Bidirectional CLLC resonant converter and control method thereof

Abstract

The invention discloses a bidirectional CLLC resonant converter and a control method thereof, which are used for solving the technical problem that the topological structure is too complicated due to the existing bidirectional CLLC resonant converter. The circuit comprises a primary side full-bridge circuit, a primary side resonance network, a secondary side resonance network, a secondary side full-bridge circuit, a primary side direct current source, a primary side filter capacitor, a secondary side direct current source and a secondary side filter capacitor. The primary side direct current source, the primary side filter capacitor and the primary side full-bridge circuit are connected in parallel; the primary side full-bridge circuit is electrically connected with one end of the primary side resonance network, and the other end of the primary side resonance network is coupled with one end of the secondary side resonance network; the other end of the secondary side resonance network is connected with the secondary side full-bridge circuit; and 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 in particular 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 profound changes. The popularity 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 bidirectional energy flow characteristics, where C represents capacitance and L represents inductance.

[0003] The bidirectional CLLC resonant converter can not only realize bidirectional energy transmission, but also has high transmission efficiency. It can realize zero voltage switching (Zero-Voltage Switching, ZVS) of the primary side switch tube and zero current shutdown (Zero-Current Switch, 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, which is more efficient than the non-resonant topology and is increasingly widely used.

[0004] Most of the existing bidirectional CLLC resonant converters use the form of connecting both the primary and secondary sides in parallel 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. Different voltage gain ranges are achieved by adjusting the series-parallel and half-full-bridge modes of the primary side. However, both the primary and secondary sides of the converter use two full-bridge parallel connections, which results in an excessive number of MOS tubes (switch tubes) participating in the resonance, resulting in an overly complex topology. 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 causes the topology structure to be too complicated.

[0006] A bidirectional CLLC resonant converter provided in a first aspect of the present invention comprises 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] 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 side resonant network is connected to the secondary side full bridge circuit;

[0010] The secondary side DC source, the secondary side filter capacitor and the secondary side 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] The first bridge arm and the second bridge arm are both electrically connected to one end of the primary resonant network.

[0014] Optionally, 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;

[0015] 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;

[0016] 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;

[0017] 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;

[0018] 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;

[0019] 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;

[0020] 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;

[0021] The first transformer primary winding and the second transformer primary winding are both coupled 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] The third bridge arm and the fourth bridge arm are both electrically connected to the other end of the secondary side resonant network.

[0025] Optionally, 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;

[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 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;

[0028] 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;

[0029] 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;

[0030] 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;

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

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

[0033] Optionally, 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.

[0034] A second aspect of the present invention provides a control method for a bidirectional CLLC resonant converter, which is applied to the bidirectional CLLC resonant converter described above, comprising:

[0035] When the first instruction is received, the first primary bidirectional switch tube in the primary resonance network, the second secondary bidirectional switch tube in the secondary resonance network, and the third secondary bidirectional switch tube are controlled to be in a normally closed state;

[0036] 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;

[0037] 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.

[0038] Optionally, it also includes:

[0039] 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;

[0040] 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;

[0041] 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.

[0042] Optionally, it also includes:

[0043] 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;

[0044] 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;

[0045] 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;

[0046] 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.

[0047] Optionally, it also includes:

[0048] 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;

[0049] 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;

[0050] 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;

[0051] 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.

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

[0053] The first aspect of the above technical scheme 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; 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 and connected 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 scheme, the bidirectional CLLC resonant converter proposed in the present invention uses only one full bridge on both the primary and secondary sides, which can reduce the number of switching tubes involved in the work, thereby simplifying the topological structure.

[0054] The second aspect of the above technical solution of the present invention provides a control method for a bidirectional CLLC resonant converter, which is applied to the bidirectional CLLC resonant converter proposed in the present invention. First, when it is necessary to make the bidirectional CLLC resonant converter operate in the forward 2x voltage mode, 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; the second primary bidirectional switch tube in the primary resonant network, the third primary bidirectional switch tube, and the first secondary bidirectional switch tube in the secondary resonant network are controlled 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, the primary full-bridge circuit is controlled to be normally open. The present invention relates to a process in which a bidirectional CLLC resonant converter operates in a forward 2-fold voltage mode by performing full-bridge inversion on a primary-side full-bridge circuit and a primary-side resonant network. The process in which a bidirectional CLLC resonant converter operates in a forward 2-fold voltage mode is performed by controlling the on / off states of the bidirectional switch tube and the switch tube 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, the primary-side full-bridge circuit and the primary-side resonant network are full-bridge inverted. The process in which the bidirectional CLLC resonant converter operates in a forward 2-fold voltage mode is performed. The present invention can achieve output in a wide gain range through coordinated control of the primary-secondary side and the resonant cavity. At the same time, the bidirectional CLLC resonant converter proposed in the present invention uses only one full-bridge on both the primary and secondary sides, which can reduce the number of switch tubes involved in the work, thereby simplifying the topological structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 1 of the present invention;

[0057] Figure 2 A flow chart of the steps of a control method for a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention;

[0058] Figure 3 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention operating in a 2-times voltage mode;

[0059] Figure 4 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention operating in a 1x voltage mode;

[0060] Figure 5 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention operating in a 0.5 times voltage mode;

[0061] Figure 6 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 2 of the present invention operating in a 0.25 times voltage mode;

[0062] Figure 7 A waveform diagram of soft switching provided in the second embodiment of the present invention.

