A Bidirectional CLLC Resonant Converter and Its Control Method

Abstract

The present invention discloses a bidirectional CLLC resonant converter and its control method, which is used to solve the technical problem that the existing bidirectional CLLC resonant converter leads to an overly complex topological structure. The present invention includes a primary full-bridge circuit, a primary resonant network, a secondary resonant network, a secondary full-bridge circuit, a primary DC source, a primary filter capacitor, a secondary DC source, and a secondary filter capacitor; the primary DC source, the primary filter capacitor, and the primary full-bridge circuit are connected in parallel; one end of the primary full-bridge circuit is electrically connected to one end of the primary resonant network, and the other end of the primary resonant network is coupled to one end of the secondary resonant network; the other end of the secondary resonant network is connected to the secondary full-bridge circuit; the secondary DC source, the secondary filter capacitor, and the secondary full-bridge circuit are connected in parallel.

Description

Technical Field

[0001] The present invention relates to the technical field of power conversion, and particularly relates to a bidirectional CLLC resonant converter and a control method thereof. Background Art

[0002] With the rapid development of new energy and energy storage technologies, the global energy structure is undergoing a profound transformation. The popularization of renewable energy and the increasing demand for efficient and flexible power management have made power converters play a key role in this transformation. In this context, the bidirectional CLLC resonant converter stands out due to its unique energy bidirectional flow characteristics, where C represents capacitance and L represents inductance, etc.

[0003] The bidirectional CLLC resonant converter can not only achieve bidirectional energy transmission, but also has a high transmission efficiency. It can achieve zero-voltage switching (ZVS) of the primary side switch tube and zero-current switching (ZCS) of the secondary side diode within the full load range. At the same time, the bidirectional CLLC resonant converter operates in a soft-switching state, with higher efficiency than non-resonant topologies, and is increasingly widely used.

[0004] Most of the existing bidirectional CLLC resonant converters use a form of parallel connection on both the primary and secondary sides to combine two CLLC resonant converters, and then use a bidirectional MOS tube switch to connect the two resonant cavities to control the series-parallel form of the resonant cavities. By adjusting the series-parallel connection and the half-full bridge mode on the primary side, different voltage gain intervals are achieved. However, both the primary and secondary sides of this converter use two full bridges in parallel, resulting in too many MOS tubes (switching tubes) participating in resonance and making the topological structure too complex. Summary of the Invention

[0005] The present invention provides a bidirectional CLLC resonant converter and a control method thereof, which are used to solve the technical problem that the existing bidirectional CLLC resonant converter leads to an overly complex topological structure.

[0006] A bidirectional CLLC resonant converter provided in the first aspect of the present invention includes a primary full-bridge circuit, a primary resonant network, a secondary resonant network, a secondary full-bridge circuit, a primary DC source, a primary filter capacitor, a secondary DC source, and a secondary filter capacitor;

[0007] The primary DC source, the primary filter capacitor, and the primary full-bridge circuit are connected in parallel;

[0008] One end of the primary full-bridge circuit is electrically connected to one end of the primary resonant network, and the other end of the primary resonant network is coupled to one end of the secondary resonant network;

[0009] The other end of the secondary resonant network is connected to the secondary full-bridge circuit;

[0010] The secondary DC source, the secondary filter capacitor and the secondary full-bridge circuit are connected in parallel.

[0011] Optionally, the primary full-bridge circuit includes a first bridge arm and a second bridge arm connected in parallel;

[0012] The primary DC source, the primary filter capacitor, the first bridge arm and the second bridge arm are connected in parallel;

[0013] Both the first bridge arm and the second bridge arm are electrically connected to one end of the primary resonant network.

[0014] Optionally, the primary resonant network includes a first primary winding of a transformer, a second primary winding of a transformer, a first primary resonant inductor, a second primary resonant inductor, a first primary resonant capacitor, a second primary resonant capacitor, a first primary exciting inductor, a second primary exciting inductor and three primary bidirectional switching tubes;

[0015] The first bridge arm includes a first switching tube and a second switching tube connected in series, and the second bridge arm includes a third switching tube and a fourth switching tube connected in series;

[0016] The upper end of the first primary winding of the transformer is connected to the connection point between the third switching tube and the fourth switching tube through the first primary resonant inductor and the first primary resonant capacitor;

[0017] The lower end of the first primary winding of the transformer is connected to the connection point between the first switching tube and the second switching tube through a second primary bidirectional switching tube;

[0018] The upper end of the second primary winding of the transformer is connected to the lower end of the first primary winding of the transformer through a first primary bidirectional switching tube and is connected to the connection point between the third switching tube and the fourth switching tube through a third primary bidirectional switching tube;

[0019] The lower end of the second primary winding of the transformer is connected to the connection point between the first switching tube and the second switching tube through the second primary resonant inductor and the second primary resonant capacitor;

[0020] The first primary winding of the transformer is connected in parallel with the first primary exciting inductor, and the second primary winding of the transformer is connected in parallel with the second primary exciting inductor;

[0021] Both the first primary winding of the transformer and the second primary winding of the transformer are coupled and connected to the secondary resonant network.

[0022] Optionally, the secondary full-bridge circuit includes a third bridge arm and a fourth bridge arm connected in parallel;

[0023] The secondary - side DC source, the secondary - side filter capacitor, the third bridge arm, and the fourth bridge arm are connected in parallel.

[0024] Both the third bridge arm and the fourth bridge arm are electrically connected to the other end of the secondary - side resonant network.

[0025] Optionally, the secondary - side resonant network includes a first secondary winding of a transformer, a second secondary winding of a transformer, a first secondary resonant inductor, a second secondary resonant inductor, a first secondary resonant capacitor, a second secondary resonant capacitor, and three secondary - side bidirectional switch tubes.

