A control method for LLC resonant circuit and LLC resonant circuit

Abstract

The embodiment of the present application discloses a control method of an LLC resonant circuit and an LLC resonant circuit. The LLC resonant circuit includes a control module and a resonant module, and the resonant module includes at least two switching devices. The method includes: the control module obtains a DC voltage component and an AC voltage component included in the input voltage of the resonant module. The control module determines a target frequency based on the DC voltage component, the AC voltage component and the output voltage of the resonant module. The control module generates a target drive signal based on the target frequency. The control module turns on or off the at least two switching devices through the target drive signal. By adopting the embodiment of the present application, the problem of the presence of an AC component in the output of the LLC resonant circuit due to the presence of an AC component in the input can be reduced or eliminated, the output ripple of the LLC resonant circuit can be reduced, and the performance of the LLC resonant circuit can be improved.

Description

Technical Field

[0001] The present application relates to the field of circuits, and in particular to a control method for an LLC resonant circuit and an LLC resonant circuit. Background Art

[0002] LLC resonant circuit (also referred to as LLC circuit) is a circuit that achieves a constant output voltage by controlling the frequency of the switching device. In recent years, LLC circuits have gradually attracted people's attention due to their excellent performance.

[0003] In the existing control method of LLC circuit, when the input of LLC circuit is a DC superimposed AC signal, when the efficiency of the control loop corresponding to LLC circuit is low, its output will usually also be superimposed with an AC component. Therefore, the existing control method of LLC circuit may cause its output ripple to be large, thereby affecting the performance of LLC circuit. Summary of the invention

[0004] The present application provides a control method for an LLC resonant circuit and an LLC resonant circuit, which can reduce or eliminate the AC component in the output caused by the input AC component, reduce the output ripple of the LLC resonant circuit, and improve the performance of the LLC resonant circuit.

[0005] In a first aspect, an embodiment of the present application provides a control method for an LLC resonant circuit. The LLC circuit includes a control module and a resonant module, and the resonant module includes at least two switching devices. The method includes: the control module obtains a DC voltage component and an AC voltage component of an input voltage of the resonant module. The control module determines a target frequency according to the DC voltage component, the AC voltage component, and the output voltage of the resonant module. The control module generates a target drive signal according to the target frequency. The control module turns on or off the at least two switching devices through the target drive signal.

[0006] In combination with the first aspect, in a feasible implementation, the control module may determine a first frequency according to the AC voltage component, the DC voltage component, and the output voltage of the resonance module. The control module may also determine a second frequency according to the output voltage. The control module may also determine a target frequency according to the first frequency and the second frequency.

[0007] In combination with the first aspect, in a feasible implementation manner, the control module may determine the first frequency by the following formula:

[0008]

[0009] Among them, f1 is the first frequency, λ is the ratio of the excitation inductance to the resonant inductance of the transformer of the resonant module, n is the turns ratio of the transformer in the resonant module, fr is the resonant frequency of the resonant module, Uin0 is the DC voltage component, UinAC is the AC voltage component, and Uo is the output voltage.

[0010] In combination with the first aspect, in a feasible implementation manner, the control module determines the first frequency by using the following formula:

[0011]

[0012] Wherein, f1 is the first frequency, Q is the quality factor of the LLC circuit, and f ndc is the DC component of the third frequency generated by the loop controller included in the control module, n is the turns ratio of the transformer in the resonance module, fr is the resonant frequency of the resonance module, Uin0 is the DC voltage component, UinAC is the AC voltage component, and Uo is the output voltage.

[0013] In combination with the first aspect, in a feasible implementation manner, the control module may determine the target frequency according to the sum of the first frequency and the second frequency.

[0014] In combination with the first aspect, in a feasible implementation manner, the control module may determine the second frequency according to a difference between the output voltage and a reference voltage preset by the LLC circuit.

[0015] In combination with the first aspect, in a feasible implementation manner, the target drive signal includes a first drive signal and a second drive signal, and the phase difference between the first drive signal and the second drive signal is 180 degrees. The control module may first generate the first drive signal according to the target frequency. Then, the control module may also generate the second drive signal according to the first drive signal.

[0016] In combination with the first aspect, in a feasible implementation manner, the at least two switch devices include a first switch device and a second switch device. The control module turns on the first switch device through the first drive signal, and turns off the second switch device through the second drive signal. Alternatively, the control module turns off the first switch device through the first drive signal, and turns on the second switch device through the second drive signal.

[0017] In combination with the first aspect, in a feasible implementation manner, the at least two switch devices include a first switch device, a second switch device, a third switch device, and a fourth switch device. The control module turns on the first switch device and the fourth switch device through the first drive signal, and turns off the second switch device and the third switch device through the second drive signal. Alternatively, the control module turns off the first switch device and the fourth switch device through the first drive signal, and turns on the second switch device and the third switch device through the second drive signal.

[0018] In combination with the first aspect, in a feasible implementation manner, the control module includes a controller and a driver. The control module determines the target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module through the controller. The control module generates the target drive signal according to the target frequency through the driver. The control module turns on or off the at least two switch devices according to the target drive signal through the driver.

[0019] In combination with the first aspect, in a feasible implementation manner, the resonance module includes an input source, a switch network, a resonant cavity, a transformer, and a secondary rectifier bridge. The input source is connected to the switch network, the switch network is connected to the resonant cavity, the resonant cavity is connected to the transformer, and the transformer is connected to the secondary rectifier bridge. The input source is used to provide the DC voltage component and the AC voltage component, the switch network is used to convert the DC voltage component and the AC voltage component into a high-frequency AC square wave, the resonant cavity is used to obtain an AC output voltage through the high-frequency AC square wave, and the transformer and the secondary rectifier bridge are used to obtain the output voltage through the AC output voltage.

