Magnetic integrated planar transformer structure for CLLC resonant converter

Abstract

The magnetic integrated planar transformer structure comprises a magnetic core assembly, the magnetic core assembly comprises a magnetic core top plate and a magnetic core base which are matched with each other, and a through groove is formed in the center of the top of the magnetic core base in the length direction, so that a first non-winding magnetic column and a second non-winding magnetic column are formed on the top of the magnetic core base; a first winding magnetic column and a second winding magnetic column are arranged in the through groove at an interval; np1 turns of first windings are wound on the first winding magnetic column, Np2 turns of second windings are wound on the second winding magnetic column, and the first windings and the second windings are connected in series to form a primary side winding of the transformer; ns1 turns of third windings are wound on the first winding magnetic column, Ns2 turns of fourth windings are wound on the second winding magnetic column, and the third windings and the fourth windings are connected in series to form a secondary side winding of the transformer. The magnetic flux density of the magnetic core top plate can be reduced, the magnetic core loss of the magnetic core assembly is reduced, the converter efficiency is improved, and the use requirement of an underwater platform is met.

Description

Technical Field

[0001] The present invention relates to the technical field of transformers, and in particular to a magnetically integrated planar transformer structure for a CLLC resonant converter. Background Art

[0002] The CLLC resonant converter includes a full-bridge inverter circuit composed of MOSFET switching tubes, a full-bridge rectifier circuit, and a resonant network; wherein, the resonant network includes two resonant capacitors, two resonant inductors, and a transformer. The resonant converter can achieve zero-voltage turn-on of the primary-side switching tubes and zero-current turn-off of the secondary-side switching tubes by utilizing the characteristics of the resonant cavity, thereby improving the efficiency of the converter as a whole. However, the CLLC resonant converter requires two resonant inductors and a transformer. If three independent magnetic components are used, the volume of the CLLC resonant converter will be relatively large. In order to miniaturize the CLLC resonant converter, a magnetic integration scheme can be adopted to reduce the volume of the CLLC resonant converter.

[0003] In the prior art, by using a low-permeability material as a magnetic shunt to form an additional magnetic path, the integration of the transformer and the resonant inductor in the CLLC resonant converter is achieved. However, the setting of the magnetic shunt makes the transformer structure very complex, resulting in a large volume; at the same time, all the leakage magnetic fluxes are concentrated on the central magnetic column, resulting in large core losses and reducing the converter efficiency, making it difficult to meet the requirements of compact volume, high power density, and high efficiency for underwater platforms. Summary of the Invention

[0004] The applicant of the present invention aims at the above-mentioned disadvantages in the existing production technology, and provides a magnetically integrated planar transformer structure for a CLLC resonant converter with a reasonable structure. By setting a magnetic core assembly, it has a compact structure and can effectively reduce the volume of the CLLC resonant converter equipped with the transformer structure of the present invention; at the same time, it can reduce the magnetic flux density on the magnetic core top plate, reduce the core loss of the magnetic core assembly, improve the converter efficiency, and meet the usage requirements of underwater platforms.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A magnetically integrated planar transformer structure for a CLLC resonant converter includes a magnetic core assembly. The magnetic core assembly includes a magnetic core top plate and a magnetic core base that cooperate with each other. A through groove is formed in the center of the top of the magnetic core base along the length direction, so as to form a first non-winding magnetic column and a second non-winding magnetic column on the top of the magnetic core base. The first non-winding magnetic column and the second non-winding magnetic column are spaced apart along the width direction of the magnetic core base, and a first winding magnetic column and a second winding magnetic column are spaced in the through groove;

[0007] The first winding magnetic column is wound with N p1The first winding is wound around the first winding magnetic post, and the second winding is wound around the second winding magnetic post with N p2 turns. The first winding and the second winding are connected in series to form the primary side winding of the transformer;

[0008] The first winding magnetic post is wound with N s1 turns of the third winding, and the second winding magnetic post is wound with N s2 turns of the fourth winding. The third winding and the fourth winding are connected in series to form the secondary side winding of the transformer;

[0009] The primary side winding is connected to an alternating current, and the secondary side winding outputs an induced electromotive force under the action of electromagnetic induction, so as to perform voltage conversion. At the same time, the leakage magnetic fluxes generated in the first winding magnetic post and the second winding magnetic post form a closed leakage magnetic flux path through the first non-winding magnetic post and the second non-winding magnetic post.

