Magnetic integrated matrix transformer suitable for single-phase high-power CLLLC resonant converter

Abstract

The invention provides a magnetic integrated matrix transformer suitable for a single-phase high-power CLLLC resonant converter, and belongs to the technical field of power electronics. The magnetic integrated matrix transformer comprises a magnetic core top plate, a magnetic core base and a PCB winding, the integrated structure comprises six magnetic cores which are all located on the magnetic core base, four magnetic cores are small circular rectangular winding magnetic columns, and two magnetic cores are large circular rectangular winding magnetic columns. The two small circular rectangular winding magnetic columns form an element transformer, namely an element 1 transformer and an element 3 transformer, the two large circular rectangular winding magnetic columns form an element transformer, namely an element 2 transformer, and primary and secondary side windings of each element transformer are unevenly wound on the upper and lower winding magnetic columns of each element transformer respectively; the coupling degree of the primary side winding and the secondary side winding is actively reduced, so that generated leakage inductance serves as resonant inductance of the primary side and the secondary side of the converter, and integration of a single-phase CLLLC converter transformer and a resonant inductor is achieved.

Description

Technical Field

[0001] The present invention relates to the field of power electronic transmission, and in particular to a high-voltage and high-power CLLLC resonant converter. Background Art

[0002] The development of electric vehicles has reduced the dependence of automobiles on non-renewable resources such as oil, which is of strategic significance to the global energy transformation in the 21st century. At the same time, electric vehicles have greatly reduced carbon emissions compared to traditional fuel vehicles and are environmentally friendly. They are also crucial to my country's "carbon peak in 2030, carbon neutrality in 2060" dual carbon strategic goals in responding to climate change. With the rapid expansion of the electric vehicle market, electric vehicles are expected to show explosive growth in the next few years. Consumers have put forward higher requirements for the charging convenience, charging efficiency and cruising range of electric vehicles. High-power, high-efficiency and high-power density on-board chargers are becoming the development trend of new energy vehicles. It is also urgent to design a low-loss, low-cost and small-sized on-board charger post-converter.

[0003] The transformer is the core of the on-board charger's post-converter. Its volume and weight account for about 30% of the overall system, and its integration directly affects the integration of the entire power system. As the charging power continues to increase, the increase in current is inevitable. The sharp increase in transformer overcurrent increases the required width of the transformer winding, which not only easily leads to the problem of core oversaturation, but also causes more winding loss and core loss, and causes its internal temperature to rise. Long-term high-temperature operation will not only accelerate the aging of the insulating material, but may also cause the transformer to overheat and be damaged, making it difficult for the converter to achieve high efficiency. Therefore, high voltage is the key to improving the high power of the on-board charger. For the transformer in the converter, high voltage will produce a higher volt-second product on the transformer, which requires the transformer to be larger or the number of turns to be increased, but this will cause the transformer to The large size is not conducive to the converter to achieve the high power density requirements. With the development and application of wide bandgap devices, the frequency in the switching power supply has increased to hundreds of kilohertz or even several megahertz, which greatly reduces the volume and weight of passive components and can be reduced to the volt-second product of the transformer, creating conditions for the development of high power density and high power. The matrix planar transformer can easily stagger the primary and secondary windings to reduce losses, reduce the height of the transformer core, and reduce the volume. The resonant inductor of the resonant converter can also be integrated into the transformer. Therefore, the matrix planar transformer has become the choice of high power, high efficiency, and high volume density power supply. Summary of the Invention

[0004] The present invention proposes a magnetically integrated matrix transformer suitable for a single-phase high-power CLLLC resonant converter, which is particularly suitable for CLLLC high-voltage and high-power applications. By increasing the series and parallel connections of the matrix transformers, the height of the transformer is reduced, its volume is reduced, and its volt-second capacity is increased. In addition, by controlling the leakage inductance of the transformer so that it replaces the resonant inductor, the integration of the inductor and the transformer is achieved, thereby reducing the number, weight, and loss of magnetic components in the resonant converter, and facilitating the development of the converter toward high power, high efficiency, and high power density.

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

[0006] The present invention proposes a magnetically integrated matrix transformer suitable for a single-phase high-power CLLLC converter. The single-phase CLLLC circuit includes an inverter unit, a rectifier unit, a resonant cavity and a six-column matrix transformer. The resonant inductor and transformer in the above-mentioned resonant network are integrated into a magnetic component.

[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 six large rectangular winding magnetic pillars and two small rectangular winding magnetic pillars. The two large rectangular winding magnetic pillars are located in the first column and constitute the element 1 transformer. The two large rectangular winding magnetic pillars are located in the third column and constitute the element 3 transformer. The two small rectangular winding magnetic pillars are located in the second column and constitute the element 2 transformer. The element 2 transformer provides a path for the magnetic flux of the element 1 and element 3 transformers. As a result, the magnetic flux density of the element 2 transformer is relatively high, making the element 2 transformer prone to oversaturation. Therefore, the cross-sectional area of ​​the rectangular magnetic pillars is larger than that of the rectangular magnetic pillars of the element 1 and 3 transformers. By increasing the cross-sectional area of ​​the rectangular magnetic pillars, the magnetic flux density of the element 2 transformer is reduced, preventing oversaturation of the element 2 transformer and making the magnetic flux density of the integrated transformer more uniform. An air gap is left between the three element transformers and the magnetic core top plate. The size of the air gap is adjusted to control the coupling degree between the primary and secondary sides, thereby meeting the inductance ratio requirements of the CLLLC resonant converter during voltage regulation.

