LLC magnetic integrated transformer with adjustable leakage inductance

Abstract

The application discloses an LLC magnetic integrated transformer with adjustable leakage inductance, which comprises a magnetic core, a middle column winding unit, a first side column winding and a second side column winding. The magnetic core comprises a middle column and a first side column and a second side column located on both sides of the middle column. The middle column winding unit is wound on the middle column, and the middle column winding unit comprises a primary winding and two secondary windings. The first side column winding is a primary winding wound on the first side column. The second side column winding is a primary winding wound on the second side column. The winding directions of the first side column winding and the second side column winding are opposite. The first side column winding and the second side column winding are connected in series with the primary winding in the middle column winding unit. The two secondary windings in the middle column winding unit have equal turns and opposite winding directions. The transformer and the leakage inductance are integrated together to achieve ingenious magnetic flux cancellation on the magnetic circuit, and the transformer function and the leakage inductance function are decoupled.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and more particularly to an LLC magnetic integrated transformer with adjustable leakage inductance. Background Technology

[0002] LLC converters are widely used due to their zero-voltage switching and high efficiency. An LLC converter requires a resonant inductor and an isolation transformer; currently, the common design approach is to integrate the isolation transformer and the resonant inductor together, which can improve power density and reduce cost.

[0003] The widely used method for magnetically integrated LLC transformers involves dividing the core's frame into two slots along the core's axis. One slot is used for the primary coil, and the other for the secondary coil. The greater the distance between the two slots, the lower the coupling coefficient between the primary and secondary coils, the longer the leakage magnetic path, and the greater the leakage inductance. The advantages of this type of LLC magnetically integrated transformer are its simple structure and the ability to directly adjust the magnetizing inductance.

[0004] However, the commonly used LLC magnetic integrated transformer has the following disadvantages: 1. Due to the use of slotted winding, and the need for larger slot spacing as leakage inductance increases, the core size increases, resulting in a larger overall transformer size. 2. Because the primary and secondary coils do not use interleaved winding, their AC resistance increases, thus increasing AC losses. 3. The leakage inductance flux path diffuses in the space surrounding the primary and secondary two-slot windings, easily generating near-field magnetic coupling with surrounding transformer components. It also generates eddy current losses in the nearby PCB copper foil, and this diffused magnetic field also produces radiated electromagnetic interference. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of traditional LLC magnetic integrated transformers where the excitation inductance and leakage inductance cannot be adjusted independently, and leakage inductance flux diffusion leads to large size and strong electromagnetic interference. The invention provides an LLC magnetic integrated transformer with adjustable leakage inductance by cleverly canceling the transformer function and leakage inductance function in the magnetic circuit.

[0006] The technical solution adopted in this invention is:

[0007] An adjustable leakage inductance LLC magnetic integrated transformer, comprising:

[0008] The magnetic core includes a central post and a first side post and a second side post located on both sides of the central post.

[0009] The center column winding unit is wound on the center column. The center column winding unit includes one primary winding and two secondary windings.

[0010] The first side column winding is the primary winding wound on the first side column;

[0011] The second side post winding is the primary winding wound on the second side post;

[0012] The first and second side column windings are wound in opposite directions, and the first and second side column windings are connected in series with the primary windings in the middle column winding unit. The two secondary windings in the middle column winding unit have the same number of turns and are wound in opposite directions.

[0013] Furthermore, the magnetic core is an EE type magnetic core or an EER type magnetic core.

[0014] Furthermore, the first and second side pillars are each provided with independent air gaps.

[0015] Furthermore, the central column of the magnetic core has a central column air gap.

[0016] Specifically, the air gap between the first and second side posts is adjusted to independently adjust the inductance of the adjustable leakage inductance. The air gap between the middle and side posts of the magnetic core is adjusted to independently adjust the magnetizing inductance of the transformer's main functional component.

[0017] Furthermore, the number of turns in the first terminal winding is equal to that in the second terminal winding.

