LLC resonant converter current control circuit and control method thereof

Abstract

The present application discloses an LLC resonant converter current control circuit and a control method thereof, wherein the LLC resonant converter current control circuit comprises: a power factor correction circuit, a half-bridge inverter circuit, a resonant circuit, an isolation transformer, a half-bridge rectifier circuit, and a bus capacitor; one end of the power factor correction circuit is used to connect to a power supply, and the other end is connected to the half-bridge inverter circuit; the half-bridge inverter circuit is also connected to the resonant circuit, the resonant circuit is connected to the half-bridge rectifier circuit through an isolation transformer, one end of the bus capacitor is used to connect to a load, and the other end is connected to the half-bridge rectifier circuit. By directly controlling the resonant cavity current, direct control and adjustment are performed when the current changes, thereby improving the control transient response rate and making the output voltage more stable.

Description

Technical Field

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

[0002] LLC (Lenz Lenz Capacity, a resonant circuit consisting of two inductors and one capacitor, referred to as LLC.) resonant circuit is a commonly used DC voltage regulation resonant circuit with many applications. The circuit consists of three parts: resonant inductor, resonant capacitor, and excitation inductor. The resonant circuit at the resonant frequency achieves the maximum power conversion efficiency. It is widely used in the field of power electronics, such as electronic transformers, power filters, DC transmission, chargers, etc.

[0003] Current LLC resonant control generally uses direct frequency control, which means that after the output voltage changes, feedback regulation is used to achieve stability. This will cause obvious control lag, resulting in a slow response rate. Summary of the invention

[0004] The main technical problem solved by the present application is to provide an LLC resonant converter current control circuit and a control method thereof, which directly controls the resonant cavity current, thereby improving the transient response rate of the current.

[0005] In order to solve the above technical problems, the first technical solution adopted in the present application is to provide an LLC resonant converter current control circuit, and the LLC resonant converter current control circuit includes: a power factor correction circuit, a half-bridge inverter circuit, a resonant circuit, an isolation transformer, a half-bridge rectifier circuit, and a bus capacitor; one end of the power factor correction circuit is used to connect to a power supply, and the other end is connected to the half-bridge inverter circuit; the half-bridge inverter circuit is also connected to the resonant circuit, and the resonant circuit is connected to the half-bridge rectifier circuit through the isolation transformer; one end of the bus capacitor is used to connect to a load, and the other end is connected to the half-bridge rectifier circuit.

[0006] Optionally, the half-bridge inverter circuit includes:

[0007] a first thin film transistor, wherein a first channel end of the first thin film transistor is respectively connected to the positive electrode of the power source and the resonant circuit;

[0008] A second thin film transistor, wherein a first channel end of the second thin film transistor is connected to a second channel end of the first thin film transistor, and a second channel end of the second thin film transistor is respectively connected to a negative electrode of the power source and the resonant circuit.

[0009] Optionally, the first thin film transistor further includes a first junction capacitor and a first parasitic diode, and the second thin film transistor further includes a second junction capacitor and a second parasitic diode;

[0010] Wherein, the first junction capacitor is connected in parallel to the first channel end and the second channel end of the first thin film transistor, the anode of the first parasitic diode is connected to the second channel end of the first thin film transistor, and the cathode of the first parasitic diode is connected to the first channel end of the first thin film transistor;

[0011] The second junction capacitor is connected in parallel to the first channel end and the second channel end of the second thin film transistor, the anode of the second parasitic diode is connected to the second channel end of the second thin film transistor, and the cathode of the second parasitic diode is connected to the first channel end of the second thin film transistor.

[0012] Optionally, the resonant circuit comprises:

[0013] A resonant capacitor, wherein the resonant capacitor is connected to the half-bridge inverter circuit and the isolation transformer;

[0014] A resonant inductor, wherein a first end of the resonant inductor is connected to a common end of the first thin film transistor and the second thin film transistor, and a second end of the resonant inductor is connected to the isolation transformer.

[0015] Optionally, the resonant capacitor includes a first resonant capacitor and a second resonant capacitor.

[0016] Two ends of the first resonant capacitor and the second resonant capacitor connected in series are respectively connected to a first path end of the first thin film transistor and a second path end of the second thin film transistor, and a common end of the first resonant capacitor and the second resonant capacitor is connected to the primary side of the isolation transformer.

