Magnetic integrated matrix transformer suitable for single-phase high-power LLC converter and optimization method thereof

Abstract

The invention provides a magnetic integration matrix transformer suitable for a single-phase high-power LLC converter and an optimization method of the magnetic integration matrix transformer, and belongs to the technical field of power electronics. The magnetic integrated matrix transformer comprises a magnetic core top plate, a magnetic core base, a primary side winding and a secondary side winding, the integrated structure comprises six magnetic cores which are all located on the magnetic core base, four magnetic cores are round winding magnetic columns, and two magnetic cores are oval winding magnetic columns and twelve irregular low-magnetic-resistance non-winding magnetic columns. The two round winding magnetic columns form an element transformer which is an element 1 transformer and an element 2 transformer, the two oval winding magnetic columns form an element transformer which is an element 3 transformer, and the primary side winding and the secondary side winding of each element transformer are unevenly wound on the upper winding magnetic column and the lower winding magnetic column of each element transformer respectively. And the coupling degree of the primary side winding and the secondary side winding is actively reduced, so that the generated leakage inductance is used as the resonant inductance of the converter, and the integration of the single-phase LLC converter transformer and the resonant inductance is realized.

Description

Technical Field

[0001] The present invention relates to the field of power supply systems, and in particular to the field of LLC resonant power supply with low voltage and high current output. Background Art

[0002] As power electronics technology becomes increasingly mature, fields such as data centers, new energy vehicles, and aviation applications are undergoing tremendous changes, and the demand for high-efficiency, high-power density power systems is increasing rapidly. Fields such as new energy vehicles and aviation applications usually require power systems with higher power density to achieve fast portable charging and long driving range. Resonant converters such as LLC and CLLC converters are widely used in switching power supplies because they can achieve soft switching and reduce the turn-on and turn-off losses of switching devices.

[0003] One of the applications with the highest requirements for LLC converters is the data center. The power supply characteristics of the data center are low voltage and high current. The characteristics of low voltage and high current will increase the required width of the transformer winding sharply, and the transformer overcurrent will increase sharply, which will not only easily cause the problem of oversaturation of the magnetic core, but also cause its internal temperature to rise. Long-term high-temperature operation will not only accelerate the aging of the insulation material, but also may cause the transformer to overheat and damage. In the resonant power supply system, magnetic components account for about 30% of the volume and weight of the entire system, especially in LLC and other resonant converters, which contain multiple magnetic components such as series resonant inductors and transformers. The integration of magnetic components directly affects the integration of the entire power supply system. Traditional LLC magnetic integrated devices usually design the resonant inductor as a part of the planar transformer alone, which leads to a decrease in winding utilization, increased losses, and an increase in the size of the device. Therefore, the integration of matrix transformers can reduce the size of the device, improve the winding utilization, improve the stability of the device, and reduce the number of PCB layers to reduce costs. Planar transformers can easily stagger the primary and secondary windings to reduce magnetomotive force and losses. At the same time, they can reduce the height of the transformer core and reduce the volume. Therefore, planar matrix transformers have become the choice for high-efficiency and high-power power supply systems. Summary of the invention

[0004] The present invention proposes a magnetically integrated matrix transformer suitable for a single-phase high-power LLC converter and an optimization method thereof, which is particularly suitable for the case of low voltage and high current on the LLC secondary side. The height of the transformer is reduced by increasing the number of magnetic columns, thereby reducing its volume and reducing the transformer core loss. In addition, the integration of the inductor and the transformer reduces the number, weight and loss of magnetic components in the resonant converter, thereby optimizing the efficiency and power density of the converter.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention proposes a resonant inductor and transformer integrated structure suitable for a single-phase high-power LLC resonant converter and an optimization method thereof. The single-phase LLC circuit comprises a single-phase bridge inverter circuit, a single-phase bridge rectifier circuit, a resonant network and a six-column matrix transformer. The resonant inductor and transformer in the resonant network are integrated into a magnetic element.

[0007] The integrated magnetic core structure includes a magnetic core top plate, a magnetic core base and a PCB winding. The magnetic core base includes four circular winding magnetic columns, two elliptical winding magnetic columns and a low magnetic resistance non-winding magnetic column, wherein two circular winding magnetic columns are located in the first column, which are element 1 transformers, two circular winding magnetic columns are located in the third column, which are element 3 transformers, and two elliptical winding magnetic columns are located in the second column, which are element 2 transformers. The element 2 transformer provides a path for the magnetic flux of the element 1 and element 3 transformers, so the magnetic flux density of the element 2 transformer is relatively large, and the element 2 transformer is prone to oversaturation. Therefore, the cross-sectional area of ​​the elliptical magnetic column is greater than the cross-sectional area of ​​the circular magnetic column. By increasing the cross-sectional area of ​​the elliptical magnetic column, the magnetic flux density of the element 2 transformer is reduced to prevent the oversaturation problem of the element 2 transformer, so that the magnetic flux density of the integrated transformer is more uniform. There are air gaps between the three element transformers and the magnetic core top plate, and the coupling degree of the primary and secondary sides is controlled by adjusting the size of the air gap, so as to meet the requirements of the LLC resonant converter for the inductance ratio during voltage regulation. There is no air gap between the low magnetic resistance non-wound magnetic column and the top plate of the magnetic core, which can be regarded as a short circuit in the magnetic circuit winding model. By increasing the low magnetic resistance path, the effective magnetic conductive area of ​​the magnetic cover is further increased, the uniform distribution of the magnetic flux in the magnetic cover and the full utilization of the magnetic cover are achieved, thereby reducing leakage flux, reducing core loss and improving converter efficiency.

