Wide-range zero-reactive LLC resonant converter based on fractional order capacitor structure

Abstract

The invention belongs to the technical field of power electronics, and discloses a wide-range zero-reactive LLC resonant converter based on a fractional order capacitor structure, which comprises a DC input voltage, an H-type inverter bridge consisting of Q1-Q4, a resonant inductor Lr, a resonant capacitor Cr and a resonant cavity structure consisting of an excitation inductor Lm, energy is transmitted to a secondary side through a transformation ratio N: 1 of a transformer, and the energy is transmitted to a secondary side through the resonant cavity structure. D1-D4 form a full-bridge rectifier which is connected with the secondary side of the transformer and is finally connected with a filter capacitor Cb and a load R, and the most important passive fractional order capacitor structure PFOC is connected in series into the resonant cavity structure. According to the invention, the inversion voltage in the passive fractional order circuit and the inversion voltage of the main circuit are controlled to be kept lagging by 90 degrees, so that the inversion voltage in the resonant cavity and the resonant cavity current realize a zero phase angle ZPA. When the ZPA is realized, the voltage gain of the LLC resonant converter is determined by the frequency, the frequency is inversely proportional to the voltage gain, and the voltage gain is less limited by the frequency.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and in particular relates to a wide-range zero-reactive LLC resonant converter based on a fractional-order capacitor structure. Background Technology

[0002] With the development of electric vehicles, industrial power supplies, and new energy power generation systems, isolated DC-DC converters have gained widespread attention for their inherent stability and reliability, playing a crucial role in these fields. Among various isolated DC-DC converters, LLC resonant converters are widely used in electric vehicles due to their higher power density, simpler topology, and lower electromagnetic interference (EMI).

[0003] Recently, to alleviate range anxiety, the charging voltage of electric vehicles has been increased from the mainstream 400V to the ultra-high voltage range (800-1000V), truly achieving the same power supply speed as hybrid vehicles. This necessitates the use of LLC resonant converters with a wider voltage gain range for voltage matching, which requires research into new topologies or regulation strategies.

[0004] The voltage gain formula can be derived from the equivalent circuit of the LLC resonant converter: ; The variables in the formula are defined as follows: ; As can be seen from the formula derivation, the voltage gain of a traditional LLC resonant converter is related to the frequency, and a function curve of voltage gain versus switching frequency can be plotted. Various researchers have proposed different methods to improve the performance and efficiency of LLC resonant converters, such as changing the LLC topology and modifying the control method.

[0005] However, the biggest drawback of traditional LLC resonant converters under PFM (frequency modulation control) is their narrow voltage range. This is because, due to the limitations imposed by magnetic components, the voltage range curve becomes flatter as the frequency increases.

[0006] While the voltage gain of a traditional LLC resonant converter under PSM / PWM (Phase-Shift / Pulse Width Control) is decoupled from its frequency, the soft-switching range is limited. To ensure the LLC circuit operates within the soft-switching range, the voltage gain remains constrained. The efficiency of a traditional LLC resonant converter decreases significantly when operating away from its resonant point. Some researchers have expanded the voltage range by connecting multiple resonant cavity circuits in series or parallel, but this undoubtedly increases the number of components, hindering LLC miniaturization and increasing circuit cost.

[0007] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: (1) Limited voltage gain range: Under pulse frequency modulation (PFM) control, the voltage gain of traditional LLC resonant converters is limited by the switching frequency. When the frequency increases to a certain level, the voltage gain curve tends to flatten and the rate of change decreases significantly, making it impossible to effectively adjust the output voltage by continuing to increase the frequency, which makes it difficult to meet the application requirements of wide-range voltage output (such as 800V-1000V charging).

[0008] (2) The contradiction between soft-switching characteristics and voltage gain: Under phase-shift modulation (PSM) or pulse width modulation (PWM) control, the range of soft switching (such as zero-voltage turn-on ZVS) of the converter will be narrowed. In order to ensure that the switching transistor can achieve soft switching in operation to reduce switching losses and electromagnetic interference (EMI), its effective voltage gain range is still limited, and it is impossible to achieve both wide gain and high efficiency.