[0020] In combination with the first aspect, in a feasible implementation manner, the switch network includes a first switch device and a second switch device. The first end of the input source is connected to the first end of the first switch device, the second end of the first switch device is respectively connected to the first end of the second switch device and one end of the resonant cavity, the second end of the second switch device is respectively connected to the second end of the input source and the other end of the resonant cavity, and the third end of the first switch device and the third end of the second switch device are respectively connected to the control module.

[0021] In combination with the first aspect, in a feasible implementation manner, the switch network includes a first switch device, a second switch device, a third switch device, and a fourth switch device. The first end of the input source is connected to the first end of the first switch device and the third switch device, the second end of the input source is connected to the first end of the second switch device and the fourth switch device, the second end of the first switch device and the second end of the second switch device are simultaneously connected to one end of the resonant cavity, the second end of the third switch device and the second end of the fourth switch device are simultaneously connected to the other end of the resonant cavity, and the third end of the first switch device, the third end of the second switch device, the third end of the third switch device, and the third end of the fourth switch device are respectively connected to the control module.

[0022] In combination with the first aspect, in a feasible implementation manner, the driver includes a pulse width modulation (PWM) signal generator and an inverter. The control module generates the first drive signal according to the target frequency through the PWM signal generator, and sends the first drive signal to the inverter. The control module generates the second drive signal according to the first drive signal through the inverter.

[0023] In combination with the first aspect, in a feasible implementation manner, the controller controls the on or off of each of the at least two switching devices according to the first drive signal and the second drive signal respectively through the PWM signal generator and the inverter.

[0024] In combination with the first aspect, in a feasible implementation manner, the PWM signal generator is connected to the third end of the first switching device, and the inverter is connected to the third end of the second switching device. The control module sends the first drive signal to the first switching device through the PWM signal generator to control the on or off of the first switching device. The control module sends the second drive signal to the second switching device through the inverter to control the on or off of the second switching device. The inverter is used to generate the second drive signal according to the first drive signal, and send the second drive signal to the second switching device.

[0025] In combination with the first aspect, in a feasible implementation manner, the PWM signal generator is connected to the third end of the second switch device, and the inverter is connected to the third end of the first switch device. The control module sends the first drive signal to the second switch device through the PWM signal generator to control the conduction or shutoff of the second switch device. The control module sends the second drive signal to the first switch device through the inverter to control the conduction or shutoff of the second switch device.

[0026] In combination with the first aspect, in a feasible implementation manner, the PWM signal generator is connected to the third end of the first switching device and the third end of the fourth switching device, and the inverter is connected to the third end of the second switching device and the third end of the third switching device. The control module sends the first drive signal to the first switching device and the fourth switching device through the PWM signal generator to control the on or off of the first switching device and the fourth switching device. The control module sends the second drive signal to the second switching device and the third switching device through the inverter to control the on or off of the second switching device and the third switching device.

[0027] In combination with the first aspect, in a feasible implementation manner, the PWM signal generator is connected to the third end of the second switching device and the third end of the third switching device, and the inverter is connected to the third end of the first switching device and the third end of the fourth switching device. The control module sends the first drive signal to the second switching device and the third switching device through the PWM signal generator to control the conduction or shutoff of the second switching device and the third switching device. The control module sends the second drive signal to the first switching device and the fourth switching device through the inverter to control the conduction or shutoff of the first switching device and the fourth switching device.

[0028] In a second aspect, an embodiment of the present application provides an LLC resonant circuit, which includes a control module and a resonance module, and the control module is used to execute the control method of the LLC resonant circuit described in any one of the above-mentioned first aspects to turn on or off the at least two switching devices included in the resonance module.

[0029] In combination with the second aspect, in an optional implementation, the resonance module includes an input source, a switch network, a resonant cavity, a transformer, and a secondary rectifier bridge, and the switch network includes the at least two switch devices. The input source is connected to the switch network, the switch network is connected to the resonant cavity, the resonant cavity is connected to the transformer, and the transformer is connected to the secondary rectifier bridge. The input source is used to provide the DC voltage component and the AC voltage component, the switch network is used to convert the DC voltage component and the AC voltage component into a high-frequency AC square wave, the resonant cavity is used to obtain an AC output voltage through the high-frequency AC square wave, and the transformer and the secondary rectifier bridge are used to obtain the output voltage through the AC output voltage.

[0030] In combination with the second aspect, in a feasible implementation manner, the switch network includes a first switch device and a second switch device. The first end of the input source is connected to the first end of the first switch device, the second end of the first switch device is respectively connected to the first end of the second switch device and one end of the resonant cavity, the second end of the second switch device is respectively connected to the second end of the input source and the other end of the resonant cavity, and the third end of the first switch device and the third end of the second switch device are respectively connected to the control module.

[0031] In combination with the second aspect, in a feasible implementation, the switch network includes a first switch device, a second switch device, a third switch device, and a fourth switch device. The first end of the input source is connected to the first end of the first switch device and the third switch device, the second end of the input source is connected to the first end of the second switch device and the fourth switch device, the second end of the first switch device and the second end of the second switch device are simultaneously connected to one end of the resonant cavity, the second end of the third switch device and the second end of the fourth switch device are simultaneously connected to the other end of the resonant cavity, the third end of the first switch device, the third end of the second switch device, and the third switch device.

[0032] In combination with the second aspect, in an optional implementation, the control module includes a controller and a driver. The control module determines the target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module through the controller. The control module generates the target drive signal according to the target frequency through the driver. The control module turns on or off the at least two switching devices according to the target drive signal through the driver.

[0033] In combination with the second aspect, in an optional implementation, the driver includes a pulse width modulation (PWM) signal generator and an inverter. The PWM signal generator is used to generate the first drive signal according to the target frequency and send the first drive signal to the inverter. The inverter is used to generate the second drive signal according to the first drive signal.

[0034] In combination with the second aspect, in an optional implementation, the PWM signal generator and the inverter are used to control the on or off of each of the at least two switching devices according to the first drive signal and the second drive signal, respectively.

