A magnetic integration structure applied to LLC resonant converters

Abstract

The present invention discloses a matrix transformer magnetic integration structure applied to an LLC resonant converter, which includes a magnetic core and windings. The magnetic core includes an upper magnetic core cover, a lower magnetic core cover, and a six-column magnetic core therebetween; the windings include a primary winding and a secondary winding; the primary winding and the secondary winding are arranged around the magnetic core columns of the six-column magnetic core to form a transformer: two magnetic columns are provided on the front surface of the six-column magnetic core, and four magnetic columns are provided on the back surface. The primary winding is wound around the front magnetic columns, and the secondary winding is wound around the four back magnetic columns, and an isolation layer is laid between the secondary windings; a air gap with a length of l <subgt;g5< / subgt; is left in the middle of the six-column magnetic core; an air gap with a length of l <subgt;g6< / subgt; is left between the upper magnetic core cover and the magnetic core; an air gap with a length of l <subgt;g1< / subgt; is left between the lower magnetic core cover and the magnetic core. The present invention controls the air gaps l <subgt;g1< / subgt>, l <subgt;g5< / subgt>, l

Description

Technical Field

[0001] The present invention belongs to the fields of power electronics technology and electrical engineering technology, and particularly relates to a magnetic integration structure of magnetic components for an LLC resonant converter using a matrix transformer with a matrix number of 4. Background Art

[0002] In order to achieve high power density, it is necessary to increase the switching frequency of the converter to reduce the volume of passive components. However, at high frequencies, the losses of magnetic components will increase, and parasitic parameters such as the leakage inductance of magnetic components will also have an adverse impact on the performance of the converter. In order to reduce the influence of the leakage inductance of magnetic components on the converter under high-frequency conditions and reduce the losses of magnetic components, for the full-bridge LLC circuit structure, a planar matrix transformer structure is usually adopted, and magnetic integration design of magnetic components is carried out.

[0003] Integrating the matrix transformer with the resonant inductor on the primary side of the LLC resonant converter helps to achieve high efficiency and high power density of the converter. The decoupled integration of the resonant inductor and the exciting inductor can be achieved by designing the size of the air gap of the transformer core. However, the leakage inductance of the matrix transformer is not sufficient to replace the exciting inductor, and the traditional four-leg core cannot achieve the decoupling of the transformer leakage inductance and the resonant inductor. If this magnetic integration method is used, the structure of the core also needs to be designed. Summary of the Invention

[0004] Aiming at the problem that the traditional four-leg core cannot achieve magnetic integration of the resonant inductor applicable to a matrix transformer with a matrix number of 4 and the matrix transformer, this application discloses a magnetic integration structure applied to an LLC resonant converter, which controls the exciting inductance and leakage inductance by using the air gap in the middle of the core and the air gaps between six magnetic columns and the core cover, so as to achieve the decoupling of the inductance values of the resonant inductor and the exciting inductor of the LLC converter and meet the requirements of the inductance ratio during voltage regulation of the LLC converter.

[0005] The present invention is realized by the following technical solutions:

[0006] A matrix transformer magnetic integration structure applied to an LLC resonant converter, comprising a core and windings. The core includes two core covers and a six-leg core. The windings include a primary winding and a secondary winding. The secondary winding further includes a first secondary winding and a second secondary winding. The primary winding and the secondary winding are arranged around the magnetic columns of the six-leg core to form a transformer. Among them:

[0007] In the core, the primary winding is wound around two magnetic columns on the front side, and the secondary winding is wound around four magnetic columns on the back side. The order of the windings on the back side arranged from top to bottom is the first secondary winding - the second secondary winding, and an isolation layer is laid between the two windings;

[0008] The core has an air gap with a length of lg5 ;

[0009] An air gap is left between the upper magnetic core cover and the magnetic core, and its length is l g6 ;

[0010] An air gap is left between the lower magnetic core cover and the magnetic core, and its length is l g1 ;

[0011] The magnetic core structure decouples the leakage inductance and magnetizing inductance of the transformer by controlling the air gaps l g1 , l g5 , l g6 , thus meeting the requirement of the inductance ratio during voltage regulation of the LLC resonant converter.

