LLC secondary balance transformer and power supply

Abstract

An LLC secondary balancing transformer and power supply, the LLC secondary balancing transformer comprises a primary winding, a secondary winding and a magnetic core. The secondary winding comprises a first secondary winding and a second secondary winding, the first secondary winding comprises a plurality of first sub-windings arranged in layers, the second secondary winding comprises a plurality of second sub-windings arranged in layers, the number of the first sub-windings is the same as the number of the second sub-windings, and one first sub-winding and one second sub-winding are arranged in the same layer. By adopting the method of arranging the first sub-winding and the second sub-winding in the same layer, the distance from the first sub-winding to the primary winding and the distance from the corresponding second sub-winding to the primary winding can be made substantially equal, the leakage inductance of the first secondary winding and the second secondary winding is more uniform, and the secondary loop current of the half-bridge LLC resonant converter can be balanced, thereby effectively reducing the temperature rise of the device and increasing the service life of the device.

Description

Technical Field

[0001] The present application belongs to the technical field of transformers, and in particular, relates to an LLC secondary balancing transformer and a power supply. Background Art

[0002] At present, with the development of semiconductors, power devices have faster switching speeds, and increasing the switching frequency can make the circuit have higher power density and reliability, low noise and fast response capabilities, so high frequency has become a development trend of switching power supplies.

[0003] The series-parallel resonant converter can be regarded as a combination of the series resonant converter and the parallel resonant converter. When the load is rated, the converter exhibits the characteristics of the series resonant converter. When the load becomes lighter, it tends to the characteristics of the parallel resonant converter. Its resonant tank current can change with the load, so the working efficiency is high. At the same time, the output voltage can be adjusted in a wide range by adjusting the switching frequency. However, the primary leakage inductance of the series-parallel resonant converter transformer cannot participate in the resonance, resulting in a large phase difference between the transformer voltage and current, which leads to an increase in reactive current in the resonant circuit and an increase in conduction loss. In order to solve the above drawbacks of the resonant converter, a resonant inductor is connected in series on the basis of the series resonant converter, so that the circuit characteristics and working mode are completely changed, and the LLC resonant converter is obtained. The LLC resonant converter has a ZVS function in the range of zero to full load, and the MOSFET has a low turn-off current and low turn-off loss.

[0004] However, the existing half-bridge LLC resonant converter usually has the problem of unbalanced secondary loop current due to hardware parameters. Summary of the invention

[0005] The purpose of the present application is to provide an LLC secondary balancing transformer and a power supply, aiming to solve the problem of unbalanced secondary loop current in traditional transformers.

[0006] A first aspect of an embodiment of the present application provides an LLC secondary balancing transformer, comprising a primary winding, a secondary winding and a magnetic core, wherein the primary winding and the secondary winding are both wound on the magnetic core; the secondary winding comprises a first secondary winding and a second secondary winding, the first secondary winding comprises a plurality of first sub-windings arranged in a stacked manner, the second secondary winding comprises a plurality of second sub-windings arranged in a stacked manner, the number of the first sub-windings is the same as the number of the second sub-windings, and one first sub-winding and one second sub-winding are arranged in the same layer; a plurality of the first sub-windings are interconnected between the first pin and the second pin of the LLC secondary balancing transformer, and a plurality of the second sub-windings are interconnected between the second pin and the third pin of the LLC secondary balancing transformer.

[0007] In one embodiment, the primary winding includes a first primary winding and a second primary winding, the first primary winding and the second primary winding are connected in series between a fourth pin and a fifth pin of the LLC secondary balancing transformer, and the first primary winding, the secondary winding and the second primary winding are stacked and wound on the magnetic core in sequence in a direction away from the magnetic core.

[0008] In one embodiment, each of the first sub-windings is connected in parallel between the first pin and the second pin, and each of the second sub-windings is connected in parallel between the second pin and the third pin.

[0009] In one embodiment, the first sub-windings are arranged in sequence and overlap each other, and the second sub-windings are arranged in sequence and overlap each other.

[0010] In one embodiment, adjacent first sub-windings do not overlap with each other, and adjacent second sub-windings do not overlap with each other.