[0063] 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 DESCRIPTION

[0065] The embodiment of 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 causes the topology structure to be too complicated.

[0066] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] See also Figure 1 , Figure 1 A schematic diagram of the structure of a bidirectional CLLC resonant converter provided in Embodiment 1 of the present invention.

[0068] The present invention provides a bidirectional CLLC resonant converter, which includes a primary full-bridge circuit 1, a primary resonant network 2, a secondary resonant network 3, a secondary full-bridge circuit 4, 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 1 are connected in parallel; the primary full-bridge circuit 1 is electrically connected to one end of the primary resonant network 2, and the other end of the primary resonant network 2 is coupled and connected to one end of the secondary resonant network 3; the other end of the secondary resonant network 3 is connected to the secondary full-bridge circuit 4; the secondary DC source, the secondary filter capacitor and the secondary 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 in the present invention comprises a primary full-bridge circuit 1, a primary resonant network 2, a secondary resonant network 3, a secondary full-bridge circuit 4, a primary DC source VP , primary filter capacitor C in , secondary DC source V s And the secondary filter capacitor C out , and both sides have symmetry properties.

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

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

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

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

[0074] As a further improvement, the primary resonant network 2 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;

[0075] 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;

[0076] 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;

[0077] 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 the second primary bidirectional switch tube;

[0078] 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 the first primary bidirectional switch tube, and is connected to the connection point between the third switch tube and the fourth switch tube through the third primary bidirectional switch tube;

[0079] 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;

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

[0081] The first transformer primary winding and the second transformer primary winding are both coupled 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 excitation inductor Lm1 and the second primary excitation inductor Lm2; wherein the upper end X1 of the primary winding of the first transformer T1 is connected to the midpoint B of the second bridge arm (the 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, the lower end Y1 of the primary winding of the first transformer T1 is connected to the midpoint A of the first bridge arm (the 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, It 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 excitation inductor Lm1 is connected in parallel with the primary winding of the first transformer T1, and the second primary excitation 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 consists 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 side DC source, the secondary side filter capacitor, the third bridge arm and the fourth bridge arm are connected in parallel;

[0086] The third bridge arm and the fourth bridge arm are both electrically connected to the other end of the secondary side 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 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;

[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 the first secondary resonant inductor and the 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 the 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 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;

[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 the second secondary resonant inductor and the 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 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; wherein the upper end Z1 of the secondary winding of the first transformer T1 is connected to the midpoint D of the fourth bridge arm (the 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 W of the secondary winding of the first transformer T1 is connected to the middle point D of the fourth bridge arm through the first secondary resonant inductor Ls1 and the first secondary resonant capacitor Cs1. 1 is connected to the midpoint C of the third bridge arm (the 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 in 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 parameters of the secondary resonant cavity satisfy Lp1= Lp2=n²Ls1=n²Ls2, Cp1= Cp2=Cs1 / n²= Cs2 / n².

[0098] Furthermore, when the resonant converter is in forward operation, the midpoint of the first bridge arm and the second bridge arm of the primary side serves as the input end of the converter, and the midpoint of the third bridge arm and the fourth bridge arm of the secondary side serves as the output end of the converter; when the resonant converter is in reverse operation, the midpoint of the third bridge arm and the fourth bridge arm of the secondary side serves as the input end of the converter, and the midpoint of the first bridge arm and the second bridge arm of the primary side serves as the output end of the converter.

[0099] As a comparison of technical effects, it can be combined with existing technologies for reference. With the rapid development of new energy and energy storage technologies, the global energy structure is undergoing profound changes. The popularity 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 for its unique bidirectional energy flow characteristics. Among them, the CLLC resonant converter is an efficient DC-DC converter that is widely used in power management systems, especially in situations where high power and high efficiency are required. It is mainly composed of inductor and capacitor components, and uses the resonance principle to achieve energy conversion. However, in order to meet the requirements of a wide output voltage range, the traditional bidirectional CLLC resonant converter 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 CLLC resonant converter: two CLLC resonant converters are combined in the form of parallel connection of the primary and secondary sides, and then a bidirectional MOS switch is used to connect the two resonant cavities to control the series-parallel form of the resonant cavities, and different voltage gain ranges are achieved by adjusting the series-parallel and primary half-full-bridge modes.

