 300KHz.

[0081] In some embodiments, with reference to the foregoing description Figure 1 The input circuit 110 includes an inverter circuit, and the output circuit 140 includes a rectifier circuit.

[0082] More specifically, the input end of the inverter circuit is connected to the DC bus, the output end of the inverter circuit is connected to the primary winding of the transformer 130, and the resonant circuit 120 is arranged between the output end of the inverter circuit and the primary winding of the transformer 130.

[0083] The inverter circuit includes a first inverter bridge arm and a second inverter bridge arm. The first end of the first inverter bridge arm and the first end of the second inverter bridge arm are connected to a node and connected to the positive DC bus. The second end of the first inverter bridge arm and the second end of the second inverter bridge arm are connected to another node and connected to the negative DC bus.

[0084] The first inverter bridge arm includes a first transistor Q11 and a second transistor Q12. The first end of the first transistor Q11 is the first end of the first inverter bridge arm. The second end of the first transistor Q11 and the first end of the second transistor Q12 are connected to a node, which is the midpoint of the first inverter bridge arm. The second end of the second transistor Q12 is the second end of the first inverter bridge arm.

[0085] The second inverter bridge arm includes a third transistor Q13 and a fourth transistor Q14. The first end of the third transistor Q13 is the first end of the second inverter bridge arm. The second end of the third transistor Q13 and the first end of the fourth transistor Q14 are connected to a node, which is the midpoint of the second inverter bridge arm. The second end of the fourth transistor Q14 is the second end of the second inverter bridge arm.

[0086] The resonant circuit 120 includes a resonant capacitor Cp and a resonant inductor Lp. The first end of the resonant inductor Lp is connected to the output end of the inverter circuit. The second end of the resonant inductor Lp is connected to the first end of the resonant capacitor Cp. The second end of the resonant capacitor Cp is connected to the primary winding of the transformer 130.

[0087] Output circuit 140 includes a first output bridge arm, a second output bridge arm, and an output capacitor Cout. The first end of the first output bridge arm and the second end of the second output bridge arm are connected to a node, serving as one output terminal of output circuit 140. The second end of the first output bridge arm and the second end of the second output bridge arm are also connected to a node, serving as another output terminal of output circuit 140. The midpoint of the first output bridge arm serves as one input terminal of output circuit 140, and the midpoint of the second output bridge arm serves as the other input terminal of output circuit 140. Output capacitor Cout is connected to the output terminal of output circuit 140.

[0088] The first output bridge arm includes a fifth transistor Q15 and a sixth transistor Q16. The first terminal of the fifth transistor Q15 is the first terminal of the first output bridge arm. The second terminal of the fifth transistor Q15 and the first terminal of the sixth transistor Q16 are connected to a node, which serves as the midpoint of the first output bridge arm. The second terminal of the sixth transistor Q16 serves as the second terminal of the first output bridge arm.

[0089] The second output bridge arm includes a seventh transistor Q17 and an eighth transistor Q18. The first end of the seventh transistor Q17 is the first end of the second output bridge arm, and the second end of the seventh transistor Q17 is connected to the first end of the eighth transistor Q18. The second end of the eighth transistor Q18 is the second end of the second output bridge arm.

[0090] In some embodiments, the controller 150 is specifically used for:

[0091] The controller output value f1 is determined using a PI control model based on the target signal and the reference signal of the resonant converter 100.

[0092] like Figure 3 The diagram shown illustrates the control principle of a controller provided in some embodiments of this application. As one implementation of a PI control model, the reference signals include a reference voltage signal VbatRefCom and a reference current signal IbatRefCom. The PI control model includes a first subtractor and a voltage loop, with the input of the voltage loop connected to the output of the first subtractor. The target signals Vbat / Ibat are processed by an amplifier circuit and an ADC conversion circuit to output a target voltage signal Vbat' and a target current signal Ibat'. The first terminal of the first subtractor receives the processed target voltage signal Vbat', and the second terminal receives the reference voltage signal VbatRefCom. The difference between the reference voltage signal VbatRefCom and the processed target voltage signal Vbat' is output to the voltage loop.

[0093] The PI control model further comprises a selector, an output terminal of the voltage loop is connected to a first input terminal of the selector, a second input terminal of the selector is connected to the reference current signal IbatRefCom, and the selector outputs the selected reference current IbatRef according to the output of the voltage loop and the reference current signal IbatRefCom. In some embodiments, the selector can be a low value selector for selecting the lower value between the output of the voltage loop and the reference current signal IbatRefCom.