[0011] In one embodiment, the winding directions of the sub-windings are the same.

[0012] In one embodiment, a first sub-winding and a corresponding second sub-winding are arranged in the same winding layer, and the winding layer includes a first winding half-section and a second winding half-section arranged in a direction from the first end of the magnetic core to the second end of the magnetic core; a winding half-section is used to wind a sub-winding in a direction from the first end of the magnetic core to the second end of the magnetic core, and the number of turns of the winding in the first winding half-section is the same as the number of turns of the winding in the second winding half-section.

[0013] In one embodiment, the wire diameter of the winding in the first winding half section is the same as the wire diameter of the winding in the second winding half section.

[0014] In one embodiment, a plane where a boundary line between the first winding half zone and the second winding half zone lies intersects with an air gap of the magnetic core.

[0015] A second aspect of an embodiment of the present application provides a power supply, comprising the LLC secondary balancing transformer as described above.

[0016] Compared with the prior art, the embodiments of the present application have the following beneficial effects: by adopting the method of arranging the first sub-winding and the second sub-winding in the same layer, the distance from the first sub-winding to the primary winding and the corresponding distance from the second sub-winding to the primary winding can be made basically equal, the leakage inductance of the first secondary winding and the second secondary winding are more uniform, and the secondary loop current of the half-bridge LLC resonant converter can be balanced, thereby effectively reducing the temperature rise of the device and increasing the service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the basic topology diagram of the traditional half-bridge LLC resonant converter;

[0018] Figure 2 A schematic diagram of the structure of an LLC secondary balancing transformer provided in one embodiment of the present application;

[0019] Figure 3 A circuit diagram of an LLC secondary balancing transformer provided in one embodiment of the present application;

[0020] Figure 4 Another structural schematic diagram of an LLC secondary balancing transformer provided in one embodiment of the present application;

[0021] Figure 5 Another circuit diagram of an LLC secondary balancing transformer provided by an embodiment of the present application;

[0022] Figure 6 The secondary loop current waveform of a traditional power supply that is not composed of a sandwich transformer;

[0023] Figure 7 The secondary loop current waveform of a power supply composed of a traditional sandwich transformer;

[0024] Figure 8 A secondary loop current waveform diagram of a power supply composed of an LLC secondary balancing transformer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0027] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] The basic topology of the half-bridge LLC resonant converter is shown in Figure 1 On the basis of the series resonant converter, Lm is added, and the circuit characteristics and working mode are completely changed.

[0030] The design method of the half-bridge LLC resonant converter has become quite mature after years of development. However, as the power density requirements of the power supply become higher and higher, the temperature rise of the device has become a bottleneck.

[0031] In the current design method, the transformer is usually regarded as an ideal transformer, ignoring the difference in leakage inductance between the two secondary windings caused by the winding structure of the actual transformer. This results in the situation where the two secondary windings should have symmetrical currents in the ideal design, but there are large and small waves, which leads to the deterioration of the temperature rise of the diodes D1 / D2 (or synchronous rectifier MOS tubes), and the power tubes in the circuit with large current suffer more losses, resulting in abnormal temperature rise.

[0032] Figure 2 The structure diagram of the LLC secondary balancing transformer provided by an embodiment of the present application is shown. For the convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0033] The LLC secondary balancing transformer includes a primary winding 100, a secondary winding 200 and a magnetic core 300. The primary winding 100 and the secondary winding 200 are both wound on the magnetic core 300. The circuit diagram of the LLC secondary balancing transformer is shown in FIG. Figure 3 shown.

[0034] The secondary winding 200 includes a first secondary winding and a second secondary winding. The first secondary winding includes a plurality of first sub-windings ( Figure 2 The first sub-winding Ns1-1 and the first sub-winding Ns1-2 are shown in FIG. 1 , and the second secondary winding includes a plurality of second sub-windings ( Figure 2 The second sub-winding Ns2-1 and the second sub-winding Ns2-2 are shown in FIG. 1 , the number of the first sub-windings is the same as the number of the second sub-windings, and one first sub-winding and one second sub-winding are arranged on the same layer ( Figure 2 In the embodiment, the first sub-winding Ns1-1 and the second sub-winding Ns2-1 are arranged on the same layer, and the first sub-winding Ns1-2 and the second sub-winding Ns2-2 are arranged on the same layer).