[0009] (3) The working efficiency drops significantly when it deviates from the resonant point: The peak working efficiency of traditional LLC resonant converter usually appears near the resonant point. Once the working point deviates from the resonant frequency, the circulating current in the resonant cavity will increase sharply, resulting in increased conduction loss and thus significantly reducing the overall working efficiency. This limits its efficient operation in scenarios requiring a wide voltage output range.

[0010] (4) Increased topology complexity and cost: In order to solve the gain range problem, some existing solutions use the method of connecting multiple resonant cavities in series or in parallel. This solution inevitably increases the number of passive components (such as inductors and capacitors) and switching devices, resulting in complex circuit topology, increased size and increased cost, which is contrary to the development trend of miniaturization and high power density of power supply systems. Summary of the Invention

[0011] To overcome the problems existing in related technologies, the present invention discloses an embodiment of a wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure, the technical solution of which is as follows: The present invention is implemented as follows: a wide-range zero-reactive LLC resonant converter based on a fractional-order capacitor structure, the LLC resonant converter including a DC input voltage source, an H-bridge inverter circuit, a resonant cavity, a transformer, a full-bridge rectifier circuit, and an output filter circuit; The H-bridge inverter circuit consists of switching transistors Q1, Q2, Q3, and Q4, and is used to convert DC input voltage into AC voltage. The resonant cavity includes a resonant inductor Lr, a resonant capacitor Cr, and a magnetizing inductor Lm. The transformer is used to transfer the energy of the resonant cavity to the secondary side; The full-bridge rectifier circuit consists of diodes D1, D2, D3, and D4, and is used to convert AC voltage into DC voltage. The output filter circuit includes a filter capacitor Cb and a load R; A passive fractional-order capacitor structure PFOC is connected in series in the resonant cavity. The passive fractional-order capacitor structure PFOC is configured to generate an inverter voltage that lags behind the output voltage of the H-bridge inverter circuit by 90 degrees, so that the output voltage of the H-bridge inverter circuit and the resonant cavity current achieve zero phase angle ZPA.

[0012] Furthermore, the passive fractional capacitor structure PFOC includes switching transistors Q5 and Q6 and a capacitor Cp. Switching transistors Q5 and Q6 are controlled to generate the inverter voltage, and the phase of the inverter voltage lags behind the output voltage of the H-bridge inverter circuit by 90 degrees.

[0013] Furthermore, the H-bridge inverter circuit is used to switch between full-bridge and half-bridge modes to expand the output voltage range. In full-bridge mode, the bridge arms of switches Q1 and Q2 and the bridge arms of switches Q3 and Q4 are turned on alternately. In half-bridge mode, switch Q3 is kept off and switch Q4 is kept on.

[0014] Furthermore, the LLC resonant converter adopts pulse frequency modulation (PFM) control, which adjusts the output voltage by adjusting the switching frequency, and the voltage gain is inversely proportional to the switching frequency.

[0015] Furthermore, the PFM control is implemented through a controller, which includes a voltage sampling circuit, an isolation chip AMC1311, and a digital signal processor (DSP). The voltage sampling circuit samples the output voltage, which is then isolated by an isolation chip and transmitted to the DSP. The DSP adjusts the switching frequency based on the comparison between the sampled voltage and the reference voltage.

[0016] Furthermore, the controller is configured to control the switching timing of the switching transistors Q5 and Q6 of the passive fractional capacitor structure PFOC, such that the inverter voltage of the passive fractional capacitor structure PFOC lags behind the output voltage of the H-bridge inverter circuit by 90 degrees.

[0017] Furthermore, the LLC resonant converter achieves full-range soft switching within the switching frequency range, wherein the soft switching condition is satisfied by the design of the resonant cavity parameters: the value of the resonant capacitor Cr is such that the imaginary part of the equivalent impedance of the resonant cavity is greater than zero.

[0018] Furthermore, the resonant inductance Lr ranges from 10 to 30 μH, the magnetizing inductance Lm ranges from 50 to 150 μH, and the resonant capacitor Cr ranges from 50 to 200 nF.

[0019] Furthermore, the DC input voltage is 400V, the output voltage range is 250-1000V, the output power is 1500W, and the switching frequency range is 50-200kHz.