[0018] Specifically, the first and second side-end windings have the same number of turns and the same magnetic flux; the magnetic fluxes of the first and second side-end windings are in the same direction at the side-ends, and in opposite directions at the middle-ends, canceling each other out at the middle-ends.

[0019] Specifically, the transformer magnetic flux generated by the central column winding unit induces voltages of equal magnitude and opposite polarity in the first and second side column windings, respectively, thus canceling each other out. This ensures that the magnetic flux generated by the main body of the transformer does not affect the inductance of the adjustable leakage inductance.

[0020] Furthermore, the primary and secondary windings of the center-column winding unit adopt a layered alternating winding structure. Specifically, as a feasible implementation, a sandwich winding method is used between the primary and secondary windings of the center-column winding unit to make the coupling between the primary and secondary windings tighter, which can reduce the AC equivalent resistance of the windings and reduce power consumption.

[0021] Furthermore, the two secondary windings of the central column winding unit with opposite winding directions are wound in parallel to make the rectified current more balanced.

[0022] Furthermore, the middle column winding unit, the first side column winding, and the second side column winding are all made of planar PCB copper foil.

[0023] Furthermore, the two secondary windings of the central column winding unit are each connected to the positive terminal of a full-wave rectifier diode. The two secondary windings of the central column winding unit are alternately turned on. The ratio of the total current of the two secondary windings of the central column winding unit to the current of the primary winding of the central column is N2 / N1; N2 is the number of turns of one secondary winding of the central column winding unit, and N1 is the number of turns of the primary winding of the central column winding unit.

[0024] The present invention adopts the above technical solutions: (1) The transformer and leakage inductance are integrated together to achieve clever magnetic flux cancellation on the magnetic circuit, thereby decoupling the transformer function and the leakage inductance function. The excitation inductance (Lm) is set by independently adjusting the parameters of the middle column, and the leakage inductance is set by independently adjusting the parameters of the side column, thereby improving the flexibility and accuracy of the LLC converter resonant parameter design. (2) The leakage inductance magnetic flux path is the side columns on both sides of the magnetic core, the air gap of the side columns, and the top of the magnetic core, and will not diffuse into the surrounding air. Compared with the traditional structure, this feature can effectively reduce the near-field coupling of the magnetic field, radiated electromagnetic interference (EMI), and eddy current losses in the nearby PCB. (3) The present invention can use common standard magnetic cores such as EE and EER without customization, further reducing costs. Attached Figure Description

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments;

[0026] Figure 1 This is a three-dimensional structural schematic diagram of an LLC magnetically integrated transformer with adjustable leakage inductance according to the present invention.

[0027] Figure 2 This is a top view of the adjustable leakage inductance LLC magnetic integrated transformer of the present invention.

[0028] Figure 3 This is a half-sectional schematic diagram of an LLC magnetic integrated transformer with adjustable leakage inductance according to the present invention.

[0029] Figure 4 This is an equivalent magnetoresistive circuit diagram of an LLC magnetic integrated transformer with adjustable leakage inductance according to the present invention.

[0030] Figure 5 This is a circuit diagram of an LLC magnetic integrated transformer with adjustable leakage inductance according to the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0032] like Figures 1 to 5 As shown in any of the accompanying drawings, this invention discloses an LLC magnetically integrated transformer with adjustable leakage inductance, comprising:

[0033] The magnetic core 10 includes a central post 20 and a first side post 21 and a second side post 22 located on both sides of the central post 20.

[0034] The center column 20 winding unit is wound on the center column 20. The center column 20 winding unit includes one primary winding and two secondary windings (23, 24).

[0035] The first side post winding 7 is the primary winding wound on the first side post 21;

[0036] The second side post winding 2 is the primary winding wound on the second side post 22;

[0037] The first side column winding 7 and the second side column winding 2 are wound in opposite directions. The first side column winding 7 and the second side column winding 2 are connected in series with the primary winding in the middle column 20 winding unit. The two secondary windings in the middle column 20 winding unit have the same number of turns and are wound in opposite directions.

