Parameter dynamic reconstruction control method and system of LLC resonant converter

Abstract

This invention discloses a method and system for dynamic parameter reconfiguration control of an LLC resonant converter, belonging to the field of power electronics technology. The system includes a decision unit, an LLC resonant converter equipped with a variable resonant capacitor module, and a control module. The decision unit detects the converter's reference voltage in real time and compares it with a preset mode switching voltage. Based on the comparison result, it issues corresponding control commands to the control module to dynamically adjust the capacitance value of the variable resonant capacitor module. The control module includes a resonant current zero-crossing detection module, a central control module, and a resonant capacitor voltage sampling module. The resonant current zero-crossing detection module detects the instant the resonant current crosses zero, generates a reference signal, and sends it to the central control module. The central control module adjusts the capacitance value of the variable resonant capacitor module directly or in conjunction with the resonant capacitor voltage sampling module based on the control commands and the reference signal. This invention significantly improves the performance and safety of the converter under wide operating range.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a method and system for dynamic parameter reconfiguration control of LLC resonant converters. Background Technology

[0002] LLC resonant converters (Inductor-Inductor-Capacitor Resonant Converters) have inherent advantages such as low switching losses and high conversion efficiency due to the characteristics of their main switching transistors achieving zero-voltage turn-on (ZVS) and secondary rectifier transistors achieving zero-current turn-off (ZCS). They have been widely used in high-performance power supply fields such as server power supplies, communication base stations, and new energy vehicle chargers.

[0003] Typical LLC converters control voltage gain by adjusting their switching frequency fs. In applications requiring a wide range of voltage output (such as lithium battery charging), fixed-parameter LLC converters must significantly alter the switching frequency fs to achieve wide-range gain adjustment. Especially at low gain (corresponding to low output voltage), fs needs to be controlled much higher than the resonant frequency fr, but this leads to problems such as loss of ZVS capability and increased circulating current losses, causing a sharp drop in converter efficiency in this operating range.

[0004] To resolve this contradiction, an effective approach is to dynamically reconstruct the resonant cavity parameters online, for example, by controlling the parallel capacitor through switching to construct two resonant frequency modes: high and low. By switching at appropriate times, the switching frequency fs can be kept within a reasonable range, thus maintaining high efficiency across the entire output range. However, the success of this approach hinges on the timing of the parallel switch's action (closing / opening). Ideal lossless switching operation involves two aspects: closing the switch must be done instantaneously when the voltage of the main resonant capacitor equals that of the auxiliary capacitor to be connected, to eliminate inrush current; while opening the switch must be done instantaneously when the current flowing through the switch branch is zero, to avoid voltage spikes and switching stress caused by inductive components. Any misoperation at any time will generate huge switching losses, seriously threatening device reliability and completely negating the efficiency gain brought by parameter reconstruction.

[0005] For the switch opening, a high-quality resonant current signal can be used to directly detect its zero-crossing point, thus accurately corresponding to the ideal moment of zero-current turn-off (ZCS), which is a relatively direct and effective solution. However, for the more challenging switch closing problem, existing technologies mainly explore two approaches. The first is the direct detection method, which uses a hardware comparator to directly measure the resonant capacitor voltage. In practice, this method is highly susceptible to noise interference due to the high frequency, high slew rate, and high common-mode voltage characteristics of the resonant capacitor voltage signal, and it requires complex and expensive isolation detection circuits, resulting in poor reliability and high cost. The second is the indirect positioning method, which uses the resonant current zero-crossing point with better signal quality as a stable reference, attempting to find the zero-crossing point of the main resonant capacitor voltage by using the phase difference between the capacitor voltage and the current. This method has two problems: First, the simple open-loop fixed delay method cannot adaptively compensate for the phase difference between the resonant capacitor current and voltage caused by parasitic parameters, resulting in insufficient positioning accuracy. Second, it can only adapt to the case where the voltage of the auxiliary capacitor to be connected is zero, because only when the voltage of the auxiliary capacitor is zero can the voltage of the main resonant capacitor and the voltage of the auxiliary capacitor to be connected be guaranteed to be equal. It cannot adapt to the case where the voltage of the auxiliary capacitor is not zero, so it cannot meet the actual requirements.

[0006] In summary, existing technologies face a dilemma for critical switching operations: direct hardware detection methods are overly complex, expensive, and unreliable; while simple open-loop methods based on stable current references lack necessary adaptability. Therefore, the industry urgently needs a novel control method that can utilize high-quality current signals as a reference while employing low-cost, high-precision software algorithms to intelligently and adaptively pinpoint the switching moment, enabling safe and lossless switching of LLC resonant cavity parameters. Summary of the Invention

[0007] To address the problems in the prior art, this invention provides a method and system for dynamic parameter reconfiguration control of LLC resonant converters.

[0008] The technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention discloses a parameter dynamic reconfiguration control system for an LLC resonant converter, comprising a decision unit, an LLC resonant converter equipped with a variable resonant capacitor module, and a control module; the decision unit is used to detect the reference voltage of the LLC resonant converter in real time and compare it with a preset mode switching voltage, and issue corresponding control commands to the control module according to the comparison result, so as to dynamically adjust the capacitance value of the variable resonant capacitor module through the control module.

[0010] The control module includes a resonant current zero-crossing detection module, a central control module, and a resonant capacitor voltage sampling module. The resonant current zero-crossing detection module is used to detect the instant the resonant current of the LLC resonant converter crosses zero, generate a reference signal, and send it to the central control module. The central control module is used to directly adjust the capacitance value of the variable resonant capacitor module based on the control command and the reference signal, or to adjust the capacitance value of the variable resonant capacitor module based on the control command and the reference signal in combination with the resonant capacitor voltage sampling module.

[0011] The central control module generates a delay time and sends a sampling command to the resonant capacitor voltage sampling module at the moment when the reference signal is received, superimposing the delay time. The resonant capacitor voltage sampling module collects the voltage of the variable resonant capacitor module and feeds it back to the central control module. The central control module compares the absolute value of the voltage with a preset threshold and updates the delay time or generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module based on the comparison result.

