Control method, control device and LLC resonant converter

Abstract

The invention discloses a control method, a control device and an LLC resonant converter, and the control method comprises the steps: obtaining a feedback signal representing the size of an output electric parameter of the LLC resonant converter, comparing the feedback signal with a reference electric parameter, and taking a comparison result as a charge quantity given value; an electric signal of the magnitude of the electric charge accumulated by the resonance circuit is obtained cycle by cycle, the electric signal is processed to serve as an electric charge sampling value, and the electric charge accumulated by the resonance circuit is the electric charge accumulated by the resonance circuit within the pulse width overlapping time of the driving signals of the first bridge arm and the second bridge arm; and comparing the electric charge quantity sampling value in the current period with the electric charge quantity given value period by period to generate a control signal, and controlling the on and off of the two switching tubes in the first bridge arm according to the control signal. According to the invention, the problem of poor dynamic response of the phase-shift LLC resonant converter can be improved.

Description

Technical Field

[0001] The present invention relates to the field of switch converter control, and in particular to a control method, a control device and an LLC resonant converter. Background Art

[0002] The phase-shift controlled LLC resonant converter can achieve ZVS of the primary-side switch tube and ZCS of the secondary-side rectifier tube. Since a fixed switching frequency is used, it is beneficial to the design optimization of the LLC resonant converter transformer. By modulating the conduction phase of the switch tube between the bridge arms in the inverter circuit for control, the defects of the traditional LLC resonant converter with a wide operating frequency range and a narrow adjustable voltage range are avoided, making it more suitable for occasions requiring a wide voltage gain.

[0003] The conventional LLC resonant converter adopts a single voltage loop phase shift control. Figure 1 As shown, the LLC resonant converter includes an inverter circuit, a resonant circuit 103, a transformer 104, a rectifier circuit 105, a filter circuit 106 and a control circuit 200, wherein the inverter circuit includes a first bridge arm 101 composed of a switch tube S1 and a switch tube S2 and a second bridge arm 102 composed of a switch tube S3 and a switch tube S4. The control circuit 200 samples the secondary side output voltage through a feedback circuit 201 and compares it with a reference voltage Vref to generate an error voltage signal, and compares it with a fixed sawtooth wave signal 203, thereby adjusting the conduction phase difference between the switch tube of the first bridge arm and the switch tube of the second bridge arm of the inverter circuit, thereby achieving a regulated voltage output of the converter.

[0004] The load switching working state waveform of the phase-shifted LLC resonant converter using the above single voltage loop is as follows: Figure 2 As shown, since the control method is to compare the error signal with the fixed sawtooth wave, when the load changes and the current flowing through the inverter circuit increases, in order to achieve output voltage stability, the changed current needs to be converted into a changing error voltage signal through the voltage loop, and the phase difference between the switches is further adjusted to achieve output voltage stability; this makes the dynamic response capability of the LLC resonant converter poor and unable to adapt to rapid changes in the load; in addition, a single voltage loop is used for control, and the transfer function of the phase-shifted LLC resonant converter is a high-order nonlinear function, which makes it difficult to design the compensation parameters of the error amplifier circuit, which is reflected in the oscillation problem of the output voltage during load change regulation, and the overcurrent on the primary side cannot be quickly limited, which brings about the problem of poor reliability of the LLC resonant converter.

[0005] In addition, U.S. Patent No. US12488851 discloses a charge-controlled resonant conversion circuit, but its control method is to adjust the switching frequency of the converter by judging the amount of charge and then adjusting the gain for voltage stabilization. The charge control of the existing resonant converter, such as the charge-type control method proposed by Patent Nos. CN102163919B, CN105634287B and US12978841, although introducing charge-type control, still has the defects of a large switching frequency variation range and inability to perform targeted optimization of magnetic components. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to propose a control method, a control device and an LLC resonant converter, which can at least to some extent solve the deficiencies of the above-mentioned prior art.

