A wide voltage range clamp boost LLC resonant converter

Abstract

This invention belongs to the field of power electrical technology and relates to a wide voltage range clamped boost LLC resonant converter, comprising: an input DC bus voltage unit, an active clamped boost unit, an inverter bridge unit, an LLC resonant tank unit, a transformer T, and a rectification and filtering unit; the active clamped boost unit includes a first feed inductor, a second feed inductor, a clamping capacitor, a third switch S3, and a fourth switch S4; the LLC resonant tank unit includes a resonant inductor and a resonant capacitor connected in series, and a magnetizing inductor of the transformer T; the rectification and filtering unit includes a first rectifier diode, a second rectifier diode, and a filter capacitor C. o Load R L This invention solves the technical problem in the prior art that traditional LLC converters have a limited gain adjustment range and cannot simultaneously meet high boost requirements.

Description

Technical Field

[0001] This invention belongs to the field of power and electrical technology, and specifically relates to a wide voltage range clamped boost LLC resonant converter. Background Technology

[0002] With the rapid development of industries such as renewable energy, electric vehicles, and artificial intelligence data centers, the performance requirements for isolated LLC resonant converters, as core components of energy conversion, are becoming increasingly stringent. Isolated LLC resonant converters are core power electronic devices that achieve electrical isolation and voltage level conversion, playing an indispensable role in modern industrial fields such as fast charging of electric vehicles, renewable energy power generation systems (such as photovoltaics and energy storage), and power supplies for AI data center servers. However, these current applications place stringent demands on converters: not only high efficiency and power density are required, but they must also handle a wide range of input or output voltages. For example, the output voltage of a photovoltaic array varies drastically with sunlight and temperature; the voltage of a battery pack fluctuates significantly during its charge and discharge cycles. However, traditional LLC converters use frequency conversion control to regulate the output voltage, resulting in a voltage gain curve with a distinct "peak-shaped" characteristic. This inherent characteristic significantly reduces their efficiency when dealing with wide voltage range applications, making them unable to handle wide input voltage ranges. Therefore, similar existing technologies employ two-stage cascaded configurations and design multi-element resonant networks to improve the adjustable gain range.

[0003] For example, Chinese invention application CN120511987A employs a cascaded hybrid topology Boost + LLC scheme, which utilizes a cascaded four-switch Buck-Boost LLC converter. The front stage is a four-switch Buck-Boost circuit, handling the main voltage regulation; the rear LLC converter can operate at a fixed frequency or a narrow frequency range, focusing on achieving high-efficiency isolation and power transfer. This scheme achieves an extremely wide overall gain range because the front stage provides continuous boost / buck capability, and the rear LLC can operate near its resonant point, maintaining high average efficiency and good soft-switching characteristics. However, the system is complex, costly, and inefficient. It requires two complete power stage circuits and corresponding control circuits, resulting in a large number of components, large size, and reduced power density.

[0004] For example, Chinese invention patent CN119921575A and the paper "Interleaved Boost-Integrated LLCResonant Converter With Fixed-Frequency PWM Control for Renewable Energy Generation Applications" integrate the Boost converter with the LLC converter, thereby achieving high voltage gain through PWM (Pulse Width Modulation) control to handle wide input voltage ranges. However, the clamping bus capacitor used will be subjected to varying high voltage stress.

[0005] Existing traditional LLC converter technology mainly has the following drawbacks: Traditional LLC converters have a limited voltage gain adjustment range, making it impossible to simultaneously meet high boost requirements. If frequency modulation is used to achieve a wide voltage gain, it leads to a cascaded hybrid topology of Boost + LLC, resulting in high cost and increased system size. Most importantly, the MOSFET of the Boost converter operates in the hard-switching phase, leading to reduced efficiency. While the solution using Chinese invention patent CN119921575A, which integrates the Boost and LLC converters, offers high efficiency and high integration, the clamping bus capacitors are subjected to varying high voltage stress.

[0006] In summary, existing LLC resonant converter technologies have significant shortcomings in terms of gain range and control complexity. Innovative topologies and control methods are urgently needed to overcome these bottlenecks and meet the pressing demands of the new energy era for efficient, stable, and wide-gain power conversion. Summary of the Invention

[0007] This invention provides a wide voltage range clamped boost LLC resonant converter, which solves the technical problem in the prior art that the gain adjustment range of traditional LLC converters is limited and cannot simultaneously meet the high boost requirements.

[0008] The technical solution adopted in this invention is a wide voltage range clamped boost LLC resonant converter, including an input DC bus voltage unit, an active clamped boost unit, an inverter bridge unit, an LLC resonant tank unit, a transformer T, and a rectifier and filter unit.

[0009] The active clamp boost unit includes a first feed inductor. Second feed inductor Clamping capacitor The third switch S3 and the fourth switch S4;

[0010] LLC resonant tank unit includes resonant inductors connected in series. Resonant capacitor And the magnetizing inductance of transformer T ;

[0011] The rectifier and filter unit includes a first rectifier diode. Second rectifier diode Filter capacitor C o Load R L ;

[0012] The inverter bridge unit includes a first bridge arm and a second bridge arm;

[0013] The first bridge arm is controlled by the first switching transistor. With the third switching transistor The bridge is composed of series components, with the second arm consisting of the second switching transistor. With the fourth switching transistor It is composed of series connections; the first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the input DC bus voltage unit.