[0035] A plurality of first sub-windings are connected to each other between the first pin C and the second pin D of the LLC secondary balancing transformer ( Figure 2 In the embodiment, the first sub-winding Ns1-1 and the first sub-winding Ns1-2 are connected to each other between the first pin C and the second pin D of the LLC secondary balancing transformer, and the plurality of second sub-windings are connected to each other between the second pin D and the third pin E of the LLC secondary balancing transformer ( Figure 2 In the embodiment, the second sub-winding Ns2-1 and the second sub-winding Ns2-2 are connected to each other between the second pin D and the third pin E of the LLC secondary balancing transformer).

[0036] By arranging the first sub-winding and the second sub-winding in the same layer, the distance from the first sub-winding to the primary winding 100 can be made substantially equal to the distance from the corresponding second sub-winding to the primary winding 100, the leakage inductance of the first secondary winding and the second secondary winding is more uniform, and the secondary loop current of the half-bridge LLC resonant converter can be balanced, thereby effectively reducing the temperature rise of the device and increasing the service life of the device.

[0037] In one embodiment, the primary winding 100 includes a first primary winding Np-1 and a second primary winding Np-2, the first primary winding Np-1 and the second primary winding Np-2 are connected in series between the fourth pin A and the fifth pin B of the LLC secondary balancing transformer, and the first primary winding Np-1, the secondary winding 200 and the second primary winding Np-2 are stacked and wound on the magnetic core 300 in sequence in a direction away from the magnetic core 300.

[0038] It should be noted that by dividing the primary winding 100 into a first primary winding Np-1 and a second primary winding Np-2, and respectively arranging them on the inner and outer sides of the secondary winding 200, the magnetic field distribution inside the LLC secondary balancing transformer can be improved, thereby improving the leakage inductance of the secondary winding 200 between the first primary winding Np-1 and the second primary winding Np-2.

[0039] In one embodiment, if Figure 3 As shown, each first sub-winding is connected in parallel between the first pin C and the second pin D, and each second sub-winding is connected in parallel between the second pin D and the third pin E.

[0040] Specifically, the same-name end of the first sub-winding Ns1-1 and the same-name end of the first sub-winding Ns1-2 are both connected to the first pin C, and the opposite-name end of the first sub-winding Ns1-1 and the opposite-name end of the first sub-winding Ns1-2 are both connected to the second pin D. The same-name end of the second sub-winding Ns2-1 and the same-name end of the second sub-winding Ns2-2 are both connected to the second pin D, and the opposite-name end of the second sub-winding Ns2-1 and the opposite-name end of the second sub-winding Ns2-2 are both connected to the third pin E.

[0041] The difficulty of winding the LLC secondary balancing transformer can be reduced by connecting in parallel, without considering the connection relationship between the various sub-windings.

[0042] Meanwhile, by changing the conventional arrangement of one winding between two pins to the above embodiment in which at least two parallel sub-windings are arranged between the two pins, the leakage inductance of the LLC secondary balancing transformer can be further reduced.

[0043] In one embodiment, the winding directions of the sub-windings are the same.

[0044] The winding direction specifically refers to the winding direction of the wire of the winding. When looking from the first end of the magnetic core 300 to the second end of the magnetic core 300, the winding direction includes a clockwise direction and a counterclockwise direction.

[0045] In some embodiments, for example, Figure 2 When looking from the left end of the magnetic core 300 to the right end of the magnetic core 300 , the winding direction of each sub-winding is clockwise.

[0046] In some embodiments, the winding directions of the primary winding 100 and the secondary winding 200 are the same.