[0017] Optionally, the primary side of the isolation transformer includes an excitation inductor; a first end of the excitation inductor is connected to a second end of the resonant inductor, and a second end of the excitation inductor is connected to the resonant capacitor.

[0018] Optionally, the half-bridge rectifier circuit includes: a first diode and a second diode, the anode of the first diode and the anode of the second diode are respectively connected to the two ends of the secondary coil of the isolation transformer, and the cathode of the first diode is respectively connected to the cathode of the second diode and the bus capacitor.

[0019] Optionally, the first end of the bus capacitor is connected to the common end of the first diode and the second diode respectively, the second end of the bus capacitor is connected to the midpoint of the secondary coil of the isolation transformer, and the two ends of the bus capacitor are also connected to the two ends of the load respectively.

[0020] In order to solve the above technical problems, the second technical solution adopted in the present application is to provide a control method of an LLC resonant converter current control circuit, wherein the LLC resonant converter current control circuit is any one of the LLC resonant converter current control circuits described above, and the control method of the LLC resonant converter current control circuit includes:

[0021] Obtaining the output voltage, input voltage and resonant current of the resonant converter;

[0022] determining an adjusted voltage value based on the output voltage and a preset reference voltage;

[0023] performing compensation processing on the regulated voltage value and the input voltage, and determining an output value after the compensation processing;

[0024] The output pulse width is controlled by comparing the output value after the compensation process with the resonant current to perform voltage stabilization control.

[0025] Optionally, the step of determining the adjusted voltage value based on the output voltage and a preset reference voltage includes:

[0026] Performing sampling and filtering processing on the output voltage, the input voltage and the resonant current;

[0027] The output voltage after sampling and filtering is compared with a preset reference voltage to obtain a difference, and the adjusted voltage value is determined according to the difference.

[0028] Optionally, the step of compensating the regulated voltage value and the input voltage and determining the output value after the compensation includes:

[0029] Acquiring the adjusted voltage value and the input voltage;

[0030] Whether to perform compensation is determined based on the adjusted voltage value and the input voltage; if compensation is determined, the feedforward compensation coefficient and the slope compensation coefficient are determined, and after the slope compensation is triggered, the cumulative compensation is calculated and the output value after the compensation is output; if no compensation is performed, the output value after the compensation is equal to the adjusted voltage value.

[0031] Optionally, the step of controlling the output pulse width by using the comparison result between the output value after the compensation process and the resonant current to perform voltage stabilization control includes:

[0032] Based on the output value after the compensation processing, the resonant current value after sampling and filtering is compared with the output value after the compensation processing, and a first adjustment instruction is obtained based on the comparison result, and at the same time, the resonant current value after sampling and filtering is inverted and compared with the output value after the compensation processing, and a second adjustment instruction is obtained based on the comparison result;

[0033] In response to the first adjustment instruction and the second adjustment instruction, the pulse width of the output voltage is controlled to perform voltage stabilization control.

[0034] The beneficial effects of the present application are: different from the prior art, by adding output ripple feedforward control, direct control and adjustment are performed when the current changes, thereby improving the control transient response rate and making the output voltage more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 is a block diagram of the LLC resonant converter current control circuit of the present application;

[0037] Figure 2 It is a circuit structure diagram of the LLC resonant converter current control circuit of the present application;

[0038] Figure 3 is a control flow chart of the LLC resonant converter current control circuit of the present application;

[0039] Figure 4 is a circuit structure diagram of the first controller of the present application;

[0040] Figure 5 is a flow chart of a first embodiment of a control method of a current control circuit of an LLC resonant converter of the present application;

[0041] Figure 6 is a flow chart of a second embodiment of a control method for a current control circuit of an LLC resonant converter of the present application;

[0042] Figure 7 It is a timing diagram of the current control circuit of the LLC resonant converter of the present application. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only 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 ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "said", and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless otherwise clearly indicated above, and "multiple" generally includes at least two, but does not exclude the inclusion of at least one.