[0007] As a first aspect of the present invention, the technical solution of an embodiment of the control method provided is as follows:

[0008] A control method is applied to an LLC resonant converter, wherein the primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit, wherein the inverter circuit includes at least a first bridge arm and a second bridge arm, and two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, wherein the control method includes:

[0009] Acquire a feedback signal representing the magnitude of an output electrical parameter of the LLC resonant converter, compare it with a reference electrical parameter, and use the comparison result as a given value of the charge amount;

[0010] Acquire an electrical signal of the amount of charge accumulated by the resonant circuit periodically, and use the signal as a charge sampling value after processing, wherein the amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm;

[0011] The charge amount sampling value of the current cycle is compared with the charge amount given value cycle by cycle to generate a control signal, and the conduction and disconnection of the two switch tubes in the first bridge arm are controlled according to the control signal.

[0012] Preferably, the electrical signal of the amount of charge accumulated in the resonant circuit is obtained by integrating the current flowing through the resonant circuit, or the electrical signal of the amount of charge accumulated in the resonant circuit is obtained by sampling the voltage across the resonant capacitor in the resonant circuit.

[0013] Furthermore, when the charge quantity sampling value is greater than the charge quantity given value, the first switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, the second switch tube in the first bridge arm is controlled to be turned on.

[0014] Furthermore, the electrical signal acquired to characterize the accumulated charge amount of the resonant circuit includes a first electrical signal and a second electrical signal, which serve as a first charge amount sampling value and a second charge amount sampling value, respectively. When the first charge amount sampling value is greater than or equal to the given charge amount value, the second charge amount sampling value will be less than the given charge amount value, thereby controlling one of the switch tubes in the first bridge arm to turn off, and after a certain delay time, controlling the other switch tube in the first bridge arm to turn on.

[0015] Preferably, the driving pulses of the two switching tubes in the second bridge arm are complementary, and the duty cycle is 50%.

[0016] Furthermore, each working cycle of the LLC resonant converter also includes: comparing the given charge value with the set charge value, and controlling the operating frequency, phase shift angle or pulse width according to the comparison result, so as to achieve that the output electrical parameters of the LLC resonant converter reach the desired value, the operating frequency includes the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm, and the phase shift angle is the phase difference between the two switch tube drive signals in the first bridge arm and the two switch tube drive signals in the second bridge arm.

[0017] Preferably, when the given value of the charge amount is less than or equal to the set value of the charge amount, the operating frequency is fixed, and the phase shift angle is adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter; when the given value of the charge amount is greater than the set value of the charge amount, the phase difference is fixed, and the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm are adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter.

[0018] Further, when the given value of the charge amount is less than or equal to the set value of the charge amount, the operating frequency is fixed to the maximum operating frequency set for the resonant converter.

[0019] Furthermore, when the given value of the charge is greater than the set value of the charge, the phase difference is fixed to a value between 0 and π.

[0020] Furthermore, the charge amount sampling value is used as a current protection signal to perform overcurrent protection on the LLC resonant converter.

[0021] As a second aspect of the present invention, the technical solution of an embodiment of the control device provided is as follows:

[0022] A control device is applied to an LLC resonant converter, wherein the primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit, wherein the inverter circuit includes at least a first bridge arm and a second bridge arm, and two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, wherein the control device includes:

[0023] The first acquisition module is used to obtain a feedback signal representing the output electrical parameter of the LLC resonant converter, and compare it with the reference electrical parameter, and use the comparison result as the given value of the charge amount.

[0024] A second acquisition module is used to acquire the electrical signal of the amount of charge accumulated by the resonant circuit period by period, and use it as a charge sampling value after processing, wherein the amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm;

[0025] The processing module is used to compare the charge quantity sampling value of the current cycle with the charge quantity given value cycle by cycle to generate a control signal, and control the conduction and disconnection of the two switch tubes in the first bridge arm according to the control signal.

[0026] Furthermore, the control device also includes a slope compensation module, which is used to perform slope compensation on the charge quantity sampling value.

[0027] As a third aspect of the present invention, the technical solution of the embodiment of the resonant converter provided is as follows:

[0028] An LLC resonant converter, the primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit, the inverter circuit includes at least a first bridge arm and a second bridge arm, two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, characterized in that: the conduction and shutdown of the switch tube in the first bridge arm are controlled by the control device described in any one of the second aspects above.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The embodiment of the present invention generates a control signal by comparing the current cycle charge sampling value with the charge given value, and controls the conduction and shutdown of the two switch tubes in the first bridge arm according to the control signal, thereby realizing the charge type control of the phase-shifted LLC resonant converter. When the circuit state changes, the charge sampling value quickly follows the change of the circuit state, thereby solving the problem of poor dynamic response of the single voltage ring type phase-shifted LLC resonant converter.