[0014] First feed inductor One end of it is connected to the positive terminal of the input DC bus voltage unit, and the other end is connected to the first switching transistor. The drain and the third switching transistor The source of the second feed inductor forms the midpoint a of the first bridge arm; One end of it is connected to the negative terminal of the input DC bus voltage unit, and the other end is connected to the second switching transistor. The drain and the fourth switching transistor The source pole forms the midpoint b of the second bridge arm.

[0015] Furthermore, the first feed inductor One end, the second feed inductor One end and clamping capacitor One end is connected to the input DC bus unit V. DC The positive pole, forming node c,

[0016] Third switching transistor Source and fourth switch The drains are connected and form node d, clamping capacitance. The other end is connected to the common connection point d;

[0017] The negative terminal of the input DC bus voltage unit is used as the reference ground potential.

[0018] Resonant inductor One end is connected to the midpoint a of the first bridge arm, resonant inductor The other end is connected to the magnetizing inductor. One end, magnetizing inductor The other end is connected to the resonant inductor With resonant capacitor The resonant capacitor is connected in parallel with the primary winding of transformer T. One end is connected to the midpoint b of the second bridge arm;

[0019] The other end of the primary winding of transformer T is connected to the reference ground potential; the secondary winding of transformer T has a center-tapped structure.

[0020] First rectifier diode D 1* The anode of the diode is connected to the first terminal of the secondary winding of transformer T, and the second rectifier diode D... 2* The anode of the first rectifier diode D is connected to the second terminal of the secondary winding of transformer T. 1* With the second rectifier diode D 2* The cathodes are connected together to the filter capacitor C. o The positive terminal, filter capacitor C o The negative terminal is connected to the center tap of the secondary winding of the transformer T, and the filter capacitor C o The load R is connected at both ends L .

[0021] Furthermore, the first switching transistor Second switching transistor Third switching transistor and the fourth switching transistor Each has a corresponding first body diode Second body diode Third-body diode and the fourth body diode and the first body capacitor Second body capacitor Third-body capacitor and the fourth body capacitor First body diode With the first body capacitor Parallel connection to the first switching transistor Between the drain and source, the second body diode With the second body capacitor Parallel connection to the second switching transistor Between the drain and source of the third body diode With third-body capacitor Parallel connection to the third switching transistor Between the drain and source, the fourth body diode With the fourth body capacitor Parallel connection to the fourth switching transistor Between the drain and source.

[0022] Furthermore, the clamping capacitor Voltage at both ends With input DC bus voltage unit and the third switching transistor and the fourth switching transistor Duty cycle The following functional relationship must be satisfied:

[0023] (1)

[0024] in: It's the duty cycle. It is the second feed inductor Terminal voltage, It is the input DC bus voltage unit.

[0025] Furthermore, the wide voltage range clamped boost LLC resonant converter includes the following four operating modes:

[0026] (1) Mode 1

[0027] exist At this moment, the first switch S1 achieves ZVS conduction, and the fourth switch S4 is already in the conducting state. The LLC resonant tank unit voltage... Satisfying the functional relationship shown in equation (2),

[0028] (2)

[0029] in: It is the voltage of the LLC resonant tank unit. The input DC bus voltage unit voltage. For the second feed inductor Terminal voltage;

[0030] exist Time period, first feed inductor The input DC bus voltage unit Charging, its current Linear ascent, storing energy;

[0031] Second feed inductor Clamping capacitor Discharge, its current Linear descent, releasing energy;

[0032] transformer excitation inductor Load voltage The clamping device's terminal voltage satisfies the functional relationship shown in equation (3).

[0033] (3)

[0034] in: It is a transformer Magnetizing inductor Terminal voltage, It is the load voltage. It is a transformer The turns ratio of the primary side to the secondary side;

[0035] Resonant inductor With resonant capacitor At the inverter bridge unit switching frequency Resonance at the point of resonance, resonant current Satisfying the functional relationship shown in equation (4):

[0036] (4)

[0037] in: It is the resonant current. It is the magnetizing current. It is the primary current of transformer T;

[0038] (2) Mode 2

[0039] The first switching transistor S1 is in Constantly off, resonant current Keeping the capacitance of the first switching transistor S1 constant, Charging begins; third switch S3 body capacitor Discharge begins when the voltage at the first switch S1 terminal rises to... At that time, the voltage across switch S3 is zero, and the body diode of the third switch S3... When the circuit is turned on, the voltage at the S3 terminal of the third switch is clamped at zero volts.