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

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

[0102] In summary, the bidirectional CLLC resonant converter proposed in the present invention connects the transformers in two resonant cavities in series and parallel in a full bridge, has multiple operating modes, can meet the operating requirements of bidirectional DC-DC converters in different fields and complex working conditions, and has a wider gain range by adjusting the switching frequency and the operating mode. The gain ratio is 8 at the same frequency; adding frequency modulation can make the actual gain ratio reach 14. At the same time, the present invention only uses one full bridge, which reduces the number of switching tubes involved in the work, and the switching tubes realize soft switching action 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; 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 and connected 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 scheme, the bidirectional CLLC resonant converter proposed in the present invention uses only one full bridge on both the primary and secondary sides, which can reduce the number of switching tubes involved in the work, thereby simplifying the topological structure, and at the same time, it can also make the coordinated control of the primary and secondary sides and the resonant cavity simpler.

[0104] See also Figure 2 , Figure 2 A flow chart of the steps of a control method for a bidirectional CLLC resonant converter provided in Embodiment 2 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, comprising:

[0106] Step 201: When a first instruction is received, a first primary bidirectional switch in a primary resonant network, a second secondary bidirectional switch, and a third secondary bidirectional switch in a secondary resonant network are controlled to be in a normally closed state.

[0107] Step 202: 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 a normally-on state.

[0108] Step 203: 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 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, the primary and secondary sides and the resonant cavity are coordinated to achieve a wide gain range output. Specifically, since the topological structure of the present invention is bilaterally symmetrical, the forward operation and reverse operation modes are symmetrical; when the system works 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 works 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] The bidirectional CLLC resonant converter proposed in the present invention has four forward operation modes, namely, a forward 2-times voltage mode, a forward 1-times voltage mode, a forward 0.5-times voltage mode and a forward 0.25-times voltage mode.

[0111] Specifically, see Figure 3 , when the first instruction is received, the first instruction is that the bidirectional CLLC resonant converter needs to operate in the forward 2-fold voltage mode, the bidirectional switches S1, S5 and S6 are normally closed, and the bidirectional switches S2, S3 and S4 are normally open; the primary side of the CLLC resonant circuit performs full-bridge inversion by controlling the switching frequency of the switches Q1, Q2, Q3 and Q4, and the switching frequencies of the switches Q1, Q2, Q3 and Q4 are kept synchronous, wherein the drive signals of the switches Q1 and Q2 are complementary, and the duty cycle is 0.5, the drive signals of the switches Q3 and Q4 are complementary, and the duty cycle is 0.5, the switches Q1 and Q4 operate in the same phase, and the switches Q2 and Q3 operate in the same phase; the secondary side switches Q5, Q6, Q7 and Q8 of the CLLC resonant circuit are not applied with drive signals, and rectification is achieved by relying on their anti-parallel diodes; in this mode, full-bridge inversion, parallel connection of the primary transformer and series connection of the secondary transformer are realized, and the system voltage gain is twice the original; wherein, Figure 3 A normally open bidirectional switch tube is represented by a straight line, and a normally closed bidirectional switch tube is represented by a translucent line.

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

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

[0114] 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;

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

[0116] Please note that Figure 4 When the second instruction is received, the second instruction is to make the bidirectional CLLC resonant converter work in the forward 1-fold voltage mode, the bidirectional switches S1 and S4 are normally closed, and the bidirectional switches 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 switches Q1, Q2, Q3, and Q4, and the switching frequencies of the switches Q1, Q2, Q3, and Q4 are kept synchronous, wherein the drive signals of the switches Q1 and Q2 are complementary, and the duty cycle is 0.5, the drive signals of the switches Q3 and Q4 are complementary, and the duty cycle is 0.5, the switches Q1 and Q4 operate in the same phase, and the switches Q2 and Q3 operate in the same phase; the secondary side switches Q5, Q6, Q7, and Q8 of the CLLC resonant circuit are not applied with drive signals, 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 times the original. 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 a forward 0.5 times voltage mode may include the following steps:

[0118] When the third instruction is received, the first primary-side bidirectional switch tube and the first secondary-side bidirectional switch tube are controlled to be in a normally closed state;

[0119] 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;

[0120] 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;

[0121] 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 the forward 0.5 times voltage mode.

