Wide gain range LLC resonant converter based on variable voltage doubling rectifying structure

Abstract

The invention discloses a wide-gain-range LLC resonant converter based on a variable voltage doubling rectifying structure, and belongs to the technical field of power electronic conversion. The converter comprises a primary side direct-current voltage input, a primary side full-bridge inversion structure, a resonant tank, a secondary side variable voltage doubling rectifying structure and an output load, the primary side full-bridge inversion structure comprises a left bridge arm and a right bridge arm which are formed by a switching tube Q1, a switching tube Q2, a switching tube Q3 and a switching tube Q4, and the resonant tank comprises a resonant inductor Lr, a resonant capacitor Cr and a transformer T; the secondary side variable voltage-multiplying rectifying structure comprises a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a switching tube Q5, a switching tube Q6, a switching tube Q7, a voltage-multiplying capacitor Cd1, a voltage-multiplying capacitor Cd2, an output capacitor Co1 and an output capacitor Co2. According to the invention, no extra resonant element is needed, the voltage gain range can be widened, the full-range working efficiency is improved, and new energy scene requirements are met.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and in particular to a wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure. Background Technology

[0002] In recent years, the global energy structure has accelerated its transformation towards a low-carbon model, with the development and utilization of new energy sources such as solar and wind power becoming a key path to achieving the "dual-carbon" goal. In new energy application scenarios such as photovoltaic power generation, electric vehicle charging, and on-board power supply, the power conversion process places higher demands on DC-DC converters. On the one hand, the characteristics of new energy power generation result in significant fluctuations in output voltage. For example, photovoltaic power generation is affected by factors such as light intensity and temperature, causing output voltage variations of up to several times. Electric vehicle batteries also have significantly different input voltage requirements depending on their state of charge. This necessitates that DC-DC converters cover a wider voltage gain range to ensure stable adaptation to fluctuations in input and output voltage. On the other hand, to improve energy utilization efficiency and reduce system heat generation and energy consumption, DC-DC converters must also ensure high-efficiency operation under all operating conditions, reducing energy losses during conversion, thereby improving the overall performance and reliability of the equipment.

[0003] LLC resonant converters have become a core solution for new energy power conversion due to their advantages such as simple structure, fewer components, zero-voltage switching of the primary-side switch, zero-current switching of the secondary-side rectifier diode, and ease of achieving high efficiency and high power density. However, traditional LLC resonant converters have significant limitations and cannot meet the wide-gain and high-efficiency requirements of new energy scenarios. In terms of voltage gain, their gain range is limited and greatly affected by the load. When faced with wide-range voltage regulation requirements, traditional LLC resonant converters need to significantly change the switching frequency to maintain stable output voltage. However, drastic changes in the switching frequency will, on the one hand, exacerbate the changes in magnetic flux density of magnetic components, increasing the design difficulty and losses of magnetic components, such as increasing the risk of core saturation and winding losses; on the other hand, when the switching frequency is far from the resonant frequency, the converter cannot fully utilize the soft-switching characteristics, the switching losses increase significantly, and the operating efficiency drops rapidly. Studies have shown that in some wide-voltage input applications, the efficiency reduction of traditional LLC resonant converters can reach 10%-20%.

[0004] Furthermore, the performance issues of traditional LLC resonant converters are more pronounced under light load conditions. Under light load, the resonant current amplitude decreases, leading to zero-voltage switching failure and a significant increase in switching losses. For example, in applications such as photovoltaic inverters and electric vehicle charging stations, the switching loss ratio can surge from 15% under heavy load to over 40% under light load, resulting in an efficiency drop of 5-8 percentage points. This not only reduces energy utilization efficiency but may also affect the stability and lifespan of the equipment.

[0005] To overcome the aforementioned bottlenecks, domestic and international research has focused on topology reconfiguration of LLC resonant converters to expand the gain range, mainly divided into three directions: primary-side inverter-side reconfiguration, resonant slot reconfiguration, and secondary-side rectifier reconfiguration. Among these, secondary-side rectifier reconfiguration, by introducing active devices to control the rectifier's operating mode and achieving the connection between different modes, has become an important path to broaden the gain range. However, existing related technologies still have many shortcomings. Although some technologies attempt to integrate voltage doubler rectification theory into LLC resonant converters, using secondary-side switching transistors to control the rectifier circuit to achieve switching between two or a few gain modes, such as switching between voltage doubler and voltage quadruple modes, the overall gain range still falls short of practical requirements. Furthermore, these technologies often employ complex PFM+PWM hybrid control strategies, which not only complicate control logic and increase the difficulty of controller design and debugging, but also easily generate significant turn-off losses during operation due to frequent mode switching and complex pulse modulation, further reducing the overall operating efficiency of the converter. In addition, some techniques that achieve finite gain mode switching by adjusting the duty cycle of the secondary-side switching transistor also have limited voltage variable ranges, usually not exceeding twice the normal range. This cannot meet the needs of large voltage changes in new energy scenarios and limits their widespread application in practice.