[0010] As a further improvement of the above technical solution:

[0011] Both the first winding magnetic post and the second winding magnetic post are cylindrical.

[0012] The first winding magnetic post and the second winding magnetic post are spaced apart along the length direction of the magnetic core base.

[0013] The first winding, the second winding, the third winding, and the fourth winding all adopt PCB windings.

[0014] Along the height direction, the magnetic core top plate is arranged above the magnetic core base at intervals.

[0015] The leakage magnetic fluxes distributed on the first non-winding magnetic post and the second non-winding magnetic post respectively generate leakage inductances, and the leakage inductances are used as the resonant inductances in the CLLC resonant converter.

[0016] The first winding and the third winding on the first winding magnetic post adopt an asymmetric distribution method.

[0017] The second winding and the fourth winding on the second winding magnetic post adopt an asymmetric distribution method.

[0018] The winding directions of the first winding and the second winding are opposite, and the winding directions of the third winding and the fourth winding are opposite.

[0019] The winding directions of the first winding and the third winding are opposite, and the winding directions of the second winding and the fourth winding are opposite.

[0020] The beneficial effects of the present invention are as follows:

[0021] The structure of the present invention is compact and reasonable, and it is convenient to operate. By setting a magnetic core top plate and a magnetic core base, one transformer and two inductors in the resonant network can be integrated into the magnetic core assembly, thereby realizing the integration of the transformer and the resonant inductor in the CLLC resonant converter, reducing the volume and weight of the converter, improving the efficiency and power density, and meeting the usage requirements of the underwater platform.

[0022] The present invention also has the following advantages:

[0023] (1) By setting the first non-winding magnetic post and the second non-winding magnetic post and arranging the first non-winding magnetic post and the second non-winding magnetic post on both sides of the first winding magnetic post and the second winding magnetic post, the magnetic flux loop of the leakage magnetic flux on the magnetic core top plate can be increased, thereby reducing the magnetic flux density on the magnetic core top plate and reducing the magnetic core loss of the magnetic core assembly.

[0024] (2) By setting the first winding, the third winding, the second winding, and the fourth winding in an asymmetric distribution manner, the coupling between the primary side winding and the secondary side winding can be actively reduced, and the leakage inductance of the primary side winding and the secondary side winding can be increased, thereby realizing the leakage inductance of the primary side winding and the leakage inductance of the secondary side winding acting as the resonant inductance of the CLLC resonant converter, and further realizing the magnetic integration of the transformer and the resonant inductance.

[0025] (3) By making both the first winding magnetic post and the second winding magnetic post cylindrical, it is beneficial to the uniform winding of the windings, improves the winding efficiency and quality, and reduces the winding loss. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the present invention.

[0027] Figure 2 It is a circuit topology diagram of the CLLC resonant converter.

[0028] Figure 3 It is a magnetic circuit equivalent model diagram of the present invention.

[0029] Figure 4 It is a front view of the present invention.

[0030] Figure 5 It is a left view of the present invention.

[0031] Figure 6 It is a schematic diagram of the result of magnetic simulation by finite element software.