[0040] exist Time period, first feed inductor Current Rise to peak point, second feed inductor Discharge;

[0041] (3) Mode 3

[0042] At that moment, in the third switch S3 body diode When the transistor is turned on, the drain-source voltage of the third switch S3 is zero, and a gate drive signal is applied to the third switch S3. The third switch S3 is turned on in ZVS mode. Afterwards, the third switch S3 and the fourth switch S4 are turned on simultaneously, and the voltages of the first switch S1 and the second switch S2 are clamped at... ,

[0043] exist Time period, resonant current Reduce excitation current Increase to peak value, first feed inductance Current As the temperature drops, the stored energy continues to be transferred to the clamping capacitor. Second feed inductor Current decline;

[0044] (4) Mode 4

[0045] exist At that moment, the resonant current Reduce to the level of excitation current When they are equal, the excitation current Satisfying the functional relationship shown in equation (5),

[0046] (5)

[0047] At this time, the primary current of transformer T When the current drops to 0, the induced current on the secondary side of transformer T also drops to 0, and the diode on the secondary side of transformer T... , Achieve ZCS shutdown, load R L Only the filter capacitor C o Power supply, the voltage at the terminals of the first switch S1 and the second switch S2 is clamped at ;

[0048] exist Time period, first feed inductor current The second feed inductor decreases. The current decreases linearly to the negative peak point.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] 1. The clamped boost LLC resonant converter proposed in this application has a wide voltage gain range, which can meet the requirements of a wide input voltage range. In addition, the MOSFET of the resonant converter can achieve ZVS (Zero-Voltage Switching) under all operating conditions, thereby improving efficiency, and the clamping capacitor has lower voltage stress.

[0051] 2. The clamped boost LLC resonant converter proposed in this application adopts the technology of inductor-capacitor clamping, so the bus input current ripple is low and the voltage stress of the clamping capacitor is smaller.

[0052] 3. All MOSFETs of the clamped boost LLC resonant converter inverter proposed in this application can achieve ZVS turn-on, and the secondary diodes can achieve ZCS (Zero-Current Switching) turn-off. It can be controlled by fixed frequency PWM (Pulse Width Modulation) and has better high-frequency characteristics.

[0053] 4. This invention effectively resolves the inherent contradiction between efficiency, power density, and cost in wide-range voltage input scenarios by deeply innovating and integrating the boost unit and LLC resonant unit at the topology level. In the electric vehicle field, this integrated design actively intervenes at low input voltages to boost the bus voltage through the boost unit, and achieves a wider voltage gain range by utilizing multi-degree-of-freedom control methods such as PWM, PFM (Pulse Frequency Modulation), and phase shift, thereby meeting the requirements of vehicle systems for different voltage specifications. In photovoltaic power generation systems, given the extremely wide range of output voltage variations of photovoltaic strings with light and temperature, the conversion efficiency of the DC-DC (Direct Current to Direct Current) stage of traditional string inverters or energy storage converters often drops sharply at low input voltages, leading to "curtailment" of solar power. The optimized solution proposed in this invention can boost the input voltage through efficient voltage boosting under low-light conditions such as dawn, dusk, and rain, ensuring stable and efficient system operation. In AI data center server power supply and communication power supply scenarios, this technology can achieve efficient power conversion and precise voltage regulation within a single topology. Its high power density and high efficiency characteristics help to directly reduce the PUE (Power Usage Effectiveness) value of data centers, thereby reducing operating costs and cooling burden. Furthermore, in 5G / 6G communication base station power supply systems, this converter can efficiently handle the wide voltage input of batteries, providing stable and reliable power support for radio frequency units, significantly improving the energy efficiency and operational reliability of network infrastructure. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 It is a current-mode half-bridge clamped boost LLC resonant converter;

[0056] Figure 2It is a current-mode full-bridge clamped boost LLC converter;

[0057] Figure 3 It is a current-mode three-phase clamped boost LLC converter;

[0058] Figure 4 These are the key voltage and current waveforms for the clamped boost LLC converter, where (a) shows the waveforms of the full-bridge clamped boost LLC resonant converter under operating conditions. Key operating voltage and current waveforms, (b) showing the devices of the full-bridge clamped boost LLC resonant converter. Key voltage and current waveforms during operation;

[0059] Figure 5 These are the four operating modes of the clamped boost LLC converter in the first half-cycle, where (a) is the operating waveform of mode 1 in the first half-cycle of the full-bridge clamped boost LLC resonant converter, (b) is the operating waveform of mode 2 in the first half-cycle of the full-bridge clamped boost LLC resonant converter, (c) is the operating waveform of mode 3 in the first half-cycle of the full-bridge clamped boost LLC resonant converter, and (d) is the operating waveform of mode 4 in the first half-cycle of the full-bridge clamped boost LLC resonant converter.

[0060] Figure 6 The output voltage waveforms are under different duty cycles, where (a) is the output simulation of the full-bridge clamped boost LLC resonant converter when D=0.4, and (b) is the output simulation of the bridge clamped boost LLC resonant converter when D=0.6.