[0012] Secondly, the present invention also discloses a method for dynamic parameter reconfiguration control of the LLC resonant converter of the control system, comprising the following steps:

[0013] 1) The resonant current zero-crossing detection module detects the instantaneous zero-crossing of the resonant current of the LLC resonant converter in real time, generates a reference signal and sends it to the central control logic module; the decision unit detects the reference voltage of the LLC resonant converter in real time and compares it with the mode switching voltage, generates a control command for adjusting the capacitance value of the variable resonant capacitor module based on the comparison result and sends it to the central control module.

[0014] 2) The central control module directly adjusts the capacitance value of the variable resonant capacitor module based on the control command and reference signal; or adjusts the capacitance value of the variable resonant capacitor module based on the control command and reference signal in conjunction with the resonant capacitor voltage sampling module, including: the central control module generates a delay time, and sends a sampling command to the resonant capacitor voltage sampling module at the moment corresponding to the delay time superimposed on the moment the reference signal is received; the resonant capacitor voltage sampling module collects the voltage of the variable resonant capacitor module and feeds it back to the central control module; the central control module compares the absolute value of the voltage with a preset threshold, and updates the delay time or generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module according to the comparison result.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. This invention provides a complete parameter dynamic reconfiguration control method. This method uses the zero-crossing point of the resonant current as a unified benchmark, which not only realizes a simple and reliable zero-current disconnection operation, but also solves the problem that existing technologies cannot accurately realize zero-voltage closing operation through an innovative adaptive search algorithm. Thus, it forms a safe, lossless, and reliable complete control closed loop, which comprehensively improves the performance and reliability of the converter under a wide operating range.

[0017] 2. This invention achieves precise zero-voltage switching through the coordinated operation of an auxiliary capacitor bleed branch and a closed-loop iterative correction mechanism with voltage feedback. The bleed branch creates reliable initial voltage conditions for subsequent iterative correction, while the closed-loop iterative correction mechanism automatically compensates for phase drift caused by parasitic parameters, ensuring precise locking of the voltage zero-crossing point. This combined approach significantly reduces switching losses and inrush current during parameter reconstruction, effectively protecting power devices. Therefore, this invention not only overcomes the shortcomings of the simple open-loop fixed-delay method in existing technologies, which cannot adapt to changing operating conditions, but also achieves precise zero-voltage switching under various operating conditions, resulting in excellent technical performance.

[0018] 3. This invention employs an indirect positioning software algorithm. Although it also requires detection of the resonant capacitor voltage, its detection purpose, method, and hardware requirements are fundamentally different from the direct hardware comparison method in existing technologies. The direct voltage zero-crossing detection method aims to capture the simulated zero-crossing moment of the voltage in real time using a high-speed hardware comparator. This requires an expensive, high-performance analog front-end that is resistant to high common-mode voltages and typically requires isolation to ensure speed and anti-interference capabilities. This invention, however, utilizes the existing standard ADC (analog-to-digital converter) within the controller to perform numerical sampling at discrete time points controlled by a software algorithm. This method eliminates the need for expensive high-speed dedicated comparators; a simple resistor divider network and a general-purpose operational amplifier are sufficient to condition the high-voltage signal to the ADC's range. This overcomes the shortcomings of high cost and poor anti-interference capability of the direct hardware detection method in existing technologies, thus achieving the technical advantages of low cost and high reliability. Therefore, this invention creatively transfers the stringent requirements of expensive, high-speed, and precise analog hardware to a low-cost and flexible software algorithm, ensuring or even exceeding the accuracy of the hardware method while reducing the system's hardware cost, complexity, and sensitivity to noise. Attached Figure Description

[0019] Figure 1 This is a circuit schematic diagram of an LLC resonant converter equipped with a variable resonant capacitor module in one embodiment of the present invention;

[0020] Figure 2 This is a structural diagram of the parameter dynamic reconfiguration control system of an LLC resonant converter in one embodiment of the present invention;

[0021] Figure 3 This is a flowchart of a parameter dynamic reconfiguration control system for an LLC resonant converter in one embodiment of the present invention;

[0022] Figure 4 This is a flowchart of the auxiliary capacitor input process in one embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the key working waveforms of the parameter dynamic reconstruction control method of the present invention during the iterative convergence process of the auxiliary capacitor input;

[0024] Figure 6 This is a comparison diagram of the current flowing through the first switching transistor during the auxiliary capacitor input stage of the present invention and the fixed delay method.

[0025] Figure 7 This is a waveform diagram of the parameter dynamic reconfiguration control system of the present invention during the process of removing the auxiliary capacitor. Detailed Implementation

[0026] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0027] This invention aims to solve the technical problem in existing technologies where LLC resonant converters, when reconfiguring parameters to adapt to a wide output range, suffer from huge inrush currents and switching losses due to the inability to precisely control the switching (on and off) timing of parallel capacitor branches. To construct a complete lossless switching control method, this invention provides precise control over both the on and off processes of the auxiliary capacitor: for the off-off of the auxiliary capacitor, the method directly achieves zero-current switch (ZCS) turn-off using the current zero-crossing point; for the more complex on-off of the auxiliary capacitor, this invention proposes an adaptive search scheme based on closed-loop feedback. This scheme first creates a reliable zero-voltage initial condition through the auxiliary capacitor bleeder circuit, and then, using the current zero-crossing as a reference, iteratively corrects the delay time to finally lock the ideal zero-voltage (ZVS) closing time. This invention overcomes the shortcomings of existing technologies, providing a low-cost, high-precision control method covering the entire switching process, significantly improving the performance and safety of the converter under wide operating range.

[0028] In a first aspect, the present invention provides a parameter dynamic reconfiguration control system for an LLC resonant converter. The system includes a decision unit, an LLC resonant converter equipped with a variable resonant capacitor module, and a control module. The decision unit is used to detect the reference voltage of the LLC resonant converter in real time and compare it with a preset mode switching voltage. Based on the comparison result, the decision unit issues corresponding control commands to the control module to dynamically adjust the capacitance value of the variable resonant capacitor module.