[0035] By using the control method of the LLC resonant circuit and the LLC resonant circuit provided in the present application, the AC component in the output caused by the input AC component can be reduced or eliminated, the output ripple of the LLC resonant circuit can be reduced, and the performance of the LLC resonant circuit can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments.

[0037] Figure 1 is a structure diagram of an LLC circuit provided in an embodiment of the present application;

[0038] Figure 2 It is another structural schematic diagram of an LLC circuit provided in an embodiment of the present application;

[0039] Figure 3 It is another structural schematic diagram of an LLC circuit provided in an embodiment of the present application;

[0040] Figure 4 It is a schematic diagram of the structure of the transformer and the secondary rectifier bridge provided in the embodiment of the present application;

[0041] Figure 5 It is a flow chart of a control method of an LLC circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical methods in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0043] When the input of the LLC circuit is a DC superimposed AC signal, the existing LLC circuit control method easily causes an AC component to be superimposed on its output, resulting in a large output ripple, which in turn affects the performance of the LLC circuit.

[0044] Therefore, the technical problem to be solved by the present application is: how to reduce or even eliminate the situation where the output of the LLC circuit has an AC component caused by the input AC component, thereby reducing the output ripple of the LLC circuit and improving the performance of the LLC circuit.

[0045] See also Figure 1 , Figure 1 1 is a schematic diagram of a structure of an LLC circuit provided in an embodiment of the present application. The LLC circuit can apply the control method of the LLC circuit provided in the present application. Figure 1 As shown, the LLC circuit may include a resonant module 10 and a control module 20 coupled to each other. In actual use, the control module 20 can determine a frequency (for the convenience of distinction, the target frequency fs will be used instead of the description below) according to the DC voltage component (here assumed to be Uin0), the AC voltage component (here assumed to be UinAC) contained in the input voltage of the resonant module 10 (here assumed to be Uin) and the output voltage of the resonant module 10 (here assumed to be Uo). Then, the control module 20 can also generate a corresponding drive signal according to the target frequency fs (for the convenience of distinction, the target drive signal will be used instead of the description below). Then, the control module 20 can turn on or off at least two switching devices contained in the above-mentioned resonant module 10 through the target drive signal, so that the LLC circuit output voltage Uo can tend to a stable preset voltage size.

[0046] It should be noted that, in actual implementation, the input voltage of the LLC circuit may be a DC voltage superimposed with an AC voltage provided by an input source. Here, the AC part of the DC voltage superimposed with the AC voltage is the AC voltage component of the input voltage, and the DC part is the DC voltage component of the input voltage. For example, in actual use, the input source of the LLC circuit may be a programmable logic controller (PLC).

[0047] For further information, see Figure 2 , Figure 2 FIG. 1 is another structural diagram of an LLC circuit provided in an embodiment of the present application. Figure 2As shown, the resonance module 10 may specifically include an input source 101, a switch network 103, a resonant cavity 104, a transformer 105, a secondary rectifier bridge 106, and a load 107. The two ends of the input source 101 are respectively connected to the switch network 103, the switch network 103 is also connected to the resonant cavity 104, the resonant cavity 104 is also connected to the transformer 105, the transformer 105 is also connected to the secondary rectifier bridge 106, and the secondary rectifier bridge 106 is also connected to the load 107.

[0048] In practical applications, the input source 101 can be used to provide a DC voltage component Ui n0 and an AC voltage component UinAC, and the switch network 103 is used to convert the DC voltage component Ui n0 and the AC voltage component Ui nAC into a high-frequency AC square wave, and transmit the high-frequency AC square wave to the resonant cavity 104. The resonant cavity 104 obtains an AC output voltage according to the high-frequency AC square wave, and provides the AC output voltage to the transformer 105. The transformer 105 and the secondary rectifier bridge 106 can process the AC output voltage, so as to provide a DC voltage of a preset magnitude (i.e., Uo mentioned above) to both ends of the load 107.

[0049] It should be noted that the method proposed in this application does not involve the change of the excitation inductance of the transformer 105. Figure 2 In the embodiment, the magnetizing inductance of the transformer 105 is hidden in the transformer 105 .

[0050] In an alternative implementation, see Figure 2 The switch network 103 may specifically include a first switch device G1 and a second switch device G2. The resonant cavity 104 may specifically include an inductor L1 and a capacitor C1. The transformer 105 may specifically include a transformer B1, and the secondary rectifier bridge 106 may specifically include a diode D1, a diode D2, and a capacitor C2.

[0051] The first end of the input source 101 is connected to the first end of the first switch device G1, and the second end of the first switch device G1 is connected to the first end of the second switch device G2 and the first end of the inductor L1. The second end of the second switch device G2 is connected to the second end of the input source 101 and the first end of the primary side of the transformer B1. The second end of the inductor L1 is connected to the first end of the capacitor C1, and the second end of the capacitor C1 is connected to the second end of the primary side of the transformer B1. The secondary side of the transformer B1 includes a first secondary side and a second secondary side connected in series. The first end of the first secondary side is connected to the first end of the second secondary side, the second end of the first secondary side is connected to the first end of the diode D1, and the second end of the second secondary side is connected to the first end of the diode D2. The second end of the diode D1 and the second end of the diode D2 are simultaneously connected to the first end of the capacitor C2, and the first end of the capacitor C2 is also connected to the positive electrode of the load 107. The first end of the first secondary side and the first end of the second secondary side are also connected to the second end of the capacitor C2, and the second end of the capacitor C2 is also connected to the negative electrode of the load 107. The third end of the first switch device G1 and the third end of the second switch device G2 are connected to the control module 20 respectively.

[0052] It should be noted here that the above-mentioned switch network 103 specifically includes a first switch device G1 and a second switch device G2, and these two switch devices are bridge-connected. Therefore, such a switch network 103 can also be called a half-bridge switch network.