[0094] The PI control model further comprises a second subtractor and a current loop, an output terminal of the selector is connected to a first terminal of the second subtractor, the first terminal of the second subtractor receives the selected reference current IbatRef output by the selector, a second terminal of the second subtractor receives the processed target current signal Ibat', and an output terminal of the second subtractor is connected to the current loop. The current loop outputs the controller output value f1 according to the difference between the selected reference current IbatRef and the processed target current signal Ibat'.

[0095] The controller 150 comprises a PI control model, an amplification circuit, an ADC (Analog to Digital Converter) conversion circuit, a frequency control module, and a driving circuit. The target output signal comprises a target current signal Ibat and a target voltage signal Vbat. The target current signal Ibat and the target voltage signal Vbat are amplified by the amplification circuit and are converted by the ADC conversion circuit to output the processed target current signal Ibat' and the processed target voltage signal Vbat'. The processed target current signal Ibat' and the processed target voltage signal Vbat', the reference current signal IbatRefCom, and the reference voltage signal VbatRefCom are processed by the PI control model to output the controller output value f1. The controller output value f1 is processed by the frequency control module to output the driving signal PWM, and the driving signal PWM controls the driving circuit to drive the resonant converter.

[0096] In some embodiments, the resonant converter described above can be applied to an on-board charger (OBC).

[0097] Some embodiments of the present application provide a control method of a resonant converter. The resonant converter 100 comprises an input circuit 110, a resonant circuit 120, a transformer 130, an output circuit 140, and a controller 150. The control method comprises:

[0098] receiving a target signal output by the output circuit 140 in a current control period, and determining the controller output value f1 according to the target signal and a reference signal of the resonant converter 100;

[0099] When the controller output value is greater than the maximum frequency value of the controller 150, the duty cycle of the enable signal is determined based on the controller output value, the maximum frequency value, and the set constant.

[0100] A drive signal is generated based on the enable signal and the pulse signal. The drive signal is used to control the operation of the resonant converter in the current control cycle. The pulse signal is a signal with a fixed frequency, where the fixed frequency value is the maximum frequency value.

[0101] In some embodiments, when the controller output value f1 is greater than the maximum frequency value f of the controller 150 max At that time, based on the controller output value f1 and the maximum frequency value f max And setting a constant k to determine the duty cycle of the enable signal, specifically including:

[0102] When the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is calculated according to the formula, which specifically includes:

[0103]

[0104] Where k is a set constant and k > 0, f1 is the controller output value, f max Where is the maximum frequency value, and D is the duty cycle.

[0105] In some embodiments, when the controller output value f1 is greater than the maximum frequency value f of the controller 150 max At that time, based on the controller output value f1 and the maximum frequency value f max In addition to setting a constant k to determine the duty cycle of the enable signal, it also includes:

[0106] When the set constant k is less than or equal to the controller output value f1 and the maximum frequency value f max When the difference is zero, the duty cycle of the enable signal is determined to be zero.

[0107] In some embodiments, the method further includes:

[0108] When the controller output value f1 is less than or equal to the maximum frequency value f max When the frequency of the drive signal is determined to be the controller output value f1, the controller output value f1 is determined to be greater than the maximum frequency value f. max At that time, the frequency values ​​of the pulse signal and the driving signal are determined to be the maximum frequency value f. max .

[0109] In some embodiments, the frequency of the enable signal is the same as the ripple frequency of the target signal.

[0110] In some embodiments, the controller output value f1 is determined based on the target signal and the reference signal of the resonant converter 100, specifically for:

[0111] The controller output value f1 is determined using a PI control model based on the target signal and the reference signal of the resonant converter 100.

[0112] like Figure 4 As shown, some embodiments of this application provide a control method for a resonant converter. The method determines whether the controller output value is greater than the maximum frequency value. If it is greater than the maximum frequency value, the method further determines whether the set constant is less than or equal to the difference between the controller output value and the maximum frequency value. If not, the method calculates the duty cycle of the enable signal based on the controller output value, the maximum frequency value, and the set constant, and uses the enable signal and the pulse signal to perform AND logic to output a drive signal. The frequency of the drive signal is the maximum frequency value.

[0113] When the controller output value is less than the maximum frequency value, the frequency of the drive signal is the controller output value. When the set constant is less than or equal to the difference between the controller output value and the maximum frequency value, the duty cycle is zero, the drive signal is low, and the resonant converter stops working.