[0006] In summary, existing LLC resonant converter technologies have significant shortcomings in terms of gain range, control complexity, and efficiency under all operating conditions. 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] The purpose of this invention is to overcome the aforementioned defects in the prior art and provide a wide-gain LLC resonant converter with a variable voltage multiplier rectifier structure for photovoltaic power generation systems. This converter enables high-efficiency energy conversion over a wide voltage gain range and a full load range, broadens the voltage gain coverage, maintains soft-switching operation under all operating conditions, and requires no additional resonant components. The number of devices is not significantly increased, the control method is simple, the switching frequency variation range is narrow, and the converter has higher operating efficiency.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure, the converter including a primary-side DC voltage input V in Primary-side full-bridge inverter structure, resonant tank, secondary-side variable voltage multiplier rectifier structure, and output load R L ;

[0010] The primary-side full-bridge inverter structure consists of switching transistors Q1, Q2, Q3, and Q4. The source of switching transistor Q1 is connected to the drain of switching transistor Q2 to form the left bridge arm, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4 to form the right bridge arm.

[0011] The primary DC voltage input V in The positive terminal is connected to the drain of switch Q1 and the drain of switch Q3, and the negative terminal is connected to the source of switch Q2 and the source of switch Q4.

[0012] The resonant groove is composed of a resonant inductor L r Resonant capacitor C r It consists of a transformer T and a resonant inductor L. r The left side is connected to the midpoint of the left bridge arm, and the right side is connected to the corresponding terminal of the primary side of transformer T; resonant capacitor C r The left side is connected to the midpoint of the right bridge arm, and the right side is connected to the opposite end of the primary side of transformer T;

[0013] The primary side of the transformer T is connected to the resonant inductor L. r The right end, the primary side opposite terminal is connected to the resonant capacitor C. r The right end of the transformer T; the same-name terminal of the secondary side of the transformer T is connected to the midpoint of the left bridge arm of the rectifier, and the opposite-name terminal of the secondary side of the transformer T is connected to the midpoint of the right bridge arm of the rectifier.

[0014] The secondary-side variable voltage multiplier rectifier structure consists of diodes D1, D2, D3, D4, D5, and D6, switching transistors Q5, Q6, and Q7, and a voltage multiplier capacitor C. d1 With voltage multiplier capacitor C d2 Output capacitor C o1 With output capacitor C o2 Composition: Diode D1's anode is connected to diode D2's cathode to form the left rectifier bridge arm; diode D3's anode is connected to diode D4's cathode to form the right rectifier bridge arm; output capacitor C o1 The lower end and the output capacitor C o2 The upper end forms the output voltage multiplier bridge arm; the voltage multiplier capacitor C d1 The lower end is connected to the drain of the switching transistor Q6 to form voltage multiplier unit 1, and voltage multiplier capacitor C d1 The upper end is connected to the midpoint of the left arm of the rectifier bridge, and the source of the switching transistor Q6 is connected to the positive terminal of the diode D2; the voltage multiplier capacitor C d2The lower end is connected to the drain of the switching transistor Q7 to form voltage multiplier unit 2, and voltage multiplier capacitor C d2 The upper end of diode D5 is connected to the cathode of diode D1, and the source of switching transistor Q7 is connected to the midpoint of the left arm of the rectifier bridge; the anode of diode D5 is connected to the cathodes of diodes D1 and D3 and the voltage multiplier capacitor C. d2 At the upper end, the negative terminal of diode D5 is connected to the output capacitor C. o1 The upper end, output load R L The upper end; the positive terminal of diode D6 is connected to the output capacitor C. o2 The lower end, output load R L At the lower end, the cathode of diode D6 is connected to the anodes of diodes D2 and D4 and the source of switching transistor Q6. The drain of switching transistor Q5 is connected to the midpoint of the output voltage multiplier bridge arm, and the source is connected to the midpoint of the rectifier right bridge arm.

[0015] Furthermore, the transformer T converts the AC voltage into the input voltage of the secondary rectifier structure, and the secondary side of the transformer does not need to have a center tap structure.