[0012] Preferably, the four magnetic posts coplanar with the magnetic core are divided into two groups, the first and the second, along the diagonal. In the first half cycle, the first secondary winding wound around the first group conducts, and the second secondary winding wound around the second group conducts; in the second half cycle, the first secondary winding wound around the second group conducts, and the second secondary winding wound around the first group conducts, so as to meet the output requirements of the secondary side of the matrix transformer.

[0013] Preferably, the edges of the two magnetic posts on the front of the magnetic core coincide with the edge of the magnetic core. The input and output of the primary winding on the two magnetic posts on the front of the magnetic core are on the same side. The four magnetic posts on the back are evenly distributed, and the cross-sectional areas of the six magnetic posts are equal, so that the magnetic flux density of each magnetic post is equal.

[0014] Preferably, the equivalent circuit of the magnetic integration structure includes four branches. The first branch is the magnetic flux branch formed by the upper left magnetic post among the four magnetic posts on the back of the six-post magnetic core and the lower magnetic core cover, and the magnetic flux is represented as Φ1. The second branch is the magnetic flux branch formed by the lower left magnetic post among the four magnetic posts on the back of the six-post magnetic core and the lower magnetic core cover, and the magnetic flux is represented as Φ2. The third branch is the magnetic flux branch formed by the upper right magnetic post among the four magnetic posts on the back of the six-post magnetic core and the lower magnetic core cover (6), and the magnetic flux is represented as Φ3. The fourth branch is the magnetic flux branch formed by the lower right magnetic post among the four magnetic posts on the back of the six-post magnetic core and the lower magnetic core cover, and the magnetic flux is represented as Φ4. Two parallel branches are connected to the fifth branch and the sixth branch. The fifth branch is the magnetic flux branch formed by the central air gap of the six-post magnetic core, and the magnetic flux is represented as Φ5. The sixth branch is the magnetic flux branch formed by the two magnetic posts on the front of the six-post magnetic core and the upper magnetic core cover, and the magnetic flux is represented as Φ6.

[0015] Preferably, the magnetizing inductance L m is expressed as:

[0016] ,

[0017] The primary leakage inductance L k is expressed as:

[0018] ,

[0019] In the formula, n l is the number of turns of the primary side of each magnetic column in the front two-magnetic-column structure, and R b is the equivalent magnetic resistance of the parallel connection of the fifth branch and the sixth branch, and R m is the equivalent magnetic resistance of the first branch, the second branch, the third branch and the fourth branch. R0 is the magnetic resistance of the fifth branch, and R u is half of the total magnetic resistance of the sixth branch. k is a constant related to R0 and R u ; By adjusting the magnetic core structure, the magnitudes of R0, R u , and R m are changed to achieve the decoupling control of the exciting inductance and the leakage inductance.

[0020] Preferably, by changing the air gaps l g1 , l g5 , and l g6 in the magnetic integration structure to change the magnitudes of R0, R u , and R m ,

[0021] It is expressed as: , , ,

[0022] In the formula, A m , A0, and A u are the cross-sectional areas of the lower magnetic column, the central air gap, and the upper magnetic column of the six-column magnetic core (3) respectively. The air gaps l g1 , l g5 , and l g6 are the air gap lengths of the first, fifth, and sixth branches respectively.

[0023] Compared with the prior art, the present invention can achieve the following beneficial technical effects:

[0024] (1) On the basis of the four-column matrix transformer, the present invention improves the magnetic core structure and realizes the scheme of decoupling control of the exciting inductance and the leakage inductance.