[0045] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0046] It should be understood that the terms "include", "comprises" or any other variations used herein are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "includes..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0047] First embodiment

[0048] See also Figure 1 , Figure 1 It is a block diagram of the current control circuit of the LLC resonant converter of the present application. In this embodiment, the LLC resonant converter 1 includes a power supply, a power factor correction circuit 101, a half-bridge inverter circuit 102, a resonant circuit 103, an isolation transformer 104, a half-bridge rectifier circuit 105, a bus capacitor 106, and a load. The power factor correction circuit 101 is connected to the power supply and the half-bridge inverter circuit 102 respectively, and the half-bridge inverter circuit 102 is also connected to the resonant circuit 103. The half-bridge inverter circuit 102 is connected to the isolation transformer 104 through the resonant circuit 103, and the half-bridge rectifier circuit 105 is connected to the other end of the isolation transformer 104, and the load is connected to the half-bridge rectifier circuit 105 through the bus capacitor 106.

[0049] In this embodiment, the power supply is a city power frequency power supply, and the power supply outputs an AC signal. After the AC signal is rectified by the power factor correction circuit 101, a DC signal is output. At this time, the DC signal will be accompanied by an industrial frequency ripple of less than 5%; the power factor correction circuit 101 is connected to the half-bridge inverter circuit 102 of the subsequent stage circuit, so as to invert the DC signal into a square wave AC signal; the half-bridge inverter circuit 102 is followed by a resonant circuit 103, and the resonant circuit 103 converts the square wave AC signal into a sinusoidal signal; then it is reduced to a certain appropriate value through the isolation transformer 104, and then the sinusoidal signal is adjusted, and then it is converted into a steamed bun wave through the half-bridge rectifier circuit 105, that is, the half-bridge rectifier circuit 105 rectifies the adjusted sinusoidal signal into a pulsating signal, and finally the bus capacitor 106 converts the pulsating signal into a DC signal to supply power to the load.

[0050] See also Figure 2 , Figure 2 It is a circuit structure diagram of the current control circuit of the LLC resonant converter of the present application. In the present embodiment, the power factor correction circuit 101 is a device for converting industrial frequency alternating current into direct current. During the conversion process, the power factor can be improved, the harmonic content can be reduced, and the voltage distortion and loss of the power grid can be reduced. The power factor correction circuit 101 can be specifically divided into active power factor correction and passive power factor correction, which can be selected according to the specific usage conditions, and no excessive restrictions are made here. The power factor correction circuit 101 can make the current track the voltage, and correct the unstable current to a sine through the power factor correction circuit 101, so that the current and voltage are in phase. The power factor correction circuit 101 is set between the power supply and the half-bridge inverter circuit 102 to reduce the harmonic content and further improve the stability of the output voltage.

[0051] In the present embodiment, the inverter circuit includes a first thin film transistor T1 and a second thin film transistor T2, and the first path end of the first thin film transistor T1 is connected to the power factor correction circuit 101 and the resonant circuit 103, respectively. The second path end of the first thin film transistor T1 is connected to the first path end of the second thin film transistor T2. The second path end of the second thin film transistor T2 is connected to the power factor correction circuit 101 and the resonant circuit 103, respectively. In the present embodiment, the first path end is specifically a drain, and the second path end is specifically a source. The first thin film transistor T1 has a built-in first parasitic diode D1 and a first junction capacitor C1, and the second thin film transistor T2 has a built-in second parasitic diode D2 and a second junction capacitor C2.

[0052] Specifically, the first junction capacitor C1 includes a first junction capacitor internal resistance Rc1, and the second junction capacitor C2 includes a second junction capacitor internal resistance Rc2. The first junction capacitor internal resistance Rc1 and the second junction capacitor internal resistance Rc2 have no actual connection relationship in the circuit, and the internal resistance is visualized for the convenience of analysis.

[0053] Among them, the first junction capacitor C1 is connected in parallel between the drain and source of the first thin film transistor T1, the anode of the first parasitic diode D1 is connected to the source of the first thin film transistor T1, and the cathode of the first parasitic diode D1 is connected to the drain of the first thin film transistor T1; the second junction capacitor C2 is connected in parallel between the drain and source of the second thin film transistor T2, the anode of the second parasitic diode D2 is connected to the source of the second thin film transistor T2, and the cathode of the second parasitic diode D2 is connected to the drain of the second thin film transistor T2.

