Dual-LLC resonant converter based on modulatable coupling inductor

Abstract

The invention discloses a dual-LLC resonant converter based on a modulatable coupling inductor. The dual-LLC resonant converter aims to meet the wide-gain application requirements of an LLC converter in the high-efficiency and high-gain power supply application fields such as a data center, energy storage conversion, direct-current adaptation and photovoltaic application. According to the invention, two connected transformers are adopted to divide a resonant cavity into two parts to form two LLC units, series connection or parallel connection application of double LLC can be realized through different switch sequences, two common resonant inductors are replaced by coupling inductors, and split capacitors are adopted as input and output filters. For the two working modes, the resonant frequency can be configured at will, and the equivalent inductance value of the coupling inductor can be changed by changing the switching sequence, thereby changing the resonant cavity parameters in different modes, and enabling the resonant cavity parameters to meet the requirements of different requirements of the converter under light load / heavy load for the parameters. Therefore, the full-range efficiency of the converter can be improved on the basis that the working modes are switched according to light and heavy load conditions to achieve wide gain.

Description

Technical Field

[0001] The present invention relates to the field of direct current converters, and in particular to a dual LLC resonant converter based on modulatable coupled inductors. Background Art

[0002] As the scale of data centers continues to expand, their energy consumption issues are becoming increasingly prominent, and the efficiency, power density, and reliability of power supply systems have become key challenges. Traditional data center power supply architectures usually adopt a two-stage conversion structure, such as PFC+LLC, but they have low efficiency and insufficient dynamic response under light load. The Double LLC Converter Based on Modulated Coupled Inductance (hereinafter referred to as D-MCI-LLC) is a new topology that significantly improves efficiency and adaptability within the full load range by flexibly switching the resonant mode, becoming a research hotspot for high-density power supply solutions. Although traditional LLC converters have the advantage of soft switching, they have limitations in scenarios with wide input voltages and fluctuating loads of data center servers: under light loads, the resonant cavity current is too small, resulting in the secondary diode being unable to turn off at zero current, increasing switching losses; under heavy loads, the timing control of the excitation inductor participating in the resonance is complex, limiting the improvement of power density. Therefore, it is urgent to propose a design method for the dual LLC topology that can effectively change the circuit equivalent inductance value without introducing external devices, inherit the soft switching and wide gain characteristics, and solve the efficiency loss problem caused by light and heavy loads, ultimately taking into account the optimization problem of both efficiency and wide gain. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art. Based on the dual LLC topology, a dual LLC converter based on a modulated coupled inductor is provided to address the problems of a wide operating frequency range, a limited gain range, and low light-load efficiency of the traditional full-bridge LLC topology. By changing the switching sequence, the converter can operate in a full-bridge series mode or a half-bridge parallel mode. For the two operating modes, the resonant frequency can be arbitrarily configured. When the resonant frequencies are different, full-bridge buck and half-bridge boost can be achieved within a narrow switching frequency range by reasonably adjusting the coupled inductor, thereby achieving a wide range of voltage gain. When the resonant frequencies are the same, the operating mode can be switched according to the light and heavy load conditions to achieve a wide gain and improve the efficiency of the converter over the entire range.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A dual LLC resonant converter based on modulatable coupled inductors includes an input power supply, a split capacitor, an inverter unit, a first resonant cavity, a second resonant cavity, a first transformer, a second transformer, a rectifier unit, a filter capacitor, and an output terminal;

[0006] The split capacitor is composed of a first capacitor and a second capacitor connected in series, with an N node provided between the first capacitor and the second capacitor;

[0007] The inverter unit consists of two bridge arms connected in parallel. Each bridge arm consists of two switching tubes connected in series. A node A and a node B are respectively set between the two switching tubes in each bridge arm.