[0029] The control module includes a resonant current zero-crossing detection module, a central control module, and a resonant capacitor voltage sampling module. The resonant current zero-crossing detection module is used to detect the instant the resonant current of the LLC resonant converter crosses zero, generate a reference signal, and send it to the central control module. The central control module is used to directly adjust the capacitance value of the variable resonant capacitor module (i.e., dynamically reconstruct the parameters of the LLC resonant converter) based on the control command and the reference signal, or to adjust the capacitance value of the variable resonant capacitor module (i.e., dynamically reconstruct the parameters of the LLC resonant converter) based on the control command and the reference signal in combination with the resonant capacitor voltage sampling module.

[0030] The central control module generates a delay time and sends a sampling command to the resonant capacitor voltage sampling module at the moment when the reference signal is received, superimposing the delay time. The resonant capacitor voltage sampling module collects the voltage of the variable resonant capacitor module and feeds it back to the central control module. The central control module compares the absolute value of the voltage with a preset threshold and updates the delay time or generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module based on the comparison result.

[0031] See Figure 1 The circuit diagram of an LLC resonant converter according to a preferred embodiment of the present invention is shown below. The LLC resonant converter specifically includes: a power MOSFET Q1, a power MOSFET Q2, a power MOSFET Q3, a power MOSFET Q4, a DC input source Vin, an input capacitor Cbus, a resonant network section, a rectifier section, an output capacitor Co, and a load RL.

[0032] The input capacitor Cbus is connected to the positive and negative terminals of the DC power supply Vin (i.e., the DC input source Vin). The drain of power device Q1 (i.e., power MOSFET Q1) is connected to the positive terminal of the DC power supply Vin, and the source of power device Q1 is connected to the drain of power device Q2 (i.e., power MOSFET Q2), while the source of power device Q2 is connected to the negative terminal of the DC power supply Vin. The drain of power device Q3 (i.e., power MOSFET Q3) is connected to the positive terminal of the DC power supply Vin, and the source of power device Q3 is connected to the drain of power device Q4 (i.e., power MOSFET Q4), while the source of power device Q4 is connected to the negative terminal of the DC power supply Vin. The gates of each of the power devices Q1, Q2, Q3, and Q4 are connected to the corresponding drive output terminals of the external drive circuit. The external drive circuit receives logic level signals (such as PWM signals) from the external controller and converts them into gate drive signals that can reliably drive the power devices. To this end, the external drive circuit amplifies the low-voltage logic signal into a high-power signal with a higher voltage (e.g., 10-15V) and a peak current in the range of several amperes, providing the voltage required for full turn-on. It also rapidly charges and discharges the input capacitor of the power device using the high peak current, thereby achieving high-speed switching and reducing losses. Furthermore, for high-side power devices (power devices Q1 and Q3) with floating source potentials, the drive circuit ensures the correct reference for the gate drive voltage through internal level shifting or isolation functions, guaranteeing reliable switching.

[0033] The resonant network includes a variable resonant capacitor module Cr, a resonant inductor Lr, and a transformer magnetizing inductor Lm. One end of the variable resonant capacitor module Cr is connected to the connection point of power devices Q1 and Q2, and the other end is connected to one end of the transformer magnetizing inductor Lm. One end of the resonant inductor Lr is connected to the connection point of power devices Q3 and Q4, and the other end is connected to the other end of the transformer magnetizing inductor Lm.

[0034] The variable resonant capacitor module Cr includes a main resonant capacitor C1, an auxiliary resonant capacitor C2, a bleeder resistor Rrst, a drive circuit (not shown in the figure), and two switches for implementing control functions: a parameter reconfiguration switch Sp and a bleeder switch Qrst. In the physical structure of this embodiment, the auxiliary resonant capacitor C2 and the parameter reconfiguration switch Sp are connected in series to form a parallel branch, which is connected in parallel with the main resonant capacitor C1. The bleeder resistor Rrst is connected in series with the bleeder switch Qrst to form a bleeder branch, which is connected in parallel across the auxiliary resonant capacitor C2. Considering the bidirectional characteristics of the resonant current and the requirement for precise control, both switches must have bidirectional conduction and bidirectional blocking capabilities. Both the parameter reconfiguration switch Sp and the bleeder switch Qrst adopt a bidirectional switching structure composed of two power MOSFETs connected back-to-back in a common source configuration.

[0035] The connection relationships of the components in the variable resonant capacitor module Cr are as follows: First, each switching transistor has three ports. Therefore, the connection relationships are as follows: one end of the main resonant capacitor, one end of the auxiliary resonant capacitor, and one end of the bleeder resistor are connected together. The other end of the main resonant capacitor is connected to the first port of the first switching transistor. The second port of the first switching transistor is connected to the first port of the second switching transistor and the other end of the auxiliary resonant capacitor, respectively. The second port of the second switching transistor is connected to the other end of the bleeder resistor. The third ports of both switching transistors are connected to the drive circuit. The drive circuit receives control from the central control module to control the conduction or disconnection of each switching transistor. This drive circuit receives logic signals from the central control module to achieve reliable and fast switching control of the power devices.

[0036] The capacitance of the variable resonant capacitor module Cr is as follows: if the switch Sp is on, the capacitance of the variable resonant capacitor module Cr is equal to the sum of the capacitance of the resonant capacitor C1 and the capacitance of the auxiliary resonant capacitor C2; if the switch Sp is off, the capacitance of the variable resonant capacitor module Cr is equal to the capacitance of the resonant capacitor C1.

[0037] The rectifier section includes transformer T1, rectifier diodes D1 and D2. The secondary winding of the rectifier circuit employs a full-wave rectifier structure with a center tap. Specifically, the secondary winding of transformer T1 is divided into two half-windings of the same polarity, with a center tap directly connected to one end of the load resistor RL. The other ends of the two half-windings (i.e., the two outer ends of the secondary windings) are connected to the cathodes of rectifier diodes D1 and D2, respectively. The anodes of these two rectifier diodes are connected in parallel and then together to the other end of the load resistor RL. The output capacitor Co is connected in parallel with the load resistor RL to smooth and filter the rectified voltage and provide a stable DC power supply to the load. Finally, the primary winding of transformer T1 is connected in parallel with the transformer magnetizing inductance Lm.