[0020] Another object of the present invention is to provide a method for controlling the aforementioned wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure, the method comprising the following steps: S1 controls the inverter voltage of the passive fractional capacitor structure PFOC to lag the output voltage of the H-bridge inverter circuit by 90 degrees, thereby achieving zero phase angle ZPA of the resonant cavity. S2 adjusts the switching frequency via PFM (Pulse Frequency Modulation) to regulate the output voltage; S3 dynamically adjusts the switching frequency based on the comparison between the output voltage sample value and the reference voltage to stabilize the output voltage within the target range.

[0021] Combining all the above technical solutions, the beneficial effects of this invention are as follows: First, this invention discloses an LLC resonant converter based on a series fractional-order capacitor structure, comprising a DC input voltage, an H-type inverter bridge composed of switching transistors Q1-Q4, a resonant inductor Lr, a resonant capacitor Cr, and a magnetizing inductor Lm forming a resonant cavity structure. Energy is transferred to the secondary side via a transformer with a turns ratio of N:1. Diodes D1-D4 form a full-bridge rectifier connected to the secondary side of the transformer, and finally connected to the filter capacitor Cb and the load R. Most importantly, the passive fractional-order capacitor structure PFOC is connected in series within the resonant cavity structure. This invention achieves zero-phase angle (ZPA) between the inverter voltage in the passive fractional-order circuit and the inverter voltage in the main circuit by maintaining a 90-degree lag between them. Furthermore, in achieving ZPA, the voltage gain of the LLC resonant converter is determined by the frequency, which is inversely proportional to the voltage gain. Compared to traditional LLC resonant converters, the voltage gain is less limited by frequency, soft switching is easier to implement, and component parameter design is simpler.

[0022] Secondly, to address the issue of significantly reduced efficiency when the circuit operates off-center, this invention employs a passive fractional-order capacitor (PFOC) structure connected in series within the resonant cavity, achieving ZPA (zero phase angle) characteristics for both input voltage and current within the operating range. To address the narrow voltage range of LLC circuits, this invention utilizes full-bridge / half-bridge mode switching on the primary-side H-bridge, doubling the output voltage range to achieve a 400V input and 250-1000V output, better meeting the charging needs of electric vehicles. This invention uses traditional PFM (frequency modulation) control, resulting in a simple closed-loop control logic and lower requirements for the controller.

[0023] Compared to the PFM (frequency modulation) control of traditional LLC resonant converters, the LLC output voltage range proposed in this invention, based on a series PFOC structure, is significantly increased, meeting the charging needs of electric vehicles. Furthermore, the voltage gain is not limited by frequency at high frequencies. This invention utilizes the PFOC structure to achieve ZPA (zero phase impedance) between the input voltage and output current of the resonant cavity, effectively improving the circuit efficiency of the LLC circuit when it deviates from the resonant point. Control is simple, employing only PFM control, thus requiring less stringent controller specifications.

[0024] Third, this invention can meet the power requirements of emerging enterprises such as electric vehicles and server power supplies. Compared with existing technologies, this solution has a wider voltage range gain, and the implementation of ZPA is beneficial to the load-carrying capacity of LLC circuits. There is limited research on the application of PFOC structures in LLC converters; the LLC converter with series PFOCs proposed in this paper provides a novel method for widening the LLC voltage gain. The technical solution of this invention solves some problems existing in LLC converters, such as the voltage gain range being limited by frequency, and improves the load-carrying capacity, thus having good industrial application value. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure; Figure 1 This is a flowchart of the control method for a wide-range zero-reactive LLC resonant converter based on a fractional-order capacitor structure provided in an embodiment of the present invention. Figure 2 This is a circuit diagram of an LLC resonant converter based on a series PFOC structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the implementation logic of automatic tuning provided in an embodiment of the present invention; Figure 4 This is the circuit equivalent circuit and phasor diagram provided in the embodiments of the present invention; Figure 5 This is a circuit diagram showing the connection of the magnetizing inductor Lm, resonant capacitor Cr, resonant inductor Lr, and equivalent resistance provided in an embodiment of the present invention. Figure 6 This is a circuit logic control diagram provided in an embodiment of the present invention; Figure 7 This is an output voltage waveform diagram provided in an embodiment of the present invention; wherein, Figure 7 (a) When the switching frequency is 200K and the H-bridge is a half-bridge structure, that is, the switching transistor Q3 is always off and the switching transistor Q4 is always on, the output voltage is 250V. Figure 7(b) When the switching frequency is 50K and the H-bridge is a full-bridge structure, the bridge arms of switching transistors Q1 and Q2, and the bridge arms of switching transistors Q3 and Q4 are alternately turned on, and the output voltage reaches 1000V. Figure 8 This is a voltage and current zero-phase angle (ZPA) waveform diagram provided in an embodiment of the present invention; wherein, Figure 8 (a) When the switching frequency is 50K, the inverter voltage and inverter current of the main circuit are in phase. Figure 8 (b) When the switching frequency is 200K, the inverter voltage of the main circuit and the phase angle between the inverter circuit are in phase. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] The innovation of the wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure provided in this invention is as follows: 1. By applying the PFOC structure to an LLC resonant converter, the ZPA (zero phase angle) characteristics of the input and output voltages are achieved through a series resonant cavity.