[0026] The third bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series.

[0027] The upper end of the first secondary winding of the transformer is connected to the connection point between the seventh switch tube and the eighth switch tube through the first secondary resonant inductor and the first secondary resonant capacitor.

[0028] The lower end of the first secondary winding of the transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through a second secondary - side bidirectional switch tube.

[0029] The upper end of the second secondary winding of the transformer is connected to the lower end of the first secondary winding of the transformer through a first secondary - side bidirectional switch tube and is connected to the connection point between the seventh switch tube and the eighth switch tube through a third secondary - side bidirectional switch tube.

[0030] The lower end of the second secondary winding of the transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through the second secondary resonant inductor and the second secondary resonant capacitor.

[0031] The first secondary winding of the transformer is coupled to the first primary winding of the transformer in the primary - side resonant network.

[0032] The second secondary winding of the transformer is coupled to the second primary winding of the transformer in the primary - side resonant network.

[0033] Optionally, both the secondary - side bidirectional switch tubes and the primary - side bidirectional switch tubes in the primary - side resonant network are composed of two back - to - back switch tubes connected in series.

[0034] A control method for a bidirectional CLLC resonant converter provided in the second aspect of the present invention is applied to the above - mentioned bidirectional CLLC resonant converter, and includes:

[0035] When receiving the first instruction, control the first primary bidirectional switch tube in the primary resonant network, the second secondary bidirectional switch tube and the third secondary bidirectional switch tube in the secondary resonant network to be in a normally closed state;

[0036] Control the second primary bidirectional switch tube and the third primary bidirectional switch tube in the primary resonant network, and the first secondary bidirectional switch tube in the secondary resonant network to be in a normally open state;

[0037] Based on the switching frequencies of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in the primary full-bridge circuit, perform full-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 2x voltage mode.

[0038] Optionally, it further includes:

[0039] When receiving the second instruction, control the first primary bidirectional switch tube and the first secondary bidirectional switch tube to be in a normally closed state;

[0040] Control the second primary bidirectional switch tube, the third primary bidirectional switch tube, the second secondary bidirectional switch tube and the third secondary bidirectional switch tube to be in a normally open state;

[0041] Based on the switching frequencies of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, perform full-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 1x voltage mode.

[0042] Optionally, it further includes:

[0043] When receiving the third instruction, control the first primary bidirectional switch tube and the first secondary bidirectional switch tube to be in a normally closed state;

[0044] Control the second primary bidirectional switch tube, the third primary bidirectional switch tube, the second secondary bidirectional switch tube and the third secondary bidirectional switch tube to be in a normally open state;

[0045] Control the first switch tube to be in a normally closed state, and control the second switch tube to be in a normally open state;

[0046] Based on the switching frequencies of the third switch tube and the fourth switch tube, perform half-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 0.5x voltage mode.

[0047] Optionally, it further includes:

[0048] When the fourth instruction is received, control the second primary bidirectional switch tube, the third primary bidirectional switch tube, and the first secondary bidirectional switch tube to be in a normally closed state;

[0049] Control the first primary bidirectional switch tube, the second secondary bidirectional switch tube, and the third secondary bidirectional switch tube to be in a normally open state;

[0050] Control the first switch tube to be in a normally closed state and control the second switch tube to be in a normally open state;

[0051] Based on the switching frequencies corresponding to the third switch tube and the fourth switch tube, perform half-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 0.25-fold voltage mode.

[0052] As can be seen from the above technical solutions, the present invention has the following advantages:

[0053] The first aspect of the above technical solution of the present invention provides a bidirectional CLLC resonant converter, which includes a primary full-bridge circuit, a primary resonant network, a secondary resonant network, a secondary full-bridge circuit, a primary DC source, a primary filter capacitor, a secondary DC source, and a secondary filter capacitor; wherein, the primary DC source, the primary filter capacitor, and the primary full-bridge circuit are connected in parallel; one end of the primary full-bridge circuit is electrically connected to one end of the primary resonant network, and the other end of the primary resonant network is coupled to one end of the secondary resonant network; the other end of the secondary resonant network is connected to the secondary full-bridge circuit; the secondary DC source, the secondary filter capacitor, and the secondary full-bridge circuit are connected in parallel; Based on the above solution, only one full-bridge is used on both the primary and secondary sides of the bidirectional CLLC resonant converter proposed by the present invention, which can reduce the number of switch tubes participating in the work, thereby simplifying the topological structure.

[0054] In the second aspect of the above technical solution of the present invention, a control method for a bidirectional CLLC resonant converter is provided, which is applied to the bidirectional CLLC resonant converter proposed by the present invention. First, when it is necessary to make the bidirectional CLLC resonant converter operate in the forward 2x voltage mode, control the first primary bidirectional switch tube in the primary resonant network, the second secondary bidirectional switch tube and the third secondary bidirectional switch tube in the secondary resonant network to be in the normally closed state; control the second primary bidirectional switch tube, the third primary bidirectional switch tube in the primary resonant network, and the first secondary bidirectional switch tube in the secondary resonant network to be in the normally open state; based on the switching frequencies corresponding to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in the primary full-bridge circuit, perform full-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 2x voltage mode; based on the above solution, by controlling the opening and closing states of the bidirectional switch tubes and the switch tubes in the bidirectional CLLC resonant converter, and based on the switching frequencies corresponding to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, perform full-bridge inversion on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 2x voltage mode. In this process, through the coordinated control of the primary and secondary sides and the resonant cavity of the present invention, a wide gain range output can be achieved. At the same time, only one full-bridge is used on both the primary and secondary sides of the bidirectional CLLC resonant converter proposed by the present invention, which can reduce the number of switch tubes participating in the work, thereby simplifying the topology structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0056] Figure 1 FIG. is a schematic structural diagram of a bidirectional CLLC resonant converter provided in Embodiment 1 of the present invention;