[0016] Furthermore, in the primary-side full-bridge inverter structure, the drive signals of switches Q1 and Q4 are the same, and the drive signals of switches Q2 and Q3 are the same. Switches Q1 and Q2, Q3 and Q4 are complementary in conduction. That is, when switch Q1 is on, switch Q2 is off, and when switch Q1 is off, switch Q2 is on. When switch Q3 is on, switch Q4 is off, and when switch Q3 is off, switch Q4 is on, outputting a square wave voltage with positive and negative symmetry.

[0017] Furthermore, in steady state, the output capacitor C... o1 With C o2 It will discharge to the load.

[0018] Furthermore, the voltage multiplier capacitor C d1 The value is equal to the voltage multiplier capacitor C. d2 Value of output capacitor C o1 The value is equal to the output capacitor C. o2 The value of .

[0019] Furthermore, the converter includes four operating modes: full-bridge mode, double voltage mode, triple voltage mode, and quadruple voltage mode. The voltage gain of the four modes increases sequentially, and gain adjustment and mode switching are achieved through frequency modulation control.

[0020] Furthermore, when the converter operates in the full-bridge mode, the primary-side full-bridge inverter switches Q1, Q2, Q3, and Q4 operate in full-bridge inverter mode. During the positive half-cycle, switches Q1 and Q4 are turned on, while switches Q2 and Q3 are turned off. During the negative half-cycle, switches Q1 and Q4 are turned off, while switches Q2 and Q3 are turned on. At this time, the secondary-side variable voltage multiplier rectifier switches Q5, Q6, and Q7 are all turned off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor C d2 Not involved in operation, output capacitor C o1 With output capacitor C o2 Without voltage multiplication, the secondary side operates in full-bridge rectification mode, and the converter adjusts the output voltage by regulating the switching frequency of the switching transistors in the primary side full-bridge inverter structure.

[0021] Furthermore, when the converter operates in the voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switching transistors Q6 and Q7 are turned off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor C d2 Since they are not involved in operation, no current flows through diodes D3 and D4, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the transformer is in operation, during the positive half-cycle, the secondary side supplies power to the output capacitor C through diodes D1 and D5 and the switching transistor Q5. o1 and output load R L During the negative half-cycle, the transformer secondary side supplies power to the output capacitor C through diodes D2 and D6, and the switching transistor Q5. o2 and output load R L Power supply, output capacitor C o1 With output capacitor C o2 The voltage amplitude on the winding is equal to the winding voltage. Therefore, at the resonant frequency, the output voltage of the double voltage mode is twice that of the full-bridge mode.

[0022] Furthermore, when the converter operates in the triple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switch Q7 is turned off, and the voltage multiplier capacitor C... d2 Since they are not involved in operation, no current flows through diodes D2 and D3, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the circuit is activated, the switching transistor Q6 turns on, causing the voltage multiplier capacitor C to operate. d1 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through diodes D1, D5, and Q5, supplying power to the output capacitor C.o1 During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through switch Q5, diode D6, and switch Q6. o2 Charging; Output capacitor C o1 With voltage multiplier capacitor C d1 The voltage amplitude on the output capacitor C is equal to the winding voltage. o2 The voltage amplitude on the winding is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the triple voltage mode is three times that of the full-bridge mode.

[0023] Furthermore, when the converter operates in the quadruple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. On the secondary side, the variable voltage multiplier rectifier switches Q5, Q6, and Q7 are all turned on. No current flows through diodes D1 and D2. The turn-on of switch Q5 causes the output voltage multiplier capacitor C to conduct. o1 With voltage multiplier capacitor C o2 When the circuit is activated, switching transistors Q6 and Q7 turn on, causing the voltage multiplier capacitor C to operate. d1 With voltage multiplier capacitor C d2 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through the switching transistor Q7 and the voltage multiplier capacitor C. d2 Diode D5 and switching transistor Q5 supply power to output capacitor C. o1 During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through the switching transistor Q7 and the diode D3. d2 Charging is achieved through switching transistor Q5, diode D6, switching transistor Q6, and voltage multiplier capacitor C. d1 Give the output capacitor C o2 Charging; voltage multiplier capacitor C d1 With voltage multiplier capacitor C d2 The voltage amplitude on the output capacitor C is equal to the winding voltage. o1 With output capacitor C o2 The voltage amplitude on the winding is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the four-times voltage mode is four times that of the full-bridge mode.

[0024] Compared with the prior art, the present invention, employing the above technical solution, has the following beneficial effects:

[0025] (1) The present invention provides a wide-gain LLC resonant converter with variable voltage multiplier rectifier structure for photovoltaic power generation system. By adjusting the switching state of the secondary rectifier structure, four modes of operation can be achieved. The voltage gain range can be widened without the need to add additional resonant components, thus meeting the wide range voltage requirements of new energy scenarios.