[0008] A magnetically integrated matrix transformer for a single-phase high-power LLC converter as described in claim 1, characterized in that the width of each layer of the secondary winding adapts to the size of the cross-sectional area of ​​the magnetic core at the corresponding position, so that the current density of the secondary winding is evenly distributed.

[0009] Furthermore, by using magnetic integration technology, N1 turns of winding are wound on magnetic column 1, and N2 turns of winding are wound on magnetic column 2 as the primary winding of element 1 transformer, N3 turns of winding are wound on magnetic column 2, and N3 turns of winding are wound on magnetic column 1 as the secondary winding of element 1 transformer, and the coupling degree between the primary and secondary windings is reduced by unbalanced distribution of the primary and secondary windings, and the leakage inductance on one side of the element 1 transformer is increased to serve as the primary resonant inductance of the converter.

[0010] Furthermore, N1 turns of winding are wound on magnetic column 3, and N2 turns of winding are wound on magnetic column 4 as the primary winding of element 2 transformer, and N3 turns of winding are wound on magnetic column 4, and N3 turns of winding are wound on magnetic column 3 as the secondary winding of element 2 transformer. The coupling degree between the primary and secondary windings is reduced by unbalanced distribution of the primary and secondary windings, and the leakage inductance of the primary side of element 2 transformer is increased to serve as the primary resonant inductance of the converter.

[0011] Furthermore, N1 turns of winding are wound on magnetic column 5, and N2 turns of winding are wound on magnetic column 6 as the primary winding of element 3 transformer, and N3 turns of winding are wound on magnetic column 6, and N3 turns of winding are wound on magnetic column 5 as the secondary winding of element 3 transformer. The coupling degree between the primary and secondary windings is reduced by unbalanced distribution of the primary and secondary windings, and the leakage inductance of the primary side of element 3 transformer is increased to serve as the primary resonant inductance of the converter.

[0012] Furthermore, the magnetic circuit winding model is as follows Figure 7 As shown, in the magnetic circuit winding model, Φ1, Φ2, Φ3, Φ4, Φ5, Φ6 are the magnetic flux of each branch, i p 、i s is the primary and secondary current of the transformer, R g is the air gap reluctance. Assuming that the magnetic permeability of the core material is much greater than that of the air and the small leakage flux in the air is negligible, according to the magnetic circuit winding model:

[0013]

[0014] L 11 is the transformer primary winding self-inductance, and similarly M 12 、M 21 is the mutual inductance between the primary and secondary windings. The two values ​​are equal and are represented by M. L 22 is the self-inductance of the secondary winding of the transformer, according to Figure 8 As shown in the overall coupling circuit model of the transformer, the matrix equation can be used to obtain the relationship between the port voltage and current:

[0015]

[0016] Where V P 、V S are the transformer primary and secondary terminal voltages respectively. Figure 8 The transformer overall coupled inductance model is decoupled, where N is the transformer primary-to-secondary ratio, and the transformer excitation inductance is L m , the primary leakage inductance is L kp , the secondary leakage inductance is L ks , the inductance is L n ,like Fig. 9The equivalent circuit diagram of transformer T is shown as follows:

[0017]

[0018] On the basis of solving the magnetic flux of each branch, the functional relationship between the core geometric parameters and the circuit parameters is established. According to Faraday's law of electromagnetic induction, the relationship between the primary and secondary voltages and the magnetic flux is:

[0019]

[0020] Combining (1), (3) and (4), we can calculate:

[0021]

[0022] Further, combined with Fig. 9 , where the transformer's magnetizing inductance L m , primary side leakage inductance L kp , secondary side leakage inductance L ks and inductance L n It can be expressed as:

[0023]

[0024] Where l g is the air gap length, A e is the magnetic cross-sectional area of ​​the magnetic column, and μ0 is the magnetic permeability of air.

[0025] Further, such as Figure 7 As shown in the magnetic circuit winding model, it can be obtained that the top plate and the base of the magnetic core are short-circuited in this magnetic circuit model, and because their magnetic potentials are equal, the magnetic flux of each magnetic column remains unchanged. Therefore, Figure 7 The magnetic circuit model is still applicable to the magnetic circuit winding model with the low magnetic resistance path added, that is, after the low magnetic resistance path is added, equations (1) to (6) are still valid.