[0057] Figure 2 FIG. is a flowchart of the steps of a control method for a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention;

[0058] Figure 3 FIG. is a schematic structural diagram of the bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention when operating in the 2x voltage mode;

[0059] Figure 4 FIG. is a schematic structural diagram of the bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention when operating in the 1x voltage mode;

[0060] Figure 5 Schematic diagram of the bidirectional CLLC resonant converter provided in the second embodiment of the present invention operating in the 0.5 - voltage - multiplication mode;

[0061] Figure 6 Schematic diagram of the bidirectional CLLC resonant converter provided in the second embodiment of the present invention operating in the 0.25 - voltage - multiplication mode;

[0062] Figure 7 Waveform schematic diagram for realizing soft - switching provided in the second embodiment of the present invention.

[0063] Among them, the meanings of the reference numerals are as follows:

[0064] 1. Primary - side full - bridge circuit; 2. Primary - side resonant network; 3. Secondary - side resonant network; 4. Secondary - side full - bridge circuit. Detailed implementation manners

[0065] The embodiment of the present invention provides a bidirectional CLLC resonant converter and its control method, which are used to solve the technical problem that the existing bidirectional CLLC resonant converter leads to an overly complex topological structure.

[0066] To make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0067] Please refer to Figure 1 , Figure 1 Schematic diagram of a bidirectional CLLC resonant converter provided in the first embodiment of the present invention.

[0068] A bidirectional CLLC resonant converter provided by the present invention includes a primary - side full - bridge circuit 1, a primary - side resonant network 2, a secondary - side resonant network 3, a secondary - side full - bridge circuit 4, a primary - side DC source, a primary - side filter capacitor, a secondary - side DC source, and a secondary - side filter capacitor; the primary - side DC source, the primary - side filter capacitor, and the primary - side full - bridge circuit 1 are connected in parallel; one end of the primary - side full - bridge circuit 1 is electrically connected to one end of the primary - side resonant network 2, and the other end of the primary - side resonant network 2 is coupled to one end of the secondary - side resonant network 3; the other end of the secondary - side resonant network 3 is connected to the secondary - side full - bridge circuit 4; the secondary - side DC source, the secondary - side filter capacitor, and the secondary - side full - bridge circuit 4 are connected in parallel.

[0069] It should be noted that the bidirectional CLLC resonant converter with a wide gain range proposed by the present invention includes a primary - side full - bridge circuit 1, a primary - side resonant network 2, a secondary - side resonant network 3, a secondary - side full - bridge circuit 4, a primary - side DC source VP , the primary side filter capacitor C in , the secondary side DC source V s and the secondary side filter capacitor C out , and both sides have symmetry properties.

[0070] As a further improvement, the primary full-bridge circuit 1 includes a first bridge arm and a second bridge arm connected in parallel;

[0071] The primary DC source, the primary side filter capacitor, the first bridge arm, and the second bridge arm are connected in parallel;

[0072] Both the first bridge arm and the second bridge arm are electrically connected to one end of the primary resonant network.

[0073] It should be noted that the primary full-bridge circuit 1 is composed of a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, and a fourth switching tube Q4. The first bridge arm is composed of the first switching tube Q1 and the second switching tube Q2, and the second bridge arm is composed of the third switching tube Q3 and the fourth switching tube Q4; among them, each group of bridge arm switching tubes is a MOSFET.

[0074] As a further improvement, the primary resonant network 2 includes a first primary winding of the transformer, a second primary winding of the transformer, a first primary resonant inductor, a second primary resonant inductor, a first primary resonant capacitor, a second primary resonant capacitor, a first primary exciting inductor, a second primary exciting inductor, and three primary bidirectional switching tubes;

[0075] The first bridge arm includes a first switching tube and a second switching tube connected in series, and the second bridge arm includes a third switching tube and a fourth switching tube connected in series;

[0076] The upper end of the first primary winding of the transformer is connected to the connection point between the third switching tube and the fourth switching tube through the first primary resonant inductor and the first primary resonant capacitor;

[0077] The lower end of the first primary winding of the transformer is connected to the connection point between the first switching tube and the second switching tube through the second primary bidirectional switching tube;

[0078] The upper end of the second primary winding of the transformer is connected to the lower end of the first primary winding of the transformer through the first primary bidirectional switching tube and is connected to the connection point between the third switching tube and the fourth switching tube through the third primary bidirectional switching tube;

[0079] The lower end of the second primary winding of the transformer is connected to the connection point between the first switching tube and the second switching tube through the second primary resonant inductor and the second primary resonant capacitor;

[0080] The first primary winding of the transformer is connected in parallel with the first primary exciting inductor, and the second primary winding of the transformer is connected in parallel with the second primary exciting inductor;

[0081] The primary winding of the first transformer and the primary winding of the second transformer are both coupled and connected to the secondary resonant network.