[0047] In one embodiment, if Figure 2 As shown, a first sub-winding and a corresponding second sub-winding are arranged in the same winding layer, and the winding layer includes a first winding half-section and a second winding half-section arranged in a direction from the first end of the magnetic core 300 to the second end of the magnetic core 300. A winding half-section is used to wind a winding in a direction from the first end of the magnetic core 300 to the second end of the magnetic core 300, and the number of turns of the winding in the first winding half-section is the same as the number of turns of the winding in the second winding half-section.

[0048] It can be understood that since the corresponding first sub-winding and second sub-winding are arranged in the same layer, when the first winding half area is used to wind the first sub-winding, the second winding half area is used to wind the corresponding second sub-winding; when the first winding half area is used to wind the second sub-winding, the second winding half area is used to wind the corresponding first sub-winding.

[0049] In one embodiment, the wire diameter of the winding in the first winding half section is the same as the wire diameter of the winding in the second winding half section.

[0050] Under the condition that the number of turns of the winding in the first winding half section is the same as the number of turns of the winding in the second winding half section and the wire diameter of the winding in the first winding half section is the same as the wire diameter of the winding in the second winding half section, the change of the inductance parameter between the pins caused by the change of the number of parallel sub-windings can be avoided, so that the leakage inductance between the first secondary winding and the second secondary winding is closer.

[0051] In one embodiment, if Figure 2 As shown, each first sub-winding is overlapped in sequence, and each second sub-winding is overlapped in sequence.

[0052] When each first sub-winding is connected in parallel between the first pin C and the second pin D, and each second sub-winding is connected in parallel between the second pin D and the third pin E, the sub-windings connected in parallel are stacked in sequence.

[0053] In one embodiment, if Figure 4 As shown, adjacent first sub-windings do not overlap each other, and adjacent second sub-windings do not overlap each other.

[0054] That is, in a direction extending away from the magnetic core 300 , the first sub-winding and the second sub-winding are alternately arranged in sequence.

[0055] In one embodiment, the secondary winding 200 includes two first sub-windings and two second sub-windings.

[0056] Correspondingly, the two first sub-windings and the two second sub-windings are wound in two winding layers.

[0057] The first secondary winding includes a first sub-winding Ns1-1 and a first sub-winding Ns1-2, and the second secondary winding includes a second sub-winding Ns2-1 and a second sub-winding Ns2-2. The two winding layers include a first winding layer and a second winding layer stacked in sequence in a direction away from the magnetic core 300.

[0058] In the first solution of this embodiment, Figure 2 As shown, the first sub-winding Ns1-1 is wound on the first winding half area of ​​the first winding layer, and the second sub-winding Ns2-1 is wound on the second winding half area of ​​the first winding layer. The first sub-winding Ns1-2 is wound on the first winding half area of ​​the second winding layer, and the second sub-winding Ns2-2 is wound on the second winding half area of ​​the second winding layer.

[0059] In the second solution of this embodiment, Figure 4 As shown, the first sub-winding Ns1-1 is wound on the first winding half area of ​​the first winding layer, and the second sub-winding Ns2-1 is wound on the second winding half area of ​​the first winding layer. The first sub-winding Ns1-2 is wound on the second winding half area of ​​the second winding layer, and the second sub-winding Ns2-2 is wound on the first winding half area of ​​the second winding layer.

[0060] Exemplarily, the specific winding method of the LLC secondary balancing transformer is:

[0061] The first primary winding Np-1 is wound from the fourth pin A to the sixth pin X in a single wire in the third winding layer, with two layers clockwise, for a total of 23 turns. After winding, it is covered with a double layer of tape for insulation.

[0062] The first sub-winding Ns1-1 is wound 4 turns clockwise in the first winding half-section of the first winding layer, starting from the first pin C to the second pin D in a single wire.

[0063] The second sub-winding Ns2-1 is wound clockwise for 4 turns in the second winding half area of ​​the first winding layer, starting from the second pin D and winding to the third pin E. After the first sub-winding Ns1-1 and the second sub-winding Ns2-1 are wound, a single layer of adhesive tape is covered on the wound first sub-winding Ns1-1 and the second sub-winding Ns2-1 to fix the first sub-winding Ns1-1 and the second sub-winding Ns2-1.