[0008] The input power supply is connected in parallel with the split capacitor and the two bridge arms in sequence;

[0009] The opposite-name ends of the primary winding of the first transformer and the like-name ends of the primary winding of the second transformer are connected to each other to form an E node; the opposite-name ends of the secondary winding of the first transformer and the like-name ends of the secondary winding of the second transformer are connected to each other to form an F node;

[0010] Node A is connected to the first resonant cavity and the same-named end of the primary winding of the first transformer in sequence;

[0011] Node B is connected to the second resonant cavity and the opposite-name end of the primary winding of the second transformer in sequence;

[0012] N nodes and E nodes are connected to each other;

[0013] The rectifier unit comprises two rectifier branches connected in parallel, each rectifier branch comprises two diodes connected in series, and a C node and a D node are respectively provided between the two diodes in each rectifier branch;

[0014] The filter capacitor is connected to the output end after being connected in parallel with the two rectifier branches, and is composed of a third capacitor and a fourth capacitor connected in series, with an O node provided between the third capacitor and the fourth capacitor;

[0015] The like-name end of the secondary winding of the first transformer is connected to the C node, and the opposite-name end of the secondary winding of the second transformer is connected to the D node;

[0016] The O node and the F node are connected to each other;

[0017] The inductance devices in the first resonant cavity and the second resonant cavity are both adjustable coupled inductors.

[0018] Furthermore, the turns ratio of the first transformer and the second transformer is n:1, and the excitation inductances corresponding to the first transformer and the second transformer are L m1 and L m2 .

[0019] Furthermore, the first resonant cavity is composed of a first resonant capacitor and a first coupling inductor connected in series, and the second resonant cavity is composed of a second resonant capacitor and a second coupling inductor connected in series.

[0020] Furthermore, the coupling coefficient of the coupled inductor is adjustable, and the equivalent inductance of the coupled inductor is changed by changing the switching sequence of the switch tube, so as to switch the resonance parameters under light load and heavy load.

[0021] Furthermore, by setting the switching sequence of different switching tubes, the converter can be operated in full-bridge series mode or half-bridge parallel mode.

[0022] Furthermore, in the full-bridge series mode, the quality factor of the converter is reduced to reduce the turn-off current at light load and improve the light load efficiency.

[0023] Furthermore, in the half-bridge parallel mode, the quality factor of the converter is increased to expand the voltage gain range under heavy load and improve the heavy load efficiency.

[0024] Furthermore, all switching tubes can achieve zero voltage switching (ZVS).

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] 1. High efficiency under light load: In full-bridge series mode, by reducing the equivalent inductance of the coupled inductor, increasing the circuit coupling coefficient (k), and reducing the quality factor (Q), the turn-off loss and reactive circulating current loss are significantly reduced, thereby improving light load efficiency.

[0027] 2. High efficiency under heavy load: In the half-bridge parallel mode, by increasing the equivalent inductance of the coupled inductor, reducing the circuit coupling coefficient (k) and increasing the quality factor (Q), the voltage gain range can be widened, effectively reducing heavy-load switching losses and improving heavy-load efficiency.

[0028] 3. Wide-range gain: By flexibly switching between full-bridge series and half-bridge parallel modes, the boost and buck requirements can be met simultaneously within a narrow switching frequency range, achieving wide output gain over a wide input voltage range. This is suitable for scenarios such as data centers, photovoltaics, and energy storage.

[0029] 4. Zero voltage switching: In any operating mode, all switches can achieve ZVS, further reducing switching losses and improving converter efficiency.

[0030] 5. Advantages of magnetic integration: The ordinary resonant inductors in the two resonant cavities are replaced with adjustable coupled inductors, which are integrated with split capacitors and two transformers to reduce the impact of parasitic parameters on resonant performance and improve power density and reliability.

[0031] 6. No additional devices are required: The present invention does not increase the number of switches and diodes, and only achieves mode switching by changing the switch sequence and coupled inductor modulation technology. No additional hardware is required, which simplifies the circuit structure and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the topological structure of the dual LLC resonant converter of the present invention;

[0033] Figure 2 This is a schematic diagram of the topology of a traditional full-bridge LLC converter;

[0034] Figure 3 This is a schematic diagram of the waveforms of each switch tube drive, resonant cavity input voltage, resonant cavity current, and secondary side current when the dual LLC resonant converter of the present invention operates in full-bridge series mode;

[0035] Figure 4 Schematic diagram of the switch tube current waveform of the dual LLC resonant converter of the present invention under light load (10% of full load);

[0036] Figure 5 This is a schematic diagram of the switch tube current waveform of a traditional full-bridge LLC converter under light load conditions (10% of full load);