[0061] Figure 7 These are the output voltage waveforms under different bus input voltages, where (a) is the bus input voltage V. DC When the voltage is 80V, the output voltage is (b) and the bus input voltage is V. DC When the voltage is 150V, the output voltage is (c) which is the bus input voltage V. DC Output voltage at 250V. Detailed Implementation

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] This invention proposes a wide-voltage-range clamped boost LLC resonant converter. The core of this invention lies in an active clamped boost unit that can be integrated into various inverter bridge architectures. This unit is fed into a magnetically coupled energy storage inductor. Figure 1 The middle is the first feed inductor ,exist Figure 2 The middle is the first feed inductor Second feed inductor ,exist Figure 3 The middle is the first feed inductor , Third feed inductor Clamping capacitor And specific switching transistors in the inverter bridge unit ( Figure 2 The fourth switching transistor in and the third switching transistor Together, they form a system used to achieve both boosting and clamping functions.

[0064] The key to this invention lies in the fourth switching transistor. and In addition to performing the inverter function, it also functions as an active clamping switch, in conjunction with the first feed inductor. Second feed inductor and clamping capacitor Together they form an integrated boost unit, which is achieved by adjusting the fourth switching transistor. and The duty cycle can be controlled. The voltage across the terminals allows for linear adjustment of the equivalent input voltage amplitude applied to the LLC resonant cavity without changing the switching frequency, achieving a wide-range voltage gain. The circuit connected after the active clamp boost unit is a standard LLC resonant cavity and voltage doubler rectifier filter section, with a resonant inductor... With resonance The series connection forms a resonant cavity, allowing only the fundamental frequency component to pass through. The magnetizing inductance of transformer T should be included inside transformer T in the actual circuit; the resonant inductance... Resonant capacitor And excitation inductance These three factors together determine the resonant characteristics of the output resonant cavity at port ab. The equivalent turns ratio of transformer T is n. Transformer T adopts a single primary winding and two secondary windings, with the two secondary windings respectively bridged to the first rectifier diode. Second rectifier diode To form a full-wave rectifier, the filter capacitor C o Connected across load R L On both sides, there is the load R L Provides a stable DC voltage.

[0065] This invention can be implemented in various topological forms, including but not limited to: Figure 1 The half-bridge clamped boost LLC resonant converter shown... Figure 2 The full-bridge clamped boost LLC resonant converter shown is... Figure 3The three-phase clamped boost LLC resonant converters shown, although differing in inverter bridge structure, number of switches, and drive phase, operate on the same principle. Specifically, they control the multiplexed switches ( Figures 1-3 The second switching transistor in and The duty cycle is used to adjust the clamping capacitor. voltage This allows for a wide range of adjustment of the equivalent input voltage amplitude applied to the LLC resonant cavity without changing the LLC resonant cavity switching frequency, while maintaining zero voltage switching (ZVS) of the primary-side switch transistor and zero current switching (ZCS) of the secondary-side diode.

[0066] Since the working process of the half-bridge boost LLC converter is completely consistent with the working principle of the full-bridge boost LLC converter, this invention only describes the key technical details of the full-bridge boost LLC converter. For clarity, the full-bridge clamped boost LLC resonant converter will be used as an example. Figure 2 Taking a specific example, its circuit structure, operating modes, control methods, and gain characteristics are described in detail.

[0067] Figure 2 Label Explanation: It is the first feed inductor. It is the second feed inductor. It is the first feed inductor With the second feed inductor Clamping capacitor, first switching transistor and the third switching transistor They are the switching transistors on the same bridge arm, the second switching transistor. and the fourth switching transistor These are switches on the same bridge arm, therefore their phases are offset by 180° and they conduct alternately. Meanwhile, the second switch... and the third switching transistor It also functions as a clamping switch for the feed inductor. It is a resonant inductor. It is a resonant capacitor. It is the magnetizing inductance of the transformer, T is the transformer, n is the turns ratio of transformer T, and D is the magnetizing inductance of the transformer. 1* It is the first rectifier diode on the secondary side of transformer T, D 2* It is the second rectifier diode on the secondary side of transformer T, C o It is the load R L Output filter capacitor, R L This is the load under actual working conditions.

[0068] like Figure 2 As shown, the topology of the full-bridge clamped boost LLC converter includes the input DC bus voltage unit V. DC Active clamp boost unit, inverter bridge unit, LLC resonant tank unit, transformer, rectifier and filter unit.

[0069] V DC It is the input DC bus unit, and the voltage V of the input DC bus unit is... DC The negative terminal is used as the reference ground potential of the primary circuit.

[0070] The active clamp boost unit includes a first feed inductor with the same inductance value. Second feed inductor Clamping capacitor The third switch S3 and the fourth switch S4, and the first feed inductor With the second feed inductor They are magnetically coupled and have the same inductance value. It is the first feed inductor With the second feed inductor The clamping capacitor, and connected in parallel to the voltage V of the input DC bus unit. DC Between the positive and negative poles.

[0071] The active clamp boost unit controls the fourth switch S4 and The duty cycle is used to adjust the clamping capacitor. The voltage across the two ends is used to adjust the amplitude of the equivalent input voltage applied to the LLC resonant cavity, thereby achieving wide-range voltage gain adjustment.