[0053] In yet another alternative implementation, see Figure 3 , Figure 3 FIG. 1 is another structural diagram of an LLC circuit provided in an embodiment of the present application. Figure 3 As shown, the switch network 103 may specifically include a first switch device G1, a second switch device G2, a third switch device G3 and a fourth switch device G4. It should be noted that: Figure 3 The circuit structure shown is Figure 2 The circuit structure shown is mainly different in the specific structure of the switch network 103, and the structures and connection relationships of other units are the same, so the following will directly quote Figure 2 The structures and connection relationships of other units shown will not be described again here.

[0054] In a specific implementation, the first end of the first switch device G1 is connected to the first end of the second switch device G2, and is also connected to the first end of the inductor L1. The first end of the third switch device G3 is connected to the first end of the fourth switch device G4, and is also connected to the second end of the primary side of the transformer B1. The second end of the first switch device G1 and the second end of the third switch device G3 are also connected to the first end of the input source 10. The second end of the second switch device G2 and the second end of the fourth switch device G4 are also connected to the second end of the input source 101. The third end of the first switch device G1, the third end of the second switch device G2, the third end of the third switch device G3, and the third end of the fourth switch device G4 are respectively connected to the control module 20.

[0055] It should be noted that the switch network 103 specifically includes a first switch device G1, a second switch device G2, a third switch device G3 and a fourth switch device G4, and these four switch devices are bridged, so such a switch network 103 can also be called a full-bridge switch network.

[0056] In another optional implementation, the transformer 105 and the secondary rectifier bridge 106 in the LLC circuit may also adopt other structures. Figure 4 , Figure 4 Schematic diagram of a transformer and a secondary rectifier bridge provided in an embodiment of the present application. Figure 4 As shown, the transformer 105 may specifically include a transformer B2, and the transformer B2 has only one primary side and one secondary side. The secondary side rectifier bridge 106 may specifically include a diode D3, a diode D4, a diode D5, a diode D6, and a capacitor C3.

[0057] The first end of the secondary side of the transformer B2 is connected to the first end of the diode D3 and the first end of the diode D4 at the same time, and the second end of the secondary side of the transformer B2 is connected to the first end of the diode D5 and the first end of the diode D6 at the same time. The second end of the diode D3 is connected to the second end of the diode D5 and is also connected to the first end of the capacitor C3, and the first end of the capacitor C3 is also connected to the positive electrode of the load 107. The second end of the diode D4 and the second end of the diode D6 are connected to the second end of the capacitor C3, and the second end of the capacitor C3 is also connected to the negative electrode of the load 107.

[0058] It should be noted here that the above Figure 4 This is only an example of the specific structure of the transformer 105 and the secondary rectifier bridge 106. In actual implementation, the transformer 105 and the secondary rectifier bridge 106 may also adopt other structures other than the above. Figure 2 as well as Figure 4 This application does not impose any specific limitation on other structures than those shown.

[0059] For further information, please see Figure 2 .like Figure 2 As shown, the control module 20 may specifically include a controller 201 and a driver 202 that are interconnected. In actual implementation, the controller 201 may be used to obtain the DC voltage component Uin0 and the AC voltage component UinAC of the input voltage Uin of the above-mentioned resonance module 10, as well as the output voltage Uo of the resonance module 10 and the preset reference voltage Uref. It should be understood here that the reference voltage Uref is the size of the ideal output DC voltage of the resonance module 10. In other words, the reference voltage Uref refers to the voltage that the output DC voltage of the resonance module 10 is to approach. The controller 201 may also be used to determine the target frequency fs according to the DC voltage component Uin0, the AC voltage component UinAC, the output voltage Uo and the preset reference voltage Uref and send it to the driver 202. The driver 202 may generate a target drive signal according to the target frequency fs, and further control the conduction or disconnection of at least two switch devices in the switch network 103 by using the target drive signal.

[0060] Optional, please continue to see Figure 2 The controller 201 may specifically include a frequency generator P1, a loop controller P2, a first coupler H1, and a second coupler H2. The driver 202 may specifically include a pulse width modulation (PWM) signal generator P3 and an inverter P4.

[0061] The loop controller P2 is connected to the first coupler H1 and the second coupler H2 respectively, and the second coupler H2 is also connected to the frequency generator P1 and the PWM signal generator P3 respectively. The PWM signal generator 103 is also connected to the inverter P4. The PWM signal generator and the inverter P4 are also connected to the third end (which can also be understood as the control end of each switch device) of the switch network 103 respectively.

[0062] The switch network 103 adopts Figure 2 In the case of the half-bridge structure shown in FIG. 1 , the output end of the PWM signal generator P3 can be connected to the third end of the first switch device G1, and the output end of the inverter P4 can be connected to the third end of the second switch device G2. Alternatively, the output end of the PWM signal generator P3 can be connected to the third end of the second switch device G2, and the output end of the inverter P4 can be connected to the third end of the first switch device G1. It should be noted that when the switch network 103 adopts Figure 2In the case of the half-bridge structure shown, the above two different connection methods have no difference for the control method of the LLC circuit provided in the present application, and the present application does not limit this.

[0063] The switch network 103 adopts Figure 3 In the case of the full-bridge structure shown in the figure, the output end of the PWM signal generator P3 can be connected to the third end of the first switch device G1 and the third end of the fourth switch device G4, and the output end of the inverter P4 can be connected to the third end of the second switch device G2 and the third end of the third switch device G3. Alternatively, the output end of the PWM signal generator P3 can be connected to the third end of the second switch device G2 and the third end of the third switch device G3, and the output end of the inverter P4 can be connected to the third end of the first switch device G1 and the third end of the fourth switch device G4. It should be noted here that when the switch network 103 adopts Figure 3 In the case of the full-bridge structure shown, the above two different connection methods have no difference for the control method of the LLC circuit provided in the present application, so the present application does not limit this.