[0038] Furthermore, the magnetic core 10 is an EE type magnetic core or an EER type magnetic core.

[0039] Furthermore, the first side post 21 and the second side post 22 are each provided with an independent air gap 30.

[0040] Furthermore, the central column 20 of the magnetic core 10 is provided with a central column air gap 40.

[0041] Specifically, the air gap between the first side post 21 and the second side post 22 is adjusted to independently adjust the inductance of the adjustable leakage inductance. The air gap between the middle post 20 and the side posts of the magnetic core 10 is adjusted to independently adjust the magnetizing inductance of the main body of the transformer.

[0042] Furthermore, the number of turns of the first side post winding 7 is equal to that of the second side post winding 2.

[0043] Specifically, the first side post winding 7 and the second side post winding 2 have the same number of turns and the same magnetic flux magnitude; the magnetic flux of the first side post winding 7 and the second side post winding 2 are in the same direction on the side post, and in opposite directions on the middle post 20, and cancel each other out at the middle post 20.

[0044] Specifically, the transformer magnetic flux generated by the central column 20 winding unit induces voltages on the first side column winding 7 and the second side column winding 2 that are equal in magnitude and opposite in polarity, thus canceling each other out. This ensures that the magnetic flux generated by the transformer functional body does not affect the inductance of the adjustable leakage inductance.

[0045] Furthermore, the primary and secondary windings of the center column 20 winding unit adopt a layered alternating winding structure. Specifically, as a feasible implementation, the primary and secondary windings (23, 24) of the center column 20 winding unit adopt a sandwich winding method to make the coupling between the primary and secondary windings tighter, which can reduce the AC equivalent resistance of the windings and reduce power consumption.

[0046] Furthermore, the two secondary windings of the 20-column winding unit with opposite winding directions are wound in parallel to make the rectified current more balanced.

[0047] Furthermore, the central column 20 winding unit, the first side column winding 7, and the second side column winding 2 are all made of planar PCB copper foil.

[0048] Furthermore, the two secondary windings (23, 24) of the central column 20 winding unit are respectively connected to the positive terminal of a full-wave rectifier diode. The two secondary windings of the central column 20 winding unit are alternately turned on. The ratio of the total current of the two secondary windings of the central column 20 winding unit to the current of the primary winding of the central column 20 is N2 / N1; N2 is the number of turns of one secondary winding of the central column 20 winding unit, and N1 is the number of turns of the primary winding of the central column 20 winding unit.

[0049] Specifically, such as Figure 5 As shown, one end 12 of one of the secondary windings 23 of the central column 20 winding unit is connected to the positive terminal of a full-wave rectifier diode D9205, and the other end 16 of the secondary winding 23 is grounded; one end 13 of the other secondary winding 24 of the central column 20 winding unit is connected to the positive terminal of a full-wave rectifier diode D9206, and the other end 9 of the secondary winding 24 is grounded; the negative terminals of the full-wave rectifier diode D9205 and the negative terminals of the full-wave rectifier diode D9206 are electrically connected.

[0050] like Figure 1 As shown, the primary winding of the LLC transformer consists of three coils connected in series. N1 turns are wound on the middle column 20 of the core 10, and N0 turns are wound on each of the two side columns of the core 10. The magnetic flux generated by the current in the side column coils is in the same direction at the side columns, but opposite in direction at the middle column 20. The secondary winding consists of two coils with the same number of turns (N2) but opposite in direction. These coils are connected to the positive terminals of two full-wave rectifier diodes on the secondary winding. The two windings conduct alternately, and the ratio of their total current to the primary winding current is N2 / N1. Therefore, the magnetic flux generated by the primary winding current in the middle column 20 of the core 10 and the magnetic flux generated by the total current in the secondary winding are equal in magnitude and opposite in direction, canceling each other out at the middle column 20 of the core 10. The voltages induced on the two side column windings of the core 10 are also equal in magnitude and opposite in direction, canceling each other out.