[0028] 2. It effectively solves the problem of voltage gain frequency limitation, and improves the output voltage to 250-1000V through the full-bridge and half-bridge conversion of the primary-side H-bridge.

[0029] 3. In the circuit control logic, this invention controls the bridge arm of the passive fractional capacitor switch Q5 / Q6 to lag the bridge arm of the main circuit switch Q1 / Q2 by 90 degrees. That is, the PFOC structure switches lag the main circuit switches by 90 degrees. The output voltage is sampled by the voltage divider resistor circuit, isolated by the AMC1311 chip, and then transmitted to the DSPTSM320F28335 control chip through the voltage follower. The voltage output can be regulated by simply changing the switching frequency of the switches in the main circuit and the PFOC.

[0030] Example 1, such as Figure 1 As shown, the control method for a wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure provided in this embodiment of the invention includes the following steps: S1 controls the inverter voltage of the passive fractional capacitor structure PFOC to lag the output voltage of the H-bridge inverter circuit by 90 degrees, thereby achieving zero phase angle ZPA of the resonant cavity. S2 adjusts the switching frequency via PFM (Pulse Frequency Modulation) to regulate the output voltage; S3 dynamically adjusts the switching frequency based on the comparison between the output voltage sample value and the reference voltage to stabilize the output voltage within the target range.

[0031] Example 2, as Figure 2 As shown, the wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure provided in this embodiment of the invention consists of an input voltage, an H-type full-bridge inverter circuit, a resonant cavity, a transformer, a full-bridge rectifier circuit, an output capacitor filter, and resistors.

[0032] Switches Q1-Q4: MOSFETs forming the H-bridge inverter bridge in the main circuit; Lr is the resonant inductor, Cr is the resonant capacitor, and Lm is the magnetizing inductance of the transformer; Switches Q5-Q6: MOSFETs in the half-bridge inverter bridge of the PFOC structure; Cp: energy storage capacitor in the PFOC structure; Diodes D1-D4: Schottky diodes for full-bridge rectification; Cb is the filter capacitor, and RL is the load.

[0033] The output voltage is connected to an H-type full-bridge inverter bridge. The resonant cavity is composed of a resonant inductor Lr, a resonant capacitor Cr, a magnetizing inductor Lm, and a PFOC structure connected in series. Energy is transferred to the secondary side through a transformer, rectified by diodes D1-D4 in a full-bridge rectifier, and filtered by the output capacitor before outputting a DC voltage.

[0034] First, let's analyze the principle behind the PFOC circuit achieving ZPA (zero phase angle) characteristics: The implementation logic of automatic tuning is as follows: Figure 3 As shown. Taking Xin>0 as an example, the working principle is as follows: 1. Similar to a typical SS network, voltage source v1 generates current iz.

[0035] 2. If the system is detuned, there will be a phase difference between the voltage source v1 and the current iz1. Therefore, the current iz1 can be decomposed into two sub-currents. The active current ia is in phase with the voltage source v1 and can supply power to the receiver. The reactive current ib lags behind the voltage source v1 by 90°. Therefore, the integral of the voltage source v1 and the reactive current ib is zero, and the energy stored in the reactive current ib is periodically transferred between the voltage source v1 and the resonant network, resulting in a decrease in output power.