[0064] In actual implementation, the frequency generator P1 can be used to determine the first frequency (here assumed to be f1) according to the DC voltage component Uin0, the AC voltage component UinAC and the output voltage Uo, and transmit the first frequency f1 to the second coupler H2. The first coupler H1 is used to calculate the difference between the reference voltage Uref and the current output voltage Uo of the resonant circuit 10 (here assumed to be E1), and transmit the difference E1 to the loop controller P2. The loop controller P2 can process the difference E1 based on its internal preset loop control algorithm to obtain the second frequency (here assumed to be f2), and transmit the second frequency f2 to the second coupler H2. The second coupler H2 can determine the target frequency fs according to the first frequency f1 and the second frequency f2, and transmit the target frequency fs to the PWM signal generator P3.

[0065] Further, the PWM signal generator P3 can be used to generate the first drive signal according to the target frequency fs, and send the first drive signal to the switch devices connected thereto in the switch network 103 to control the on or off of these switch devices. At the same time, the PWM signal generator P3 can also transmit the first drive signal to the inverter P4, and the inverter P4 is used to generate the second drive signal according to the first drive signal, and send the second drive signal to the switch devices connected thereto in the switch network 103 to control the on or off of these switch devices. Here, both the first drive signal and the second drive signal are PWM signals, and the phase difference between the two is 180 degrees. In other words, the first drive signal and the second drive signal are complementary PWM signals.

[0066] It should be noted here that in actual implementation, the loop controller P2 and the frequency generator P1 may be the same device, and this application does not impose any specific limitation on this.

[0067] It should also be noted that the switching devices provided in the present application may specifically be insulated gate devices, such as insulated gate bipolar transistors (IGBT) or metal-oxide-semiconductor field-effect transistors (MOSFET), etc. These switching devices may also be wide bandgap semiconductor devices, such as silicon carbide, gallium nitride, etc., and the present application does not impose specific restrictions on this. The control devices such as the loop controller P2 in the LLC circuit provided in the present application may be composed of discrete components or logic devices, such as complex programmable logic devices (CPLD), field-programmable gate arrays (FPGA), single-chip microcomputers, digital signal processors (DSP), etc., and the present application does not impose specific restrictions on this.

[0068] It should also be understood that the above text specifically describes the structure of the LLC circuit to which the control method provided by the present application is applicable, and also specifically describes the structure of each functional module or unit in the LLC circuit. For various different implementations, various different combination schemes can be further formed. Figure 4 The implementation shown can be Figure 2 or Figure 3Since there are many foreseeable combinations, this application will not list them one by one, but these combinations should be considered within the protection scope of this application.

[0069] The above text has described in detail the structure and function of the LLC circuit provided by the present application. The following will describe in detail the specific implementation process of a control method of an LLC circuit provided by the present application in combination with the LLC circuit described in the above text. It should be noted here that in order to avoid repetition, the following text will directly quote the specific description of the LLC circuit in the above text.

[0070] See also Figure 5 , Figure 5 1 is a flow chart of a control method of an LLC circuit provided in an embodiment of the present application. The control method of the LLC circuit can be specifically executed by the control module 20 described above. Figure 5 As shown, the method includes:

[0071] S501: A control module obtains a DC voltage component and an AC voltage component included in an input voltage of a resonance module.

[0072] In some feasible implementations, when it is determined that a new driving signal needs to be generated, the control module 20 can obtain the input voltage Uin of the resonance module 10 at the current moment (here, it is assumed to be moment T1). Then, the control module 20 can further obtain the DC voltage component UinAC and the AC voltage component Uni0 contained therein according to the input voltage Uin.

[0073] Specific, combined Figure 2 The structure of the controller 201 shown in the figure, when the control module 20 determines that a new drive signal needs to be generated, the control module 10 can first obtain the input voltage Uin of the above-mentioned resonance module 10 through the controller 201. For example, the controller 201 can detect the voltage across the input source 101 through the voltage detection circuit connected to it to obtain the input voltage Uin. Then, the controller 201 can provide the electrical signal corresponding to the input voltage Uin to a preset low-pass filter for filtering through the low-pass filter. Then, the controller 201 can obtain the electrical signal output by the low-pass filter, and determine the value of the electrical signal output by the low-pass filter as the DC voltage component UinAC corresponding to the input voltage Uin. Furthermore, the controller 201 can also determine the difference between the input voltage Uin and the DC voltage component UinAC as the AC voltage component Uin0 corresponding to the input voltage Uin.

[0074] S502: The control module determines a target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module.

[0075] In some feasible implementations, after obtaining the above-mentioned DC voltage component UinAC and AC component Uin0, the control module 20 can also obtain the output voltage Uo of the resonance module 10. Then, the control module 20 can determine the target frequency fs according to the DC voltage component UinAC, the AC component Uin0 and the output voltage Uo. Here, the target frequency fs can be used by the control module 20 to generate a new drive signal (i.e., a target drive signal).

[0076] Specifically, after obtaining the DC voltage component UinAC and the AC voltage component Uin0, the control module 20 may also detect the terminal voltage of the load 107 through the voltage detection circuit connected to the controller 201 to obtain the output voltage Uo. Then, the control module 10 may calculate the first frequency f1 according to the DC voltage component Uin0, the AC voltage component UinAC and the output voltage Uo through the frequency generator P1 included in the controller 201.

[0077] In an optional implementation, when the LLC circuit operates near its resonance point, the frequency generator P1 can specifically calculate the first frequency f1 according to the following formula (1) and the above-mentioned DC voltage component Uin0, AC voltage component UinAC and output voltage Uo. Here, formula (1) is as follows:

[0078]

[0079] Wherein, λ is the ratio of the transformer excitation inductance to the resonant inductance, n is the transformer turns ratio of the transformer 105 in the resonant module 10, and fr is the resonant frequency corresponding to the resonant module 10. The frequency generator P1 substitutes the values ​​of the above parameters into the above formula (1) to calculate the above first frequency f1.