[0031] (2) In the embodiment of the present invention, when the given value of the charge is greater than or equal to the set value of the charge, the frequency of the two switch tube driving signals in the first bridge arm and the frequency of the two switch tube driving signals in the second bridge arm are adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter. The switching frequency has a small variation range, which is conducive to the optimal design of the magnetic element, and achieves the combination of high dynamic performance and small switching frequency variation.

[0032] (3) The control method of the present invention is accurate, reliable, and easy to implement. The charge sampling value can be used as a current protection signal to perform overcurrent protection on the LLC resonant converter, ensuring that the switch tube can be quickly responded to and turned off when overcurrent occurs, thereby improving the stability and reliability of the phase-shifted LLC resonant converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the principle diagram of the traditional single voltage loop controlled phase-shifted LLC resonant converter;

[0034] Figure 2 This is a working state waveform diagram of load switching of a traditional single voltage loop controlled phase-shifted LLC resonant converter;

[0035] Figure 3 is a flow chart of a control method according to a first embodiment of the present invention;

[0036] Figure 4 is a schematic structural diagram of a control device according to a second embodiment of the present invention;

[0037] Figure 5 A schematic diagram of a control device according to a second embodiment of the present invention applied to a charge-controlled phase-shifted LLC resonant converter;

[0038] Figure 6 for Figure 5 A graph showing the relationship between the frequency fs of the two switch tube drive signals of the second bridge arm of the charge-controlled phase-shifted LLC resonant converter and the phase difference Φ between the first bridge arm and the second bridge arm drive signals and the given value Vcomp of the charge quantity;

[0039] Figure 7 for Figure 5 Driving timing diagram of the charge-controlled phase-shifted LLC resonant converter in steady-state operation;

[0040] Figure 8 for Figure 5 Working state waveform of load switching of charge-controlled phase-shifted LLC resonant converter. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution 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 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 creative work should fall within the scope of protection of the present application.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0044] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0045] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0046] First embodiment

[0047] This embodiment provides a control method, which is applied to an LLC resonant converter. The primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit. The inverter circuit includes at least a first bridge arm and a second bridge arm. Two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference. The control method includes:

[0048] S101, obtaining a feedback signal representing the magnitude of an output electrical parameter of the LLC resonant converter, and comparing it with a reference electrical parameter, and using the comparison result as a given value of the charge amount;

[0049] S102, acquiring an electrical signal of the amount of charge accumulated by the resonant circuit period by period, and processing the signal as a charge sampling value, wherein the amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm;

[0050] S103, comparing the current cycle charge sampling value with the charge given value cycle by cycle to generate a control signal, and controlling the on and off of the two switch tubes in the first bridge arm according to the control signal.

[0051] It should be noted that the action performed by the above-mentioned S101 link can be acquired cycle by cycle or once for multiple cycles. When the action performed by the S101 link is acquired cycle by cycle, the S101, S102 and S103 links are performed serially in each cycle. When the action performed by the S101 link is acquired once for multiple cycles, the S101, S102 and S103 links are still performed serially in each cycle, except that the S101 link is reused in each cycle before the next acquisition of the given value of the charge.

[0052] In addition, the present invention does not limit the electrical parameters of the S101 link, and technicians in this field can choose according to needs. For example, when the control purpose is to achieve regulated voltage output, the electrical parameter can be voltage; when the control purpose is to achieve constant current output, the electrical parameter can be current; when the control purpose is to achieve constant power output, the electrical parameter can be voltage and current.

[0053] The control method of this embodiment generates a control signal by comparing the current cycle charge sampling value with the given charge value, and controls the on and off of the two switching tubes in the first bridge arm according to the control signal, thereby realizing the charge-type control of the phase-shifted LLC resonant converter. When the circuit state changes, the charge sampling value quickly follows the change of the circuit state, thereby solving the problem of poor dynamic response of the single voltage ring phase-shifted LLC resonant converter.

[0054] Preferably, the electrical signal of the amount of charge accumulated in the resonant circuit is obtained by integrating the current flowing through the resonant circuit, or the electrical signal of the amount of charge accumulated in the resonant circuit is obtained by sampling the voltage across the resonant capacitor in the resonant circuit.