[0064] The first sub-winding Ns1-2 is wound 4 turns clockwise in the first winding half section of the second winding layer, starting from the first pin C to the second pin D in a single wire.

[0065] The second sub-winding Ns2-2 is wound clockwise for 4 turns in the second winding half area of ​​the first winding layer, starting from the second pin D and winding to the third pin E. After the first sub-winding Ns1-2 and the second sub-winding Ns2-2 are wound, a double layer of adhesive tape is covered on the wound first sub-winding Ns1-2 and the second sub-winding Ns2-2 to achieve insulation and fixation of the first sub-winding Ns1-2 and the second sub-winding Ns2-2.

[0066] The second primary winding Np-2 is wound from the sixth pin X to the fifth pin B in the fourth winding layer, with two layers clockwise, for a total of 9 turns. After winding, it is covered with a double layer of tape for insulation.

[0067] The third winding layer, the first winding layer, the second winding layer and the fourth winding layer are stacked in sequence along a direction away from the magnetic core 300 .

[0068] Specifically, the windings in the third winding layer, the first winding layer, the second winding layer and the fourth winding layer (the first primary winding Np-1, the first sub-winding Ns1-1, the second sub-winding Ns2-1, the first sub-winding Ns1-2, the second sub-winding Ns2-2 and the second primary winding Np-2) can be wound according to the steps and parameters shown in Table 1.

[0069]

[0070] Table 1

[0071] When other conditions remain unchanged and only the winding scheme of the transformer is changed, the leakage inductance obtained by testing the ordinary non-sandwich transformer, the ordinary sandwich transformer, the transformer having some technical features of the present embodiment, and the first scheme and the second scheme of the present embodiment is shown in Table 2, and the current parameters are shown in Table 3:

[0072]

[0073] Table 2

[0074]

[0075] Table 3

[0076] Based on Table 2 and Table 3, it can be seen that the leakage inductance consistency and current consistency of the secondary circuit of the first and second schemes are significantly better than those of the ordinary winding transformer.

[0077] In some embodiments, Figure 5 As shown, the secondary winding 200 includes three first sub-windings ( Figure 5 The first sub-winding Ns1-1, the first sub-winding Ns1-2 and the first sub-winding Ns1-3) and three second sub-windings ( Figure 5 A second sub-winding Ns2-1, a second sub-winding Ns2-2 and a second sub-winding Ns2-3) are shown.

[0078] The three first sub-windings are connected in parallel with each other, and the three second sub-windings are connected in parallel with each other.

[0079] It should be noted that when a larger current of the secondary loop is required, the number of the first sub-windings and the second sub-windings connected in parallel may be increased.

[0080] In one embodiment, if Figure 2 As shown, the plane where the boundary line between the first winding half zone and the second winding half zone lies intersects with the air gap 330 of the magnetic core 300 .

[0081] It should be noted that in the transformer, the air gap 330 of the magnetic core 300 can reduce the magnetic permeability of the core, so that when the transformer is subjected to a large pulse current impact, the core is not easy to enter a saturation state. At the same time, the position of the air gap 330 will affect the size of the leakage inductance. In particular, the boundary line between the first winding half zone and the second winding half zone is in the middle of the skeleton, which is also the position of the air gap 330 of the magnetic core 300. The leakage inductance is more significantly affected by the position of the air gap 330 than the original sandwich and non-sandwich transformer structures.

[0082] By adjusting the width of the air gap 330 , the leakage inductance consistency of the secondary loop can be further improved.

[0083] The magnetic core 300 specifically includes a first sub-core 310 and a second sub-core 320 , and an air gap 330 is disposed between the first sub-core 310 and the second sub-core 320 .

[0084] In one embodiment, the width of the air gap 330 is 0.6 mm to 1 mm.

[0085] Preferably, the width of the air gap 330 is 0.8 mm.

[0086] Exemplarily, in one embodiment, the corresponding relationship between the width of the air gap 330 and the leakage inductance is shown in Table 4.