[0038] Furthermore, as described above, based on the comparison results, corresponding control commands are issued to the control module to dynamically adjust the capacitance value of the variable resonant capacitor module; this is achieved through the following steps:

[0039] If the reference voltage of the LLC resonant converter is greater than the mode switching voltage, the decision unit sends a command to the control module to disconnect the first switch, and the auxiliary resonant capacitor is removed from the LLC resonant converter circuit. If the reference voltage of the LLC resonant converter is less than the mode switching voltage, the decision unit sends a command to the control module to turn on the first switch, and the auxiliary resonant capacitor is connected to the LLC resonant converter circuit. If the reference voltage of the LLC resonant converter is equal to the mode switching voltage, the command output by the decision unit remains unchanged, i.e., it maintains the previous output command, and the first switch remains in its previous state. The mode switching voltage should be set at the output voltage point where the efficiencies of the two resonant modes (high frequency and low frequency) are comparable or where the performance curves cross, to ensure the smoothest performance transition when switching modes at that point.

[0040] In this invention, the central control module directly adjusts the capacitance value of the variable resonant capacitor module based on control commands and reference signals. This is achieved through the following steps: the central control module receives control commands and reference signals, and upon receiving the second reference signal after receiving the control command, the central control module controls the switching transistor Sp to disconnect via the drive circuit. The auxiliary resonant capacitor is removed from the circuit of the LLC resonant converter, and the capacitance value of the variable resonant capacitor module changes.

[0041] In a specific embodiment of the present invention, the central control module includes a central control logic module, a variable delay timing module, and a delay time correction module. The central control logic module is used to receive control commands and reference signals, as well as the voltage fed back from the resonant capacitor voltage sampling module, and compare the absolute value of the voltage with a preset threshold. If the absolute value of the voltage is greater than or equal to the threshold, the central control logic module inputs the voltage to the delay time correction module. If the absolute value of the voltage is less than the threshold, the central control logic module generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module, that is, by adding the auxiliary resonant capacitor C2 into the circuit of the LLC resonant converter to change the capacitance value of the variable resonant capacitor module. The delay time correction module is used to update the delay time based on the received voltage and send the updated delay time to the variable delay timing module. The variable delay timing module is used for timing. After receiving the reference signal, the central control logic module sends a timing command to the variable delay timing module. The variable delay timing module receives the timing command and starts timing. The timing duration is equal to the delay time received by the variable delay timing module. When the timing is completed, the variable delay timing module notifies the central control logic module, and then the central control logic module sends a sampling command to the resonant capacitor voltage sampling module.

[0042] Reference Figure 2 The diagram shows the functional block diagram of the control system that achieves the above control objectives. In this diagram, 1 is the resonant current zero-crossing detection module, 2 is the resonant capacitor voltage sampling module, 3 is the central control logic module, 4 is the variable delay timing module, and 5 is the delay time correction module.

[0043] The resonant current zero-crossing detection module is typically a precision circuit consisting of a current sensing element and a signal comparison element. Specifically, the current sensing element at the front end can be a current transformer (CT) or a sampling resistor connected in series in the resonant circuit. Its function is to linearly and proportionally convert the high-frequency resonant current signal into a low-voltage signal. To improve anti-interference capability, this voltage signal can first pass through a simple filtering and buffering circuit. Subsequently, this conditioned analog voltage signal representing the resonant current is fed to the positive input of a high-speed hardware comparator, while the negative input of the comparator is connected to reference ground (0V). To prevent noise near the current zero-crossing point from causing "jitter" or false flipping of the comparator output, the comparator is preferably configured with hysteresis characteristics, i.e., it forms a Schmitt trigger. In this way, when the resonant current flowing through the variable resonant capacitor module Cr crosses zero, the comparator output will generate a digital square wave signal with steep edges. The rising and falling edges of this square wave correspond to the instantaneous zero-crossing of the resonant current. To form a precise event trigger marker, this square wave signal is then sent to an edge detection logic unit, which is configured to generate a high-precision, extremely narrow unit pulse signal at the rising, falling, or double edges of the square wave. This instantaneous pulse signal serves as the reference signal zc_event.

[0044] The physical carrier of the central control logic module can be a high-performance digital signal processor (DSP) or a microcontroller (MCU) integrating advanced control peripherals. Its core consists of the central processing unit (CPU) or programmable logic unit of these chips, combined with firmware running in internal memory or configured hardware circuitry. This module acts as the command center of the entire parameter reconfiguration system, responsible for coordinating the opening and closing of the switching transistors. When the auxiliary capacitor (i.e., the auxiliary resonant capacitor C2) needs to be removed, the module will directly use the reference signal zc_event from the resonant current zero-crossing detection module. However, due to the unavoidable reaction time between the digital controller making a decision and preparing to execute, the switch can be precisely issued at the next current zero-crossing point. When the auxiliary capacitor needs to be connected, the module first triggers the leakage resistor Rrst of the auxiliary capacitor to ensure that it is pre-discharged. After the leakage is completed, the reference signal zc_event is used as a reference to precisely control the timing, sampling and comparison process. The absolute value of the voltage sample value (Vcr, which is the voltage collected by the resonant capacitor voltage sampling module) obtained from the resonant capacitor voltage sampling module is compared with the preset success threshold (V_th). Based on the comparison result, a decision is made, that is, to directly generate the final trigger signal Trigger_Sp or call the delay time correction module to dynamically update the delay time τ, thereby executing the core closed-loop control algorithm and coordinating the work of the entire system.

[0045] In its physical implementation, the variable delay timing module is not a standalone hardware device, but rather a programmable hardware timer / counter peripheral integrated within modern digital controllers (such as DSPs or high-performance MCUs). Specifically, it is typically a dedicated hardware unit that counts based on a high-speed system clock. When the central control logic module receives the reference signal zc_event, it first converts the received delay time into a corresponding clock cycle count value and loads this count value into the comparison register of this hardware timer. Subsequently, the timer is enabled and begins counting. When the internal count value equals the set value in the comparison register, the hardware peripheral automatically generates an interrupt event or an output trigger signal. This interrupt or trigger signal corresponds to the end of the delay timing, thereby triggering subsequent voltage sampling operations.