[0032] Wherein: 1. The first winding magnetic post; 2. The second winding magnetic post; 3. The first non-winding magnetic post; 4. The second non-winding magnetic post; 5. The magnetic core top plate; 6. The magnetic core base; 7. The first concave arc surface; 8. The second concave arc surface; 9. The through groove. Detailed Embodiments

[0033] The following will describe the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0034] The structure and function of the present invention are as follows:

[0035] As Figures 1-6 shown, a magnetically integrated planar transformer structure for a CLLC resonant converter includes a magnetic core assembly. The magnetic core assembly includes a magnetic core top plate 5 and a magnetic core base 6 that cooperate with each other. A through groove 9 is formed in the center of the top of the magnetic core base 6 along the length direction, thereby forming a first non-winding magnetic column 3 and a second non-winding magnetic column 4 on the top of the magnetic core base 6. The first non-winding magnetic column 3 and the second non-winding magnetic column 4 are spaced apart along the width direction of the magnetic core base 6. A first winding magnetic column 1 and a second winding magnetic column 2 are disposed at intervals in the through groove 9; an N p1 turn first winding is wound on the first winding magnetic column 1, and an N p2 turn second winding is wound on the second winding magnetic column 2. The first winding and the second winding are connected in series to form the primary side winding of the transformer; an N s1 turn third winding is wound on the first winding magnetic column 1, and an N s2 turn fourth winding is wound on the second winding magnetic column 2. The third winding and the fourth winding are connected in series to form the secondary side winding of the transformer; the primary side winding is connected to an alternating current, and the secondary side winding outputs an induced electromotive force under the action of electromagnetic induction, thereby performing voltage conversion. At the same time, the leakage magnetic flux generated in the first winding magnetic column 1 and the second winding magnetic column 2 forms a closed leakage magnetic flux path through the first non-winding magnetic column 3 and the second non-winding magnetic column 4. By providing the magnetic core top plate 5 and the magnetic core base 6, a transformer and two inductors in the resonant network can be integrated into the magnetic core assembly, thereby realizing the integration of the transformer and the resonant inductor in the CLLC resonant converter; by providing the first non-winding magnetic column 3 and the second non-winding magnetic column 4 distributed on both sides of the first winding magnetic column 1 and the second winding magnetic column 2, the magnetic flux loop of the leakage magnetic flux on the magnetic core top plate 5 can be increased, thereby reducing the magnetic flux density on the magnetic core top plate 5 and reducing the core loss of the magnetic core assembly.

[0036] The transformer structure of the present invention is used in a CLLC resonant converter. The circuit topology diagram of the CLLC resonant converter is as Figure 2 shown, which includes a primary side inverter network composed of an input capacitor C in , a metal-oxide-semiconductor field-effect transistor Q1, a metal-oxide-semiconductor field-effect transistor Q2, a metal-oxide-semiconductor field-effect transistor Q3, and a metal-oxide-semiconductor field-effect transistor Q4, a secondary side inverter network composed of a metal-oxide-semiconductor field-effect transistor Q5, a metal-oxide-semiconductor field-effect transistor Q6, a metal-oxide-semiconductor field-effect transistor Q7, a metal-oxide-semiconductor field-effect transistor Q8, and an output capacitor C out , and a resonant network between the two inverter networks. The resonant network includes two resonant inductors L r1 , L r2 , a transformer T, and two resonant capacitors Cr1 , C r2 , and an exciting inductance L m . The transformer structure of the present invention integrates two resonant inductances L r1 , L r2 in the resonant network and a transformer T. In the present invention, a primary side winding formed by connecting in series a first winding wound around a first winding magnetic post 1 and a second winding wound around a second winding magnetic post 2, and a secondary side winding formed by connecting in series a third winding wound around the first winding magnetic post 1 and a fourth winding wound around the second winding magnetic post 2, as Figure 4 shown, a coupled magnetic flux path is formed between the primary side winding and the secondary side winding to realize the voltage conversion function of the transformer T; by providing a first non-winding magnetic post 3 and a second non-winding magnetic post 4, a path is provided for the leakage magnetic flux generated in the first winding magnetic post 1 and the second winding magnetic post 2. The leakage magnetic flux path is as Figure 5 shown. The leakage magnetic fluxes distributed on the first non-winding magnetic post 3 and the second non-winding magnetic post 4 respectively generate leakage inductances, and the leakage inductances are used as the resonant inductances L r1 , L r2 in the CLLC resonant converter, thereby realizing the integration of two resonant inductances L r1 , L r2 and a transformer T, which can compact the structure, effectively reduce the volume of the CLLC resonant converter, and is more suitable for the use requirements of underwater platforms.