[0008] A magnetically integrated matrix transformer suitable for a single-phase high-power CLLLC converter as described in claim 1, characterized in that the width of each layer of primary and secondary windings adapts to the size of the cross-sectional area of ​​the magnetic core at the corresponding position, so that the current density of the primary and secondary windings 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, and N1 turns of winding are wound on magnetic column 2, and N2 turns of winding are wound on magnetic column 1 as the secondary winding of element 1 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 on both sides of the element 1 transformer is increased to serve as the primary and secondary 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. N2 turns of winding are wound on magnetic column 4, and N1 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 on both sides of element 2 transformer is increased to serve as the primary and secondary 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. N2 turns of winding are wound on magnetic column 6, and N1 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 the 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 5 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 air and the small leakage flux in the air is negligible, according to the magnetic circuit winding model:

[0013]

[0014] L 11 is the self-inductance of the primary winding of the transformer, and similarly M 12 、M 21 The mutual inductance between the primary and secondary windings is equal in value and is represented by M. L 22 is the self-inductance of the secondary winding of the transformer, according to Figure 4 As shown in the transformer coupled inductor model diagram, the matrix equation can be obtained to obtain the relationship between the port voltage and current:

[0015]

[0016] Where V P 、V S They are the transformer primary and secondary terminal voltages respectively. Figure 6 The transformer overall coupled inductance model is decoupled, where N is the transformer primary-to-secondary ratio and the transformer's magnetizing inductance is L. m , the primary side leakage is L kp , the secondary side leakage inductance is L ks , the inductance is L n ,like Figure 7 The equivalent circuit diagram of the T-type transformer 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 Figure 7 , where the transformer's magnetizing inductance L is m , primary side leakage sense 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] From formula (6), we can see 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

[0026] Figure 1 1 is a circuit block diagram of a single-phase CLLLC resonant converter in one embodiment of the present invention;

[0027] Figure 2 The overall top view and front view of the magnetic integrated transformer in one embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the overall structure of the magnetic integrated transformer and the PCB winding in one embodiment of the present invention;

[0029] Figure 4 A diagram of a coupled inductor model of a magnetic integrated transformer in one embodiment of the present invention;

[0030] Figure 5 A diagram showing a magnetic circuit winding model of a magnetic integrated transformer in one embodiment of the present invention;

[0031] Figure 6 1 is a diagram of an overall coupled inductance model of a magnetic integrated transformer in one embodiment of the present invention;

[0032] Figure 7 1 is a diagram of a T-type equivalent model of a magnetic integrated transformer in one embodiment of the present invention;

[0033] Figure 8 This is a magnetic density map of the magnetic simulation using Maxwell finite element software in one embodiment of the present invention.

Claims

1. A magnetic integrated matrix transformer suitable for single-phase high-power CLLLC converter, characterized in that: The single-phase CLLLC circuit includes an inverter unit, a rectifier unit, a resonant cavity and a six-magnetic column matrix transformer, wherein the matrix transformer has a total of six magnetic columns, which are arranged in three columns. The two magnetic columns in each column constitute an element transformer, i.e., 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 and N2 and the secondary windings N2 and N1 of the element 1 transformer are respectively distributed and wound on the magnetic columns 1 and 2, thereby reducing the coupling degree of the primary and secondary windings, so that the leakage inductance of the primary and secondary sides of the element 1 transformer is increased, and replaced by the resonant inductance of the primary and secondary sides in the resonant network of the element 1 transformer. Similarly, the primary windings N1 and N2 and the secondary windings N2 and N1 of the element 2 transformer are wound on the magnetic columns 3 and 4, thereby reducing the coupling degree of the primary and secondary windings, so that the leakage inductance of the primary and secondary sides of the element 2 transformer is increased, and replaced by the resonant inductance of the primary and secondary sides in the resonant network of the element 2. The same applies to 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 large circular wound magnetic columns and two small rectangular wound magnetic columns integrated on the magnetic plate. The two large circular magnetic columns form a column and are distributed in the first and third columns, and the two small elliptical magnetic columns form a column and are in the second column in the middle, together forming 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 in element 1 are wound on magnetic poles 1 and 2, respectively, with opposite winding directions and different numbers of turns to ensure the magnetic flux generated by them is oriented in the same direction. Similarly, the primary windings N1 and N2 of the transformer in element 2 are wound on magnetic poles 3 and 4, respectively, and the primary windings N1 and N2 of the transformer in element 3 are wound on magnetic poles 5 and 6, respectively.

4. The integrated structure according to claim 1, 2 or 3, characterized in that: The secondary windings N2 and N1 of the transformer in element 1 are wound on magnetic poles 1 and 2, respectively, with opposite winding directions and the same number of turns to ensure the generated magnetic flux is closed in the same direction. Similarly, the secondary windings N2 and N1 of the transformer in element 2 are wound evenly on magnetic poles 3 and 4, and the same applies to the transformer in 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 frequencies 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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