[0055] Furthermore, when the charge amount sampling value is greater than or equal to the charge amount given value, the first switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, the second switch tube in the first bridge arm is controlled to be turned on. The present invention does not limit the control strategy when the charge amount sampling value is less than the charge amount given value, and those skilled in the art can select it as needed, for example, one switch tube in the first bridge arm can be controlled to be continuously turned on, and the other switch tube in the first bridge arm can be continuously turned off.

[0056] Furthermore, the electrical signal characterizing the accumulated charge amount of the resonant circuit includes a first electrical signal and a second electrical signal, which are respectively used as the first charge amount sampling value and the second charge amount sampling value. When the first charge amount sampling value is greater than or equal to the given charge amount value, the second charge amount sampling value will be less than the given charge amount value, and a switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, another switch tube in the first bridge arm is controlled to be turned on. When the first charge amount sampling value is less than the given charge amount value, the second charge amount sampling value will be greater than or equal to the given charge amount value. The control strategy during this period is not limited by the present invention, and those skilled in the art can choose it according to their needs. For example, it can also be used to control a switch tube in the first bridge arm to be continuously turned on, and another switch tube in the first bridge arm to be continuously turned off.

[0057] Preferably, the driving pulses of the two switching tubes in the second bridge arm are complementary, and the duty cycle is 50%.

[0058] Furthermore, each working cycle of the LLC resonant converter also includes: comparing the given value of the charge with the set value of the charge, controlling the operating frequency, phase shift angle or pulse width according to the comparison result, so as to achieve the output electrical parameter of the LLC resonant converter to reach the desired value, the operating frequency includes the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm, and the phase shift angle is the phase difference between the two switch tube drive signals in the first bridge arm and the two switch tube drive signals in the second bridge arm. The electrical parameter reaching the desired value refers to achieving the constant voltage output, constant current output or constant power output of the LLC resonant converter, etc. The present invention does not specify which specific electrical parameter reaches the desired value, and technicians in this field can design it according to their needs.

[0059] Preferably, when the given value of the charge is less than or equal to the set value of the charge, the operating frequency is fixed, and the phase shift angle is adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter; when the given value of the charge is greater than the set value of the charge, the phase difference is fixed, and the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm are adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter. When the given value of the charge is greater than the set value of the charge, the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm are adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter, and the switching frequency has a small variation range, which is conducive to the optimal design of the magnetic element, and realizes the combination of the two advantages of high dynamic performance and small switching frequency variation.

[0060] Further, when the given value of the charge amount is less than or equal to the set value of the charge amount, the operating frequency is fixed to the maximum operating frequency set by the resonant converter.

[0061] Furthermore, when the given value of the charge is greater than the set value of the charge, the phase difference is fixed to a value between 0 and π.

[0062] Furthermore, the charge sampling value is used as a current protection signal to perform overcurrent protection on the LLC resonant converter, ensuring that the switch tube can be quickly responded to and turned off when overcurrent occurs, thereby improving the stability and reliability of the phase-shifted LLC resonant converter.

[0063] Second embodiment

[0064] This embodiment provides a control device, which is applied to an LLC resonant converter. The primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit. The inverter circuit includes at least a first bridge arm and a second bridge arm. Two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference. The control device includes:

[0065] The first acquisition module is used to acquire a feedback signal representing the magnitude of an output electrical parameter of the LLC resonant converter, and compare it with a reference electrical parameter, and use the comparison result as a given value of the charge amount;

[0066] The second acquisition module is used to acquire the electrical signal of the amount of charge accumulated by the resonant circuit period by period, and use it as the charge sampling value after processing. The amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm;

[0067] The processing module is used to compare the current cycle charge quantity sampling value with the charge quantity given value cycle by cycle to generate a control signal, and control the conduction and disconnection of the two switch tubes in the first bridge arm according to the control signal.

[0068] The control device of this embodiment generates a control signal by comparing the current cycle charge sampling value with the given charge value, and controls the on and off of the two switching tubes in the first bridge arm according to the control signal, thereby realizing the charge-type control of the phase-shifted LLC resonant converter. When the circuit state changes, the charge sampling value quickly follows the change of the circuit state, thereby solving the problem of poor dynamic response of the single voltage ring phase-shifted LLC resonant converter.