[0046] The resonant capacitor voltage sampling module is physically a mixed-signal processing link connecting the analog and digital domains. Its implementation typically involves two main stages: First, an analog front-end conditioning circuit, whose function is to safely and accurately acquire the high-voltage floating resonant capacitor voltage signal. The core component of this circuit is usually a high-speed differential amplifier with a high common-mode rejection ratio (CMRR), whose input is connected to the two ends of the variable resonant capacitor module Cr via a high-impedance voltage divider network. This differential amplifier can accurately extract the differential voltage Vcr across the variable resonant capacitor module Cr while suppressing the superimposed, large-amplitude common-mode voltage interference. Then, to protect the downstream low-voltage controller, the output signal of this differential amplifier is usually electrically isolated by an isolation amplifier or a high-speed analog optocoupler. After conditioning and isolation, the resulting low-voltage analog signal is connected to a channel of the analog-to-digital converter (ADC) integrated within the central control logic module.

[0047] The delay time correction module is not a standalone hardware device in terms of physical structure, but rather a core algorithm implemented within modern digital control devices (such as DSPs or high-performance MCUs). When implemented using a digital signal processor (DSP) or microcontroller (MCU), this module mainly consists of the following parts: a dedicated firmware instruction set stored in program memory, an arithmetic logic unit (ALU) or floating-point unit (FPU) inside the central processing unit (CPU), and random access memory (RAM) or registers for storing control parameters (such as Kp, Ki, Kd) and state variables (such as integral accumulation values ​​and historical error values). In each correction cycle, the CPU, according to the firmware instructions, obtains the voltage error value from the ADC, reads the current state variables and parameters from RAM, performs mathematical operations of closed-loop control algorithms such as PID using the ALU / FPU, and updates the calculated correction amount to the corresponding state variables for use by the variable delay timing module in the next cycle.

[0048] Secondly, this invention also provides a method for dynamic parameter reconfiguration control of an LLC resonant converter. The core of this method lies in proposing an adaptive search scheme based on closed-loop feedback for the operation of the auxiliary resonant capacitor. This scheme utilizes an auxiliary capacitor leakage circuit (i.e., by conducting...) Figure 1 The system uses a bleeder switch (Qrst forming the bleeder circuit of the auxiliary resonant capacitor C2) and an adaptively correctable delay time to iteratively find and ultimately lock the turn-on time of the switch. The function of the auxiliary capacitor bleeder circuit is to ensure that the voltage of the auxiliary resonant capacitor C2 is zero before the switch is turned on. This ensures that the zero-crossing moment of the voltage of the main resonant capacitor C1 is the moment when the voltage of the main resonant capacitor is equal to that of the auxiliary resonant capacitor to be connected. The adaptively correctable delay time is used to compensate for the phase difference between the current and voltage of the resonant capacitor caused by parasitic parameters.

[0049] Specifically, the control logic of the control method of this invention is as follows: When it is necessary to disconnect the parallel capacitor branch (i.e., disconnect the auxiliary resonant capacitor C2), this method utilizes the zero-crossing point of the resonant current to directly correspond to the ideal zero-current turn-off timing. At the instant the second reference signal after receiving the received control command is received, the branch switch is immediately commanded to open, achieving a simple and reliable lossless turn-off. When it is necessary to engage the parallel capacitor branch (i.e., engage the auxiliary resonant capacitor C2), the following adaptive search steps are executed: First, the bleeder switch of the auxiliary capacitor bleeder circuit is closed (i.e., the bleeder switch Qrst is turned on). Then, the zero-crossing point of the resonant current is detected, and a delay timer is started. The delay time of this timer is a variable control quantity. After the timing is completed, the voltage of the main resonant capacitor C1 is sampled. The absolute value of the sampled voltage is compared with a very small success threshold. If it is less than the success threshold, it is considered that the voltage zero-crossing point has been successfully found, and a trigger signal is generated to control the switch of a parallel capacitor branch in the resonant cavity (i.e., the parameter reconstruction switch Sp) to turn on, thereby changing the capacitance value of the variable resonant capacitor module and completing parameter reconstruction. If the absolute value of the sampled voltage is greater than or equal to the success threshold, it indicates that the current delay time is inaccurate. The delay time correction module will calculate a correction amount based on the error value of the current voltage using a closed-loop control algorithm, and use this correction amount to update the delay time. Subsequently, the above process will be repeated using this updated, more accurate delay time at the next resonant current zero-crossing reference. This iterative loop will continue until the voltage zero-crossing point is successfully found.

[0050] Reference Figure 3It shows the top-level control logic flowchart of the parameter dynamic reconfiguration control system of LLC resonant converter to realize parameter dynamic reconfiguration, and shows the two sub-processes triggered by the decision unit: "switch on process" (i.e., the auxiliary resonant capacitor is put on) and "switch off process" (i.e., the auxiliary resonant capacitor is removed).

[0051] The entire control method begins with a top-level decision unit. This unit determines, based on the real-time operating state of the LLC resonant converter (e.g., the relationship between the reference voltage and the mode switching voltage), whether to "add the auxiliary resonant capacitor" to increase gain or "disconnect the auxiliary resonant capacitor" to accommodate the high-voltage output. When the decision unit issues the command to "disconnect the auxiliary resonant capacitor," the control module executes the switching transistor disconnection process: the central control logic module sets the "disconnect" command to a pending state upon receiving the reference signal zc_event, waits and captures the next natural zero-crossing of the resonant current, and precisely triggers the switching transistor disconnection operation at that moment to achieve zero-current turn-off. After the decision-making unit issues the command to "put the auxiliary resonant capacitor into operation", the control module executes a more precise switching transistor turn-on process: This process first triggers the bleeder resistor Rrst to ensure that the auxiliary resonant capacitor to be connected in parallel is pre-discharged to a zero-voltage state; then, the core adaptive ZVS search method is started, which uses the zero-crossing point of the resonant current as a reference and intelligently finds and locks the ideal turn-on time through closed-loop iteration; finally, after the algorithm converges successfully, the switching transistor is triggered to turn on, thereby completing the entire safe and lossless parameter reconstruction process.