[0082] It should be noted that the primary resonant network 2 includes the primary windings of the first transformer T1 and the second transformer T2, the first primary resonant inductor Lp1 and the second primary resonant inductor Lp2, the first primary resonant capacitor Cp1 and the second primary resonant capacitor Cp2, the first primary exciting inductor Lm1 and the second primary exciting inductor Lm2; among them, the upper end X1 of the primary winding of the first transformer T1 is connected to the midpoint B of the second bridge arm (this midpoint B is the connection point between the third switch tube and the fourth switch tube) through the first primary resonant inductor Lp1 and the first primary resonant capacitor Cp1, and the lower end Y1 of the primary winding of the first transformer T1 is connected to the midpoint A of the first bridge arm (this midpoint A is the connection point between the first switch tube and the second switch tube) through the second primary bidirectional switch tube S2; the upper end X2 of the primary winding of the second transformer T2 is connected to the lower end Y1 of the primary winding of the first transformer T1 through the first primary bidirectional switch tube S1, and is also connected to the midpoint B of the second bridge arm through the third primary bidirectional switch tube S3, and the lower end Y2 of the primary winding of the second transformer T2 is connected to the midpoint A of the first bridge arm through the second primary resonant inductor Lp2 and the second primary resonant capacitor Cp2; the first primary exciting inductor Lm1 is connected in parallel with the primary winding of the first transformer T1, and the second primary exciting inductor Lm2 is connected in parallel with the primary winding of the second transformer T2.

[0083] It is worth mentioning that a bidirectional switch tube is composed of two back-to-back MOSFETs.

[0084] As a further improvement, the secondary full-bridge circuit 4 includes a third bridge arm and a fourth bridge arm connected in parallel;

[0085] The secondary DC source, the secondary filter capacitor, the third bridge arm and the fourth bridge arm are connected in parallel;

[0086] Both the third bridge arm and the fourth bridge arm are electrically connected to the other end of the secondary resonant network.

[0087] It should be noted that the secondary full-bridge circuit is composed of a fifth switch tube Q5, a sixth switch tube Q6, a seventh switch tube Q7 and an eighth switch tube Q8. The third bridge arm is composed of the fifth switch tube Q5 and the sixth switch tube Q6, and the fourth bridge arm is composed of the seventh switch tube Q7 and the eighth switch tube Q8.

[0088] As a further improvement, the secondary resonant network 3 includes the secondary winding of the first transformer, the secondary winding of the second transformer, the first secondary resonant inductor, the second secondary resonant inductor, the first secondary resonant capacitor, the second secondary resonant capacitor and three secondary bidirectional switch tubes;

[0089] The third bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series;

[0090] The upper end of the secondary winding of the first transformer is connected to the connection point between the seventh switch tube and the eighth switch tube through a first secondary resonant inductor and a first secondary resonant capacitor;

[0091] The lower end of the secondary winding of the first transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through a second secondary bidirectional switch tube;

[0092] The upper end of the secondary winding of the second transformer is connected to the lower end of the secondary winding of the first transformer through a first secondary bidirectional switch tube, and is connected to the connection point between the seventh switch tube and the eighth switch tube through a third secondary bidirectional switch tube;

[0093] The lower end of the secondary winding of the second transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through a second secondary resonant inductor and a second secondary resonant capacitor;

[0094] The secondary winding of the first transformer is coupled to the primary winding of the first transformer in the primary resonant network;

[0095] The secondary winding of the second transformer is coupled to the primary winding of the second transformer in the primary resonant network.

[0096] It should be noted that the secondary resonant network 3 includes the secondary windings of the first transformer T1 and the second transformer T2, the first secondary resonant inductor Ls1 and the second secondary resonant inductor Ls2, the first secondary resonant capacitor Cs1 and the second secondary resonant capacitor Cs2; among them, the upper end Z1 of the secondary winding of the first transformer T1 is connected to the midpoint D of the fourth bridge arm (this midpoint D is the connection point between the seventh switch tube and the eighth switch tube) through the first secondary resonant inductor Ls1 and the first secondary resonant capacitor Cs1, and the lower end W1 of the secondary winding of the first transformer T1 is connected to the midpoint C of the third bridge arm (this midpoint C is the connection point between the fifth switch tube and the sixth switch tube) through the second secondary bidirectional switch tube S5; the upper end Z2 of the secondary winding of the second transformer T2 is connected to the lower end W1 of the secondary winding of the first transformer T1 through the first secondary bidirectional switch tube S4, and is also connected to the midpoint D of the fourth bridge arm through the third secondary bidirectional switch tube S6, and the lower end W2 of the secondary winding of the second transformer T2 is connected to the midpoint C of the third bridge arm through the second secondary resonant inductor Ls2 and the second secondary resonant capacitor Cs2.

[0097] It is worth mentioning that the turns ratio N1 of the transformer T1 of the bidirectional CLLC resonant converter proposed by the present invention is equal to the turns ratio N1 of the transformer T2, that is, N1 = N2 = n; the parameters of the primary resonant cavity and the secondary resonant cavity satisfy Lp1 = Lp2 = n²Ls1 = n²Ls2, and Cp1 = Cp2 = Cs1 / n² = Cs2 / n².

[0098] Further, when the resonant converter is operating in the forward direction, the midpoints of the first and second arms of the primary side serve as the input terminals of the converter, and the midpoints of the third and fourth arms of the secondary side serve as the output terminals of the converter; when the resonant converter is operating in the reverse direction, the midpoints of the third and fourth arms of the secondary side serve as the input terminals of the converter, and the midpoints of the first and second arms of the primary side serve as the output terminals of the converter.

[0099] As a comparison of technical effects, reference can be made in combination with the prior art. With the rapid development of new energy and energy storage technologies, the global energy structure is undergoing a profound transformation. The popularization of renewable energy and the increasing demand for efficient and flexible power management have made power converters play a key role in this transformation. In this context, the bidirectional CLLC resonant converter stands out due to its unique energy bidirectional flow characteristics. Among them, the CLLC resonant converter is an efficient DC-DC converter, widely used in power management systems, especially in occasions where high power and high efficiency are required. It is mainly composed of inductance and capacitance elements and uses the resonance principle to achieve energy conversion. However, for the traditional bidirectional CLLC resonant converter to meet the requirements of a wide output voltage range, it requires an ultra-wide switching frequency, which brings great difficulties to the design of filters and transformers. At the same time, there is an existing parallel-type CLLC resonant converter: it combines two CLLC resonant converters in a form where both the primary and secondary sides are in parallel, and then uses a bidirectional MOS tube switch to connect the two resonant cavities to control the series-parallel form of the resonant cavities, and realizes different voltage gain intervals by adjusting the series-parallel connection and the half-full bridge mode of the primary side.