[0026] (2) The present invention provides a wide-gain LLC resonant converter with variable voltage multiplier rectifier structure for photovoltaic power generation system. By using multi-mode connection, the switching frequency variation range is reduced, the excitation inductor can be designed to be larger to reduce circulating current loss, and the primary and secondary side devices basically achieve soft switching, which can improve the full range of working efficiency without complex control.

[0027] (3) The present invention provides a wide-gain LLC resonant converter with variable voltage multiplier rectifier structure for photovoltaic power generation system. The transformer secondary side does not require a center tap structure, the number of devices is not significantly increased, and high power can be achieved at full load without additional hardware. It is suitable for various new energy power consumption and power generation occasions.

[0028] (4) The variable voltage multiplier rectifier structure wide gain LLC resonant converter of photovoltaic power generation system provided by the present invention adopts a single PFM modulation strategy, which can realize the connection and gain adjustment of different modes without the need for complex PFM+PWM hybrid control, thereby reducing the complexity of control logic and turn-off loss.

[0029] (5) The variable voltage multiplier rectifier structure wide-gain LLC resonant converter for photovoltaic power generation system provided by the present invention can achieve gain adjustment and connection of various gain modes simply by frequency tuning, and the switching frequency range is greatly reduced, which is beneficial to the design of inductance ratio and quality factor to reduce circulating current loss when deviating from the resonant point, and maintains high efficiency while expanding the gain. Attached Figure Description

[0030] Figure 1 This is a topology diagram of a wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to the present invention;

[0031] Figure 2 This is the full-bridge modal equivalent circuit of the present invention;

[0032] Figure 3 This is the equivalent circuit of the double-voltage mode working mode of the present invention;

[0033] Figure 4 This is the equivalent circuit of the tripler mode operating mode of the present invention;

[0034] Figure 5 This is the equivalent circuit of the four-fold voltage mode operation mode of the present invention;

[0035] Figure 6 This is a full-bridge modal waveform diagram of the present invention;

[0036] Figure 7 This is a waveform diagram of the double-pressure mode of the present invention;

[0037] Figure 8 This is a waveform diagram of the triple-voltage mode of the present invention;

[0038] Figure 9 This is a waveform diagram of the four-fold compression mode of the present invention;

[0039] Figure 10 This is the steady-state waveform diagram of the invention in full-bridge mode when the frequency is 100kHz and the output voltage is 185V.

[0040] Figure 11 This is the steady-state waveform diagram of the invention in full-bridge mode when the frequency is 200kHz and the output voltage is 105V.

[0041] Figure 12 This is the steady-state waveform of the present invention in the double voltage mode at a frequency of 100kHz and an output voltage of 363V.

[0042] Figure 13 This is the steady-state waveform of the present invention in the double voltage mode at a frequency of 200kHz and an output voltage of 170V.

[0043] Figure 14 This is the steady-state waveform of the present invention in the triple voltage mode at a frequency of 110kHz and an output voltage of 480V.

[0044] Figure 15 This is the steady-state waveform of the present invention in the triple voltage mode at a frequency of 170kHz and an output voltage of 100V.

[0045] Figure 16 This is the steady-state waveform of the present invention in the triple voltage mode at a frequency of 110kHz and an output voltage of 610V.

[0046] Figure 17 This is the steady-state waveform diagram of the present invention under the triple voltage mode at a frequency of 160kHz and an output voltage of 425V. Detailed Implementation

[0047] The technical solutions in 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 of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0048] A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure, such as Figure 1 As shown, the converter includes a primary-side DC voltage input V. in Primary-side full-bridge inverter structure, resonant tank, secondary-side variable voltage multiplier rectifier structure, and output load R L ;

[0049] The primary-side full-bridge inverter structure consists of switching transistors Q1, Q2, Q3, and Q4. The source of switching transistor Q1 is connected to the drain of switching transistor Q2 to form the left bridge arm, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4 to form the right bridge arm.

[0050] The primary DC voltage input V in The positive terminal is connected to the drain of switch Q1 and the drain of switch Q3, and the negative terminal is connected to the source of switch Q2 and the source of switch Q4.

[0051] The resonant groove is composed of a resonant inductor L r Resonant capacitor C r It consists of a transformer T and a resonant inductor L. r The left side is connected to the midpoint of the left bridge arm, and the right side is connected to the corresponding terminal of the primary side of transformer T; resonant capacitor C r The left side is connected to the midpoint of the right bridge arm, and the right side is connected to the opposite end of the primary side of transformer T;

[0052] The primary side of the transformer T is connected to the resonant inductor L. r The right end, the primary side opposite terminal is connected to the resonant capacitor C. r The right end of the transformer T; the same-name terminal of the secondary side of the transformer T is connected to the midpoint of the left bridge arm of the rectifier, and the opposite-name terminal of the secondary side of the transformer T is connected to the midpoint of the right bridge arm of the rectifier.