[0080] In another optional implementation, when the LLC circuit operates far away from its resonance point, the frequency generator P1 can specifically calculate the first frequency f1 according to the following formula (2), the above-mentioned DC voltage component Uin0, the AC voltage component UinAC, the output voltage Uo and other parameters of the LLC circuit. Here, formula (2) is as follows:

[0081]

[0082] Where, Q is the quality factor of the LLC circuit, f ndcThe DC component of the third frequency (here assumed to be f3) generated by the loop controller P2 included in the control module 20 at the above-mentioned time T1 or at the time T2 before the time T1 based on the preset control algorithm. Here, the loop controller P2 processes the voltage difference received from the first coupler H1 based on the preset control algorithm to obtain a frequency (for the convenience of distinction, the fourth frequency f3 will be referred to below). n Instead of describing). The third frequency f3 is the fourth frequency f n It should be understood that, according to the working principle of the loop controller P3, it mainly processes the difference between the voltage Uo obtained from the first coupler H1 and the reference voltage Uref or the absolute value of the difference through a preset control algorithm to obtain the fourth frequency f n , and this fourth frequency f n The voltage Uo may be a DC voltage with an AC component superimposed thereon, so the loop controller P3 generates a fourth frequency f based on the difference between the voltage Uo and the reference voltage Uref or the difference. n There are also DC and AC components in the circuit. The fourth frequency f n By filtering out the AC component in the n The corresponding DC component. Therefore, the f ndc It can be obtained by filtering out the AC component contained in the third frequency f3. n is the turns ratio of the transformer in the resonance module, fr is the resonance frequency of the resonance module, Uin0 is the DC voltage component, UinAC is the AC voltage component, and Uo is the output voltage.

[0083] It should be explained that, in actual implementation, the above formula (1) and formula (2) can be derived from the DC gain formula corresponding to the LLC circuit. Now assume that the DC gain of the LLC circuit is M(f n ), then the DC gain formula corresponding to the DC gain is the following formula (3):

[0084]

[0085] Wherein, λ is the ratio of the magnetizing inductance to the resonant inductance of the transformer 105, corresponding to Figure 2 In the LLC circuit shown in the figure, λ is the magnetizing inductance of transformer B1 (here the value is assumed to be L m ) and inductor L1 (here it is assumed that the inductance value of L1 is L r ), that is,

[0086] fn is the normalized frequency, which is a variable, and f n The following formula (4) is satisfied:

[0087]

[0088] Among them, f s That is, the switching frequency corresponding to each switch device in the switch network 103, that is, the frequency value finally output by the second coupler H2 to the PWM signal generator P3. r is the resonant frequency of the LLC circuit, which is a fixed value and satisfies the following formula (5):

[0089]

[0090] Among them, C r is the resonant capacitance corresponding to the resonant cavity 104, corresponding to Figure 2 The structure shown is the capacitance value of capacitor C1.

[0091] Q is the quality factor of the LLC circuit, and it satisfies the following formula (6):

[0092]

[0093] Among them, R eq This is the equivalent load of the LLC circuit, and the equivalent load satisfies the following formula (7):

[0094]

[0095] Among them, R ld That is the actual load of the rectifier bridge in the LLC circuit, corresponding to Figure 2 The structure shown in R ld That is, the actual load of the secondary rectifier bridge 106 .

[0096] According to the above formula (3), the DC gain M(f n ) satisfies the following formula (8):

[0097]

[0098]

[0099] When the LLC circuit operates near its resonance point, f n The initial value (here we assume that f n0 ) can be taken as 1, and then combined with the normalized frequency f n The Taylor series and its first-order component can obtain the DC gain M(f n ) is the first-order component of Among them, f1 is the first frequency to be obtained, which is also the normalized frequency f n The first-order AC component of .

[0100] Similarly, yes By performing Taylor expansion, we can infer that the corresponding first-order component is Since the first-order components on both sides of equation (3) are also equal, the following equation (9) can be obtained:

[0101]

[0102] Then, by combining formula (9), the above formula (1) for calculating the first frequency f1 can be derived.

[0103] When the LLC circuit works far from its resonance point, combined with the above formula (8), it can be seen that the DC gain M(f n ) is the first-order component of and The corresponding first-order component is By combining these two formulas, we can deduce the formula (2) for calculating the first frequency f1.

[0104] It should also be noted that in the LLC circuit, the various parameters (such as the ratio of the excitation inductance to the resonant inductance λ, the excitation inductance value L m After setting the parameters, the DC gain M(f n ) is also determined accordingly and will not change. Therefore, as long as the structure of the LLC circuit does not change, the calculation results of the above formulas (1) and (2) are always accurate, which can ensure that the target frequency obtained by subsequent calculation based on the control module 20 is also accurate and applicable.

[0105] Furthermore, after the control module 20 calculates the first frequency f1 through the frequency generator P1, it can transmit the first frequency f1 to the second coupler H2 through the frequency generator P1.

[0106] In addition, the control module 20 can also determine another frequency according to the output voltage Uo and the reference voltage Uref (for the convenience of distinction, the second frequency f2 will be used in the following description).

[0107] Specifically, the control module 20 can obtain the above-mentioned output voltage Uo and the preset reference voltage Uref of the LLC circuit through the first coupler H1. Then, the control module 20 can calculate the difference between the output voltage Uo and the reference voltage Uref or the absolute value of the difference through the first coupler H1, and transmit the difference between the output voltage Uo and the reference voltage Uref, or the absolute value of the difference between the output voltage Uo and the reference voltage Uref to the loop controller P2. Then, the control module 20 can control the loop controller P2 so that the loop controller P2 can process the difference between the output voltage Uo and the reference voltage Uref, or the absolute value of the difference between the output voltage Uo and the reference voltage Uref in combination with the internal preset loop control algorithm to obtain the above-mentioned second frequency f2. Then, the control module 20 can control the loop controller P2 to transmit the above-mentioned second frequency f2 to the above-mentioned second coupler H2.