[0025] (2) Compared with the traditional four-magnetic-core structure, the present invention has a higher coupling degree between the primary winding and the magnetic core, a shorter primary winding length, and smaller primary copper loss. Description of the Drawings

[0026] Figure 1 is a three-dimensional view of the magnetic core of an embodiment of the present invention;

[0027] Figure 2 The primary winding structure of an embodiment of the present invention;

[0028] Figure 3 is the first secondary winding structure of an embodiment of the present invention;

[0029] Figure 4 The second secondary winding structure of an embodiment of the present invention;

[0030] Figure 5 The magnetic flux loop diagram of an embodiment of the present invention within a half cycle of the LLC resonant converter.

[0031] Figure 6 The equivalent magnetic circuit diagram of the magnetic flux loop within a half cycle of the LLC resonant converter of an embodiment of the present invention.

[0032] Figure 7 The equivalent magnetic circuit further simplified from the equivalent magnetic circuit diagram of the magnetic flux loop within a half cycle of the LLC resonant converter of an embodiment of the present invention.

[0033] Reference numerals:

[0034] 1 - upper magnetic core cover, 2 - primary winding, 3 - magnetic core, 4 - first secondary winding, 5 - second secondary winding, 6 - lower magnetic core cover. Detailed implementation manners

[0035] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0036] As Figure 1 shown is the proposed magnetic integration structure. The magnetic core 2 is a six - column magnetic core, with two magnetic columns on the front and four magnetic columns on the back. The cross - sectional area of each magnetic column on the back is the same as that of the magnetic columns on the front. The primary winding is wound around the two magnetic columns on the front, and the secondary winding is wound around the four magnetic columns on the back. The two magnetic columns on the front are located near the edge of the magnetic core. The magnetic core columns are arranged along the side rather than at the center, which is convenient for the connection of the windings.

[0037] The four magnetic columns on the front of the magnetic core are divided into the first and second groups along the diagonal. In one working cycle, within the first half - cycle, the first secondary winding wound around the first group conducts, and the second secondary winding wound around the second group conducts; within the second half - cycle, the first secondary winding wound around the second group conducts, and the second secondary winding wound around the first group conducts, achieving the requirements for the secondary output of the matrix transformer. Figure 2 The PCB winding in Figure 2 is divided into two layers, the first layer and the second layer. The windings in the two layers are connected through two through - holes close to the magnetic columns, and the two through - holes far from the magnetic columns are connected to the primary side of the transformer. The structure of the primary winding is as Figure 3 and Figure 4 are the same, consisting of a two - layer PCB board. The windings in the upper - left corner and the lower - right corner are located in the first layer, and the windings in the lower - left corner and the upper - right corner are located in the second layer.Figure 3 and Figure 4 is used to connect the secondary side of the transformer.

[0038] The magnetic circuit of the magnetic component is analyzed below. Since the electromagnetic distribution of the LLC resonant converter is similar within one working cycle, only a half-cycle needs to be analyzed. The magnetic resistance model of the first half-cycle is analyzed below. Figure 5 The magnetic circuit structure of the first half-cycle of the LLC resonant converter before operation is shown as follows.

[0039] The equivalent circuit of the magnetic integration structure is as follows: It includes four branches. The first branch is the magnetic flux branch formed by the upper left magnetic column and the lower magnetic core cover 6 among the four magnetic columns on the back of the six-column magnetic core 3, and the magnetic flux is represented as Φ1. The second branch is the magnetic flux branch formed by the lower left magnetic column and the lower magnetic core cover 6 among the four magnetic columns on the back of the six-column magnetic core 3, and the magnetic flux is represented as Φ2. The third branch is the magnetic flux branch formed by the upper right magnetic column and the lower magnetic core cover 6 among the four magnetic columns on the back of the six-column magnetic core 3, and the magnetic flux is represented as Φ3. The fourth branch is the magnetic flux branch formed by the lower right magnetic column and the lower magnetic core cover 6 among the four magnetic columns on the back of the six-column magnetic core 3, and the magnetic flux is represented as Φ4. The first and second branches are in parallel, and the third and fourth branches are in parallel. The fifth and sixth branches are connected between the two parallel branches. The fifth branch is the magnetic flux branch formed by the central air gap of the six-column magnetic core 3, and the magnetic flux is represented as Φ5. The sixth branch is the magnetic flux branch formed by the two magnetic columns on the front of the six-column magnetic core 3 and the upper magnetic core cover 1, and the magnetic flux is represented as Φ6.