[0053] The secondary-side variable voltage multiplier rectifier structure consists of diodes D1, D2, D3, D4, D5, and D6, switching transistors Q5, Q6, and Q7, and a voltage multiplier capacitor C. d1 With voltage multiplier capacitor C d2 Output capacitor C o1 With output capacitor C o2 Composition: Diode D1's anode is connected to diode D2's cathode to form the left rectifier bridge arm; diode D3's anode is connected to diode D4's cathode to form the right rectifier bridge arm; output capacitor C o1 The lower end and the output capacitor C o2 The upper end forms the output voltage multiplier bridge arm; the voltage multiplier capacitor C d1 The lower end is connected to the drain of the switching transistor Q6 to form voltage multiplier unit 1, and voltage multiplier capacitor C d1 The upper end is connected to the midpoint of the left arm of the rectifier bridge, and the source of the switching transistor Q6 is connected to the positive terminal of the diode D2; the voltage multiplier capacitor C d2 The lower end is connected to the drain of the switching transistor Q7 to form voltage multiplier unit 2, and voltage multiplier capacitor C d2 The upper end of diode D5 is connected to the cathode of diode D1, and the source of switching transistor Q7 is connected to the midpoint of the left arm of the rectifier bridge; the anode of diode D5 is connected to the cathodes of diodes D1 and D3 and the voltage multiplier capacitor C. d2At the upper end, the negative terminal of diode D5 is connected to the output capacitor C. o1 The upper end, output load R L The upper end; the positive terminal of diode D6 is connected to the output capacitor C. o2 The lower end, output load R L At the lower end, the cathode of diode D6 is connected to the anodes of diodes D2 and D4 and the source of switching transistor Q6. The drain of switching transistor Q5 is connected to the midpoint of the output voltage multiplier bridge arm, and the source is connected to the midpoint of the rectifier right bridge arm.

[0054] Furthermore, the transformer T converts the AC voltage into the input voltage of the secondary rectifier structure, and the secondary side of the transformer does not require a center tap structure.

[0055] Furthermore, in the primary-side full-bridge inverter structure, the drive signals of switches Q1 and Q4 are the same, and the drive signals of switches Q2 and Q3 are the same. Switches Q1 and Q2, Q3 and Q4 are complementary in conduction. That is, when switch Q1 is on, switch Q2 is off, and when switch Q1 is off, switch Q2 is on. When switch Q3 is on, switch Q4 is off, and when switch Q3 is off, switch Q4 is on, outputting a square wave voltage with positive and negative symmetry.

[0056] Furthermore, in steady state, the output capacitor C... o1 With output capacitor C o2 Discharge to the load.

[0057] Furthermore, the voltage multiplier capacitor C d1 The value is equal to the voltage multiplier capacitor C. d2 Value of output capacitor C o1 The value is equal to the output capacitor C. o2 The value of .

[0058] Furthermore, the converter includes four operating modes: full-bridge mode, double voltage mode, triple voltage mode, and quadruple voltage mode. The voltage gain of the four modes increases sequentially, and gain adjustment and mode switching are completed through frequency modulation control to achieve a wide range of output voltage variation.

[0059] Furthermore, such as Figure 2 As shown, when the converter operates in the full-bridge mode, the primary-side full-bridge inverter switches Q1, Q2, Q3, and Q4 operate in full-bridge inverter mode. During the positive half-cycle, switches Q1 and Q4 are turned on, while switches Q2 and Q3 are turned off. During the negative half-cycle, switches Q1 and Q4 are turned off, while switches Q2 and Q3 are turned on. At this time, the secondary-side variable voltage multiplier rectifier switches Q5, Q6, and Q7 are all turned off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor Cd2 Not involved in operation, output capacitor C o1 With output capacitor C o2 Without voltage multiplication, the secondary side operates in full-bridge rectification mode. The converter adjusts the output voltage by regulating the switching frequency of the switching transistors in the primary-side full-bridge inverter structure. The primary-side switching transistors achieve ZVS turn-on, and the secondary-side diodes achieve ZCS turn-off. The modal waveform diagram is shown below. Figure 6 As shown.