[0054] Specifically, the first thin film transistor T1 and the second thin film transistor T2 are connected in series to form a half bridge, and the first thin film transistor T1 and the second thin film transistor T2 can be connected in series to form a half bridge by PWM driving (Pulse Width Modulation). In this embodiment, the gate of the first thin film transistor T1 is connected to the PWMA1 driving, and the gate of the second thin film transistor T2 is connected to the PWMA2 driving. The first thin film transistor T1 and the second thin film transistor T2 of the half-bridge inverter circuit 102 can be controlled to alternately turn on by PWMA1 driving and PWMA2 driving. During the process of turning off or turning on the first thin film transistor T1 and the second thin film transistor T2, the first junction capacitor C1 and the second junction capacitor C2 provide a charging or discharging circuit for the corresponding thin film transistor, so as to realize the zero voltage turning on of the first thin film transistor T1 and the second thin film transistor T2 during the switching process, thereby reducing the conduction loss of the thin film transistor. The first parasitic diode D1 and the second parasitic diode D2 are used to realize the freewheeling work in the dead time, that is, the first thin film transistor T1, the second thin film transistor T2 and their corresponding parasitic diodes and junction capacitors are controlled together to generate a square wave AC signal. The frequency at which the first thin film transistor T1 and the second thin film transistor T2 are alternately turned on is the operating frequency of the LLC resonant converter 1. The dead time is the time during which both the first thin film transistor T1 and the second thin film transistor T2 are not turned on, that is, the charging and discharging time of the first junction capacitor C1 and the second junction capacitor C2. The dead time is set to prevent the first thin film transistor T1 and the second thin film transistor T2 from being burned out by a large current during a short circuit.

[0055] The resonant circuit 103 includes a resonant capacitor and a resonant inductor Lr. The resonant capacitor is connected to the half-bridge inverter circuit 102 and the isolation transformer 104 , a first end of the resonant inductor Lr is connected to the common end between the first thin film transistor T1 and the second thin film transistor T2 , and a second end of the resonant inductor Lr is connected to the isolation transformer 104 .

[0056] The resonant capacitor includes a first resonant capacitor Cr1 and a second resonant capacitor Cr2, the two ends of the first resonant capacitor Cr1 and the second resonant capacitor Cr2 connected in series are respectively connected to the drain of the first thin film transistor T1 and the source of the second thin film transistor T2, and the common end of the first resonant capacitor Cr1 and the second resonant capacitor Cr2 is connected to the primary side of the isolation transformer 104. The primary side of the isolation transformer 104 is specifically the excitation inductor Lm, the first end of the excitation inductor Lm is connected to the second end of the resonant inductor Lr, and the second end of the excitation inductor Lm is connected to the common end of the first resonant capacitor Cr1 and the second resonant capacitor Cr2. The square wave AC signal enters the resonant circuit 103 to resonate, so only a sinusoidal electrical signal is output.

[0057] Specifically, the first resonant capacitor Cr1 includes a first resonant capacitor internal resistance Rcr1, and the second resonant capacitor Cr2 includes a second resonant capacitor internal resistance Rcr2. The first resonant capacitor internal resistance Rcr1 and the second resonant capacitor internal resistance Rcr2 have no actual connection relationship in the circuit, and the internal resistance is visualized for the convenience of analysis.

[0058] In this embodiment, the isolation transformer 104 is used to adjust the waveform amplitude of the sinusoidal electrical signal to a suitable preset value. The preset value can be set according to actual conditions, and no further discussion will be given here.

[0059] In this embodiment, the half-bridge rectifier circuit 105 includes: a first diode D3 and a second diode D4, the anode of the first diode D3 and the anode of the second diode D4 are respectively connected to the two ends of the secondary coil of the isolation transformer 104, and the cathode of the first diode D3 is respectively connected to the cathode of the second diode D4 and the bus capacitor 106.

[0060] Specifically, the adjusted sinusoidal electrical signal is input to the half-bridge rectifier circuit 105, and the first diode D3 and the second diode D4 use the unidirectional conductivity of the diode to rectify the adjusted sinusoidal electrical signal to output a pulsating electrical signal. The pulsating electrical signal is the waveform of the lower half of the sinusoidal electrical signal flipped up, and its waveform is positive.

[0061] In this embodiment, a power factor correction circuit 101 is provided between the power supply and the half-bridge inverter circuit 102 to directly control the resonant cavity current, thereby improving the response rate of the resonant circuit 103, reducing the harmonic content, and making the output voltage more stable.