[0036] 3. The essence of storing energy through electric current lies in the flow of charge. Therefore, when the reactive current ib flows from left to right, the charge carried by the reactive current ib will be stored in capacitor Ci2, which facilitates the extraction of reactive power.

[0037] 4. As the energy in capacitor Ci2 increases, an auxiliary voltage v2 is generated. This auxiliary voltage v2 then generates a new current ic in the network, with the active direction of the new current ic being from left to right.

[0038] 5. Similar to current iz1, the new current ic can also be decomposed into two distinct sub-currents. The real part Re(ic) is out of phase with v2, and the imaginary part Im(ic) is 90° away from v2. That is, Im(ic) and ia are in phase, while Re(ic) and ib are out of phase. Therefore, the total active current ia + Re(ic) will increase, while the reactive current ib will decrease. Im(ic) will decrease. Compared to iz1, the phase difference between v1 and iz1+ic is smaller, and the detuning state is weakened.

[0039] 6. It is worth noting that as long as v1 and iz1 are not in a zero-phase (ZPA) state, the amplitude of v2 will continue to increase to reduce their phase difference. Therefore, v1 and iz1 will eventually return to the resonant state.

[0040] Next, we analyze the working principle of the circuit. When ZPA characteristics are achieved in the resonant cavity, we can analyze, for example... Figure 4 The circuit phasor diagram is shown.

[0041] From the phasor diagram, it can be seen that the voltage across the magnetizing inductor increases relative to the input voltage, and is inversely proportional to the frequency. As the frequency increases, the voltage across the magnetizing inductor approaches the input voltage. Based on the equivalent circuit, the gain formula for the circuit is derived as follows: ; Therefore, voltage conversion can be achieved simply by changing the switching frequency. Unlike the traditional LLC resonant converter PFM, the voltage gain range under the proposed PFM control is significantly increased, especially after exceeding the resonant frequency.

[0042] To ensure high circuit efficiency, the circuit must operate with soft switching across its entire operating range. The following is a derivation of the conditions for achieving soft switching.

[0043] Soft switching requires ensuring the circuit operates in an inductive-resistive state. An equivalent analysis of the circuit is then performed.

[0044] Magnetizing inductance Lm, resonant capacitance Cr, resonant inductance Lr, and equivalent resistance are as follows: Figure 5 As shown.

[0045] in, .

[0046] At this point, the equivalent resistance of the circuit is: To ensure the device is inductively resistive, meaning the imaginary part must be greater than 0, we can deduce that: ; Therefore, to ensure that the value of Cr is satisfied within the full range (50-200K), soft switching of the circuit can be achieved across the entire operating range.

[0047] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0048] The information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of the present invention. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0049] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this invention. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments.

[0050] According to embodiments of this application, the present invention also provides a computer device comprising: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor executes the computer program to implement the steps in any of the above-described method embodiments.

[0051] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, can implement the steps described in the various method embodiments above.

[0052] This invention also provides an information data processing terminal, which, when executed on an electronic device, provides a user input interface to implement the steps described in the above method embodiments. The information data processing terminal is not limited to mobile phones, computers, or switches.

[0053] This invention also provides a server that, when executed on an electronic device, provides a user input interface to implement the steps described in the above method embodiments.

[0054] This invention also provides a computer program product that, when run on an electronic device, enables the electronic device to implement the steps described in the various method embodiments above.

[0055] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying the computer program code to a photographic device / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks.

[0056] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0057] To further demonstrate the positive effects of the above embodiments, the present invention conducts the following experiments based on the above technical solution. As can be seen from the analysis of the working principle above, the structure of the series-type LLC resonant converter proposed in this invention can achieve the ZPA (zero phase angle) characteristic of the resonant cavity as long as the inverter voltage of the PFOC section lags the inverter voltage of the main circuit by 90 degrees. Simultaneously, the output voltage exhibits a monotonic output characteristic at the frequency. Furthermore, the addition of half-bridge / full-bridge switching on the primary side doubles the output voltage range, better meeting the wide-range charging requirements of electric vehicles.