[0037] As Figure 6 shown, among them, Figure (a) shows the Maxwell simulation result diagram of the integration scheme of the transformer and the resonant inductance in the CLLC resonant converter based on low magnetic permeability materials in the prior art, and Figure (b) shows the Maxwell simulation result of the transformer structure of the present invention; by comparing Figure (a) with Figure (b), it can be seen that compared with the prior art, the overall magnetic flux density of the transformer structure of the present invention is significantly reduced, and the core loss is significantly decreased, having more excellent performance.

[0038] As Figures 2-3 shown, by controlling the number of turns N p1 of the first winding, the number of turns N p2 of the second winding, the number of turns N s1 of the third winding, the number of turns N s2 of the fourth winding, and the air gaps of the first winding magnetic post 1, the second winding magnetic post 2, the first non-winding magnetic post 3 and the second non-winding magnetic post 4, jointly control the inductance value of the exciting inductance L m , the inductance value of the resonant inductance L r1 , the inductance value of the resonant inductance L r2 , and the inductance ratio K. The specific parameter adjustment process is as follows:

[0039] The magnetic circuit equivalent model of the transformer structure of the present invention is as follows Figure 3 As shown, based on Ohm's law of the magnetic circuit, the magnitudes of the magnetic fluxes flowing through each magnetic circuit are derived:

[0040]

[0041] In (Equation 1), Φ1 represents the magnetic flux on the first winding magnetic column 1; Φ2 represents the magnetic fluxes on the first non-winding magnetic column 3 and the second non-winding magnetic column 4; Φ3 represents the magnetic flux on the second winding magnetic column 2;

[0042] N p1 represents the number of turns of the first winding; N p2 represents the number of turns of the second winding; N s1 represents the number of turns of the third winding; N s2 represents the number of turns of the fourth winding;

[0043] i p represents the primary side winding current; i s represents the secondary side winding current;

[0044] R g1 represents the total magnetic resistance value after parallel connection of the magnetic resistances formed by opening air gaps in the first non-winding magnetic column 3 and the second non-winding magnetic column 4; R g2 represents the magnetic resistance values formed by opening air gaps in the first winding magnetic column 1 and the second winding magnetic column 2 respectively. At this time, since the magnetic permeability of the magnetic core assembly is much greater than the vacuum magnetic permeability, the magnetic resistance of the magnetic core assembly is ignored in all calculation processes of the present invention, and only the air gap magnetic resistance is considered;

[0045] l g1 represents the air gap length of the first non-winding magnetic column 3 and the second non-winding magnetic column 4; l g2 represents the air gap length of the first winding magnetic column 1 and the second winding magnetic column 2; μ0 represents the air magnetic permeability; A e1 represents the magnetic conduction cross-sectional area of the first non-winding magnetic column 3 and the second non-winding magnetic column 4; A e2 represents the magnetic conduction cross-sectional area of the first winding magnetic column 1 and the second winding magnetic column 2;

[0046] According to Faraday's law of electromagnetic induction, the primary side winding voltage V p and the secondary side winding voltage V s are represented by (Equation 2):

[0047]

[0048] According to (Equation 1) and (Equation 2), the relationship between the port voltage and current (Equation 3) is obtained:

[0049]

[0050] In Equation (3), L p represents the self-inductance of the primary winding; L s represents the self-inductance of the secondary winding; M represents the mutual inductance between the primary winding and the secondary winding;

[0051] According to Equation (3), the self-inductance L of the primary winding of the transformer structure of the present invention p , the self-inductance L of the secondary winding s , and the mutual inductance M between the primary winding and the secondary winding are calculated by the following formula:

[0052]

[0053] Furthermore, the exciting inductance L m , the primary leakage inductance L kp , the secondary leakage inductance L ks and the inductance coefficient K of the transformer structure of the present invention are expressed by the following formula:

[0054]

[0055] It can be seen from the above formula that the magnetic core assembly can adjust N p1 , N p2 , N s1 , N s2 to adjust the inductance coefficient K of the CLLC resonant converter to meet its gain requirements, and adjust the leakage inductance by adjusting the air-gap reluctance R g to act as the resonant inductance L r1 , L r2 required by the CLLC resonant converter, realizing the full integration of the two resonant inductances L r1 , L r2 and a transformer T.