[0062] Second embodiment

[0063] See also Figure 3 , Figure 31 is a control flow chart of the current control circuit of the LLC resonant converter of the present application. In this embodiment, the control circuit of the resonant circuit 103 includes a sampling and filtering processing unit, a first controller, a second controller, a data processing unit, and a PWM unit, wherein the data processing unit is respectively connected to the first controller, the second controller, and the sampling and filtering processing unit. The PWM unit is connected to the second controller, and the sampling and filtering processing unit is respectively connected to the first controller, the data processing unit, and the second controller.

[0064] refer to Figure 4 , Figure 4 It is a circuit structure diagram of the first controller of the present application. Among them, the first controller is a PI controller. The PI controller includes a first input port, a second input port, a first output port and an operational amplifier. The bus output voltage V0 flows through a resistor from the first input port and enters the operational amplifier. The reference voltage Vref enters the operational amplifier from the second input port. The operational amplifier calculates and then obtains the difference between the bus output voltage V0 and the reference voltage Vref. The calculated difference is used to output the adjusted voltage value VPI, and the adjusted voltage value VPI is output from the first output port. A capacitor C1 and a resistor R2 are also connected in parallel between the line segment after the first input port flows through a resistor and the line segment output from the first output port.

[0065] Third embodiment

[0066] See also Figure 5 , Figure 5 1 is a flow chart of the first embodiment of the control method of the LLC resonant converter current control circuit of the present application. It should be noted that if there is substantially the same result, the method of the present invention is not limited to Figure 5 The process sequence shown is limited. Figure 5 As shown, the method comprises the following steps:

[0067] S101: Obtaining the output voltage, input voltage and resonant current of the resonant converter.

[0068] In this embodiment, the output voltage V0 is the voltage value obtained after filtering and correcting the voltage V0 across the capacitor; the input voltage VAC is the voltage value obtained after filtering and correcting the AC power voltage VAC; the resonant current Ir is the current value obtained after filtering and correcting the resonant current in the resonant converter.

[0069] S102: Determine an adjusted voltage value based on the output voltage and a preset reference voltage.

[0070] In this embodiment, the reference voltage Vref is obtained and compared with the output voltage V0, the difference is obtained, the difference between the output voltage V0 and the reference voltage Vref is determined, the adjusted voltage value VPI is determined and output, and the stability of the output voltage V0 is ensured. The preset reference voltage Vref can be set according to the actual situation and the needs of the user, and this application does not make specific limitations on this.

[0071] S103: performing compensation processing on the adjusted voltage value and the input voltage, and determining an output value after the compensation processing.

[0072] In this embodiment, the compensation processing is mainly responsible for the transformation of the feedforward control compensation, superimposing the input of the feedforward control and the input of the slope compensation value, outputting the output value Vth after the compensation processing, and using the output value Vth after the compensation processing as a threshold for subsequent judgment.

[0073] S104: Controlling the output pulse width by comparing the output value after the compensation process with the resonant current to perform voltage stabilization control.

[0074] In this embodiment, the output value Vth after compensation is compared with the resonant current Ir. Two comparators are used, namely CMP1 and CMP2. The output value Vth after compensation is input to CMP1L and CMP2L at the same time. The resonant current Ir is divided into two paths, one path is positively input to the comparator CMP1H, and the other path is negatively input to the comparator CMP2H. The PWM1A drive and the PWM1B drive are two complementary drives. When the resonant current Ir is greater than the output value Vth threshold after compensation, the PWM1A drive will be set to zero, and the PWM1B drive will be set high after extending a shadow part dead zone. When the resonant current Ir is greater than the output value Vth threshold after compensation, the PWM1B drive will be set to zero, and the PWM1A drive will be set high after extending a shadow part dead zone, that is, the PWM1A drive and the PWM1B drive will extend a shadow part dead zone time when they are set high. Alternate cycle control is performed to achieve voltage stabilization output.

[0075] Fourth embodiment

[0076] See also Figure 6 , Figure 6 1 is a flow chart of a second embodiment of the control method of the LLC resonant converter current control circuit of the present application. It should be noted that if there is substantially the same result, the method of the present invention is not limited to Figure 6 The process sequence shown is limited. Figure 6 As shown, the method comprises the following steps:

[0077] S201: Obtain the output voltage, input voltage and resonant current value of the resonant converter.