[0108] Furthermore, after acquiring the first frequency f1 and the second frequency f2, the control module 20 may also determine the target frequency fs according to the first frequency f1 and the second frequency f2.

[0109] Specifically, the control module 20 can calculate the sum of the first frequency f1 and the second frequency f2 through the second coupler H2, and determine the sum of the first frequency f1 and the second frequency f2 as the target frequency fs. Then, the control module 20 can control the second coupler H2 to transmit the target frequency fs to the PWM signal generator P3 included therein.

[0110] S503: The control module generates a target driving signal according to the target frequency.

[0111] In some feasible implementations, after acquiring the target frequency fs, the control module 20 can control the driver 202 contained therein to further generate a corresponding drive signal according to the target frequency fs (for the sake of distinction, the target drive signal will be used instead of the description below).

[0112] In a specific implementation, after obtaining the target frequency fs, the control module 20 may provide the target frequency fs to the PWM signal generator P3 included in the driver 202. After obtaining the target frequency fs, the PWM signal generator P3 may generate a PWM signal with the target frequency fs, and determine the PWM signal as the driving signal required by the resonance module 10. Here, for the convenience of distinction, the first driving signal will be used instead in the following description.

[0113] Further, after the PWM signal generator P3 generates the first drive signal, the control module 20 may also control the PWM signal generator P3 to transmit the first drive signal to the inverter P4 included therein. Then, the control module 20 may invert the first drive signal through the inverter P4, and then obtain a new drive signal (for the sake of distinction, the second drive signal will be used instead of the description below). The first drive signal and the second drive signal are complementary PWM signals, or in other words, the phase difference between the first drive signal and the second drive signal is 180 degrees.

[0114] At this point, the control module 20 obtains the target driving signal including the first driving signal and the second driving signal.

[0115] S504: The control module turns on or off at least two switch devices included in the resonance module through the target driving signal.

[0116] In some feasible implementations, after generating a target drive signal including a first drive signal and a second drive signal, the control module 20 may send the target drive signal to at least two switching devices included in the resonance module 10 to control the on or off of the at least two switching devices.

[0117] In an optional specific implementation, the resonance module 10 adopts Figure 2 In the case of the structure shown (i.e., the switch network 103 includes the first switch device G1 and the second switch device G2), when the output end of the PWM signal generator P3 is connected to the third end of the first switch device G1, and the output end of the inverter P4 is connected to the third end of the second switch device G2, the control module 20 can transmit the first drive signal to the first switch device G1 through the output end of the PWM signal generator P3, and transmit the second drive signal to the second switch device G2 through the output end of the inverter P4, so that the first switch device G1 and the second switch G2 are alternately turned on. That is, the first switch device G1 is turned on while the second switch device G2 is turned off, and the first switch device G1 is turned off while the second switch device G2 is turned on, and the above actions are repeated cyclically. In this way, the switch network 103 can be in a normal working state, so that the resonance module 10 can resonate and work in a suitable frequency range to achieve the purpose of constant output voltage of the LLC circuit.

[0118] Alternatively, when the output end of the PWM signal generator P3 is connected to the third end of the second switch device G2, and the output end of the inverter P4 is connected to the third end of the first switch device G2, the control module 20 can transmit the first drive signal to the second switch device G2 through the output end of the PWM signal generator P3, and transmit the second drive signal to the first switch device G1 through the output end of the inverter P4. In this way, the first switch device G1 and the second switch G2 can be alternately turned on, thereby achieving the purpose of constant output voltage of the LLC circuit.

[0119] In another optional specific implementation, the resonance module 10 adopts Figure 3 In the case of the structure shown (i.e., the switch network 103 includes the first switch device G1, the second switch device G2, the third switch device G3 and the fourth switch device G4), when the output end of the above-mentioned PWM signal generator P3 is connected to the third end of the first switch device G1 and the third end of the fourth switch device G4, and the output end of the above-mentioned inverter P4 is connected to the third end of the second switch device G2 and the third end of the third switch device G3, the control module 20 can transmit the above-mentioned first drive signal to the first switch device G1 and the fourth switch device G4 through the output end of the PWM signal generator P3, and transmit the above-mentioned second drive signal to the second switch device G2 and the third switch device G3 through the output end of the inverter P4, so that the first switch device G1 and the second switch device G4 are synchronously turned on or off, the second switch device G2 and the third switch device G3 are also synchronously turned on or off, and the first switch device G1 and the third switch device G3 are alternately turned on. It can also be understood that the first switch device G1 and the fourth switch device G4 are turned on while the second switch device G2 and the third switch device G3 are turned off, and the second switch device G2 and the third switch device G3 are turned on while the first switch device G1 and the fourth switch G4 are turned off, and the above actions are repeated in a cycle. In this way, the switch network 103 can be in a normal working state to achieve the purpose of constant output voltage of the LLC circuit.

[0120] Alternatively, when the output end of the PWM signal generator P3 is connected to the third end of the second switch device G2 and the third end of the third switch device G3, and the output end of the inverter P4 is connected to the third end of the first switch device G1 and the third end of the fourth switch device G4, the control module 20 can transmit the first drive signal to the second switch device G2 and the third switch device G3 through the output end of the PWM signal generator P3, and transmit the second drive signal to the first switch device G1 and the fourth switch device G4 through the output end of the inverter P4, so that the first switch device G1 and the second switch device G4 are synchronously turned on or off, and the second switch device G2 and the third switch device G3 are synchronously turned on or off, and the above actions are repeated cyclically. In this way, the switch network 103 can also be in a normal working state to achieve the purpose of constant output voltage of the LLC circuit.