[0052] In a specific embodiment of the present invention, the present invention provides a parameter dynamic reconfiguration control method for the LLC resonant converter of the control system. Initially, the switch Sp and switch Qrst of the LLC resonant converter are off. When switch Sp is on, only the operation of disconnecting the auxiliary resonant capacitor is performed; when switch Sp is off, only the operation of connecting the auxiliary resonant capacitor is performed. The method includes the following steps:

[0053] 1) The decision unit monitors the reference voltage of the LLC resonant converter in real time and compares it with the mode switching voltage. If the reference voltage is greater than the mode switching voltage, the decision unit sends a control command to the central control logic module to disconnect the switch Sp and executes step 2). If the reference voltage is less than the mode switching voltage, the decision unit sends a control command to the central control logic module to turn on the switch Sp and executes steps 3)-5). If the reference voltage is equal to the mode switching voltage, the command output by the decision unit remains unchanged, that is, the switch Sp maintains its original state (on or off).

[0054] 2) The resonant current zero-crossing detection module detects the instantaneous zero-crossing of the resonant current of the LLC resonant converter in real time, generates a reference signal, and sends it to the central control logic module; the central control logic module receives the control command and the reference signal, and when it receives the second reference signal after receiving the control command, it controls the switch transistor Sp to be disconnected through the drive circuit and adjusts the capacitance value of the variable resonant capacitor module.

[0055] 3) The resonant current zero-crossing detection module detects the instantaneous zero-crossing of the resonant current of the LLC resonant converter in real time, generates a reference signal and sends it to the central control logic module; the central control logic module receives the control command and controls the switching transistor Qrst to turn on through the drive circuit, so that the voltage of the auxiliary resonant capacitor drops to zero; then, after the switching transistor Qrst has been turned on for a preset time, the central control logic module controls the switching transistor Qrst to turn off.

[0056] The total duration of this preset time is typically on the order of hundreds of nanoseconds to a few microseconds. Compared to the tens of microseconds of switching cycles corresponding to LLC converters operating at tens or hundreds of kHz, this is a very small preprocessing stage that can be completed quickly and therefore will not affect the dynamic response performance of the system.

[0057] 4) When the central control logic module receives the reference signal, it sends a timing command to the variable delay timing module. The variable delay timing module receives the timing command and starts timing, and the timing duration is equal to the delay time stored in it at the current moment. When the timing is completed, the variable delay timing module notifies the central control logic module, and the central control logic module immediately sends a sampling command to the resonant capacitor voltage sampling module.

[0058] 5) The resonant capacitor voltage sampling module collects the voltage of the variable resonant capacitor module and feeds it back to the central control logic module. The central control logic module compares the absolute value of the voltage with a preset threshold. If the absolute value of the voltage is greater than or equal to the threshold, the central control logic module inputs the voltage to the delay time correction module. The delay time correction module updates the delay time based on the voltage and sends the updated delay time to the variable delay timing module, and repeats steps 4)-5). If the absolute value of the voltage is less than the threshold, the central control logic module generates a trigger signal, controls the switching transistor Sp to turn on through the drive circuit, and adjusts the capacitance value of the variable resonant capacitor module.

[0059] Reference Figure 4 and Figure 5 The control method and process for the input of auxiliary resonant capacitor are described in detail. Figure 4 The flowchart for the auxiliary resonant capacitor stage is shown; Figure 5 This demonstrates the resonant current Ir during the auxiliary resonant capacitor input phase (i.e., Figure 5In the case of I_Cr), the resonant capacitor voltage Vcr (i.e. Figure 5 The relationship between V_Cr and key signals within the control system as a function of time.

[0060] The process of adding the auxiliary resonant capacitor includes the following steps:

[0061] Step 1: Trigger the bleeder circuit. After receiving the control command to add the auxiliary capacitor, the central control logic module immediately triggers the bleeder circuit (i.e., turns on the bleeder switch Qrst), reducing the voltage of the auxiliary resonant capacitor C2 to zero, preparing for the subsequent parameter reconstruction switch Sp to turn on at zero voltage.

[0062] Step Two: Waiting for and detecting the zero-crossing point of the resonant current. After the control system is powered on, it first enters a waiting state. The resonant current zero-crossing detection module continuously monitors the resonant current Ir. For example... Figure 5 As shown, when the Ir waveform crosses the time axis (e.g., at t...), n At any given moment, the module immediately sends a reference signal zc_event to the central control logic module.

[0063] Step 3: Start the variable delay timer. Upon receiving the reference signal zc_event, the central control logic module immediately starts the variable delay timer module, with a timing duration equal to the stored delay time τ at the current moment. During initial execution or system reset, the initial value τ0 of the delay time τ can be set to one-quarter of the current operating cycle Ts of the variable resonant capacitor module, i.e., τ0 = Ts / 4.

[0064] Step 4: Sample the resonant capacitor voltage. For example... Figure 5 Chinese n As shown in the first period after time τ, when the delay time is τ n After the end (at t) n +τ n At the specified time, the variable delay timing module notifies the central control logic module, which then instructs the resonant capacitor voltage sampling module to sample the voltage of the variable resonant capacitor module, obtaining the sampled value Vcr(t). n +τ n To clearly represent the decision moment on the graph, an internal signal Is_checking is introduced, which is... n +τ n A narrow pulse is generated at any given moment.

[0065] Step 5: Logical Judgment. The resonant capacitor voltage sampling module will sample the absolute value of the voltage, abs(Vcr(t)). n +τ n It is compared with a preset, very small success threshold V_th.

[0066] Step Six: Trigger or Correct.

[0067] Scenario 1: Correction. For example... Figure 5 As shown by the period n, at t n +τ n At time, abs(Vcr(t) n +τ n The value is significantly greater than V_th. The judgment result is negative. The central control logic module will not generate a trigger signal Trigger_Sp, but will instead pass the sampled voltage to the delay time correction module.