[0060] Furthermore, such as Figure 3 As shown, when the converter operates in the voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switches Q6 and Q7 are turned off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor C d2 Since they are not involved in operation, no current flows through diodes D3 and D4, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the transformer is in operation, during the positive half-cycle, the secondary side supplies power to the output capacitor C through diodes D1 and D5 and the switching transistor Q5. o1 and output load R L During the negative half-cycle, the transformer secondary side supplies power to the output capacitor C through diodes D2 and D6, and the switching transistor Q5. o2 and output load R L Power supply, output capacitor C o1 With output capacitor C o2 The voltage amplitude on the circuit is equal to the winding voltage. Therefore, at the resonant frequency, the output voltage of the double-voltage mode is twice that of the full-bridge mode. The primary-side switch can achieve ZVS turn-on, and the secondary-side diode can achieve ZCS turn-off. The mode waveform diagram is shown below. Figure 7 As shown.

[0061] Furthermore, such as Figure 4 As shown, when the converter operates in the triple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switching transistor Q7 is turned off, and the voltage multiplier capacitor C... d2 Since they are not involved in operation, no current flows through diodes D2 and D3, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the circuit is activated, the switching transistor Q6 turns on, causing the voltage multiplier capacitor C to operate. d1 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through diodes D1, D5, and Q5, supplying power to the output capacitor C. o1During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through switch Q5, diode D6, and switch Q6. o2 Charging; Output capacitor C o1 With voltage multiplier capacitor C d1 The voltage amplitude on the output capacitor C is equal to the winding voltage. o2 The voltage amplitude on the circuit is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the triple voltage mode is three times that of the full-bridge mode. The primary-side switch can achieve ZVS turn-on, and the secondary-side diode can achieve ZCS turn-off. The mode waveform diagram is shown below. Figure 8 As shown.

[0062] Furthermore, such as Figure 5 As shown, when the converter operates in the quadruple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. On the secondary side, the variable voltage multiplier rectifier switches Q5, Q6, and Q7 are all turned on. No current flows through diodes D1 and D2. The turn-on of switch Q5 causes the output voltage multiplier capacitor C to conduct. o1 With voltage multiplier capacitor C o2 When the circuit is activated, switching transistors Q6 and Q7 turn on, causing the voltage multiplier capacitor C to operate. d1 With voltage multiplier capacitor C d2 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through the switching transistor Q7 and the voltage multiplier capacitor C. d2 Diode D5 and switching transistor Q5 supply power to output capacitor C. o1 During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through the switching transistor Q7 and the diode D3. d2 Charging is achieved through switching transistor Q5, diode D6, switching transistor Q6, and voltage multiplier capacitor C. d1 Give the output capacitor C o2 Charging; voltage multiplier capacitor C d1 With voltage multiplier capacitor C d2 The voltage amplitude on the output capacitor C is equal to the winding voltage. o1 With output capacitor C o2 The voltage amplitude on the circuit is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the four-voltage mode is four times that of the full-bridge mode. The primary-side switch can achieve ZVS turn-on, and the secondary-side diode can achieve ZCS turn-off. The mode waveform diagram is shown below. Figure 9 As shown.

[0063] Furthermore, the steady-state waveforms of the converter in the four operating modes are as follows: Figures 10-17 As shown, with a constant output current of 4A, this converter achieves an output voltage variation over a wide range of 100–610V with an input voltage of 390V. Simultaneously, the converter's switching frequency varies from 100 to 200kHz. Figure 10 and Figure 11 f s =100kHz, V o =185V, I o =4A and f s =200kHz, V o =105V, I o Steady-state waveform of the full-bridge mode at 4A. Figure 12 and Figure 13 f s =100kHz, V o =363V, I o =4A and f s =200kHz, V o =170V, I o Steady-state waveform under double-voltage mode at 4A. Figure 14 and Figure 15 f s =110kHz, V o =480V, I o =4A and f s =170kHz, V o =100V, I o Steady-state waveform under triple-voltage mode at 4A. Figure 16 and Figure 17 f s =110kHz, V o =610V, I o =4A and f s =160kHz, V o =425V, I o =4A, steady-state waveform under four-times voltage mode, therefore, when designing the converter, the magnetizing inductance L m The magnetizing inductor current can be designed to be large, thus reducing the primary-side conduction and turn-off losses significantly, thereby greatly improving the converter's efficiency across the entire operating range.

[0064] Furthermore, the proposed wide-gain-range LLC resonant converter based on the variable voltage multiplier rectifier structure was simulated using PLECS, and the simulation parameters are shown in Table 1.

[0065] Table 1

[0066]

[0067] Furthermore, the proposed structure is qualitatively and quantitatively compared with similar existing solutions, as shown in Table 2.