[0122] Please note that Figure 5When the third instruction is received, the third instruction is to make the bidirectional CLLC resonant converter work in the forward 0.5 times voltage mode, the bidirectional switches S1 and S4 are normally closed, and the bidirectional switches 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 inverter by controlling the switching frequency of the switch tubes Q3 and Q4, and the switching frequency of the switch tubes Q3 and Q4 is kept synchronous, the drive signals of the switch tubes Q3 and Q4 are complementary, and the duty cycle is 0.5; the secondary side switches Q5, Q6, Q7, and Q8 of the CLLC resonant circuit are not applied with drive signals, and rectification is achieved by relying on their anti-parallel diodes; in this mode, half-bridge inverter, primary transformer parallel connection, and secondary transformer parallel connection are realized, and the system voltage gain reaches 0.5 times the original.

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

[0124] When the fourth instruction is received, 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;

[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 a normally-on state;

[0126] 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;

[0127] 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 the forward 0.25 times voltage mode.

[0128] Please note that Figure 6 When the fourth instruction is received, the fourth instruction is to make the bidirectional CLLC resonant converter work in the forward 0.25 times voltage mode, the bidirectional switches S2, S3, and S4 are normally closed, and the bidirectional switches 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 inverter by controlling the switching frequency of the switch tubes Q3 and Q4, and the switching frequency of the switch tubes Q3 and Q4 is kept synchronous, the drive signals of the switch tubes Q3 and Q4 are complementary, and the duty cycle is 0.5; the secondary side switches Q5, Q6, Q7, and Q8 of the CLLC resonant circuit are not applied with drive signals, and rectification is achieved by relying on their anti-parallel diodes; in this mode, half-bridge inverter, primary side transformer series connection and secondary side transformer parallel connection are realized, and the system voltage gain reaches 0.25 times the original.

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

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

[0131] In the forward 2x voltage mode, by adjusting the switching frequency of the switch tubes Q1, Q2, Q3 and Q4 between 80khz and 116khz, the output voltage range can be 144V~70V;

[0132] In the forward 1x voltage mode, by adjusting the switching frequency of the switch tubes Q1, Q2, Q3 and Q4 between 80khz and 130khz, the output voltage range can be 70V to 35V;

[0133] In the forward 0.5 times voltage mode, by adjusting the switching frequency of the switch tubes Q3 and Q4 between 80khz and 160khz, the output voltage range can be 35V~15V;

[0134] In the forward 0.25 times voltage mode, by adjusting the switching frequency of the switch tubes Q3 and Q4 between 80khz and 130khz, the output voltage range can be 15V~10V;

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

[0136] Table 1 Simulation 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 with a wide gain range and can meet the soft switching of the bridge arm switch tube within a certain frequency, such 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 2 times voltage mode, reverse 1 times voltage mode, reverse 0.5 times voltage mode and reverse 0.25 times voltage mode, and their control principles are consistent with the control principles of the above-mentioned forward operating mode.

[0140] For example, when the bidirectional CLLC resonant converter is controlled to be in the reverse 2-times voltage mode, the second secondary bidirectional switch tube, the third secondary bidirectional switch tube, and the first primary bidirectional switch tube in the primary resonant network are controlled to be in the normally open state. Based on the switching frequencies corresponding to the fifth switch tube, the sixth switch tube, the seventh switch tube, and the eighth switch tube in the secondary full-bridge circuit, the secondary full-bridge circuit and the secondary resonant network are fully inverted, so that the bidirectional CLLC resonant converter operates in the reverse 2-times 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 the bidirectional CLLC resonant converter needs to operate in a forward 2-fold voltage mode, 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; the second primary bidirectional switch tube in the primary resonant network, the third primary bidirectional switch tube, and the first secondary bidirectional switch tube in the secondary resonant network are controlled 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, the primary full-bridge circuit and the primary resonant network are controlled to be normally open. Full-bridge inversion is performed to make the bidirectional CLLC resonant converter work in the forward 2-times voltage mode; based on the above scheme, by controlling the on-off state of the bidirectional switch tube and the switch tube 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, the primary full-bridge circuit and the primary resonant network are full-bridge inverted to make the bidirectional CLLC resonant converter work in the forward 2-times voltage mode. The present invention can achieve a wide gain range output through the coordinated control of the primary and secondary sides and the resonant cavity. At the same time, the bidirectional CLLC resonant converter proposed in the present invention uses only one full-bridge on both the primary and secondary sides, which can reduce the number of switch tubes involved in the work, thereby simplifying the topological structure.

[0142] In the 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 only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as 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 mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

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

[0144] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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.

2. The bidirectional CLLC resonant converter according to claim 1, characterized in that: 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.

3. The bidirectional CLLC resonant converter according to claim 2, characterized in that: 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.

4. 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.

5. The bidirectional CLLC resonant converter according to claim 4, 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.

6. The bidirectional CLLC resonant converter according to claim 5, 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.

7. 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.

8. The control method of the bidirectional CLLC resonant converter according to claim 7, 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.

9. The control method of the bidirectional CLLC resonant converter according to claim 7, 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.

10. The control method of the bidirectional CLLC resonant converter according to claim 7, 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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