[0037] Figure 6 This is a schematic diagram of the waveforms of each switch drive, resonant cavity input voltage, resonant cavity current, and secondary current when the dual LLC resonant converter of the present invention operates in half-bridge parallel mode;

[0038] Figure 7 Schematic diagram of the switch tube current waveform of the dual LLC resonant converter of the present invention under full load;

[0039] Figure 8 This is a schematic diagram of the switch tube current waveform of a traditional full-bridge LLC converter under full load;

[0040] Figure 9 FIG. 4 is a schematic diagram of a voltage gain curve drawn using the dual LLC resonant converter of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] In order to solve the problems of wide operating frequency range, limited gain range and low light load efficiency of traditional full-bridge LLC topology based on dual LLC topology, the present invention is based on the traditional LLC resonant topology, does not increase the number of switches and diodes, adopts split capacitors to replace the original input and filter capacitors, and uses coupled inductor modulation technology to change the equivalent inductance of the coupled inductor by changing the switching sequence, thereby changing the resonant cavity parameters. By adjusting the coupled inductance coefficient, the k value and Q value of the resonant cavity in different modes can be changed, inheriting the soft switching and wide gain characteristics, and solving the problem of efficiency loss caused by light and heavy loads, ultimately taking into account the optimization problems of narrow range, wide gain and high efficiency.

[0043] Specifically, the dual LLC resonant converter proposed in this embodiment is as follows: Figure 1 As shown, including the input power supply V dc , split capacitor, inverter unit, first resonant cavity, second resonant cavity, first transformer, second transformer, rectifier unit, filter capacitor and output terminal V o ; With this circuit topology, the equivalent inductance of the coupled inductor can be changed by changing the switching sequence, thereby changing the resonant cavity parameters, and the k value and Q value of the resonant cavity of different modes can be changed by adjusting the coupled inductance coefficient.

[0044] The split capacitance consists of the first capacitor C i1 and the second capacitor C i2 are connected in series, the first capacitor C i1 and the second capacitor C i2 There are N nodes between them;

[0045] The inverter unit consists of two bridge arms connected in parallel. One bridge arm consists of two switching tubes Q1 and Q2 connected in series, and the other bridge arm consists of two switching tubes Q3 and Q4 connected in series. A node A is set between the switching tubes Q1 and Q2, and a node B is set between the switching tubes Q3 and Q4.

[0046] The input power supply is connected in parallel with the split capacitor and the two bridge arms in sequence;

[0047] The opposite-name ends of the primary winding of the first transformer and the same-name ends of the primary winding of the second transformer are connected to each other to form an E node; the opposite-name ends of the secondary winding of the first transformer and the same-name ends of the secondary winding of the second transformer are connected to each other to form an F node; the turns ratio of the first transformer and the second transformer is n:1, and the corresponding excitation inductances of the first transformer and the second transformer are L respectively. m1 and L m2 . The N nodes and the E nodes are connected to each other.

[0048] Node A is connected to the first resonant cavity and the same-name end of the primary winding of the first transformer in sequence; the first resonant cavity is connected to the first resonant capacitor C r1 and the first coupled inductor L r1 Series composition.

[0049] Node B is connected to the second resonant cavity and the opposite-name end of the primary winding of the second transformer in sequence; the second resonant cavity is connected to the second resonant capacitor C r2 and the second coupled inductor L r2 Series composition.

[0050] The rectifier unit consists of two parallel rectifier branches. The first rectifier branch consists of two series-connected diodes D1 and D2, and the other rectifier branch consists of two series-connected diodes D3 and D4. A node C is located between diodes D1 and D2, and a node D is located between diodes D3 and D4.

[0051] The filter capacitor is connected in parallel with the two rectifier branches and then connected to the output end. o1 and the fourth capacitor C o2 are connected in series, the third capacitor C o1 and the fourth capacitor C o2 There is an O node between them;

[0052] The like-name end of the secondary winding of the first transformer is connected to the C node, and the opposite-name end of the secondary winding of the second transformer is connected to the D node; the O node and the F node are connected to each other.