[0068] Scenario 2: Successfully triggered. For example... Figure 5 As shown in the period n+k, after multiple iterations, at t n+k +τ n+k At time, abs(Vcr(t) n+k +τ n+k The result is less than V_th. The judgment result is yes. The central control logic module will generate a high-level trigger signal Trigger_Sp at this time, controlling the switch Sp to turn on and complete the parameter reconstruction, that is, to connect the auxiliary resonant capacitor C2 into the resonant cavity (variable resonant capacitor module Cr). At this time, the capacitance of the variable resonant capacitor module Cr is equal to the sum of the capacitances of the main resonant capacitor C1 and the auxiliary resonant capacitor C2. The resonant frequency will be lower than when the switch Sp is off, thereby optimizing the low output voltage operating range.

[0069] Step 7: Update the delay time. If a trigger signal (Trigger_Sp) is generated, there is no need to update the delay time; otherwise, the delay time needs to be corrected. When correction is required, the delay time correction module will execute its internal closed-loop control algorithm to calculate a new delay time based on the current error.

[0070] In a preferred embodiment of the present invention, the algorithm is a proportional-integral-derivative (PID) control algorithm to achieve fast, stable convergence with no steady-state error.

[0071] The input to this PID control algorithm is the voltage sampled in the current cycle. Its core principle lies in its comprehensive consideration of three dimensions: the magnitude of the current voltage (proportional action), the accumulated historical error (integral action), and the trend of the current error (derivative action), thereby calculating an overall, forward-looking phase correction. .

[0072] The delay time correction module then uses the phase correction amount. To update the internal phase state variable at the current time step Obtain the updated phase state variables ,Right now

[0073]

[0074] Finally, the delay time correction module then updates the phase state variables. Get the updated delay time ,Right now

[0075]

[0076] To improve system stability and robustness, a preferred implementation also includes limiting the updated delay time, which can be achieved by limiting the phase state variable. Specifically, the code within the delay time correction module checks the updated phase state variable. Does it exceed a preset reasonable upper or lower limit (those skilled in the art can set the upper and lower limits based on experience)? If the calculated updated phase state variable If the value exceeds this range, it will be forcibly set to the corresponding limit. This step prevents the delay time from being updated to an unreasonable value due to a large instantaneous voltage error during system startup or when encountering large external disturbances, thus ensuring the stability of the correction process.

[0077] Step 8: Iterate through the loop. The system uses the updated delay time. Returning to step two, we wait for the next current zero-crossing point to begin a new, more precise positioning cycle. This process continues until the error converges to within the success threshold V_th.

[0078] The reason why it can reliably wait for and capture the next zero-crossing point is that the high-performance digital controller has a much faster operation speed than the resonant period, and the phase state variable is set with upper and lower limits, so it has enough time to complete all sampling, comparison and correction tasks of the current cycle before the next current zero-crossing point arrives.

[0079] See Figure 5 Chinese n+k +τ n+k The key waveform information at each moment can be found that abs(Vcr(t) n+k +τ n+k If the voltage is less than V_th, the trigger condition is met, the trigger signal Trigger_Sp increases in level, the switching transistor Sp turns on, and the auxiliary resonant capacitor C2 is connected to the resonant cavity. Figure 5 It was observed that the voltage change of the resonant capacitor C2 was smooth at the moment it was connected to the resonant cavity, indicating that there was no inrush current at the moment the switching tube was turned on, thus achieving the purpose of safe and lossless switching.

[0080] See Figure 6This graph compares the current flowing through the switch during the auxiliary capacitor input stage of the present invention and the fixed delay method. The top line graph represents the change in the reference voltage Vref, the middle waveform represents the current flowing through the switch Sp (Isp_a) when the auxiliary resonant capacitor C2 is input under the reference voltage change (from a state greater than the mode switching voltage to less than the mode switching voltage), and the bottom waveform represents the current flowing through the switch Sp (Isp_b) when the auxiliary resonant capacitor C2 is input under the reference voltage change in the fixed delay method. The graph shows that the current at the moment the switch is turned on is significantly less than that of the fixed delay method, demonstrating the significant effect of the present invention.

[0081] See Figure 7 This is a waveform diagram of the control system of the present invention during the process of removing the auxiliary resonant capacitor, combined with... Figure 5 A complete closed-loop operation of the auxiliary resonant capacitor's connection and disconnection can be presented. Two schematic diagrams illustrate the dynamic waveforms of the voltage (Vcr) of the variable resonant capacitor module and the current (Isp_a) flowing through the switching transistor Sp during the connection and disconnection of the auxiliary resonant capacitor. From Figure 5 As can be seen, the auxiliary resonant capacitor switching operation controlled by this invention can be performed smoothly at the zero-crossing point of the resonant capacitor voltage; from Figure 7 As can be seen, the corresponding auxiliary resonant capacitor removal operation can also be smoothly completed at the zero-crossing point of the switching transistor's Sp current. This fully demonstrates that the control strategy proposed in this invention can achieve ideal control over the entire parameter reconstruction process. Specifically, this is reflected in two aspects: First, the zero-voltage turn-on achieved when the auxiliary resonant capacitor is engaged fundamentally eliminates the turn-on losses and destructive inrush currents caused by residual capacitor voltage, greatly reducing the electrical stress on the switching transistor. Second, the zero-current turn-off achieved when the auxiliary resonant capacitor is removed avoids the current-voltage overlap loss and inductive voltage spike at the moment of turn-off, ensuring the safe turn-off of the switching transistor. In summary, this complete "zero-voltage engagement, zero-current disengagement" soft-switching operation closed loop ensures that the switching process of the resonant cavity parameters between different modes is efficient, smooth, and reliable, fully demonstrating the advanced nature and practical value of this invention in practical applications.