[0058] The input DC voltage Vin is used. Q1, Q2, Q3, and Q4 are MOSFET switches, forming an H-type inverter bridge structure to convert the DC voltage Vin into AC voltage. The magnetizing inductor Lr, resonant capacitor Cr, and the magnetizing inductor Lm in the transformer form a resonant cavity, which can maximize the transfer of the fundamental energy of the AC voltage to the secondary side. On the secondary side, D1, D2, D3, and D4 are diodes that convert the transferred AC voltage into DC voltage. After filtering by the filter capacitor Cb and R, the DC voltage is more stable. Note that this invention incorporates a passive fractional-order capacitor structure in series in the resonant cavity. Q5 and Q6 are MOSFETs, which control the absorption of reactive power through switching. Cp in the passive fractional-order capacitor can store or release reactive power. The passive fractional-order circuit effectively generates a current opposite to the imaginary part of the resonant cavity current, neutralizing the reactive power in the resonant cavity and achieving zero-phase (ZPA) between the main circuit inverter voltage and the resonant cavity current.

[0059] The circuit consists of an input voltage, an H-type full-bridge inverter circuit, a resonant cavity, a transformer, a full-bridge rectifier circuit, an output capacitor, a filter, and a resistor. The output voltage is connected to the H-type full-bridge inverter bridge. The resonant cavity is composed of a resonant inductor Lr, a resonant capacitor Cr, a magnetizing inductor Lm, and a PFOC structure connected in series. Energy is transferred to the secondary side through the transformer, rectified by the D1-D4 full-bridge rectifier, and filtered by the output capacitor before outputting a DC voltage.

[0060] Circuit control logic diagram as follows Figure 6 As shown. The main circuit diagram is consistent with the above, and the functions of each component in the main circuit have been described above. The control logic circuit uses a voltage divider resistor circuit for sampling. After sampling, the signal is isolated by an AMC1311 chip, and the isolated signal is transmitted to the DSP through a voltage follower. In the DSP program, the main circuit inverter voltage (Q1, Q2, Q3, Q4) is kept 90 degrees ahead of the PFOC part inverter voltage (Q5, Q6) to meet the characteristics of ZPA. After receiving the voltage signal, the DSP compares it with the given voltage value Vref. When the sampled voltage is greater than the given value, the DSP increases the switching frequency, thereby reducing the voltage; conversely, it decreases the switching frequency, thereby increasing the output voltage.

[0061] This invention was simulated using SIMULINK.

[0062] Output voltage waveform as follows Figure 7 As shown in the figure. Therefore, with an input voltage of 400V, the output voltage range can reach 250-1000V, which is a significant improvement in voltage range compared to traditional LLC resonant converters. Among these, Figure 7 Figure (a) shows the output voltage of 250V when the switching frequency is 200K and the H-bridge is a half-bridge structure, that is, Q3 is always off and Q4 is always on. Figure 7Figure (b) shows the output voltage reaching 1000V when the switching frequency is 50K and the H-bridge is a full-bridge structure, with bridge arms Q1 and Q2 and bridge arms Q3 and Q4 conducting alternately.

[0063] Voltage and current zero phase angle ZPA waveform as follows Figure 8 As shown, the input resonant cavity achieves zero-phase-angle (ZPA) characteristics for both voltage and current. Achieving ZPA improves circuit efficiency and effectively solves the problem of significant power drop when the traditional LLC resonant converter deviates from the resonant point. Figure 8 Figure (a) shows that when the switching frequency is 50K, the inverter voltage and inverter current of the main circuit are in phase. Figure 8 Figure (b) shows that when the switch is at 200K, the inverter voltage of the main circuit and the inverter circuit are in phase. Within the circuit's operating range, the circuit achieves zero phase angle across the entire range.