[0053] The dual LLC resonant converter of this embodiment can switch between full-bridge series mode and half-bridge parallel mode by changing the switching sequence. Figure 2 As shown in FIG, it is composed of two full-bridge LLC converters connected in series.

[0054] Compared with the traditional LLC resonant topology, the dual LLC topology adopted by the present invention does not increase the number of switches and diodes, replaces the ordinary resonant inductor with a coupled inductor, adopts a split capacitor instead of the original input and filter capacitor, and sets two transformers corresponding to two resonant cavities. By adopting different switching sequences, the resonant converter can operate in full-bridge series mode or half-bridge parallel mode. For the two working modes, the resonant frequency can be arbitrarily configured, and the equivalent inductance value of the coupled inductor can be changed by changing the drive, thereby changing the resonant cavity parameters in different modes to meet the different parameter requirements of the converter under light load / heavy load, and then the working mode can be switched according to the light and heavy load conditions to achieve a wide gain and improve the efficiency of the converter over the entire range.

[0055] By adopting a positive coupling coefficient, when the resonant converter operates in half-bridge parallel mode, the equivalent inductance of the modulated coupled inductor increases by increasing the mutual inductance, the circuit k value decreases accordingly, and the Q value increases. Compared with the ordinary full-bridge LLC converter, the voltage gain is wider when carrying a heavier load, the shutdown current is smaller, and the heavy-load efficiency is higher.

[0056] When the resonant converter operates in full-bridge series mode, the equivalent inductance of the modulated coupled inductor decreases due to the corresponding mutual inductance. At this time, the circuit k value becomes larger and the Q value becomes smaller. At this time, compared with the ordinary full-bridge LLC converter, when carrying a lighter load and the voltage gain is satisfied, the shutdown current is smaller and the light-load efficiency is higher.

[0057] In addition, the control method of the resonant converter of this embodiment adopts pulse frequency modulation (PFM).

[0058] Specifically: When the dual LLC resonant converter of this embodiment operates in the full-bridge series mode, the key waveforms of this mode are as follows: Figure 3 As shown. It can be seen that in this mode, the driving signals of the switch tubes Q1 and Q4 are the same, the driving signals of the switch tubes Q2 and Q3 are the same, and the switch tubes Q1 and Q2, Q3 and Q4 are respectively turned on in a complementary manner. In this mode, the voltage v applied to point A and point N is AN The voltage v applied to point B and point N BN On the contrary, the voltage v applied to points C and O AN The voltage v applied to points D and O BN On the contrary, so there is v Ci1 =v Ci2 =v in / 2,v AN =-v BN ,v CO =-v DO , so i r1 and i r2 The direction is opposite, so that no current flows into nodes N and O. r1 、C r2 , L r1 , L r2 Together they form a resonant cavity, the first capacitor C i1 and the second capacitor C i2 Together they form the input filter capacitor, the third capacitor C o1 and the fourth capacitor C o2 Together they form the output filter capacitor. For the positive coupled inductor in this converter, its mathematical model can be expressed as:

[0059]

[0060] Where, v L1 and v L2 are the voltages on the two windings of the coupled inductor. r1 and L r2 is the self-inductance, M is the mutual inductance. Due to the symmetry of the converter, let L r1 =L r2 =L r In this mode, i r1 and i r2 The amplitude and direction are opposite, i r1 =-i r2 Substituting into (1) we get:

[0061]

[0062] The LLC equivalent inductance in this mode is L r -M, let the coupling coefficient k = M / L r , the resonant frequency of the resonant converter is:

[0063]

[0064] At this time, the inductance ratio of the circuit is k=L m / (L r -M), quality factor Equivalent AC resistance Among them, L m is the transformer excitation inductance, L r is the resonant inductor, C r is the resonant capacitor, R o is the load resistance, and n is the transformer ratio. Compared with the ordinary full-bridge LLC, the k value of the circuit becomes larger and the Q value becomes smaller; L m＝ L m1 =L m2 , C r =C r1 =C r2 .

[0065] like Figure 4 FIG. 1 shows the current waveform of the Q1 tube under light load (10% of full load) of the converter proposed in this embodiment. As can be seen from the figure, its turn-off current IQ1_Propsed is approximately 1.86A.