[0072] The inverter bridge unit is a full-bridge inverter circuit, including a first switch S1 and a second switch S2. Third switching transistor Fourth switching transistor The first switch S1 and the third switch The first bridge arm is formed by series connection, and the second switching transistor... With the fourth switching transistor The second bridge arm is formed by series connection, and the two switches on the same bridge arm are complementary in conduction, and the third switch... Fourth switching transistor It can also be reused as a clamping switch in an active clamping boost unit.

[0073] In addition, the first switch S1 and the second switch Third switching transistor and the fourth switching transistor Each has its corresponding body diode and body capacitance; the body diode is the first body diode. Second body diode , Fourth body diode The body capacitance is the first body capacitance. , Third-body capacitor Fourth body capacitor First body capacitor , Third-body capacitor Fourth body capacitor This is the equivalent bridging capacitance between the drain and source of each switching transistor.

[0074] LLC resonant tank unit, including resonant inductors connected in series. Resonant capacitor The magnetizing inductance of transformer T .

[0075] The rectifier and filter unit includes a first rectifier diode. Second rectifier diode Filter capacitor C o The load R under actual working conditions L .

[0076] Transformer T has a center-tapped secondary winding structure for electrical isolation and voltage level conversion. The turns ratio of the primary to the secondary winding is n.

[0077] The electrical connections of the LLC resonant converter are as follows:

[0078] Input DC bus voltage V DC The positive terminal is simultaneously connected to the first feed inductor. One end, the second feed inductor One end and clamping capacitor One end;

[0079] First feed inductor The other end is connected to the first switching transistor. Drain and third switching transistor (Clamping switch) Source;

[0080] Second feed inductor The other end is connected to the second switching transistor. Drain, fourth switching transistor Source.

[0081] Resonant inductor Resonant capacitor One end is connected to the second switching transistor and the first switching transistor The drain of the transformer T is connected to the primary winding of the resonant inductor. or resonant capacitor The other end.

[0082] Clamping capacitor Connected in parallel across the first feed inductor Second feed inductor and the third switching transistor and the fourth switching transistor Specifically, the clamping capacitor The first terminal is connected to the first feed inductor With the second feed inductor Connection node c, clamping capacitor The second end is connected to the third switching transistor. With the fourth switching transistor The connection node d.

[0083] The full-bridge inverter unit includes a first bridge arm and a second bridge arm, the first bridge arm being composed of a first switching transistor. With the third switching transistor Series connection, first feed inductor One end is connected to the first switching transistor. Drain and third switching transistor The source of the (clamping switch) is connected at point a, which forms the midpoint of the first bridge arm. The second bridge arm is formed by the second switching transistor. Fourth switching transistor Series connection, second feed inductor One end is connected to the second switching transistor. Drain, fourth switching transistor The source terminal and the connection point form the midpoint b of the second bridge arm. The first bridge arm and the second bridge arm are connected in parallel to the input DC bus unit V. DC Between the positive and negative terminals, i.e., the input DC bus unit V DC The positive terminal is simultaneously connected to the second feed inductor. The DC bus voltage V DC The negative terminal is simultaneously connected to the second switching transistor. and the fourth switching transistor Source.

[0084] LLC resonant tank unit, including resonant inductor Resonant capacitor And the magnetizing inductance of transformer T resonant inductor One end is connected to the midpoint a of the first bridge arm, resonant inductor The other end is connected to the magnetizing inductor. One end, magnetizing inductor The other end is connected to the resonant inductor With resonant capacitor It is connected in parallel with the primary winding of transformer T.

[0085] Resonant capacitor One end is connected to the midpoint b of the second bridge arm.

[0086] The rectifier and filter unit is connected to the secondary side of transformer T and is used to supply power to the load R. L Provides DC output voltage, rectifier and filter circuit, including first rectifier diode D 1* Second rectifier diode D 2* and filter capacitor C o The secondary winding of transformer T has a center-tapped structure, and the first rectifier diode D... 1* The anode is connected to the first end of the secondary winding, and the second rectifier diode D 2* The anode of the first rectifier diode D is connected to the second terminal of the secondary winding of transformer T. 1* Second rectifier diode D 2* The cathodes are connected together to the filter capacitor C. o The positive terminal, filter capacitor C o The negative terminal is connected to the center tap of the secondary winding, and the output filter capacitor C o The load R is connected at both ends L .

[0087] Filter capacitor C o The voltage across the terminals is equal to the load voltage.

[0088] In summary, this invention addresses several technical pain points of traditional LLC converters: First, traditional LLC converters have a limited voltage gain adjustment range, making it impossible to simultaneously meet the demands of high boost and high buck conversion; second, their optimal efficiency region is typically concentrated in a narrow gain range near the resonant frequency point. When the system is forced to adjust within a wide frequency range to adapt to a wide input voltage, most operating points will deviate from the optimal efficiency region, leading to a decrease in overall efficiency; third, under high boost conditions (i.e., low input voltage scenarios), a large circulating current will cause significant conduction losses; and fourth, traditional solutions often require sacrificing power density and control costs to achieve a wide gain range.