[0114] The explanation of the control method for the resonant converter provided in this application is the same as that of the resonant converter itself, and will not be repeated here.

[0115] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0116] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A resonant converter, characterized by, The resonant converter comprises an input circuit, a resonant circuit, a transformer and an output circuit connected in sequence. An output end of the input circuit is connected to an input end of the resonant circuit, an output end of the resonant circuit is connected to a primary side of the transformer, and a secondary side of the transformer is connected to an input end of the output circuit. The controller is configured to: receive a target signal of the resonant converter in a current control period, and determine a controller output value according to at least the target signal and a reference signal of the resonant converter; when the controller output value is greater than a maximum frequency value, determine a duty cycle of an enable signal according to the controller output value, the maximum frequency value and a set constant; generate a drive signal according to the enable signal and a pulse signal, the drive signal being used to control the resonant converter to work in the current control period.

2. The resonant converter of claim 1, characterized in that, when the controller output value is less than or equal to the maximum frequency value, determine the duty cycle of the enable signal as 1.

3. The resonant converter of claim 1, wherein, An input end of the controller is connected to an output end of the output circuit, the target signal is an output of the output circuit, and an output end of the controller is connected to a control end of the resonant converter.

4. The resonant converter of claim 1, wherein, The controller is specifically configured to: when the controller output value is greater than the maximum frequency value, calculate the duty cycle of the enable signal according to a formula, the formula specifically comprising: where k is the set constant and k > 0, f1 is the controller output value, f max is the maximum frequency value, and D is the duty cycle.

5. The resonant converter of claim 1, wherein, The controller is further configured to: when the set constant is less than or equal to a difference between the controller output value and the maximum frequency value, determine the duty cycle of the enable signal as 0.

6. The resonant converter of claim 2, wherein, The controller is further configured to: when the controller output value is less than or equal to the maximum frequency value, determine a frequency value of the drive signal as the controller output value; when the controller output value is greater than the maximum frequency value, determine the frequency value of the pulse signal and the frequency value of the drive signal as the maximum frequency value.

7. The resonant converter of claim 1, wherein, The frequency of the enable signal is the same as a ripple frequency of the target signal.

8. The resonant converter of claim 1, wherein, The controller is specifically configured to: determine the controller output value according to the target signal and the reference signal of the resonant converter by using a PI control model.

9. The resonant converter of claim 1, wherein, The input circuit comprises an inverter circuit, and the output circuit comprises a rectifier circuit.

10. A control method of a resonant converter, characterized by, The resonant converter comprises an input circuit, a resonant circuit, a transformer, an output circuit and a controller, and the control method comprises: receive a target signal of the resonant converter in a current control period, and determine a controller output value according to at least the target signal and a reference signal of the resonant converter; when the controller output value is greater than a maximum frequency value, determine a duty cycle of an enable signal according to the controller output value, the maximum frequency value and a set constant; generate a drive signal according to the enable signal and a pulse signal, the drive signal being used to control the resonant converter to work in the current control period.

11. The control method according to claim 10, characterized by, when the controller output value is less than or equal to the maximum frequency value, determine the duty cycle of the enable signal as 1.

12. The control method according to claim 10, characterized by, When the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value and the set constant, specifically comprising: When the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is calculated according to a formula, and the formula specifically comprises: where k is the set constant and k > 0, f1 is the controller output value, f max is the maximum frequency value, and D is the duty cycle.

13. The control method according to claim 10, characterized by, When the controller output value is greater than the maximum frequency value, the duty cycle of the enable signal is determined according to the controller output value, the maximum frequency value and the set constant, and further comprising: When the set constant is less than or equal to the difference between the controller output value and the maximum frequency value, the duty cycle of the enable signal is determined to be zero.

14. The control method according to claim 11, characterized by, The method further comprises: When the controller output value is less than or equal to the maximum frequency value, the frequency value of the drive signal is determined to be the controller output value; when the controller output value is greater than the maximum frequency value, the frequency value of the pulse signal and the frequency value of the drive signal are determined to be the maximum frequency value.

15. The control method according to claim 10, characterized by, The frequency of the enable signal is the same as the ripple frequency of the target signal.

16. The control method according to claim 10, wherein A controller output value is determined according to the target signal and the reference signal of the resonant converter, specifically for: The controller output value is determined according to the target signal and the reference signal of the resonant converter using a PI control model.

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