[0066] Figure 5 The current waveform of Q1 in a traditional full-bridge LLC converter topology (uncoupled with the same parameters) under light load (10% of full load) is shown. The turn-off current, IQ1_Full_Bridge, is approximately 2.29 A. Due to the implementation of soft switching, turn-off losses and circulating reactive current are the primary losses. A larger inductor effectively suppresses circulating reactive current and turn-off current, resulting in higher efficiency at light loads, as shown in the simulation.

[0067] When it works in half-bridge parallel mode, the key waveforms of this mode are as follows: Figure 6 As shown. It can be seen that in this mode, the driving signals of Q1 and Q3 are the same, the driving signals of Q2 and Q4 are the same, Q1 and Q2, Q3 and Q4 are complementary turned on respectively. In this mode, the voltage v applied to point A and point N is AN The voltage v applied to point B and point N BN The voltage v applied to points C and O is the same. AN The voltage v applied to points D and O BN Same, so there is v AN =v BN ,v CO=v DO , so i r1 and i r2 The direction is the same. i1 、C i2 , C1, C2, L r1 , L r2 In this mode, i r1 and i r2 The amplitude and direction are the same, i.e. r1 =i r2 Substituting into (1) we get:

[0068]

[0069] The LLC equivalent inductance in this mode is L r +M, let the coupling coefficient k=M / L r , the resonant frequency of the resonant converter is:

[0070]

[0071] At this time, the inductance ratio of the circuit is k=L m / (L r +M), quality factor Equivalent AC resistance At this time, compared with the ordinary full-bridge LLC, the k value of the circuit becomes smaller, the voltage gain range becomes wider, the Q value becomes larger, and the efficiency is improved.

[0072] like Figure 7 The figure shows the current waveform of Q1 tube under full load of the converter proposed in this embodiment. It can be seen from the figure that its shutdown current IQ1_Propsed is about 1.92A;

[0073] Figure 8 The current waveform of Q1 in a traditional full-bridge LLC converter topology under full load shows that its turn-off current, IQ1_Full_Bridge, is approximately 2.42 A. Because the current is high under heavy load, switching losses are the primary loss. Simulation results show that the resonant converter of this embodiment exhibits lower turn-off current under heavy load, leading to higher efficiency.

[0074] The resonant converter of this embodiment has k=2, Q=0.6 in half-bridge parallel mode and k=4, Q=0.3 in full-bridge series mode. Its voltage gain curve is shown as follows: Figure 9 shown.

[0075] Therefore, the dual LLC resonant converter disclosed in the present invention can be applied to wide-gain, high-efficiency research fields such as data centers, energy storage conversion, DC adaptation, and photovoltaic applications. Specifically, based on the traditional LLC resonant topology, based on the coupled inductor modulation technology, the equivalent inductance of the coupled inductor can be changed by changing the switching sequence, thereby changing the resonant cavity parameters. Using a positive coupling coefficient, when the converter operates in the half-bridge parallel mode, the equivalent inductance of the modulated coupled inductor increases by increasing the mutual inductance, the circuit k value decreases accordingly, and the Q value increases. At this time, compared with the ordinary full-bridge LLC converter, the voltage gain is wider, the turn-off current is smaller, and the heavy-load efficiency is higher when carrying a heavier load; on the contrary, when the converter operates in the full-bridge series mode, the equivalent inductance of the modulated coupled inductor decreases by the corresponding mutual inductance, and the circuit k value increases and the Q value decreases. At this time, compared with the ordinary full-bridge LLC converter, when carrying a lighter load and the voltage gain is satisfied, the turn-off current is smaller and the light-load efficiency is higher. The proposed dual LLC resonant converter can achieve a wide range of gain within a narrow switching frequency range, and each switch can achieve zero voltage switching, providing a new idea for the wide gain and high efficiency application of resonant converters.