[0100] Based on the above, for the traditional CLLC to achieve wide gain, the switching frequency range is wide, which brings difficulties to the design of EMI filters and magnetic components; at the same time, for the parallel-type CLLC converter, both the primary and secondary sides use two full bridges in parallel, which can increase the gain ratio to a certain extent, but the number of MOS tubes participating in resonance is more.

[0101] To solve the above problems, the present invention proposes a bidirectional CLLC resonant converter with wide gain adjustment, which can use the combination of a full bridge and two resonators to achieve a wider gain range. Specifically, the present invention connects two resonators to a full bridge, and can achieve a higher gain ratio than the parallel-type CLLC converter through series-parallel combination, and the number of MOS tubes participating in resonance is less.

[0102] In summary, the bidirectional CLLC resonant converter proposed by the present invention connects the transformers in the two resonant cavities in series and parallel within a full bridge, has multiple operating modes, can meet the operating requirements of bidirectional DC-DC converters in different fields and complex working conditions, has a wider gain range by adjusting the switching frequency and operating mode, and the gain ratio is 8 at the same frequency; additionally, with frequency modulation, the actual gain ratio can reach 14. Meanwhile, the present invention only uses one full bridge, reducing the number of switching tubes participating in the work, and the switching tubes achieve soft-switching actions within a certain frequency range.

[0103] In an embodiment of the present invention, the present invention provides a bidirectional CLLC resonant converter, which includes a primary full-bridge circuit, a primary resonant network, a secondary resonant network, a secondary full-bridge circuit, a primary DC source, a primary filter capacitor, a secondary DC source, and a secondary filter capacitor; wherein, the primary DC source, the primary filter capacitor, and the primary full-bridge circuit are connected in parallel; one end of the primary full-bridge circuit is electrically connected to one end of the primary resonant network, and the other end of the primary resonant network is coupled to one end of the secondary resonant network; the other end of the secondary resonant network is connected to the secondary full-bridge circuit; the secondary DC source, the secondary filter capacitor, and the secondary full-bridge circuit are connected in parallel; based on the above solution, the primary and secondary sides of the bidirectional CLLC resonant converter proposed by the present invention only use one full bridge, which can reduce the number of switching tubes participating in the work, thereby simplifying the topological structure. At the same time, it can also make the coordinated control of the primary and secondary sides and the resonant cavity simpler.

[0104] Please refer to Figure 2 , Figure 2 which is a step flowchart of a control method for a bidirectional CLLC resonant converter provided in the second embodiment of the present invention.

[0105] A control method for a bidirectional CLLC resonant converter provided by the present invention is applied to the above-mentioned bidirectional CLLC resonant converter and includes:

[0106] Step 201, when receiving a first instruction, control the first primary bidirectional switch tube in the primary resonant network, the second secondary bidirectional switch tube and the third secondary bidirectional switch tube in the secondary resonant network to be in a normally closed state.

[0107] Step 202, control the second primary bidirectional switch tube, the third primary bidirectional switch tube, and the first secondary bidirectional switch tube in the secondary resonant network to be in a normally open state.

[0108] Step 203, based on the switching frequencies of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube in the primary full-bridge circuit, perform full-bridge inversion on the primary full-bridge circuit and the primary resonant network to make the bidirectional CLLC resonant converter operate in the forward 2-fold voltage mode.

[0109] It should be noted that based on the topology of the bidirectional CLLC resonant converter proposed in the present invention, through the coordinated control of the primary and secondary sides and the resonant cavity, a wide gain range output can be achieved. Specifically, since the topological structure of the present invention is symmetric left and right, the forward and reverse operation modes are symmetric; when the system operates in the forward transmission mode, the first bridge arm and the second bridge arm form the inverter side, which is the power input side, and the third bridge arm and the fourth bridge arm form the rectifier side, which is the power output side; when the system operates in the reverse transmission mode, the third bridge arm and the fourth bridge arm form the inverter side, which is the power input side, and the first bridge arm and the second bridge arm form the rectifier side, which is the power output side.

[0110] There are four forward operation modes of the bidirectional CLLC resonant converter proposed in the present invention, namely the forward 2x voltage mode, the forward 1x voltage mode, the forward 0.5x voltage mode, and the forward 0.25x voltage mode.

[0111] Specifically, please refer to Figure 3 , when the first instruction is received, this first instruction is to make the bidirectional CLLC resonant converter operate in the forward 2x voltage mode. The bidirectional switch tubes S1, S5, and S6 are normally closed, and the bidirectional switch tubes S2, S3, and S4 are normally open; the primary side of the CLLC resonant circuit performs full-bridge inversion by controlling the switching frequencies of the switch tubes Q1, Q2, Q3, and Q4, and the switching frequencies of the switch tubes Q1, Q2, Q3, and Q4 are kept synchronous. Among them, the drive signals of the switch tubes Q1 and Q2 are complementary, and the duty cycle is 0.5. The drive signals of the switch tubes Q3 and Q4 are complementary, and the duty cycle is 0.5. The switch tubes Q1 and Q4 operate in the same phase, and the switch tubes Q2 and Q3 operate in the same phase; no drive signals are applied to the secondary side switch tubes Q5, Q6, Q7, and Q8 of the CLLC resonant circuit, and rectification is achieved by relying on their anti-parallel diodes; in this mode, full-bridge inversion, parallel connection of the primary side transformer, and series connection of the secondary side transformer are realized, and at this time the system voltage gain reaches 2 times the original; among them, Figure 3 the normally open bidirectional switch tubes in are represented by straight lines, and the normally closed bidirectional switch tubes are represented by semi-transparent lines.