[0078] In this embodiment, the data to be used in the adjustment process are first obtained, namely, the output voltage V0, the input voltage VAC and the resonant voltage. The input voltage VAC is the voltage V0 across the capacitor on the resonant converter, and the input voltage VAC is the output voltage V0 of the AC power supply. In this embodiment, it is specifically the output voltage V0 of the mains frequency power supply. In other embodiments, it can also be powered by other methods, and the voltage is not limited. The resonant current value is the resonant current Ir in the resonant converter.

[0079] S202: performing sampling and filtering processing on the output voltage, the input voltage and the resonant current.

[0080] In this embodiment, in order to make the data more accurate, the data sampling must be screened to remove the burrs with large errors, and filtering is generally used to improve the sampling accuracy. The obtained output voltage V0, input voltage VAC and resonant current Ir are sampled and filtered to obtain the output voltage V0 value, input voltage VAC value and resonant current Ir value after filtering and correction.

[0081] S203: Compare the sampled and filtered output voltage with a preset reference voltage to obtain a difference, and determine an adjusted voltage value according to the difference.

[0082] In this embodiment, the reference voltage Vref is obtained and compared with the output voltage V0 after sampling and filtering, the difference is obtained, the difference between the output voltage V0 and the reference voltage Vref is determined, the adjusted voltage value VPI is determined and output, and the stability of the output voltage V0 is ensured. The preset reference voltage Vref can be set according to the actual situation and the needs of the user, and this application does not make specific limitations on this.

[0083] S204: Acquire the adjusted voltage value and the input voltage.

[0084] In this embodiment, the adjusted voltage value VPI and the input voltage VAC are obtained to facilitate subsequent compensation processing based on the two voltage values, further reduce the voltage fluctuation, and then perform voltage stabilization output.

[0085] S205: Determine whether to perform compensation based on the adjusted voltage value and the input voltage; if compensation is determined, determine the feedforward compensation coefficient and the slope compensation coefficient, and after triggering the slope compensation, perform cumulative compensation calculation and output the compensated output value; if no compensation is performed, the compensated output value is equal to the adjusted voltage value.

[0086] In this embodiment, it is first necessary to determine whether the AC power needs to be compensated based on the adjusted voltage value VPI and the input voltage VAC. If compensation is required, the corresponding feedforward compensation coefficient is Kac, and the slope compensation coefficient is Kslope. After the slope compensation is triggered, the cumulative compensation begins. The calculation formula for data processing is:

[0087] Vth=VPI-KAC*VAC-∑Kslope;

[0088] Among them, Vth is the output value after compensation processing; VPI is the adjusted voltage value VPI; Kac is the feedforward compensation coefficient; VAC is the input voltage VAC after sampling and filtering; Kslope is the slope compensation coefficient.

[0089] In this embodiment, if it is determined that the AC power does not need to be compensated, there is no need to consider the feedforward compensation and the slope compensation, and the calculation formula for the compensation process is:

[0090] Vth = VPI;

[0091] Among them, Vth is the output value after compensation processing; VPI is the adjusted voltage value, that is, no processing is required, and the obtained adjusted voltage value VPI can be directly output to make it equivalent to the output value after compensation processing.

[0092] S206: Based on the output value after the compensation process, compare the resonant current value after sampling and filtering with the output value after the compensation process, and obtain a first adjustment instruction based on the comparison result.

[0093] See also Figure 7 , Figure 7 It is a timing diagram of the current control circuit of the LLC resonant converter of the present application. In this embodiment, the voltage waveform after compensation processing is compared with the waveform of the resonant capacitor voltage after sampling and filtering. The waveform of the resonant capacitor voltage, i.e., the resonant current Ir, has the same trajectory. It can be seen from the figure that the two graphs intersect at two places, and the first adjustment instruction is formed based on the above-mentioned graph comparison result.

[0094] S207: At the same time, the resonant current value after sampling and filtering is inverted and compared with the output value after the compensation processing, and a second adjustment instruction is obtained based on the comparison result.

[0095] In this embodiment, the value of the resonant current Ir after sampling and filtering is first inverted, and the corresponding waveform after inversion is compared with the waveform corresponding to the output value after compensation processing. It can be found that the waveform lines of the resonant current Ir, that is, the resonant capacitor voltage, are respectively located on one side of the voltage graph after compensation processing, and the two graphs intersect at two points. Based on the above-mentioned graph comparison results, a second adjustment instruction is formed.