[0069] Furthermore, the control device also includes a slope compensation module, which is used to perform slope compensation on the charge sampling value. When the electrical signal of the charge amount accumulated in the resonant circuit is obtained by integrating the current flowing through the resonant circuit, it is used to compensate the acquired electrical signal of the charge amount accumulated in the resonant circuit to avoid problems such as subharmonic oscillation.

[0070] Figure 5 This is a schematic diagram of a control device according to the second embodiment of the present invention applied to a charge-controlled phase-shifted LLC resonant converter. Figure 5 The LLC resonant converter includes a switch tube S1 and a switch tube S2 in the first bridge arm, a switch tube S3 and a switch tube S4 in the second bridge arm, and a resonant circuit includes a resonant inductor Lr and a resonant capacitor Cr.

[0071] Figure 5 The control device for the two switch tubes in the first bridge arm and the two switch tubes in the second bridge arm is 300. In addition to configuring the two switch tube drive signals in the first bridge arm and the two switch tube drive signals in the second bridge arm to have a phase difference, the control device of this embodiment is also integrated, specifically, including:

[0072] The first acquisition module acquires the output electrical parameters ( Figure 5 The feedback signal V_FB whose electrical parameter is the output voltage Vo of the LLC resonant converter is compared with the reference electrical parameter Vref through the error amplifier circuit 302, and the comparison result is used as the given value Vcomp of the charge amount;

[0073] The second acquisition module acquires the electric signal of the amount of charge accumulated by the resonant circuit period by period by the charge sampling circuit 307, and after being processed and compensated by the slope compensation circuit 308, it is used as the charge sampling values ​​Vcs1 and Vcs2. The amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm;

[0074] The processing module generates a control signal after comparing the current cycle charge sampling values ​​Vcs1 and Vcs2 with the charge given value Vcomp cycle by cycle through the first drive logic judgment circuit 303 and the second drive logic judgment circuit 304, and controls the conduction and shutdown of the two switching tubes in the first bridge arm according to the control signal.

[0075] Figure 5 The control logic of the processing module for the first bridge arm is: when the first charge amount sampling value Vcs1 is greater than or equal to the charge amount given value Vcomp, the second charge amount Vcs2 sampling value will be less than the charge amount given value Vcomp, and one switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, another switch tube in the first bridge arm is controlled to be turned on; therefore Figure 5 When the processing module in the embodiment is implemented, in addition to the first driving logic judgment circuit 303 and the second driving logic judgment circuit 304, other auxiliary circuits are also required. Figure 5 A specific implementation circuit is given in the figure, wherein the processing module also includes a first delay circuit 305, a second delay circuit 306, a logic circuit 309, a first bridge arm tube gate drive circuit 311 and a second bridge arm tube gate drive circuit 312, and the specific implementation principle of turning on and off the switch tube S1 and the second switch tube S2 in the first bridge arm is as follows:

[0076] The output end of the first driving logic judgment circuit 303 is connected to the input end of the first delay circuit 305. The signal outputted from the output end of the first driving logic judgment circuit 303 is also connected to the first input end of the logic circuit 309 as the first driving reset signal RESET1, which is used to control the reset of the driving signal of the switch tube S1 in the first bridge arm, so that the switch tube S1 is turned off. The output end of the first delay circuit 305 outputs the first set signal SET1 to be connected to the second input end of the logic circuit 309, which is used to control the setting of the driving signal of the switch tube S2 in the first bridge arm, so that the switch tube S2 is turned on. Specifically, when the charge quantity sampling value Vcs1 is greater than or equal to the charge quantity given value Vcomp, the first drive logic judgment circuit 303 outputs a high level as the first drive reset signal RESET1, and the logic circuit 309 obtains the rising edge of the first drive reset signal RESET1 as a trigger signal, and resets the drive signal of the first bridge arm switch tube S1 through the first bridge arm tube gate drive circuit 311, and the switch tube S1 is turned off; the first drive reset signal RESET1 outputs the first drive set signal SET1 through the first delay circuit 305, and the logic circuit 309 obtains the rising edge of the first drive set signal SET1 as a trigger signal, and sets the drive signal of the first bridge arm switch tube S2 through the first bridge arm tube gate drive circuit 311, and the switch tube S2 is turned on.