[0064] The specific component parameters of this circuit are as follows: Lr: 10-30uH Lm: 50-150uH Cr: 50-200nF Input voltage: 400V Output voltage: 250-1000V Output power: 1500W Load: 170 ohms Switching frequency: 50-200K (required parameters for this experiment) The input voltage is provided by a DC voltage source, the load is provided by an electronic load instrument, and the circuit waveform is observed with an oscilloscope. The specific parameters of each component in the circuit are shown below: Input voltage: 400V Output voltage: 250-1000V Output power: 1500W Load: 170 ohms Q1-Q4: C2M0080120D D1-D4: MBR20300FCT The waveforms for soft switching are shown. The yellow waveform represents Vgs of the MOSFET, and the green waveform represents Vds. When Vds is zero, Vgs conducts, indicating zero-voltage turn-on. The waveforms between the main circuit voltage and current show that they are in zero phase, proving the feasibility of the theory.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure, characterized in that, The LLC resonant converter includes a DC input voltage source, an H-bridge inverter circuit, a resonant cavity, a transformer, a full-bridge rectifier circuit, and an output filter circuit. The H-bridge inverter circuit consists of switching transistors Q1, Q2, Q3, and Q4, and is used to convert DC input voltage into AC voltage. The resonant cavity includes a resonant inductor Lr, a resonant capacitor Cr, and a magnetizing inductor Lm. The transformer is used to transfer the energy of the resonant cavity to the secondary side; The full-bridge rectifier circuit consists of diodes D1, D2, D3, and D4, and is used to convert AC voltage into DC voltage. The output filter circuit includes a filter capacitor Cb and a load R; A passive fractional-order capacitor structure PFOC is connected in series in the resonant cavity. The passive fractional-order capacitor structure PFOC is configured to generate an inverter voltage that lags behind the output voltage of the H-bridge inverter circuit by 90 degrees, so that the output voltage of the H-bridge inverter circuit and the resonant cavity current achieve zero phase angle ZPA.

2. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 1, characterized in that, The passive fractional capacitor structure PFOC includes switching transistors Q5 and Q6 and a capacitor Cp. Switches Q5 and Q6 are controlled to generate the inverter voltage, and the phase of the inverter voltage lags behind the output voltage of the H-bridge inverter circuit by 90 degrees.

3. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 2, characterized in that, The H-bridge inverter circuit is used to switch between full-bridge and half-bridge modes to expand the output voltage range. In full-bridge mode, the bridge arms of switches Q1 and Q2 and the bridge arms of switches Q3 and Q4 are turned on alternately. In half-bridge mode, switch Q3 is kept off and switch Q4 is kept on.

4. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 1, characterized in that, The LLC resonant converter uses pulse frequency modulation (PFM) control, which adjusts the output voltage by adjusting the switching frequency, and the voltage gain is inversely proportional to the switching frequency.

5. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 4, characterized in that, The PFM control is implemented through a controller, which includes a voltage sampling circuit, an isolation chip AMC1311, and a digital signal processor (DSP). The voltage sampling circuit samples the output voltage, which is then isolated by an isolation chip and transmitted to the DSP. The DSP adjusts the switching frequency based on the comparison between the sampled voltage and the reference voltage.

6. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 5, characterized in that, The controller is configured to control the switching timing of the switching transistors Q5 and Q6 of the passive fractional capacitor structure PFOC, such that the inverter voltage of the passive fractional capacitor structure PFOC lags behind the output voltage of the H-bridge inverter circuit by 90 degrees.

7. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 1, characterized in that, The LLC resonant converter achieves full-range soft switching within the switching frequency range, wherein the soft switching condition is satisfied by the design of the resonant cavity parameters: the value of the resonant capacitor Cr is such that the imaginary part of the equivalent impedance of the resonant cavity is greater than zero.

8. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 1, characterized in that, The resonant inductance Lr ranges from 10 to 30 μH, the magnetizing inductance Lm ranges from 50 to 150 μH, and the resonant capacitor Cr ranges from 50 to 200 nF.

9. The wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure according to claim 1, characterized in that, The DC input voltage is 400V, the output voltage range is 250-1000V, the output power is 1500W, and the switching frequency range is 50-200kHz.

10. A method for controlling a wide-range zero-reactive-mode LLC resonant converter based on a fractional-order capacitor structure as described in any one of claims 1-9, characterized in that, The method includes the following steps: S1 controls the inverter voltage of the passive fractional capacitor structure PFOC to lag the output voltage of the H-bridge inverter circuit by 90 degrees, thereby achieving zero phase angle ZPA of the resonant cavity. S2 adjusts the switching frequency via PFM (Pulse Frequency Modulation) to regulate the output voltage; S3 dynamically adjusts the switching frequency based on the comparison between the output voltage sample value and the reference voltage to stabilize the output voltage within the target range.

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