[0089] Assuming clamping capacitor Large enough, the voltage across its terminals The ripple is negligible, assuming the circuit is in The system has already entered a steady state. The voltage and current waveforms of key components over one cycle are shown below. Figure 4 As shown.

[0090] (1) Mode 1

[0091] like Figure 4 (a), Figure 5 (a) in Time (of which) The time is the start time of mode 1, and its physical meaning is based on the start time of the drive signal of switch S1. The first switch S1 achieves ZVS conduction, and the fourth switch S4 is already in the conducting state at this time. LLC resonant tank unit voltage Satisfying the functional relationship shown in equation (1),

[0092] (1)

[0093] in: This refers to the voltage of the LLC resonant slot unit. The input DC bus voltage unit voltage. For the second feed inductor Terminal voltage;

[0094] exist Time period, first feed inductor It is charged by the input DC bus voltage unit, and its current Linear rise, energy storage, terminal voltage is ;in The time period is the duration of mode 1, and its physical meaning is the on-time of switch S1.

[0095] Second feed inductor Clamping capacitor Discharge, its current Linear decrease, energy release, terminal voltage is ;

[0096] transformer excitation inductor Load voltage The clamping device's terminal voltage satisfies the functional relationship shown in equation (2).

[0097] (2)

[0098] in: It is the magnetizing inductance of the transformer. Terminal voltage, It is the load voltage. It is a transformer The turns ratio of the primary side to the secondary side;

[0099] Resonant inductor With resonant capacitor Inverter bridge unit switching frequency Resonance at the point of resonance, resonant current Satisfying the functional relationship shown in equation (3):

[0100] (3)

[0101] in: It is the resonant current. It is the magnetizing current. It is the primary current of transformer T;

[0102] (2) Mode 2

[0103] The time is the start time of mode 2, which refers to the end time of the drive signal of the first switch S1; , The time period is the duration of mode 2, referring to the time from the end of the drive signal of the second switch S1 to the start of the drive signal of the third switch S3 (i.e., the dead zone of switches S1 and S3). For example... Figure 4 (a), Figure 5 (b) The first switch S1 is in Constantly off, resonant current The secondary current of the transformer remains continuous, and the body capacitance of the first switching transistor S1 is... Charging begins; third switch S3 body capacitor Discharge begins when the voltage at the first switch S1 terminal rises to... At that time, the voltage across switch S3 is zero, and the body diode of the third switch S3... When the circuit is turned on, the voltage at the terminal of the third switch S3 is clamped to zero volts.

[0104] exist Time period, first feed inductor Current Rise to peak point, second feed inductor Discharge;

[0105] (3) Mode 3

[0106] The time is the start time of mode 3, which refers to the start time of the drive signal for the third switch S3; , The time period is longer than that of mode 3, referring to the time from the start of the drive signal for the third switch S3 to the resonant current. Equal to excitation current It takes a long time. For example... Figure 4 (a), Figure 5 (c) At that moment, in the third switch S3 body diode With the circuit turned on, the drain-source voltage of the third switch S3 is zero. A gate drive signal is then applied to the third switch S3. The third switch S3 is turned on in ZVS mode. Afterwards, the third switch S3 and the fourth switch S4 are turned on simultaneously, and the voltages of the first switch S1 and the second switch S2 are clamped at... ,

[0107] exist Time period, resonant current Reduce excitation current Increase to peak value, first feed inductance Current As the temperature drops, the stored energy is continuously transferred to the clamping capacitor. Second feed inductor Current decline;

[0108] (4) Mode 4

[0109] The time is the starting moment of mode 4, which refers to the resonant current. Just equal to the excitation current The moment; , The time period is longer than that of mode 4, which refers to the resonant current. Equal to excitation current The time between the start of the drive signal for switch S2 and the start of the signal is long. For example... Figure 4 (a), Figure 5 (d) exist At that moment, the resonant current Reduce to the level of excitation current When they are equal, the excitation current Satisfying the functional relationship shown in equation (4),

[0110] (4)

[0111] At this time, the primary current of transformer T When the current drops to 0, the induced current on the secondary side of transformer T also drops to 0, and the diode on the secondary side of transformer T... , Achieve ZCS shutdown, load R L Only the filter capacitor C o Power supply, the voltage at the terminals of the first switch S1 and the second switch S2 is clamped at ;

[0112] exist Time period, first feed inductor current The second feed inductor decreases. The current decreases linearly to the negative peak point.

[0113] Since S1, S4 and S2, S3 are interleaved with a 180° phase shift, therefore, The analysis process for the second half of the cycle remains consistent with that for the first half.

[0114] Similarly, Figure 4 As shown in (b). The analysis process is consistent with the above. Based on the analysis of the half-cycle working mode, the first feed inductor in one cycle... The volt-second balance is satisfied, therefore the clamping capacitor voltage can be obtained. Satisfying the functional relationship shown in equation (5):

[0115] (5)

[0116] in: This refers to the duty cycle.