[0077] The output end of the second driving logic judgment circuit 306 is connected to the input end of the second delay circuit 306. The signal outputted from the output end of the second driving logic judgment circuit 306 is also connected to the third input end of the logic circuit 309 as the second driving reset signal RESET2, which is used to control the reset of the driving signal of the switch tube S2 in the first bridge arm, so that the switch tube S2 is turned off. The output end of the second delay circuit 306 outputs the second set signal SET2 to be connected to the fourth input end of the logic circuit 309, which is used to control the setting of the driving signal of the switch tube S1 in the first bridge arm, so that the switch tube S1 is turned on. Specifically, the second drive logic judgment circuit 304 compares the charge sampling value Vcs2 and the charge given value Vcomp. When the charge sampling value Vcs2 is greater than or equal to the charge given value Vcomp, the second drive logic judgment circuit 304 outputs a high level as the second drive reset signal RESET2. The logic circuit 309 obtains the rising edge of the second drive reset signal RESET2 as a trigger signal, and resets the first bridge arm switch tube S2 through the first bridge arm tube gate drive circuit 311, and the switch tube S2 is turned off. The second drive reset signal RESET2 outputs the second drive set signal SET2 through the second delay circuit 306. The logic circuit 309 obtains the rising edge of the second drive set signal SET2 as a trigger signal, and drives the first bridge arm switch tube S1 for setting control through the first bridge arm tube gate drive circuit 311, and the switch tube S1 is turned off.

[0078] Figure 5 An optimal working process of the LLC resonant converter to achieve constant voltage output after adding the control logic of the second bridge arm in the processing module is analyzed as follows:

[0079] When the control circuit 300 is powered on, it resets itself, and then detects the given value Vcomp of the charge through the logic circuit 309, and obtains the frequency of the driving signal of the two switch tubes of the second bridge arm after processing, and the control circuit 300 starts to enter the working state;

[0080] When the control circuit 300 starts working, the logic circuit 309 controls the second bridge arm gate drive circuit 312 to drive the second bridge arm switch tubes S3 and S4 to work alternately with the same pulse width and in a complementary manner. The duty ratios of the second bridge arm switch tubes S3 and S4 are both 50% after ignoring the dead time, and the switching frequencies of the second bridge arm switch tubes S3 and S4 are both fs.

[0081] After power-on, the control circuit 300 controls the first bridge arm gate drive circuit 311 through the logic circuit 309 to drive the first bridge arm switch tubes S1 and S2 to turn on and off. The specific control logic is: when the first charge amount sampling value Vcs1 is greater than or equal to the charge amount given value Vcomp, the second charge amount Vcs2 sampling value will be less than the charge amount given value Vcomp, and one switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, the other switch tube in the first bridge arm is controlled to be turned on. It has been described in detail above and will not be repeated here.

[0082] The given charge value Vcomp is used as a feedback quantity to act on the control circuit 300 to adopt different control strategies for the partitioned areas, as follows:

[0083] The first interval is when the given charge value Vcomp is less than or equal to the set charge value Vcomp_set. At this time, the operating frequency is fixed, and the phase shift angle is adjusted to achieve the stability of the output voltage of the LLC resonant converter. Specifically, when the given charge value Vcomp is less than or equal to the set charge value Vcomp_set, the frequency fs of the second bridge arm switch tube drive signal is kept constant at fmax, and the setting and resetting operations of the switch tube S1 and S2 drive signals in the first bridge arm cause the first bridge arm switch tube drive signal and the second bridge arm switch tube drive signal to have a phase deviation, and thus the drive signals of the switch tubes between the diagonals of the first bridge arm and the second bridge arm have an overlapping area, and the pulse length of the overlapping area of ​​the two depends on the given charge value Vcomp. The larger the given charge value Vcomp is, the larger the overlapping pulse length between the diagonal switch tubes is, and the smaller the phase difference Φ of the drive signal between the first bridge arm and the second bridge arm is, and thus the more energy is transferred to the secondary side, so that the control circuit 300 can control the energy transfer and the stability of the output voltage by adjusting the given charge value.