[0068] Table 2. Comparison of the proposed structure with existing similar solutions

[0069]

[0070] As shown in Table 2, the proposed wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure, compared to existing methods, achieves a wider gain range by changing the gain mode of the converter through altering the engagement state of the secondary voltage multiplier circuit. This is achieved without adding resonant components, and the number of devices is not significantly increased. The proposed converter can achieve a wide gain range [1-6.1], which is wider than existing methods, and reaches a full-load power of 2.4kW in simulations, making it more suitable for various applications such as new energy power consumption and generation. Furthermore, the multi-mode connection reduces the switching frequency range, allowing for a larger magnetizing inductor design, thus reducing circulating current losses. Since soft switching is almost fully implemented, the overall efficiency is improved compared to existing solutions. In summary, the proposed converter reduces size while maintaining a certain voltage gain range and improving overall efficiency, making it a better choice for wide-range DC-DC converters in new energy power generation and consumption applications.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure, characterized in that, The converter includes a primary-side DC voltage input V. in Primary-side full-bridge inverter structure, resonant tank, secondary-side variable voltage multiplier rectifier structure, and output load R L ; The primary-side full-bridge inverter structure consists of switching transistors Q1, Q2, Q3, and Q4. The source of switching transistor Q1 is connected to the drain of switching transistor Q2 to form the left bridge arm, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4 to form the right bridge arm. The primary DC voltage input V in The positive terminal is connected to the drain of switch Q1 and the drain of switch Q3, and the negative terminal is connected to the source of switch Q2 and the source of switch Q4. The resonant groove is composed of a resonant inductor L r Resonant capacitor C r It consists of a transformer T and a resonant inductor L. r The left side is connected to the midpoint of the left bridge arm, and the right side is connected to the corresponding terminal of the primary side of transformer T; resonant capacitor C r The left side is connected to the midpoint of the right bridge arm, and the right side is connected to the opposite end of the primary side of transformer T; The primary side of the transformer T is connected to the resonant inductor L. r The right end, the primary side opposite terminal is connected to the resonant capacitor C. r The right end of the transformer T; the same-name terminal of the secondary side of the transformer T is connected to the midpoint of the left bridge arm of the rectifier, and the opposite-name terminal of the secondary side of the transformer T is connected to the midpoint of the right bridge arm of the rectifier. The secondary-side variable voltage multiplier rectifier structure consists of diodes D1, D2, D3, D4, D5, and D6, switching transistors Q5, Q6, and Q7, and a voltage multiplier capacitor C. d1 With voltage multiplier capacitor C d2 Output capacitor C o1 With output capacitor C o2 Composition: Diode D1's anode is connected to diode D2's cathode to form the left rectifier bridge arm; diode D3's anode is connected to diode D4's cathode to form the right rectifier bridge arm; output capacitor C o1 The lower end and the output capacitor C o2 The upper end forms the output voltage multiplier bridge arm; the voltage multiplier capacitor C d1 The lower end is connected to the drain of the switching transistor Q6 to form voltage multiplier unit 1, and voltage multiplier capacitor C d1 The upper end is connected to the midpoint of the left arm of the rectifier bridge, and the source of the switching transistor Q6 is connected to the positive terminal of the diode D2; the voltage multiplier capacitor C d2 The lower end is connected to the drain of the switching transistor Q7 to form voltage multiplier unit 2, and voltage multiplier capacitor C d2 The upper end of diode D5 is connected to the cathode of diode D1, and the source of switching transistor Q7 is connected to the midpoint of the left arm of the rectifier bridge; the anode of diode D5 is connected to the cathodes of diodes D1 and D3 and the voltage multiplier capacitor C. d2 At the upper end, the negative terminal of diode D5 is connected to the output capacitor C. o1 The upper end, output load R L The upper end; the positive terminal of diode D6 is connected to the output capacitor C. o2 The lower end, output load R L At the lower end, the cathode of diode D6 is connected to the anodes of diodes D2 and D4 and the source of switching transistor Q6. The drain of switching transistor Q5 is connected to the midpoint of the output voltage multiplier bridge arm, and the source is connected to the midpoint of the rectifier right bridge arm.

2. The wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 1, characterized in that, The transformer T converts AC voltage into input voltage for the secondary rectifier structure, and the secondary side of the transformer does not require a center tap structure.

3. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 1, characterized in that, In the primary-side full-bridge inverter structure, the drive signals of switches Q1 and Q4 are the same, and the drive signals of switches Q2 and Q3 are the same. Furthermore, switches Q1 and Q2, as well as switches Q3 and Q4, are mutually complementary in conduction. That is, when switch Q1 is on, switch Q2 is off, and when switch Q1 is off, switch Q2 is on. When switch Q3 is on, switch Q4 is off, and when switch Q3 is off, switch Q4 is on, resulting in a symmetrical positive and negative square wave voltage output.

4. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 1, characterized in that, In steady state, the output capacitor C o1 With output capacitor C o2 Discharge to the load.

5. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 1, characterized in that, The voltage multiplier capacitor C d1 The value is equal to the voltage multiplier capacitor C. d2 Value of output capacitor C o1 The value is equal to the output capacitor C. o2 The value of .

6. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 1, characterized in that, The converter includes four operating modes: full-bridge mode, double voltage mode, triple voltage mode, and quadruple voltage mode. The voltage gain of the four modes increases sequentially, and gain adjustment and mode switching are achieved through frequency modulation control.

7. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure as described in claim 6, characterized in that, When the converter operates in full-bridge mode, the primary-side full-bridge inverter switches Q1, Q2, Q3, and Q4 operate in full-bridge inverter mode. During the positive half-cycle, switches Q1 and Q4 are on, while switches Q2 and Q3 are off. During the negative half-cycle, switches Q1 and Q4 are off, while switches Q2 and Q3 are on. At this time, the secondary-side variable voltage multiplier rectifier switches Q5, Q6, and Q7 are all off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor C d2 Not involved in operation, output capacitor C o1 With output capacitor C o2 Without voltage multiplication, the secondary side operates in full-bridge rectification mode, and the converter adjusts the output voltage by regulating the switching frequency of the switching transistors in the primary side full-bridge inverter structure.

8. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 6, characterized in that, When the converter operates in the voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switches Q6 and Q7 are turned off, and the voltage multiplier capacitor C... d1 With voltage multiplier capacitor C d2 Since they are not involved in operation, no current flows through diodes D3 and D4, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the transformer is in operation, during the positive half-cycle, the secondary side supplies power to the output capacitor C through diodes D1 and D5 and the switching transistor Q5. o1 and output load R L During the negative half-cycle, the transformer secondary side supplies power to the output capacitor C through diodes D2 and D6, and the switching transistor Q5. o2 and output load R L Power supply, output capacitor C o1 With output capacitor C o2 The voltage amplitude on the winding is equal to the winding voltage. Therefore, at the resonant frequency, the output voltage of the double voltage mode is twice that of the full-bridge mode.

9. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 6, characterized in that, When the converter operates in the triple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. The secondary-side variable voltage multiplier rectifier switch Q7 is turned off, and the voltage multiplier capacitor C... d2 Since they are not involved in operation, no current flows through diodes D2 and D3, and switching transistor Q5 conducts, causing the output capacitor C to... o1 With output capacitor C o2 When the circuit is activated, the switching transistor Q6 turns on, causing the voltage multiplier capacitor C to operate. d1 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through diodes D1, D5, and Q5, supplying power to the output capacitor C. o1 During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through switch Q5, diode D6, and switch Q6. o2 Charging; Output capacitor C o1 With voltage multiplier capacitor C d1 The voltage amplitude on the output capacitor C is equal to the winding voltage. o2 The voltage amplitude on the winding is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the triple voltage mode is three times that of the full-bridge mode.

10. A wide-gain-range LLC resonant converter based on a variable voltage multiplier rectifier structure according to claim 6, characterized in that, When the converter operates in the quadruple voltage multiplier mode, the switching transistors of the primary-side full-bridge inverter structure operate in the same manner as in the full-bridge mode. On the secondary side, the variable voltage multiplier rectifier transistors Q5, Q6, and Q7 are all turned on. No current flows through diodes D1 and D2. The turn-on of transistor Q5 causes the output voltage multiplier capacitor C to conduct. o1 With voltage multiplier capacitor C o2 When the circuit is activated, switching transistors Q6 and Q7 turn on, causing the voltage multiplier capacitor C to operate. d1 With voltage multiplier capacitor C d2 The transformer is put into operation; during the positive half-cycle, the secondary side of the transformer supplies power to the voltage multiplier capacitor C through the switching transistor Q6 and the diode D4. d1 Charging is achieved through the switching transistor Q7 and the voltage multiplier capacitor C. d2 Diode D5 and switching transistor Q5 supply power to output capacitor C. o1 During charging, in the negative half-cycle, the secondary side of the transformer supplies power to the output capacitor C through the switching transistor Q7 and the diode D3. d2 Charging is achieved through switching transistor Q5, diode D6, switching transistor Q6, and voltage multiplier capacitor C. d1 Give the output capacitor C o2 Charging; voltage multiplier capacitor C d1 With voltage multiplier capacitor C d2 The voltage amplitude on the output capacitor C is equal to the winding voltage. o1 With output capacitor C o2 The voltage amplitude on the winding is equal to twice the winding voltage. Therefore, at the resonant frequency, the output voltage of the four-times voltage mode is four times that of the full-bridge mode.

Images