[0096] S208: In response to the first adjustment instruction and the second adjustment instruction, the pulse width of the output voltage is controlled to perform voltage stabilization control.

[0097] In this embodiment, the first adjustment instruction and the second adjustment instruction are first obtained. The first adjustment instruction and the second adjustment instruction are both PWM signals in this embodiment. The first adjustment instruction and the second adjustment instruction are respectively input into the PWM1A drive and the PWM1B drive. The PWM1A drive and the PWM1B drive are complementary drives. The PWM signal is used to adjust the inductor current of the resonant converter so that the inductor current waveform tracks the input voltage VAC waveform, thereby achieving a regulated voltage output and improving the stability of the equipment operation.

[0098] Specifically, the first adjustment instruction is to set the corresponding part of the resonant capacitor voltage greater than the voltage after compensation processing, the PWM1A driver sets the voltage to zero, and the PWM1B driver extends the corresponding part by a shaded dead zone and sets it high, that is, the PWM1A driver stops outputting, and the PWM1B driver extends the output after a certain period of time. The dead zone time is set to prevent the thin film transistor from being burned out by a large current during a short circuit, and to protect the hardware through regulation.

[0099] The second adjustment instruction is that the inverted resonant capacitor voltage is greater than the corresponding part of the voltage after compensation processing. The PWM1B driver sets the voltage to zero, and the PWM1A driver extends the corresponding part by a shaded dead zone and sets it high. That is, the PWM1B driver stops outputting, while the PWM1A driver extends the output for a certain period of time.

[0100] In this embodiment, based on the first adjustment instruction and the second adjustment instruction, the thin film transistors corresponding to the PWM1A drive and the PWM1B drive are alternately turned on and cyclically adjusted, so that the LLC resonant converter 1 can output a stable voltage.

[0101] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An LLC resonant converter current control circuit, characterized in that: The LLC resonant converter current control circuit comprises: Power factor correction circuit, half-bridge inverter circuit, resonant circuit, isolation transformer, half-bridge rectifier circuit, bus capacitor; One end of the power factor correction circuit is used to connect to the power supply, and the other end is connected to the half-bridge inverter circuit; the half-bridge inverter circuit is also connected to the resonant circuit, and the resonant circuit is connected to the half-bridge rectifier circuit through the isolation transformer; one end of the bus capacitor is used to connect to the load, and the other end is connected to the half-bridge rectifier circuit; The half-bridge inverter circuit comprises: a first thin film transistor, wherein a first channel end of the first thin film transistor is connected to the positive electrode of the power supply and the resonant circuit respectively; a second thin film transistor, wherein a first channel end of the second thin film transistor is connected to a second channel end of the first thin film transistor, and a second channel end of the second thin film transistor is connected to a negative electrode of the power supply and the resonant circuit respectively; The gate of the first thin film transistor is connected to a first PWM driver, and the gate of the second thin film transistor is connected to a second PWM driver, so that the first PWM driver and the second PWM driver control the first thin film transistor and the second thin film transistor of the half-bridge inverter circuit to be alternately turned on; The LLC resonant converter current control circuit further includes: a sampling and filtering processing unit, a first controller, a second controller, a data processing unit, and a PWM unit, wherein the data processing unit is respectively connected to the first controller, the second controller, and the sampling and filtering processing unit, the PWM unit is connected to the second controller, and the sampling and filtering processing unit is respectively connected to the first controller, the data processing unit, and the second controller; the PWM unit includes the first PWM drive and the second PWM drive; The LLC resonant converter current control circuit is used to obtain the output voltage, input voltage and resonant current of the resonant converter, determine the adjusted voltage value based on the output voltage and a preset reference voltage, compensate the adjusted voltage value and the input voltage, and determine the output value after compensation; using the comparison result of the output value after compensation and the resonant current, the first PWM drive or the second PWM drive is extended by a shadow part dead time when it is set high, and the output pulse width of the first PWM drive and the second PWM drive is alternately and cyclically controlled to perform voltage stabilization control.