[0112] Optionally, controlling the bidirectional CLLC resonant converter to operate in the forward 1x voltage mode may include the following steps:

[0113] When the second instruction is received, control the first primary side bidirectional switch tube and the first secondary side bidirectional switch tube to be in the normally closed state;

[0114] Control the second primary side bidirectional switch tube, the third primary side bidirectional switch tube, the second secondary side bidirectional switch tube, and the third secondary side bidirectional switch tube to be in the normally open state;

[0115] Based on the switching frequencies corresponding to the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube, full-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 1x voltage mode.

[0116] It should be noted that, please refer to Figure 4 , when the second instruction is received, this second instruction is to make the bidirectional CLLC resonant converter operate in the forward 1x voltage mode. The bidirectional switching tubes S1 and S4 are normally closed, and the bidirectional switching tubes S2, S3, S5, and S6 are normally open; the primary side of the CLLC resonant circuit performs full-bridge inversion by controlling the switching frequencies of the switching tubes Q1, Q2, Q3, and Q4, and the switching frequencies of the switching tubes Q1, Q2, Q3, and Q4 are kept synchronized. Among them, the driving signals of the switching tubes Q1 and Q2 are complementary, and the duty cycle is 0.5. The driving signals of the switching tubes Q3 and Q4 are complementary, and the duty cycle is 0.5. The switching tubes Q1 and Q4 operate in the same phase, and the switching tubes Q2 and Q3 operate in the same phase; no driving signals are applied to the secondary side switching tubes Q5, Q6, Q7, and Q8 of the CLLC resonant circuit, and rectification is achieved by relying on their anti-parallel diodes; in this mode, full-bridge inversion, parallel connection of the primary transformer, and parallel connection of the secondary transformer are realized, and the system voltage gain reaches 1 time of the original at this time. Among them, the waveforms of the switching tubes Q1, Q2, Q3, and Q4 are different.

[0117] Optionally, controlling the bidirectional CLLC resonant converter to operate in the forward 0.5x voltage mode may include the following steps:

[0118] When the third instruction is received, control the first primary side bidirectional switching tube and the first secondary side bidirectional switching tube to be in the normally closed state;

[0119] Control the second primary side bidirectional switching tube, the third primary side bidirectional switching tube, the second secondary side bidirectional switching tube, and the third secondary side bidirectional switching tube to be in the normally open state;

[0120] Control the first switching tube to be in the normally closed state and control the second switching tube to be in the normally open state;

[0121] Based on the switching frequencies corresponding to the third switching tube and the fourth switching tube, half-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 0.5x voltage mode.

[0122] It should be noted that, please refer to Figure 5, when the third instruction is received, this third instruction is to make the bidirectional CLLC resonant converter operate in the forward 0.5 - voltage - multiplication mode. The bidirectional switch tubes S1 and S4 are normally closed, and the bidirectional switch tubes S2, S3, S5, and S6 are normally open; the switch tube Q1 is normally closed, and the switch tube Q2 is normally open; the primary side of the CLLC resonant circuit performs half - bridge inversion by controlling the switching frequencies of the switch tubes Q3 and Q4, and the switching frequencies of the switch tubes Q3 and Q4 are kept synchronous, the drive signals of the switch tubes Q3 and Q4 are complementary, and the duty cycle is 0.5; no drive signals are applied to the secondary - side switch tubes Q5, Q6, Q7, and Q8 of the CLLC resonant circuit, and rectification is achieved by relying on their anti - parallel diodes; in this mode, half - bridge inversion, primary - side transformer parallel connection, and secondary - side transformer parallel connection are realized, and at this time, the system voltage gain reaches 0.5 times the original value.

[0123] Optionally, controlling the bidirectional CLLC resonant converter to operate in the forward 0.25 - voltage - multiplication mode may include the following steps:

[0124] When the fourth instruction is received, control the second primary - side bidirectional switch tube, the third primary - side bidirectional switch tube, and the first secondary - side bidirectional switch tube to be in the normally - closed state;

[0125] Control the first primary - side bidirectional switch tube, the second secondary - side bidirectional switch tube, and the third secondary - side bidirectional switch tube to be in the normally - open state;

[0126] Control the first switch tube to be in the normally - closed state and control the second switch tube to be in the normally - open state;

[0127] Based on the switching frequencies corresponding to the third switch tube and the fourth switch tube, perform half - bridge inversion on the primary - side full - bridge circuit and the primary - side resonant network, so that the bidirectional CLLC resonant converter operates in the forward 0.25 - voltage - multiplication mode.

[0128] It should be noted that, please refer to Figure 6 , when the fourth instruction is received, this fourth instruction is to make the bidirectional CLLC resonant converter operate in the forward 0.25 - voltage - multiplication mode. The bidirectional switch tubes S2, S3, and S4 are normally closed, and the bidirectional switch tubes S1, S5, and S6 are normally open; the switch tube Q1 is normally closed, and the switch tube Q2 is normally open; the primary side of the CLLC resonant circuit performs half - bridge inversion by controlling the switching frequencies of the switch tubes Q3 and Q4, and the switching frequencies of the switch tubes Q3 and Q4 are kept synchronous, the drive signals of the switch tubes Q3 and Q4 are complementary, and the duty cycle is 0.5; no drive signals are applied to the secondary - side switch tubes Q5, Q6, Q7, and Q8 of the CLLC resonant circuit, and rectification is achieved by relying on their anti - parallel diodes; in this mode, half - bridge inversion, primary - side transformer series connection, and secondary - side transformer parallel connection are realized, and at this time, the system voltage gain reaches 0.25 times the original value.