[0076] In summary, the dual LLC resonant converter (D-MCI-LLC) based on modulated coupled inductors involved in this embodiment can operate in full-bridge series mode or half-bridge parallel mode by changing the switching sequence converter. For the two working modes, the resonant frequencies can be the same or different. When the resonant frequencies are different, by reasonably adjusting the coupled inductors, full-bridge buck and half-bridge boost can be achieved within a narrow switching frequency range, thereby achieving the purpose of a wide range of voltage gain; when the resonant frequencies are the same, the working mode can be switched according to the light and heavy load conditions to achieve a wide gain and improve the efficiency of the converter over the entire range. In addition, its magnetic integration design further reduces the influence of parasitic parameters, which meets the demand for high power density of the 24V bus architecture of the data center. The resonant converter effectively solves the problem of efficiency loss caused by light and heavy loads, and ultimately takes into account the optimization problem of efficiency and wide gain.

[0077] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, those skilled in the art may make various specific modifications based on the teachings of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A dual LLC resonant converter based on modulatable coupled inductors, characterized in that: It includes an input power supply, a split capacitor, an inverter unit, a first resonant cavity, a second resonant cavity, a first transformer, a second transformer, a rectifier unit, a filter capacitor and an output end; The split capacitance consists of the first capacitor (C i1 ) and the second capacitor (C i2 ) are connected in series, the first capacitor (C i1 ) and the second capacitor (C i2 ) are provided with N nodes; The inverter unit consists of two bridge arms connected in parallel. Each bridge arm consists of two switching tubes connected in series. A node A and a node B are respectively set between the two switching tubes in each bridge arm. The input power supply is connected in parallel with the split capacitor and the two bridge arms in sequence; The opposite-name ends of the primary winding of the first transformer and the like-name ends of the primary winding of the second transformer are connected to each other to form an E node; the opposite-name ends of the secondary winding of the first transformer and the like-name ends of the secondary winding of the second transformer are connected to each other to form an F node; Node A is connected to the first resonant cavity and the same-named end of the primary winding of the first transformer in sequence; Node B is connected to the second resonant cavity and the opposite-name end of the primary winding of the second transformer in sequence; N nodes and E nodes are connected to each other; The rectifier unit comprises two rectifier branches connected in parallel, each rectifier branch comprises two diodes connected in series, and a C node and a D node are respectively provided between the two diodes in each rectifier branch; The filter capacitor is connected in parallel with the two rectifier branches and then connected to the output end. o1 ) and the fourth capacitor (C o2 ) are connected in series, the third capacitor (C o1 ) and the fourth capacitor (C o2 ) is provided with an O node between; The like-name end of the secondary winding of the first transformer is connected to the C node, and the opposite-name end of the secondary winding of the second transformer is connected to the D node; The O node and the F node are connected to each other; The inductance devices in the first resonant cavity and the second resonant cavity both adopt adjustable coupled inductance.

2. The dual LLC resonant converter based on modulatable coupled inductors according to claim 1, characterized in that: The turns ratio of the first transformer and the second transformer is n:1, and the excitation inductances of the first transformer and the second transformer are L m1 and L m2 .

3. The dual LLC converter based on modulatable coupled inductors according to claim 1, characterized in that: The first resonant cavity is composed of the first resonant capacitor (C r1 ) and the first coupled inductor (L r1 ) in series, the second resonant cavity is composed of the second resonant capacitor (C r2 ) and the second coupled inductor (L r2 ) are connected in series.

4. A dual LLC resonant converter based on modulatable coupled inductors according to claim 1 or 3, characterized in that: The coupling coefficient of the coupled inductor is adjustable, and the equivalent inductance value of the coupled inductor is changed by changing the switching sequence of the switch tube, so as to switch the resonance parameters under light load and heavy load.

5. The dual LLC resonant converter based on modulatable coupled inductors according to claim 1, characterized in that: By changing the switching sequence of different switching tubes, the converter can be operated in full-bridge series mode or half-bridge parallel mode.

6. A dual LLC resonant converter based on modulatable coupled inductors according to claim 1 or 5, characterized in that: In full-bridge series mode, the converter quality factor is reduced to reduce the turn-off current at light load and improve light load efficiency.

7. A dual LLC resonant converter based on modulatable coupled inductors according to claim 1 or 5, characterized in that: In half-bridge parallel mode, the quality factor of the converter is increased to expand the voltage gain range under heavy load and improve the heavy load efficiency.

8. The dual LLC resonant converter based on modulatable coupled inductors according to claim 1, characterized in that: All switches can achieve zero voltage switching (ZVS).

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