[0082] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A parameter dynamic reconfiguration control system for an LLC resonant converter, characterized in that, It includes a decision unit, an LLC resonant converter equipped with a variable resonant capacitor module, and a control module; the decision unit is used to detect the reference voltage of the LLC resonant converter in real time and compare it with the preset mode switching voltage, and issue corresponding control commands to the control module according to the comparison result, so as to dynamically adjust the capacitance value of the variable resonant capacitor module through the control module. The control module includes a resonant current zero-crossing detection module, a central control module, and a resonant capacitor voltage sampling module. The resonant current zero-crossing detection module is used to detect the instantaneous zero-crossing of the resonant current of the LLC resonant converter, generate a reference signal, and send it to the central control module. The central control module is used to directly adjust the capacitance value of the variable resonant capacitor module based on the control command and the reference signal, or to adjust the capacitance value of the variable resonant capacitor module based on the control command and the reference signal in combination with the resonant capacitor voltage sampling module. The central control module generates a delay time and sends a sampling command to the resonant capacitor voltage sampling module at the moment when the reference signal is received, superimposing the delay time. The resonant capacitor voltage sampling module collects the voltage of the variable resonant capacitor module and feeds it back to the central control module. The central control module compares the absolute value of the voltage with a preset threshold and updates the delay time or generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module based on the comparison result. The variable resonant capacitor module of the LLC resonant converter includes a main resonant capacitor, an auxiliary resonant capacitor, a bleed resistor, a drive circuit, and two bidirectional switching transistors; wherein, each switching transistor adopts a bidirectional switching structure composed of two power MOSFETs connected back to back in common source, and each switching transistor has three ports. One end of the main resonant capacitor, one end of the auxiliary resonant capacitor, and one end of the bleeder resistor are connected together. The other end of the main resonant capacitor is connected to the first port of the first switching transistor. The second port of the first switching transistor is connected to the first port of the second switching transistor and the other end of the auxiliary resonant capacitor, respectively. The second port of the second switching transistor is connected to the other end of the bleeder resistor. The third ports of both switching transistors are connected to the drive circuit. The drive circuit is controlled by the central control module to control the conduction or disconnection of each switching transistor.

2. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 1, characterized in that, The step of issuing corresponding control commands to the control module based on the comparison results, so as to dynamically adjust the capacitance value of the variable resonant capacitor module through the control module, includes: If the reference voltage of the LLC resonant converter is greater than the mode switching voltage, the decision unit sends a command to the control module to disconnect the first switch, and the auxiliary resonant capacitor is removed from the circuit of the LLC resonant converter; if the reference voltage of the LLC resonant converter is less than the mode switching voltage, the decision unit sends a command to the control module to turn on the first switch, and the auxiliary resonant capacitor is connected to the circuit of the LLC resonant converter.

3. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 1, characterized in that, The central control module directly adjusts the capacitance value of the variable resonant capacitor module based on control commands and reference signals, including: The central control module receives control commands and reference signals. Upon receiving the second reference signal after receiving the control command, the central control module controls the first switching transistor to disconnect via the drive circuit. The auxiliary resonant capacitor is removed from the LLC resonant converter circuit, and the capacitance value of the variable resonant capacitor module changes.

4. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 1, characterized in that, The central control module includes a central control logic module, a variable delay timing module, and a delay time correction module; The central control logic module is used to receive the control command and reference signal, as well as the voltage fed back by the resonant capacitor voltage sampling module, and compare the absolute value of the voltage with a preset threshold. If the absolute value of the voltage is greater than or equal to the threshold, the central control logic module inputs the voltage to the delay time correction module. If the absolute value of the voltage is less than the threshold, the central control logic module generates a trigger signal to adjust the capacitance value of the variable resonant capacitor module. The delay time correction module is used to update the delay time based on the received voltage and send the updated delay time to the variable delay timing module; The variable delay timing module is used for timing. After receiving the reference signal, the central control logic module sends a timing command to the variable delay timing module. The variable delay timing module receives the timing command and starts timing. The timing duration is equal to the delay time received by the variable delay timing module. When the timing is completed, the variable delay timing module notifies the central control logic module, and the central control logic module immediately sends a sampling command to the resonant capacitor voltage sampling module.

5. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 4, characterized in that, The LLC resonant converter also features a DC input source with a preset threshold setting between 0.5% and 2% of the DC input voltage of the DC input source.

6. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 4, characterized in that, The delay time correction module sets an initial delay time and sends the set initial delay time to the variable delay timing module; wherein, the initial delay time is one-quarter of the working cycle of the variable resonant capacitor module at the current moment.

7. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 4, characterized in that, The delay time correction module updates the delay time based on the received voltage, including: The delay time correction module generates a phase correction amount based on voltage using a PID control algorithm. Then, it subtracts the phase correction amount from the phase state variable corresponding to the current delay time to obtain the updated phase state variable. Finally, it generates an updated delay time based on the updated phase state variable. Specifically, if the updated phase state variable is greater than the preset upper limit threshold, the updated phase state variable is corrected to the upper limit threshold; if the updated phase state variable is less than the preset lower limit threshold, the updated phase state variable is corrected to the lower limit threshold.

8. The parameter dynamic reconfiguration control system for the LLC resonant converter according to claim 7, characterized in that, The formula for calculating the updated delay time based on the updated phase state variables is as follows: ； in, Indicates the delay time after the update; This indicates the current operating cycle of the variable resonant capacitor module; This represents the updated phase state variable.

9. A method for dynamic parameter reconfiguration control of an LLC resonant converter using the control system described in any one of claims 1-8; characterized in that, Includes the following steps: 1) The resonant current zero-crossing detection module detects the instantaneous zero-crossing of the resonant current of the LLC resonant converter in real time, generates a reference signal and sends it to the central control logic module; the decision unit detects the reference voltage of the LLC resonant converter in real time and compares it with the mode switching voltage, generates a control command for adjusting the capacitance value of the variable resonant capacitor module based on the comparison result and sends it to the central control module. 2) The central control module directly adjusts the capacitance value of the variable resonant capacitor module based on the control commands and reference signals; Alternatively, the capacitance value of the variable resonant capacitor module can be adjusted based on the control command and reference signal combined with the resonant capacitor voltage sampling module. This includes: the central control module generating a delay time and sending a sampling command to the resonant capacitor voltage sampling module at the moment corresponding to the delay time superimposed on the moment the reference signal is received; the resonant capacitor voltage sampling module acquiring the voltage of the variable resonant capacitor module and feeding it back to the central control module; the central control module comparing the absolute value of the voltage with a preset threshold; and updating the delay time or generating a trigger signal to adjust the capacitance value of the variable resonant capacitor module based on the comparison result.

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