[0051] The two end posts each have a primary winding with the same number of turns, and the magnetic flux generated by the current in the two windings is the same in magnitude and direction on the end posts, but opposite in direction on the middle post 20, thus canceling each other out. Therefore, the magnetic flux generated by the current in the two end post windings does not couple to the primary and secondary windings of the middle post 20, and has no effect on the transformer inductance formed by the primary and secondary windings of the middle post 20.

[0052] Therefore, the transformer function composed of the primary and secondary windings of the central column 20 of the magnetic core 10 and the leakage inductance function composed of the primary windings on the two side columns are decoupled from each other, so that the transformer and leakage inductance functions can be designed independently.

[0053] like Figure 4 As shown, the equivalent reluctance circuit diagram of the LLC transformer of the present invention is illustrated. In the diagram, R1 is the reluctance of a single-sided column core 10, Rg1 is the air gap reluctance of a single-sided column, R2 is the reluctance of the middle column 20 core 10, and Rg2 is the air gap reluctance of the middle column 20. φ1 is the magnetic flux of the left column of core 10, φ2 is the magnetic flux of the right column of core 10, and φ3 is the magnetic flux of the middle column 20 of core 10. V1 is the magnetomotive force of the primary winding on the left column of core 10, with N0 turns; V4 is the magnetomotive force of the primary winding on the right column of core 10, with N0 turns; V2 is the magnetomotive force of the primary winding on the middle column 20 of core 10, with N1 turns; V3 and V5 are the magnetomotive forces of the two secondary full-wave rectifier windings on the middle column 20 of core 10, each with N2 turns. Specifically, based on... Figure 4 The theoretical calculation expressions for magnetizing inductance and leakage inductance are as follows:

[0054] 10-magnetic-resistance single-sided column core: ;

[0055] Single-sided column air gap magnetic reluctance: ;

[0056] 20 cores, 10 reluctance: ;

[0057] 20 air gap reluctance in the middle column: ;

[0058] Magnetizing inductor: ;

[0059] Leakage: ;

[0060] in, It is the effective magnetic circuit length of the 10-sided column of the magnetic core; It is the effective magnetic circuit length of the column 20 in the magnetic core 10; It is the air gap length of the 10-sided post of the magnetic core; It is the air gap length of column 20 in core 10; It is the vacuum permeability; It is the relative permeability of the magnetic material of core 10; It is the effective cross-sectional area of ​​the 10-sided column of the magnetic core; It is the effective cross-sectional area of ​​column 20 in magnetic core 10. It is the current flowing through the primary winding.

[0061] This invention integrates the transformer and leakage inductance into an LLC magnetic integrated transformer structure, simultaneously decoupling the transformer and leakage inductance functions. It utilizes a conventional EE or EER magnetic core 10, eliminating the need for a custom core 10. The transformer function is achieved by simultaneously winding the primary and secondary windings in the winding slots of the central column 20 of the magnetic core 10. The leakage inductance function is achieved by winding the same number of primary windings in the winding slots of the two side columns of the magnetic core 10. Because the two side column magnetic cores 10 each have the same number of primary windings, the magnetic fluxes they generate are opposite in direction and equal in magnitude at the central column 20 of the magnetic core 10, canceling each other out. Therefore, the magnetic fluxes of the two side columns will not couple with the primary and secondary windings on the central column 20, and will not affect the inductance of the central column 20 winding. Furthermore, the magnetic flux generated from the primary and secondary windings of the central column 20 of the magnetic core 10 induces equal and opposite voltages in each side column winding of the magnetic core 10, thus canceling each other out. Therefore, the transformer flux of the central column 20 does not affect the inductance of the side column leakage inductance. Consequently, its transformer function and leakage inductance function are decoupled from each other.