2. The LLC resonant converter current control circuit according to claim 1, characterized in that: The first thin film transistor further includes a first junction capacitor and a first parasitic diode, and the second thin film transistor further includes a second junction capacitor and a second parasitic diode; Wherein, the first junction capacitor is connected in parallel to the first channel end and the second channel end of the first thin film transistor, the anode of the first parasitic diode is connected to the second channel end of the first thin film transistor, and the cathode of the first parasitic diode is connected to the first channel end of the first thin film transistor; The second junction capacitor is connected in parallel to the first channel end and the second channel end of the second thin film transistor, the anode of the second parasitic diode is connected to the second channel end of the second thin film transistor, and the cathode of the second parasitic diode is connected to the first channel end of the second thin film transistor.

3. The LLC resonant converter current control circuit according to claim 1, characterized in that: The resonant circuit comprises: A resonant capacitor, wherein the resonant capacitor is connected to the half-bridge inverter circuit and the isolation transformer; A resonant inductor, wherein a first end of the resonant inductor is connected to a common end of the first thin film transistor and the second thin film transistor, and a second end of the resonant inductor is connected to the isolation transformer.

4. The LLC resonant converter current control circuit according to claim 3, characterized in that: The resonant capacitor includes a first resonant capacitor and a second resonant capacitor. Two ends of the first resonant capacitor and the second resonant capacitor connected in series are respectively connected to a first path end of the first thin film transistor and a second path end of the second thin film transistor, and a common end of the first resonant capacitor and the second resonant capacitor is connected to the primary side of the isolation transformer.

5. The LLC resonant converter current control circuit according to claim 3, characterized in that: The primary side of the isolation transformer includes an excitation inductor; a first end of the excitation inductor is connected to a second end of the resonant inductor, and a second end of the excitation inductor is connected to the resonant capacitor.

6. The LLC resonant converter current control circuit according to claim 1, characterized in that: The half-bridge rectifier circuit includes: a first diode and a second diode, the anode of the first diode and the anode of the second diode are respectively connected to the two ends of the secondary coil of the isolation transformer, and the cathode of the first diode is respectively connected to the cathode of the second diode and the bus capacitor.

7. The LLC resonant converter current control circuit according to claim 6, characterized in that: The first end of the bus capacitor is connected to the common end of the first diode and the second diode respectively, the second end of the bus capacitor is connected to the midpoint of the secondary coil of the isolation transformer, and the two ends of the bus capacitor are also connected to the two ends of the load respectively.

8. A control method for a current control circuit of an LLC resonant converter, characterized in that: The LLC resonant converter current control circuit is the control circuit according to any one of claims 1 to 7, and the control method of the LLC resonant converter current control circuit includes: Obtaining the output voltage, input voltage and resonant current of the resonant converter; determining an adjusted voltage value based on the output voltage and a preset reference voltage; performing compensation processing on the regulated voltage value and the input voltage, and determining an output value after the compensation processing; The output pulse width is controlled by comparing the output value after the compensation process with the resonant current to perform voltage stabilization control.

9. The control method of the LLC resonant converter current control circuit according to claim 8, characterized in that: The step of determining the adjusted voltage value based on the output voltage and a preset reference voltage comprises: Performing sampling and filtering processing on the output voltage, the input voltage and the resonant current; The output voltage after sampling and filtering is compared with a preset reference voltage to obtain a difference, and the adjusted voltage value is determined according to the difference.

10. The control method of the LLC resonant converter current control circuit according to claim 8, characterized in that: The step of compensating the regulated voltage value and the input voltage and determining the output value after the compensation includes: Acquiring the adjusted voltage value and the input voltage; Whether to perform compensation is determined based on the adjusted voltage value and the input voltage; if compensation is determined, the feedforward compensation coefficient and the slope compensation coefficient are determined, and after the slope compensation is triggered, the cumulative compensation is calculated and the output value after the compensation is output; if no compensation is performed, the output value after the compensation is equal to the adjusted voltage value.

11. The control method of the LLC resonant converter current control circuit according to claim 8, characterized in that: The step of controlling the output pulse width by comparing the output value after the compensation process with the resonant current to perform voltage stabilization control comprises: Based on the output value after the compensation processing, the resonant current value after sampling and filtering is compared with the output value after the compensation processing, and a first adjustment instruction is obtained based on the comparison result, and at the same time, the resonant current value after sampling and filtering is inverted and compared with the output value after the compensation processing, and a second adjustment instruction is obtained based on the comparison result; In response to the first adjustment instruction and the second adjustment instruction, the pulse width of the output voltage is controlled to perform voltage stabilization control.

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