[0117] Mode This indicates that the clamping capacitor The voltage can be changed through duty cycle control (PWM). Finally, if the existence of the switching dead zone is ignored, combining equations (1) and (5), as follows: Figure 4 As shown in (a) and (b), the voltage at the resonant port ab during one period can be expressed as:

[0118] (6)

[0119] in It is the end time of mode 4, which refers to the moment when the drive signal of switch S2 begins; It is the moment when the drive signal for switch S2 ends (i.e., the moment when S4 achieves zero-voltage turn-on). It is the moment when a complete cycle ends (i.e., the moment when the drive signal of the switch S1 begins in the next cycle).

[0120] Mode This indicates that the LLC resonant port voltage The duty cycle can be controlled, thus enabling the boost converter of the LLC converter through PWM, thereby realizing an LLC converter with a wide input voltage range. Port voltage passes through Behind the resonant cavity, only the fundamental component is allowed to pass through, therefore Satisfying Fourier series decomposition, we can obtain The fundamental component amplitude phasor The ratio of the input bus voltage to the boost gain of the full-bridge boost LLC converter. yes:

[0121] (7)

[0122] in: The boost gain of the full-bridge boost LLC converter. for The fundamental component amplitude phasor.

[0123] because Figure 2 The topological resonant cavity mentioned above still possesses the frequency conversion gain characteristics of a traditional LLC resonant converter, therefore the DC-DC voltage gain of the final boost LLC converter is... As shown in equation (8):

[0124] (8)

[0125] in: It is a magnetizing inductor and resonant inductor The ratio, It is the normalized frequency, i.e., the switching frequency. and the free oscillation frequency of the resonant cavity The ratio of Q to Q' is where Q is the quality factor of the loaded resonant cavity. It is the turns ratio of the transformer.

[0126] Equation (8) reflects that the boosted LLC converter can achieve voltage boosting through the duty cycle of the switching transistor, such as... Figure 6 (a) and Figure 6 (b) The output voltage can be adjusted under different duty cycles, thus meeting the requirements of a wide input voltage range and a wide output voltage range. Therefore, this boost LLC converter can achieve a fixed switching frequency. It is controlled by PWM waveform, has wide input voltage gain characteristics, and the LLC resonant cavity itself can be controlled by frequency. The voltage gain is adjusted, so in practical engineering applications, this boost converter can also be controlled via a combination of PFM and PWM. Furthermore, the active clamp switch and input feed inductor essentially regulate energy; therefore, theoretically, a wider input and output voltage gain for the boost LLC converter can be achieved through multi-objective parameter control of phase shift, pulse width, and frequency. Figure 7 (a) Figure 7 (b) and Figure 7 As shown in (c), the load voltage can be stably maintained at 30V when the bus input voltage changes from 80V to 250V. The duty cycle of the fixed-frequency drive transistor changes in real time with the bus voltage to ensure that the load voltage is stable at 30V, thus verifying the superiority of the proposed topology.

[0127] In summary, this invention proposes a wide-voltage-range clamped boost LLC resonant converter, including half-bridge, full-bridge, and three-phase clamped boost LLC resonant converters. This circuit structure has a wider voltage gain, which can meet the requirements of a wide input voltage range. All switches in the converter can achieve ZVS turn-on, and the secondary diodes can also achieve ZCS turn-off, resulting in high conversion efficiency. Due to the use of coupled-feed inductor-switched capacitor clamping, the clamped boost LLC resonant converter has lower bus input current ripple. This converter can employ a fixed-frequency PWM control method, thus simplifying transformer design and better adapting to high-frequency, high-power-density requirements. Similarly, this converter can also employ a combination of PWM, PFM, and phase-shift control methods to achieve an even wider voltage gain range.

[0128] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A wide voltage range clamped boost LLC resonant converter, characterized in that, It includes an input DC bus voltage unit, an active clamp boost unit, an inverter bridge unit, an LLC resonant tank unit, a transformer T, and a rectifier and filter unit; The active clamp boost unit includes a first feed inductor. Second feed inductor Clamping capacitor The third switch S3 and the fourth switch S4; LLC resonant tank unit includes resonant inductors connected in series. Resonant capacitor And the magnetizing inductance of transformer T ; The rectifier and filter unit includes a first rectifier diode. Second rectifier diode Filter capacitor C o Load R L ; The inverter bridge unit includes a first bridge arm and a second bridge arm; The first bridge arm is controlled by the first switching transistor. With the third switching transistor The bridge is composed of series components, with the second arm consisting of the second switching transistor. With the fourth switching transistor It is composed of series connections; the first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the input DC bus voltage unit. First feed inductor One end of it is connected to the positive terminal of the input DC bus voltage unit, and the other end is connected to the first switching transistor. The drain and the third switching transistor The source of the second feed inductor forms the midpoint a of the first bridge arm; One end of it is connected to the negative terminal of the input DC bus voltage unit, and the other end is connected to the second switching transistor. The drain and the fourth switching transistor The source pole forms the midpoint b of the second bridge arm.