[0084] The second interval is when the given charge value Vcomp is greater than the set charge value Vcomp_set. At this time, the phase difference Φ is fixed. The frequencies of the two switch tube drive signals in the first bridge arm and the two switch tube drive signals in the second bridge arm are adjusted to achieve the desired values ​​of the output electrical parameters of the LLC resonant converter. Specifically, when the given charge value Vcomp is greater than the set charge value Vcomp_set, the phase difference Φ is fixed to a value between 0 and π, and the frequency fs of the two switch tube drive signals in the second bridge arm is adjusted so that the frequency of the set-reset signal follows the frequency fs of the two switch tube drive signals in the second bridge arm, that is, the frequency of the two switch tube drive signals in the first bridge arm follows the frequency fs of the two switch tube drive signals in the second bridge arm. When the given charge value Vcomp is larger, the frequency fs of the two switch tube drive signals in the second bridge arm is smaller, thereby more energy is transferred to the secondary side, thereby controlling the stability of the output voltage.

[0085] The relationship between the phase difference Φ between the two intervals and the given value Vcomp of the charge, and the change of the frequency fs of the driving signal of the two switch tubes of the second bridge arm and the given value Vcomp of the charge is as follows: Figure 6 shown.

[0086] The control device of this embodiment can quickly respond to energy changes caused by load changes or input voltage changes because the changes in the charge sampling values ​​Vcs1 and Vcs2 can reflect the energy currently transmitted by the primary side of the converter in real time, thereby significantly improving the dynamic response characteristics of the traditional single voltage loop phase-shifted LLC resonant converter and the hysteresis of overcurrent protection.

[0087] It should be noted that, due to the symmetry between the first bridge arm and the second bridge arm of the inverter circuit, in specific implementation, the bridge arm composed of S3 and S4 can also be regarded as the first bridge arm, and the bridge arm composed of S1 and S2 can be regarded as the second bridge arm.

[0088] Third embodiment

[0089] The present embodiment provides an LLC resonant converter. The primary side of the LLC resonant converter of the present embodiment includes an inverter circuit and a resonant circuit. The inverter circuit includes at least a first bridge arm and a second bridge arm. Two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, wherein: the on and off of the switch tube in the first bridge arm is controlled by any control device in the second embodiment.

[0090] In order to illustrate the beneficial effects of the LLC resonant converter of this embodiment, the inventors of this application use Figure 5 Taking the LLC resonant converter as an example, a simulation circuit is used to test an optimal working process after adding the above-mentioned control strategy of the second bridge arm. During the test, only the load size of the converter is debugged to realize the charge-type control of the phase-shifted LLC resonant converter, reflecting the dynamic response capability and steady-state operation of the charge-type control of the phase-shifted LLC resonant converter, and the same circuit parameters are used during the test. Figure 8 for Figure 5 The load switching working state waveform diagram of the charge-controlled phase-shifted LLC resonant converter, wherein Vcs is the identifier of the Vcs1 and Vcs2 signals placed in the same coordinate system, the VAB identifier represents the voltage difference between the midpoint of the first bridge arm and the midpoint of the second bridge arm, the IOUT identifier represents the current value output by the rectifier circuit 105, and the ILOAD identifier represents the current flowing through the load resistor Rload.

[0091] Depend on Figure 2 and Figure 8From the comparison of the waveform diagrams, it can be seen that the phase-shifted LLC resonant converter provided in this embodiment performs charge-type control, which is different from the traditional single-voltage-loop phase-shifted LLC resonant converter. When the load switches quickly, the output voltage adjustment amount is small and there is no oscillation phenomenon, which is beneficial to the design of the compensation circuit of the error amplifier circuit; and the output voltage and current regulation speed is faster, and the maximum current of the converter can be effectively limited by the given value of the charge amount, thereby achieving good dynamic response capability of the converter and reliability of steady-state operation.

[0092] The description of the above embodiments is only used to help understand the inventive concept of the present invention and is not intended to limit the present invention. For ordinary technicians in this technical field, any modifications, equivalent substitutions, improvements, etc. made without departing from the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method, applied to an LLC resonant converter, wherein the primary side of the LLC resonant converter includes an inverter circuit and a resonant circuit, wherein the inverter circuit includes at least a first bridge arm and a second bridge arm, and two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, characterized in that: The control method comprises: Acquire a feedback signal representing the magnitude of an output electrical parameter of the LLC resonant converter, compare it with a reference electrical parameter, and use the comparison result as a given value of the charge amount; Acquire an electrical signal of the amount of charge accumulated by the resonant circuit periodically, and use the signal as a charge sampling value after processing, wherein the amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm; The charge amount sampling value of the current cycle is compared with the charge amount given value cycle by cycle to generate a control signal, and the conduction and disconnection of the two switch tubes in the first bridge arm are controlled according to the control signal.