[0129] It is worth mentioning that through the coordinated control of the inverter side and the resonant cavity, the present invention can achieve an eight-fold gain ratio at the resonant frequency point.

[0130] Exemplarily, first, the parameters are set. The voltage of the primary DC source Vp is 480V, the voltage of the secondary DC source Vs is 10 - 144V. The inductance values of the primary resonant inductors Lp1 and Lp2 are both 246uH, and the inductance values of the secondary resonant inductors Ls1 and Ls2 are both 2.46uH; the inductance values of the exciting inductors Lm1 and Lm2 are both 73.9 uH; the capacitance values of the primary resonant capacitors Cp1 and Cp2 are both 10nF, and the capacitance values of the secondary resonant capacitors Cs1 and Cs2 are both 1uF; the resonant frequency fr of the two resonators is 100kHz, and the turns ratio of the transformers T1 and T2 is both 10:1.

[0131] In the forward 2 - voltage - multiplier mode, by adjusting the switching frequencies of the switching transistors Q1, Q2, Q3, and Q4 between 80kHz and 116kHz, an output voltage range of 144V - 70V can be obtained;

[0132] In the forward 1 - voltage - multiplier mode, by adjusting the switching frequencies of the switching transistors Q1, Q2, Q3, and Q4 between 80kHz and 130kHz, an output voltage range of 70V - 35V can be obtained;

[0133] In the forward 0.5 - voltage - multiplier mode, by adjusting the switching frequencies of the switching transistors Q3 and Q4 between 80kHz and 160kHz, an output voltage range of 35V - 15V can be obtained;

[0134] In the forward 0.25 - voltage - multiplier mode, by adjusting the switching frequencies of the switching transistors Q3 and Q4 between 80kHz and 130kHz, an output voltage range of 15V - 10V can be obtained;

[0135] In summary, the above data are integrated into Table 1.

[0136] Table 1 Simulation and Actual Test Results

[0137]

[0138] Furthermore, it can be seen from Table 1 that the actual gain ratio under this topology can reach more than 14 times, which can well meet the application scenarios of a wide gain range, and can meet the soft - switching of the bridge - arm switching transistors within a certain frequency, as Figure 7 shown.

[0139] It is worth mentioning that there are also four reverse operating modes for the bidirectional CLLC resonant converter proposed in the present invention, namely, reverse 2x voltage mode, reverse 1x voltage mode, reverse 0.5x voltage mode, and reverse 0.25x voltage mode. The control principle is the same as that of the above-mentioned forward operating mode.

[0140] For example, when controlling the bidirectional CLLC resonant converter to operate in the reverse 2x voltage mode, the second secondary bidirectional switch, the third secondary bidirectional switch in the secondary resonant network, and the first primary bidirectional switch in the primary resonant network are controlled to be always on. Based on the switching frequencies of the fifth, sixth, seventh, and eighth switches in the secondary full-bridge circuit, full-bridge inversion is performed on the secondary full-bridge circuit and the secondary resonant network, so that the bidirectional CLLC resonant converter operates in the reverse 2x voltage mode.

[0141] In an embodiment of the present invention, the present invention provides a control method for a bidirectional CLLC resonant converter. First, when it is necessary to make the bidirectional CLLC resonant converter operate in the forward 2x voltage mode, the first primary bidirectional switch in the primary resonant network, the second secondary bidirectional switch, and the third secondary bidirectional switch in the secondary resonant network are controlled to be always off; the second primary bidirectional switch, the third primary bidirectional switch in the primary resonant network, and the first secondary bidirectional switch in the secondary resonant network are controlled to be always on; based on the switching frequencies of the first, second, third, and fourth switches in the primary full-bridge circuit, full-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 2x voltage mode; based on the above scheme, by controlling the opening and closing states of the bidirectional switches and switches in the bidirectional CLLC resonant converter, and based on the switching frequencies of the first, second, third, and fourth switches, full-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in the forward 2x voltage mode. In the process, through the coordinated control of the primary and secondary sides and the resonant cavity of the present invention, wide-gain-range output can be achieved. At the same time, only one full-bridge is used on both the primary and secondary sides of the bidirectional CLLC resonant converter proposed in the present invention, which can reduce the number of switches participating in the work, thereby simplifying the topology structure.

[0142] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections between each other can be through some interfaces. The indirect couplings or communication connections of devices or units can be electrical, mechanical or other forms.

[0143] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0144] As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional CLLC resonant converter, characterized in that: It includes a primary full-bridge circuit, a primary resonant network, a secondary resonant network, a secondary full-bridge circuit, a primary DC source, a primary filter capacitor, a secondary DC source and a secondary filter capacitor; The primary DC source, the primary filter capacitor and the primary full-bridge circuit are connected in parallel; The primary full-bridge circuit is electrically connected to one end of the primary resonant network, and the other end of the primary resonant network is coupled to one end of the secondary resonant network; The other end of the secondary side resonant network is connected to the secondary side full bridge circuit; The secondary side DC source, the secondary side filter capacitor and the secondary side full bridge circuit are connected in parallel; The primary full-bridge circuit comprises a first bridge arm and a second bridge arm connected in parallel; The primary DC source, the primary filter capacitor, the first bridge arm and the second bridge arm are connected in parallel; The first bridge arm and the second bridge arm are both electrically connected to one end of the primary resonant network; The primary resonant network includes a first transformer primary winding, a second transformer primary winding, a first primary resonant inductor, a second primary resonant inductor, a first primary resonant capacitor, a second primary resonant capacitor, a first primary magnetizing inductor, a second primary magnetizing inductor and three primary bidirectional switch tubes; The first bridge arm includes a first switch tube and a second switch tube connected in series, and the second bridge arm includes a third switch tube and a fourth switch tube connected in series; The upper end of the primary winding of the first transformer is connected to the connection point between the third switch tube and the fourth switch tube through the first primary resonant inductor and the first primary resonant capacitor; The lower end of the primary winding of the first transformer is connected to the connection point between the first switch tube and the second switch tube through a second primary bidirectional switch tube; The upper end of the primary winding of the second transformer is connected to the lower end of the primary winding of the first transformer through a first primary bidirectional switch tube, and is connected to a connection point between the third switch tube and the fourth switch tube through a third primary bidirectional switch tube; The lower end of the primary winding of the second transformer is connected to the connection point between the first switch tube and the second switch tube through the second primary resonant inductor and the second primary resonant capacitor; The first transformer primary winding is connected in parallel with the first primary excitation inductor, and the second transformer primary winding is connected in parallel with the second primary excitation inductor; The first transformer primary winding and the second transformer primary winding are both coupled to the secondary resonant network.