[0026] From formula (6), we can know that the integrated magnetic core can adjust the inductance coefficient L of the converter by adjusting N1 and N2. n To meet the converter gain requirements, the air gap length l is adjusted g To adjust the air gap reluctance R g The leakage inductance is adjusted to act as the resonant inductor required by the converter, achieving full integration of magnetic components, reducing the volume and weight of the converter, improving efficiency and power density, and adopting a staggered arrangement of the primary and secondary windings to reduce the magnetomotive force, reduce AC winding losses and reduce EMI interference problems of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a circuit block diagram of a single-phase LLC resonant converter in one embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of a magnetic integrated transformer before optimization in one embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the structure of an optimized magnetic integrated transformer in one embodiment of the present invention;

[0030] Figure 4 A coupled inductance model of each element transformer in an embodiment of the present invention;

[0031] Figure 5 The figure is a front view of the whole magnetic integrated transformer and a schematic diagram of the PCB winding in one embodiment of the present invention;

[0032] Figure 6 The figure is a rear view of the whole magnetic integrated transformer and a schematic diagram of the PCB winding in one embodiment of the present invention;

[0033] Figure 7 is a model diagram of a magnetic circuit winding before optimization in one embodiment of the present invention;

[0034] Figure 8 A diagram of an overall coupled inductance model of a magnetic integrated transformer in one embodiment of the present invention;

[0035] Fig. 9 is an overall T-type equivalent circuit diagram of a magnetic integrated transformer in one embodiment of the present invention;

[0036] Fig.10 This is a magnetic density map of the magnetic simulation using the Maxwell finite element software before optimization in one embodiment of the present invention.

[0037] Fig.11 This is a magnetic density map of the optimized Maxwell finite element software magnetic simulation in one embodiment of the present invention.

Claims

1. A magnetic integrated matrix transformer suitable for single-phase high-power LLC converter and an optimization method thereof, characterized in that: The single-phase LLC circuit includes a single-phase bridge inverter circuit, a single-phase bridge rectifier circuit, a resonant network and a six-magnetic column matrix transformer, wherein the matrix transformer has a total of six magnetic columns arranged in three columns, and the two magnetic columns in each column form an element transformer, that is, three element transformers. The resonant inductor and transformer in the above-mentioned resonant network are integrated into a magnetic element through the matrix magnetic columns. Specifically, the primary windings N1, N2 and the secondary windings N3, N3 of the element 1 transformer are respectively distributed and wound on magnetic columns 1 and 2 to reduce the coupling degree of the primary and secondary windings, so that the leakage inductance of the primary side of the element 1 transformer is increased and replaced by the resonant inductance of the primary side in the resonant network of the element 1 transformer. Similarly, the primary windings N1, N2 and the secondary windings N3, N3 of the element 2 transformer are wound on magnetic columns 3 and 4 to reduce the coupling degree of the primary and secondary windings, so that the leakage inductance of the primary side of the element 2 transformer is increased and replaced by the resonant inductance of the primary side in the resonant network of the element 2. The same is true for the element 3 transformer.

2. The integrated structure according to claim 1, characterized in that: The integrated magnetic element structure includes a magnetic core top plate and a magnetic core base, wherein the magnetic core base includes a planar magnetic plate and four circular wound magnetic columns, two elliptical wound magnetic columns, and low magnetic resistance non-wound magnetic columns integrated on the magnetic plate, wherein the two circular magnetic columns form a column and are distributed in the first and third columns, and the two elliptical magnetic columns form a column and are in the second column in the middle, together constituting three columns of magnetic columns.

3. The integrated structure according to claim 1 or 2, characterized in that: The primary windings N1 and N2 of the transformer of element 1 are wound on magnetic column 1 and magnetic column 2 respectively, and the winding directions of the two are opposite and the number of turns is different, so as to ensure that the magnetic flux closure direction they generate is the same. Similarly, the primary windings N1 and N2 of the transformer of element 2 are also wound on magnetic columns 3 and 4 respectively, and the primary windings N1 and N2 of the transformer of element 3 are also wound on magnetic columns 5 and 6.

4. The integrated structure according to claim 1, 2, or 3, characterized in that: The secondary windings N3 and N3 of the transformer of element 1 are respectively wound on magnetic column 1 and magnetic column 2, and the two winding directions are opposite and the number of turns is the same, ensuring that the magnetic flux closure direction they generate is the same. Similarly, the secondary windings N3 and N3 of the transformer of element 2 are also evenly wound on magnetic columns 3 and 4, and the same is true for the transformer of element 3.

5. The integrated structure according to claim 3 or 4, characterized in that: The transformer material is soft ferrite because it is suitable for high frequency and has the characteristics of high magnetic permeability and low loss. The transformer winding is made of PCB because it can be staggered and reduce the size of the device.

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