2. The control method according to claim 1, characterized in that: An electrical signal of the amount of charge accumulated in the resonant circuit is obtained by integrating the current flowing through the resonant circuit, or an electrical signal of the amount of charge accumulated in the resonant circuit is obtained by sampling the voltage across the resonant capacitor in the resonant circuit.

3. The control method according to claim 1, characterized in that: When the charge quantity sampling value is greater than the charge quantity given value, the first switch tube in the first bridge arm is controlled to be turned off, and after a certain delay time, the second switch tube in the first bridge arm is controlled to be turned on.

4. The control method according to claim 3, characterized in that: The electrical signal obtained for characterizing the accumulated charge amount of the resonant circuit includes a first electrical signal and a second electrical signal, which are respectively used as a first charge amount sampling value and a second charge amount sampling value. When the first charge amount sampling value is greater than or equal to the given charge amount value, the second charge amount sampling value will be less than the given charge amount value, and one of the switch tubes in the first bridge arm is controlled to be turned off, and after a certain delay time, the other switch tube in the first bridge arm is controlled to be turned on.

5. The control method according to claim 1, characterized in that: The driving pulses of the two switching tubes in the second bridge arm are complementary, and the duty cycle is 50%.

6. The control method according to claim 1, characterized in that: Each working cycle of the LLC resonant converter also includes: comparing the given charge value with the set charge value, and controlling the operating frequency, phase shift angle or pulse width according to the comparison result to achieve the desired value of the output electrical parameter of the LLC resonant converter, wherein the operating frequency includes the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm, and the phase shift angle is the phase difference between the two switch tube drive signals in the first bridge arm and the two switch tube drive signals in the second bridge arm.

7. The control method according to claim 6, characterized in that: When the given value of the charge is less than or equal to the set value of the charge, the operating frequency is fixed, and the phase shift angle is adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter; when the given value of the charge is greater than the set value of the charge, the phase difference is fixed, and the frequency of the two switch tube drive signals in the first bridge arm and the frequency of the two switch tube drive signals in the second bridge arm are adjusted to achieve the desired value of the output electrical parameter of the LLC resonant converter.

8. The control method according to claim 7, characterized in that: When the given value of the charge amount is less than or equal to the set value of the charge amount, the operating frequency is fixed to the maximum operating frequency set for the resonant converter.

9. The control method according to claim 7, characterized in that: When the given value of the charge is greater than the set value of the charge, the phase difference is fixed to a value between 0 and π.

10. The control method according to claim 1, characterized in that: The charge amount sampling value is used as a current protection signal to perform overcurrent protection on the LLC resonant converter.

11. A control device, applied to an LLC resonant converter, wherein the primary side of the LLC resonant converter comprises an inverter circuit and a resonant circuit, wherein the inverter circuit comprises at least a first bridge arm and a second bridge arm, and two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, characterized in that: The control device comprises: The first acquisition module is used to obtain a feedback signal representing the output electrical parameter of the LLC resonant converter, and compare it with the reference electrical parameter, and use the comparison result as the given value of the charge amount. A second acquisition module is used to acquire the electrical signal of the amount of charge accumulated by the resonant circuit period by period, and use it as a charge sampling value after processing, wherein the amount of charge accumulated by the resonant circuit is the amount of charge accumulated by the resonant circuit during the overlap time of the pulse width of the driving signal of the first bridge arm and the second bridge arm; The processing module is used to compare the charge quantity sampling value of the current cycle with the charge quantity given value cycle by cycle to generate a control signal, and control the conduction and disconnection of the two switch tubes in the first bridge arm according to the control signal.

12. The control device according to claim 11, characterized in that: The control device also includes a slope compensation module, which is used to perform slope compensation on the charge quantity sampling value.

13. An LLC resonant converter, wherein the primary side of the LLC resonant converter comprises an inverter circuit and a resonant circuit, wherein the inverter circuit comprises at least a first bridge arm and a second bridge arm, wherein two switch tube drive signals in the first bridge arm and two switch tube drive signals in the second bridge arm are configured to have a phase difference, and wherein: The on and off of the switch tube in the first bridge arm is controlled by the control device according to any one of claims 11 to 12.

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