[0040] For Figure 5 the equivalent magnetic circuit in l I p is in series with the magnetic resistance R u of the two magnetic columns. In the magnetic circuit, n ! l is the number of primary turns of each magnetic column in the structure of the two magnetic columns on the front, I p is the primary current, I s1 is the total secondary current in the first half-cycle, and n is the total number of primary turns. The magnetic resistances of the four magnetic columns on the back of the magnetic core are the same as R m , the magnetic resistance of the central air gap of the magnetic core 3 is R0, and the magnetic resistances of the two magnetic columns on the front of the magnetic core are R u .

[0041] The magnetic resistances R m and R u of the magnetic columns of the magnetic core legs and the magnetic resistance R0 formed by the central gap of the magnetic core are functions of their respective cross-sectional areas and air gaps, and are expressed as:

[0042] (1)

[0043] (2)

[0044] (3)

[0045] Wherein, A m , A0, and A u are the cross-sectional areas of the lower magnetic columns, the central air gap, and the upper magnetic columns of the six-column magnetic core 3 respectively. The air gaps l g1 , l g5 , and l g6 are the air gap lengths of the first, fifth, and sixth branches respectively.

[0046] For the convenience of calculation, the magnetic circuit in Figure 5 can be equivalently transformed. According to the series equivalent principle, the two magnetic potentials and two magnetic resistances of the six magnetic circuits can be connected in series equivalently, and thus the equivalent structure of the magnetic circuit in Figure 6 can be obtained. Further, according to the parallel equivalent principle, the equivalent magnetic circuit in Figure 7 can be obtained.

[0047] Wherein

[0048] (4)

[0049] (5)

[0050] For the magnetic fluxes of each branch, there is

[0051] (6)

[0052] (7)

[0053] (8)

[0054] Then there is:

[0055] (9)

[0056] (10)

[0057] Then for the sixth branch and the fifth branch, according to KVL, there is

[0058] (11)

[0059] According to the KCL law, there is

[0060] (12)

[0061] By combining (11) and (12), we get

[0062] (13)

[0063] (14)

[0064] The self - inductance of the primary side of the transformer is

[0065] (15)

[0066] The mutual inductance between the primary winding and the secondary winding of the transformer is

[0067] (16)

[0068] The exciting inductance L m is

[0069] (17)

[0070] The primary leakage inductance L k is

[0071] (18)

[0072] As can be seen from the above formula, the exciting inductance L of this magnetic integration structure m is related to R0, R u , R m . The primary leakage inductance L k is also related to the three variables R0, R u , R m . By adjusting the magnetic core structure and changing the magnitudes of the three, the decoupling control of the exciting inductance and the leakage inductance can be achieved.