2. The wide voltage range clamped boost LLC resonant converter according to claim 1, characterized in that, The first feed inductor One end, the second feed inductor One end and clamping capacitor One end is connected to the input DC bus unit V. DC The positive pole, forming node c, Third switching transistor Source and fourth switch The drains are connected and form node d, clamping capacitance. The other end is connected to the common connection point d; The negative terminal of the input DC bus voltage unit is used as the reference ground potential. Resonant inductor One end is connected to the midpoint a of the first bridge arm, resonant inductor The other end is connected to the magnetizing inductor. One end, magnetizing inductor The other end is connected to the resonant inductor With resonant capacitor The resonant capacitor is connected in parallel with the primary winding of transformer T. One end is connected to the midpoint b of the second bridge arm; The other end of the primary winding of transformer T is connected to the reference ground potential; the secondary winding of transformer T has a center-tapped structure. First rectifier diode D 1* The anode of the diode is connected to the first terminal of the secondary winding of transformer T, and the second rectifier diode D... 2* The anode of the first rectifier diode D is connected to the second terminal of the secondary winding of transformer T. 1* With the second rectifier diode D 2* The cathodes are connected together to the filter capacitor C. o The positive terminal, filter capacitor C o The negative terminal is connected to the center tap of the secondary winding of the transformer T, and the filter capacitor C o The load R is connected at both ends L .

3. The wide voltage range clamped boost LLC resonant converter according to claim 1, characterized in that, The first switching transistor Second switching transistor Third switching transistor and the fourth switching transistor Each has a corresponding first body diode Second body diode Third-body diode and the fourth body diode and the first body capacitor Second body capacitor Third-body capacitor and the fourth body capacitor First body diode With the first body capacitor Parallel connection to the first switching transistor Between the drain and source of the second body diode With the second body capacitor Parallel connection to the second switching transistor Between the drain and source of the third body diode With third-body capacitor Parallel connection to the third switching transistor Between the drain and source, the fourth body diode With the fourth body capacitor Parallel connection to the fourth switching transistor Between the drain and source.

4. The wide voltage range clamped boost LLC resonant converter according to claim 1, characterized in that, Clamping capacitor Voltage at both ends With input DC bus voltage unit and the third switching transistor and the fourth switching transistor Duty cycle The following functional relationship must be satisfied: （1） in: It's the duty cycle. It is the second feed inductor Terminal voltage, It is the input DC bus voltage unit.

5. A wide voltage range clamped boost LLC resonant converter according to claim 1, characterized in that, The wide voltage range clamped boost LLC resonant converter includes the following four operating modes: (1) Mode 1 ; exist At this moment, the first switch S1 achieves ZVS conduction, and the fourth switch S4 is already in the conducting state. The LLC resonant tank unit voltage... Satisfying the functional relationship shown in equation (2), （2） in: It is the voltage of the LLC resonant tank unit. The input DC bus voltage unit voltage. For the second feed inductor Terminal voltage; exist Time period, first feed inductor The input DC bus voltage unit Charging, its current Linear ascent, storing energy; Second feed inductor Clamping capacitor Discharge, its current Linear descent, releasing energy; transformer excitation inductor Load voltage The clamping device's terminal voltage satisfies the functional relationship shown in equation (3). （3） in: It is a transformer Magnetizing inductor Terminal voltage, It is the load voltage. It is a transformer The ratio of the number of turns on the primary side to the number of turns on the secondary side; Resonant inductor With resonant capacitor At the inverter bridge unit switching frequency Resonance at the point of resonance, resonant current Satisfying the functional relationship shown in equation (4): （4） in: It is the resonant current. It is the magnetizing current. It is the primary current of transformer T; (2) Mode 2 ; The first switching transistor S1 is in Constantly off, resonant current Keeping the capacitance of the first switching transistor S1 constant, Charging begins; third switch S3 body capacitor Discharge begins when the voltage at the first switch S1 terminal rises to... At that time, the voltage across switch S3 is zero, and the body diode of the third switch S3... When the circuit is turned on, the voltage at the S3 terminal of the third switch is clamped at zero volts. exist Time period, first feed inductor Current Rise to peak point, second feed inductor Discharge; (3) Mode 3 ; At that moment, in the third switch S3 body diode When the transistor is turned on, the drain-source voltage of the third switch S3 is zero, and a gate drive signal is applied to the third switch S3. The third switch S3 is turned on in ZVS mode. Afterwards, the third switch S3 and the fourth switch S4 are turned on simultaneously, and the voltages of the first switch S1 and the second switch S2 are clamped at... , exist Time period, resonant current Reduce excitation current Increase to peak value, first feed inductance Current As the temperature drops, the stored energy continues to be transferred to the clamping capacitor. Second feed inductor Current decline; (4) Mode 4 ; exist At that moment, the resonant current Reduce to the level of excitation current When they are equal, the excitation current Satisfying the functional relationship shown in equation (5), （5） At this time, the primary current of transformer T When the current drops to 0, the induced current on the secondary side of transformer T also drops to 0, and the diode on the secondary side of transformer T... , Achieve ZCS shutdown, load R L Only the filter capacitor C o Power supply, the voltage at the terminals of the first switch S1 and the second switch S2 is clamped at ; exist Time period, first feed inductor current The second feed inductor decreases. The current decreases linearly to the negative peak point.

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