2. The bidirectional CLLC resonant converter according to claim 1, characterized in that: The secondary full-bridge circuit comprises a third bridge arm and a fourth bridge arm connected in parallel; The secondary side DC source, the secondary side filter capacitor, the third bridge arm and the fourth bridge arm are connected in parallel; The third bridge arm and the fourth bridge arm are both electrically connected to the other end of the secondary side resonant network.

3. The bidirectional CLLC resonant converter according to claim 2, characterized in that: The secondary resonant network includes a first transformer secondary winding, a second transformer secondary winding, a first secondary resonant inductor, a second secondary resonant inductor, a first secondary resonant capacitor, a second secondary resonant capacitor and three secondary bidirectional switch tubes; The third bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series; The upper end of the secondary winding of the first transformer is connected to the connection point between the seventh switch tube and the eighth switch tube through the first secondary resonant inductor and the first secondary resonant capacitor; The lower end of the secondary winding of the first transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through the second secondary bidirectional switch tube; The upper end of the secondary winding of the second transformer is connected to the lower end of the secondary winding of the first transformer through the first secondary bidirectional switch tube, and is connected to the connection point between the seventh switch tube and the eighth switch tube through the third secondary bidirectional switch tube; The lower end of the secondary winding of the second transformer is connected to the connection point between the fifth switch tube and the sixth switch tube through the second secondary resonant inductor and the second secondary resonant capacitor; The secondary winding of the first transformer is coupled to the primary winding of the first transformer in the primary resonant network; The secondary winding of the second transformer is coupled to the primary winding of the second transformer in the primary resonant network.

4. The bidirectional CLLC resonant converter according to claim 3, characterized in that: The secondary bidirectional switch tube and the primary bidirectional switch tube in the primary resonant network are both composed of two back-to-back switch tubes connected in series.

5. A control method for a bidirectional CLLC resonant converter, characterized in that: Applied to the bidirectional CLLC resonant converter according to claim 1, the method comprises: When the first instruction is received, the first primary bidirectional switch tube in the primary resonant network, the second secondary bidirectional switch tube in the secondary resonant network, and the third secondary bidirectional switch tube are controlled to be in a normally closed state; Controlling the second primary bidirectional switch tube, the third primary bidirectional switch tube in the primary resonant network, and the first secondary bidirectional switch tube in the secondary resonant network to be in a normally open state; Based on the switching frequencies corresponding to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in the primary full-bridge circuit, full-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in a forward 2-fold voltage mode.

6. The control method of the bidirectional CLLC resonant converter according to claim 5, characterized in that: Also includes: When receiving the second instruction, controlling the first primary bidirectional switch tube and the first secondary bidirectional switch tube to be in a normally closed state; Controlling the second primary bidirectional switch tube, the third primary bidirectional switch tube, the second secondary bidirectional switch tube, and the third secondary bidirectional switch tube to be in a normally open state; Based on the switching frequencies corresponding to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, full-bridge inversion is performed on the primary full-bridge circuit and the primary resonant network, so that the bidirectional CLLC resonant converter operates in a forward 1 times voltage mode.

7. The control method of the bidirectional CLLC resonant converter according to claim 5, characterized in that: Also includes: When receiving the third instruction, controlling the first primary-side bidirectional switch tube and the first secondary-side bidirectional switch tube to be in a normally closed state; Controlling the second primary bidirectional switch tube, the third primary bidirectional switch tube, the second secondary bidirectional switch tube, and the third secondary bidirectional switch tube to be in a normally open state; Controlling the first switch tube to be in a normally closed state, and controlling the second switch tube to be in a normally open state; Based on the switching frequencies corresponding to the third switch tube and the fourth switch tube, the primary full-bridge circuit and the primary resonant network are half-bridge inverted, so that the bidirectional CLLC resonant converter operates in a forward 0.5 times voltage mode.

8. The control method of the bidirectional CLLC resonant converter according to claim 5, characterized in that: Also includes: When receiving the fourth instruction, the second primary bidirectional switch tube, the third primary bidirectional switch tube, and the first secondary bidirectional switch tube are controlled to be in a normally closed state; Controlling the first primary bidirectional switch tube, the second secondary bidirectional switch tube, and the third secondary bidirectional switch tube to be in a normally open state; Controlling the first switch tube to be in a normally closed state, and controlling the second switch tube to be in a normally open state; Based on the switching frequencies corresponding to the third switch tube and the fourth switch tube, the primary full-bridge circuit and the primary resonant network are half-bridge inverted, so that the bidirectional CLLC resonant converter operates in a forward 0.25 times voltage mode.

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