[0073] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A matrix transformer magnetic integration structure applied to an LLC resonant converter, comprising a magnetic core and windings, characterized in that the magnetic core includes an upper magnetic core cover (1), a lower magnetic core cover (6) and a six-column magnetic core (3) located between the upper and lower magnetic core covers; the windings include a primary winding (2) and a secondary winding, and the secondary winding includes a first secondary winding (4) and a second secondary winding (5); the primary winding and the secondary winding are arranged around the magnetic core columns of the six-column magnetic core (3) to form a transformer, wherein: two magnetic columns are provided on the front of the six-column magnetic core (3), and four magnetic columns are provided on the back. The primary winding (2) is wound around the two magnetic columns on the front, and the first and second secondary windings are wound around the four magnetic columns on the back. An isolation layer is laid between the first and second secondary windings; The equivalent circuit of the magnetic integration structure includes four branches. The first to fourth branches are the magnetic flux branches formed by the four magnetic columns on the back of the six-column magnetic core (3) and the lower magnetic core cover (6), and the magnetic fluxes are respectively represented as Φ1, Φ2, Φ3, and Φ4, and the air gap lengths are all l g1 , the magnetic flux branches formed by the magnetic columns on the same side are in parallel. The two parallel branches are connected to the fifth branch and the sixth branch. The fifth branch is the magnetic flux branch formed by the central air gap of the six-column magnetic core (3), and the magnetic flux is represented as Φ5, and the air gap length is l g5 , the sixth branch is the magnetic flux branch formed by the two magnetic columns on the front of the six-column magnetic core (3) and the upper magnetic core cover (1), and the magnetic flux is represented as Φ6, and the air gap length is l g6 ; The middle part of the six-column magnetic core (3) has an air gap with a length of l g5 ; There is an air gap between the upper magnetic core cover (1) and the magnetic core (3), and its length is l g6 ; An air gap is left between the lower magnetic core cover (6) and the magnetic core (3), and its length is l g1 ; The magnetic core controls the air gaps l g1 , l g5 , l g6 , so that the leakage inductance and magnetizing inductance of the transformer are decoupled from each other, meeting the requirement of the inductance ratio for voltage regulation of the LLC resonant converter.

2. The matrix transformer magnetic integration structure according to claim 1, characterized in that, the four magnetic columns coplanar with the magnetic core (3) are divided into a first group and a second group according to the diagonal. In the first half cycle, the first secondary winding wound around the first group is conducted, and the second secondary winding wound around the second group is conducted; in the second half cycle, the first secondary winding wound around the second group is conducted, and the second secondary winding wound around the first group is conducted, to meet the requirements of the secondary output of the matrix transformer.

3. The matrix transformer magnetic integration structure according to claim 1, characterized in that, the edges of the two magnetic columns on the front of the magnetic core (3) coincide with the edge of the magnetic core. The input and output of the primary winding (2) on the two magnetic columns on the front of the magnetic core (3) are on the same side. The four magnetic columns on the back are evenly distributed, and the cross-sectional areas of the six magnetic columns are equal, so that the magnetic flux density of each magnetic column is equal.

4. The matrix transformer magnetic integration structure according to claim 1, characterized in that, The exciting inductance L of the magnetic integration structure m is expressed as: ， Primary leakage inductance L k It is expressed as: ， Where n l is the number of primary turns of each magnetic column in the front two-magnetic-column structure, R b is the equivalent magnetic resistance of the parallel connection of the fifth branch and the sixth branch, R m is the equivalent magnetic resistance of the first branch, the second branch, the third branch and the fourth branch, R0 is the magnetic resistance of the fifth branch, R u is half of the total magnetic resistance of the sixth branch, and k is a constant related to R0 and R u ; By adjusting the magnetic core structure, change the magnitudes of R0, R u , R m to achieve decoupled control of the exciting inductance and the leakage inductance.

5. The matrix transformer magnetic integration structure according to claim 4, characterized in that By changing the sizes of the air gaps l g1 , l g5 , l g6 to change the sizes of R0, R u , R m . Expressed as: , , , Wherein, A m , A0, A u are respectively the cross-sectional areas of the lower magnetic column, the central air gap and the upper magnetic column of the six-column magnetic core (3), and the air gaps l g1 , l g5 , l g6 are respectively the air gap lengths of the first, fifth and sixth branches.

6. The matrix transformer magnetic integration structure according to claim 4, characterized in that The connection of the windings is realized based on a PCB. The PCB winding is divided into two layers, and four connection through holes are opened on the PCB winding. The windings between the two layers are connected through the two through holes close to the magnetic columns, and the two through holes far from the magnetic columns are used to connect the primary side of the transformer.

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