[0056] According to Ampere's circuital law and Faraday's law of electromagnetic induction, it can be used to calculate the magnitudes of the primary leakage inductance, secondary leakage inductance and exciting inductance, so that the number of turns of the primary winding, the number of turns of the secondary winding of the transformer structure of the present invention, and the sizes of the air gaps opened in the first winding magnetic post 1, the second winding magnetic post 2, the first non-winding magnetic post 3 and the second non-winding magnetic post 4 can be determined according to the design parameter specifications; in addition, in the present invention, in order to ensure that the primary leakage inductance and the secondary leakage inductance can respectively act as the primary resonant inductance and the secondary resonant inductance, it is necessary to ensure that the ratio of the primary leakage inductance to the secondary leakage inductance is the square of the transformer structure turns ratio.

[0057] The transformer structure of the present invention includes a magnetic core assembly, which includes a magnetic core top plate 5 and a magnetic core base 6. Along the height direction, the magnetic core top plate 5 is arranged above the magnetic core base 6 at intervals; since both the leakage flux and the coupling flux of the transformer structure need to pass through the magnetic core top plate 5 to form a closed magnetic circuit, it causes a very high magnetic flux density on the magnetic core top plate 5; in order to reduce the magnetic flux density on the magnetic core top plate 5 and reduce the loss of the magnetic core assembly, in the present invention, the first winding magnetic column 1 and the second winding magnetic column 2 are distributed at intervals along the length direction of the magnetic core base 6, and the first non-winding magnetic column 3 and the second non-winding magnetic column 4 are distributed at intervals along the width direction of the magnetic core base 6, that is, by arranging the first non-winding magnetic column 3 and the second non-winding magnetic column 4 on both sides of the first winding magnetic column 1 and the second winding magnetic column 2, it is possible to increase the magnetic flux loop of the leakage flux on the magnetic core top plate 5, thereby reducing the magnetic flux density on the magnetic core top plate 5 and reducing the magnetic core loss of the magnetic core assembly.

[0058] Both the first winding magnetic column 1 and the second winding magnetic column 2 are cylindrical, which is conducive to the uniform winding of the windings, improving the winding efficiency and quality, and reducing the winding loss.

[0059] In addition, in the present invention, both the first non-winding magnetic column 3 and the second non-winding magnetic column 4 are irregular-shaped magnetic columns. As Figure 1 shown, on the two side walls opposite to the through groove 9, a first concave arc surface 7 and a second concave arc surface 8 are respectively arranged in an abutting arrangement, thereby forming the first non-winding magnetic column 3 and the second non-winding magnetic column 4 with an irregular shape and symmetric arrangement.

[0060] The first winding, the second winding, the third winding, and the fourth winding all adopt PCB windings. The PCB winding can achieve a higher-density winding layout, thereby effectively reducing the volume of the transformer structure, especially reducing the height of the transformer structure.

[0061] The first winding and the third winding on the first winding magnetic column 1 adopt an asymmetric distribution method; the second winding and the fourth winding on the second winding magnetic column 2 adopt an asymmetric distribution method, which can actively reduce the coupling between the primary winding and the secondary winding, increase the leakage inductance of the primary winding and the secondary winding, so as to realize using the leakage inductance of the primary winding and the leakage inductance of the secondary winding as the resonant inductance of the CLLC resonant converter, and further achieve the magnetic integration of the transformer and the resonant inductance.

[0062] The winding directions of the first winding and the second winding are opposite, and the winding directions of the third winding and the fourth winding are opposite; the winding directions of the first winding and the third winding are opposite, and the winding directions of the second winding and the fourth winding are opposite; this helps to optimize the coupling magnetic flux path, make the AC electric energy input by the primary winding more accurately coupled to the secondary winding, reduce the loss and interference during the energy transmission process, improve the accuracy and stability of voltage conversion, and ensure that the output voltage meets the load requirements.