[0121] It should be understood here that the foregoing only describes a complete execution process of the control method of the LLC circuit provided by the present application. In actual implementation, the control module 20 in the LLC circuit can repeatedly execute the above control method. That is, after the control module 20 obtains the above target drive signal and controls at least two switching devices in the resonant module 10 according to the above target drive signal, when the preset trigger condition is triggered again, the control module 10 can obtain the new DC voltage component, new AC voltage component and new output voltage of the LLC circuit again, and repeat the above process to generate a new drive signal, and control at least two switching devices in the resonant module 10 again through this new drive signal.

[0122] In an embodiment of the present application, the control module 20 of the LLC circuit can determine a target frequency according to the DC voltage component, AC voltage component and output voltage of the resonance module 10 included in the input voltage of the resonance module 10, and then generate a target drive signal according to the target frequency, and then turn on or off at least two switch devices included in the resonance module through the target drive signal. Since the quality factor Q of the LLC circuit is positively correlated with its output power, reducing the output ripple of the LLC circuit is to ensure that the output power of the LLC circuit does not change. Therefore, the present application determines the target frequency by the DC voltage component, AC voltage component and output voltage corresponding to the resonance module 10 in the LLC circuit, and generates a corresponding target drive signal, so that the change of the quality factor Q of the LLC circuit caused by the presence of an AC component in the input can be overcome, so that the output power of the LLC circuit remains stable, thereby overcoming the output ripple caused by the presence of an AC component in the LLC circuit input, and improving the performance of the LLC circuit.

[0123] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0124] In short, the above is only a preferred embodiment of the technical solution of this application, and is not intended to limit the protection scope of this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application should be included in the protection scope of this application.

Claims

1. A control method for an LLC resonant circuit, characterized in that: The LLC resonant circuit comprises a control module and a resonant module, wherein the resonant module comprises at least two switching devices; The method comprises: The control module obtains a DC voltage component and an AC voltage component included in an input voltage of the resonance module; The control module determines a target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module; The control module generates a target driving signal according to the target frequency; The control module turns on or off the at least two switch devices through the target driving signal; The control module determines the target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module, including: The control module determines the first frequency by the following formula: Wherein, f1 is the first frequency, λ is the ratio of the excitation inductance to the resonant inductance of the transformer of the resonant module, n is the turns ratio of the transformer in the resonant module, fr is the resonant frequency of the resonant module, Uin0 is the DC voltage component, UinAC is the AC voltage component, and Uo is the output voltage; Alternatively, the control module determines the first frequency by the following formula: Wherein, f1 is the first frequency, Q is the quality factor of the LLC resonant circuit, and f ndc is the DC component of the third frequency generated and output by the loop controller in the control module, n is the turns ratio of the transformer in the resonance module, fr is the resonance frequency of the resonance module, Uin0 is the DC voltage component, UinAC is the AC voltage component, and Uo is the output voltage; The control module determines a second frequency according to the output voltage; The control module determines a target frequency according to the first frequency and the second frequency.

2. The method according to claim 1, characterized in that: The control module determines the target frequency according to the first frequency and the second frequency, comprising: The control module determines the target frequency according to the sum of the first frequency and the second frequency.

3. The method according to claim 2, characterized in that The control module determines the second frequency according to the output voltage, comprising: The control module determines the second frequency according to a difference between the output voltage and a reference voltage preset in the LLC resonant circuit.

4. The method according to claim 1, characterized in that: The target driving signal includes a first driving signal and a second driving signal, and a phase difference between the first driving signal and the second driving signal is 180 degrees; The control module generates a target driving signal according to the target frequency, including: The control module generates the first driving signal according to the target frequency; The control module generates the second driving signal according to the first driving signal.

5. The method according to claim 4, characterized in that The at least two switching devices include a first switching device and a second switching device; The control module turns on or off the at least two switch devices according to the target driving signal, including: The control module turns on the first switch device through the first drive signal, and turns off the second switch device through the second drive signal; Alternatively, the control module turns off the first switch device through the first drive signal, and turns on the second switch device through the second drive signal.

6. The method according to claim 4, characterized in that The at least two switching devices include a first switching device, a second switching device, a third switching device and a fourth switching device; The control module turns on or off the at least two switch devices according to the target driving signal, including: The control module turns on the first switch device and the fourth switch device through the first drive signal, and turns off the second switch device and the third switch device through the second drive signal; Alternatively, the control module turns off the first switching device and the fourth switching device through the first driving signal, and turns on the second switching device and the third switching device through the second driving signal.

7. The method according to any one of claims 4 to 6, characterized in that: The control module includes a controller and a driver; The control module determines a target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module, including: The control module determines the target frequency according to the DC voltage component, the AC voltage component and the output voltage of the resonance module through the controller; The control module generates a target driving signal according to the target frequency, including: The control module generates the target driving signal according to the target frequency through the driver; The control module turns on or off the at least two switch devices according to the target driving signal, including: The control module turns on or off the at least two switching devices according to the target driving signal through the driver.

8. An LLC resonant circuit, characterized in that: The LLC resonant circuit comprises a control module and a resonant module; The control module is used to execute the method according to any one of claims 1 to 7 to turn on or off at least two switching devices included in the resonance module.

9. The LLC resonant circuit according to claim 8, characterized in that: The resonance module includes an input source, a switch network, a resonant cavity, a transformer and a secondary rectifier bridge, and the switch network includes the at least two switch devices; The input source is connected to the switch network, the switch network is connected to the resonant cavity, the resonant cavity is connected to the transformer, and the transformer is connected to the secondary rectifier bridge; The input source is used to provide the DC voltage component and the AC voltage component, the switching network is used to convert the DC voltage component and the AC voltage component into a high-frequency AC square wave, the resonant cavity is used to obtain an AC output voltage through the high-frequency AC square wave, and the transformer and the secondary rectifier bridge are used to obtain the output voltage through the AC output voltage.

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