[0062] This invention allows for precise design of leakage inductance to meet diverse application requirements by adjusting the number of turns in the side post windings (ensuring equal turns on both side post windings) and the air gap. The magnetizing inductance is determined by the number of turns in the primary winding on the middle post 20 of the core 10, the air gap between the middle post 20 and the side posts, thus achieving independent design of the magnetizing inductance and leakage inductance. The leakage inductance flux path is through the side posts on both sides of the core 10, the air gap between the side posts, and the top of the core 10, preventing diffusion into the surrounding air. Compared to traditional structures, this characteristic effectively reduces near-field coupling of the magnetic field, radiated electromagnetic interference (EMI), and eddy current losses in nearby PCBs.

[0063] The present invention adopts the above technical solutions: (1) The transformer and leakage inductance are integrated together to achieve clever magnetic flux cancellation on the magnetic circuit, thereby decoupling the transformer function and the leakage inductance function. The excitation inductance (Lm) is set by independently adjusting the parameters of the middle column 20, and the leakage inductance is set by independently adjusting the parameters of the side column, thereby improving the flexibility and accuracy of the LLC converter resonant parameter design. (2) The leakage inductance magnetic flux path is the side columns on both sides of the magnetic core 10, the air gap of the side columns, and the top of the magnetic core 10, and will not diffuse into the surrounding air. Compared with the traditional structure, this feature can effectively reduce the near-field coupling of the magnetic field, radiated electromagnetic interference (EMI), and eddy current losses in the nearby PCB. (3) The present invention can use the common EE, EER and other standard magnetic cores 10 without customization, further reducing the cost.

[0064] Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Without conflict, the embodiments and features in the embodiments of this application can be combined with each other. The components of the embodiments of this application described and illustrated herein can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An LLC magnetically integrated transformer with adjustable leakage inductance, characterized in that, include: The magnetic core includes a central post and a first side post and a second side post located on both sides of the central post. The center column winding unit is wound on the center column. The center column winding unit includes one primary winding and two secondary windings. The first side column winding is the primary winding wound on the first side column; The second side post winding is the primary winding wound on the second side post; The first and second side column windings are wound in opposite directions, and the first and second side column windings are connected in series with the primary windings in the middle column winding unit. The two secondary windings in the middle column winding unit have the same number of turns and are wound in opposite directions.

2. The LLC magnetically integrated transformer with adjustable leakage inductance according to claim 1, characterized in that, The magnetic core is either an EE type or an EER type.

3. The LLC magnetically integrated transformer with adjustable leakage inductance according to claim 1, characterized in that, The first and second side pillars each have independent air gaps.

4. The LLC magnetically integrated transformer with adjustable leakage inductance according to claim 1, characterized in that, The magnetic core has a central column air gap.

5. An adjustable leakage inductance LLC magnetic integrated transformer according to claim 1, characterized in that, The number of turns in the first and second side column windings are equal.

6. The LLC magnetically integrated transformer with adjustable leakage inductance according to claim 1, characterized in that, The primary and secondary windings of the center column winding unit adopt a layered alternating winding structure.

7. An adjustable leakage inductance LLC magnetic integrated transformer according to claim 1, characterized in that, The two secondary windings of the center column winding unit with opposite winding directions are wound in parallel.

8. An adjustable leakage inductance LLC magnetic integrated transformer according to claim 1, characterized in that, The center column winding unit, the first side column winding, and the second side column winding are all made of planar PCB copper foil.

9. An adjustable leakage inductance LLC magnetic integrated transformer according to claim 1, characterized in that, The two secondary windings of the central column winding unit are each connected to the positive terminal of a full-wave rectifier diode. The two secondary windings of the central column winding unit are turned on alternately. The ratio of the total current of the two secondary windings of the central column winding unit to the current of the primary winding of the central column is N2 / N1. N2 is the number of turns of one secondary winding of the central column winding unit, and N1 is the number of turns of the primary winding of the central column winding unit.

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