[0087]

[0088] Table 4

[0089] The air gap width of the first sub-core 310 specifically refers to the width of the air gap 330 located at the center occupied by the first sub-core 310. Similarly, the air gap width of the first sub-core 310 specifically refers to the width of the air gap 330 located at the center occupied by the second sub-core 320. Based on Table 2 and Table 3, it can be seen that in this embodiment, by adjusting the position of the air gap 330, the leakage inductance of the secondary circuit can be adjusted, and the leakage inductance of the first secondary winding and the second secondary winding can be completely equal, thereby achieving the balance of the secondary circuit current of the LLC converter.

[0090] Figure 6 , Figure 7 , Figure 8 The secondary diode current waveforms of the 24V / 12.5A power supply made based on the ordinary non-sandwich transformer, the ordinary sandwich transformer and the LLC secondary balancing transformer of this embodiment are shown in FIG. The red and blue waveforms are the currents of the first secondary winding and the second secondary winding respectively, and the yellow waveform is the voltage across the lower tube of the LLC converter.

[0091] pass Figure 6 , Figure 7 , Figure 8 It can be seen that the currents of the first secondary winding and the second secondary winding of the power supply made by the LLC secondary balancing transformer of this embodiment are more balanced.

[0092] An embodiment of the present application provides a power supply, comprising an LLC secondary balancing transformer as described in any of the above embodiments.

[0093] The power supply may specifically include an LLC resonant converter.

[0094] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0095] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0096] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An LLC secondary balancing transformer, comprising a primary winding, a secondary winding and a magnetic core, wherein the primary winding and the secondary winding are both wound on the magnetic core; characterized in that: The secondary winding comprises a first secondary winding and a second secondary winding, the first secondary winding comprises a plurality of first sub-windings arranged in layers, the second secondary winding comprises a plurality of second sub-windings arranged in layers, the number of the first sub-windings is the same as the number of the second sub-windings, and one first sub-winding and one second sub-winding are arranged in the same layer; A plurality of the first sub-windings are mutually connected between the first pin and the second pin of the LLC secondary balancing transformer, and a plurality of the second sub-windings are mutually connected between the second pin and the third pin of the LLC secondary balancing transformer.

2. The LLC secondary balancing transformer according to claim 1, characterized in that: The primary winding includes a first primary winding and a second primary winding, the first primary winding and the second primary winding are connected in series between the fourth pin and the fifth pin of the LLC secondary balancing transformer, and the first primary winding, the secondary winding and the second primary winding are stacked and wound on the magnetic core in sequence in a direction away from the magnetic core.

3. The LLC secondary balancing transformer according to claim 1, characterized in that: Each of the first sub-windings is connected in parallel between the first pin and the second pin, and each of the second sub-windings is connected in parallel between the second pin and the third pin.

4. The LLC secondary balancing transformer according to claim 1, wherein: The first sub-windings are arranged overlappingly in sequence, and the second sub-windings are arranged overlappingly in sequence.

5. The LLC secondary balancing transformer according to claim 1, wherein: Adjacent first sub-windings do not overlap with each other, and adjacent second sub-windings do not overlap with each other.

6. The LLC secondary balancing transformer according to claim 1, wherein: The winding directions of the sub-windings are the same.

7. The LLC secondary balancing transformer according to claim 1, wherein: A first sub-winding and a corresponding second sub-winding are arranged in the same winding layer, and the winding layer includes a first winding half-section and a second winding half-section arranged along the direction from the first end of the magnetic core to the second end of the magnetic core; a winding half-section is used to wind a sub-winding along the direction from the first end of the magnetic core to the second end of the magnetic core, and the number of turns of the winding in the first winding half-section is the same as the number of turns of the winding in the second winding half-section.

8. The LLC secondary balancing transformer according to claim 7, characterized in that: The wire diameter of the winding in the first winding half section is the same as the wire diameter of the winding in the second winding half section.

9. The LLC secondary balancing transformer according to claim 7, characterized in that: A plane where a boundary line between the first winding half zone and the second winding half zone lies intersects with an air gap of the magnetic core.

10. A power supply, characterized in that: Comprising the LLC secondary balancing transformer as claimed in any one of claims 1 to 9.

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