[0063] The working process of the present invention is as follows:

[0064] DC excitation power supply V bus After being inverted by the primary-side inverter network, the output alternating current serves as the input voltage of the primary-side winding. After voltage conversion, the alternating current with the target amplitude is output through the secondary-side winding and serves as the input source of the secondary-side inverter network. It is converted into the alternating current with the target frequency and target amplitude by the secondary-side inverter network for output.

[0065] During the process of voltage amplitude conversion through the primary-side winding and the secondary-side winding, the leakage magnetic flux generated forms a closed leakage magnetic flux loop through the first non-winding magnetic column 3, the second non-winding magnetic column 4, and the magnetic core top plate 5, thereby forming the required resonant inductance L r1 、L r2 in the CLLC resonant converter, and then a resonant network is formed to reduce the switching loss and improve the system efficiency.

[0066] The above description is an explanation of the present invention, not a limitation of the invention. For the scope defined by the present invention, refer to the claims. Any form of modification can be made within the protection scope of the present invention.

Claims

1. A magnetic integrated planar transformer structure for a CLLC resonant converter, characterized in that: It includes a magnetic core assembly, the magnetic core assembly includes a mutually cooperating magnetic core top plate (5) and a magnetic core base (6), a through groove (9) is formed along the length direction at the center of the top of the magnetic core base (6), so as to form a first non-winding magnetic column (3) and a second non-winding magnetic column (4) on the top of the magnetic core base (6), the first non-winding magnetic column (3) and the second non-winding magnetic column (4) are spaced apart along the width direction of the magnetic core base (6), and a first winding magnetic column (1) and a second winding magnetic column (2) are arranged at intervals in the through groove (9); The first winding magnetic column (1) is wound with N p1 turns of the first winding, and the second winding magnetic column (2) is wound with N p2 turns of the second winding. The first winding and the second winding are connected in series to form the primary side winding of the transformer; The first winding magnetic post (1) is wound with N s1 turns of the third winding, and the second winding magnetic post (2) is wound with N s2 turns of the fourth winding. The third winding and the fourth winding are connected in series to form the secondary side winding of the transformer; The primary side winding is connected to an alternating current, and the secondary side winding outputs an induced electromotive force under the action of electromagnetic induction, so as to perform voltage conversion. At the same time, the leakage magnetic flux generated in the first winding magnetic column (1) and the second winding magnetic column (2) forms a closed leakage magnetic flux path through the first non-winding magnetic column (3) and the second non-winding magnetic column (4).

2. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, wherein: Both the first winding magnetic column (1) and the second winding magnetic column (2) are cylindrical.

3. The magnetic integrated planar transformer structure for a CLLC resonant converter as claimed in claim 1, wherein: The first winding magnetic column (1) and the second winding magnetic column (2) are spaced apart along the length direction of the magnetic core base (6).

4. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: The first winding, the second winding, the third winding and the fourth winding all adopt PCB windings.

5. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: Along the height direction, the magnetic core top plate (5) is arranged at intervals above the magnetic core base (6).

6. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: The leakage magnetic fluxes distributed on the first non-winding magnetic column (3) and the second non-winding magnetic column (4) respectively generate leakage inductances, and the leakage inductances are used as the resonant inductances in the CLLC resonant converter.

7. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: The first winding and the third winding on the first winding magnetic column (1) adopt an asymmetric distribution method.

8. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: The second winding and the fourth winding on the second winding magnetic column (2) adopt an asymmetric distribution method.

9. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 1, characterized in that: The winding directions of the first winding and the second winding are opposite, and the winding directions of the third winding and the fourth winding are opposite.

10. The magnetic integrated planar transformer structure for a CLLC resonant converter according to claim 9, characterized in that: The winding directions of the first winding and the third winding are opposite, and the winding directions of the second winding and the fourth winding are opposite.

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