A transformer and an on-board charger system

Abstract

This utility model discloses a transformer, which includes an iron core (100) having at least two parallel winding arms (101) extending along the length direction of the iron core, each winding arm having an alternately arranged primary coil (200) and secondary coil (300) wound on it; wherein, air gaps (103) are respectively provided at two ends (102) along the length direction (L) of the iron core, and the extension direction of the air gaps is consistent with the length direction of the iron core; along the length direction of the iron core, the secondary coil is closer to the air gap than the primary coil.

Description

Technical Field

[0001] This utility model relates to an electrical component, and more particularly to a transformer. Background Technology

[0002] The transformer is one of the important electrical components in the on-board charger system (OBC system). Currently, in order to improve the performance of the on-board charger, it is often necessary to optimize the design of the transformer.

[0003] In transformers used for on-board chargers (OBCs), one approach is to use a secondary coil winding with a center tap to match the secondary-side diodes. This method effectively reduces the number of secondary-side semiconductor devices by half, thereby lowering the cost of the OBC.

[0004] However, in center-tapped transformers used with diodes, the secondary leakage inductance interacts with the diode's parasitic capacitance, creating an unexpected resonant circuit. This resonance causes significant voltage fluctuations on the secondary side, which directly stress the diode. In severe cases, these voltage spikes can even degrade diode performance or cause electronic device malfunctions. Utility Model Content

[0005] One of the objectives of this invention is to provide a transformer that can eliminate secondary leakage inductance as much as possible while retaining a large primary leakage inductance, thereby eliminating potential voltage fluctuations on the secondary side and ensuring stable operation of the transformer.

[0006] To achieve the above objectives, this utility model provides a transformer comprising an iron core having at least two parallel winding arms extending along the length of the iron core, each winding arm having a primary coil and a secondary coil wound on it; wherein:

[0007] An air gap is provided at each of the two ends along the length of the iron core, and the air gap extends in the same direction as the length of the iron core.

[0008] Along the length of the iron core, the secondary coil is closer to the air gap than the primary coil.

[0009] Furthermore, in the transformer described in this utility model, the air gap is located at the center position in the width direction of the iron core.

[0010] Furthermore, in the transformer described in this utility model, the width of the air gap is 0.5 to 2 mm.

[0011] Furthermore, in the transformer described in this utility model, each of the two ends of the iron core along its length is provided with an air gap.

[0012] Furthermore, in the transformer described in this utility model, at least one soft magnetic material sheet is provided in the air gap, which is arranged parallel to the length direction of the iron core, so as to divide the air gap into several sub-air gaps.

[0013] Furthermore, in the transformer described in this utility model, at least one primary coil is wound with at least two layers on the iron core, and the number of turns of the outer layer of the primary coil away from the iron core is less than or equal to the number of turns of the inner layer of the primary coil relatively close to the iron core.

[0014] Furthermore, in the transformer described in this utility model, at least one secondary coil is wound with at least two layers on the iron core, and the number of turns of the outer layer of the secondary coil away from the iron core is less than or equal to the number of turns of the inner layer of the secondary coil relatively close to the iron core.

[0015] Furthermore, in the transformer described in this utility model, the secondary coil of the transformer has a center tap.

[0016] Furthermore, in the transformer described in this utility model, a baffle is provided between adjacent primary and secondary coils.

[0017] Furthermore, in the transformer described in this utility model, a shielding shell is provided around the iron core.

[0018] Another objective of this invention is to provide an on-board charger system with stable performance.

[0019] For the purposes described above, this utility model also provides an on-board charger system, which includes the transformer as described above.

[0020] The transformer described in this invention maintains the primary leakage inductance at the desired level while minimizing secondary leakage inductance, thereby eliminating potential voltage fluctuations on the secondary side and ensuring stable operation of the transformer.

[0021] The transformer described in this utility model has a simple structure and low manufacturing cost. Attached Figure Description

[0022] Figure 1 This shows a common transformer circuit structure.

[0023] Figure 2 The circuit structure of a transformer with a center tap is shown.

[0024] Figure 3 A schematic diagram of the transformer according to one embodiment of the present invention is shown.

[0025] Figure 4The structure of the core of the transformer according to one embodiment of the present invention is shown.

[0026] Figure 5 The structure of the transformer described in this utility model is shown in one embodiment from both sectional and top-view perspectives.

[0027] Figure 6 The diagram shows a baffle of the transformer according to one embodiment of the present invention.

[0028] Figure 7 The structure of the transformer described in this utility model is shown in one embodiment from both sectional and top-view perspectives. Detailed Implementation

[0029] The transformer and on-board charger system of this utility model will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, such explanation and description do not constitute an undue limitation on the technical solution of this utility model.

[0030] Transformers are important electrical components in charging systems. Figure 1 This diagram illustrates a common transformer circuit structure, where Lr represents the resonant inductance, Cr represents the resonant capacitor, and Lm represents the transformer magnetizing inductance. In this transformer, the primary side connects to the input capacitor C1 and two power switches Q1 and Q2, while the secondary side connects to four diodes D1, D2, D3, and D4 and the output capacitor Co. For this resonant-based DC-DC converter, an inductor is required on the primary side of the transformer to participate in the resonance. To achieve this, transformer design often intentionally reduces coupling between windings through a specific winding arrangement, thereby increasing leakage inductance. This leakage inductance then acts as the resonant inductance Lr, eliminating the need for an additional discrete inductor and simplifying the circuit design. In... Figure 1 In the transformer shown, leakage inductance is introduced on both the primary and secondary sides, but the leakage inductance on the secondary side has a smaller impact.

[0031] To further simplify the design of electronic components and reduce the cost of transformers, Figure 1 The conventional transformer shown is replaced with a center-tapped transformer.

[0032] like Figure 2 As shown, in this type of transformer, the secondary coil has a center tap P, and the secondary coil is connected to two diodes D1 and D2. This type of transformer, compared to... Figure 1 The transformer shown reduces the number of diodes on the secondary side by half, thereby reducing the cost of the transformer and also reducing conduction losses.

[0033] However, in center-tapped transformers used with diodes, the secondary leakage inductance interacts with the diode's parasitic capacitance, creating an unexpected resonant circuit. This resonance causes significant voltage fluctuations on the secondary side, which directly stress the diode. In severe cases, these voltage spikes can even degrade diode performance or cause electronic device malfunctions.

[0034] To address the aforementioned problems, this invention provides a transformer in some embodiments that can eliminate secondary leakage inductance as much as possible while retaining a large primary leakage inductance, thereby eliminating potential voltage fluctuations on the secondary side and ensuring stable operation of the transformer.

[0035] Figure 3 A schematic diagram of the transformer according to one embodiment of the present invention is shown.

[0036] Figure 4 The structure of the core of the transformer according to one embodiment of the present invention is shown.

[0037] like Figure 3 and Figure 4 As shown, in one embodiment, the transformer includes a core 100 having at least two parallel winding arms 101 extending along the length direction L of the core, for example... Figure 2 The two winding arms 101 shown have air gaps 103 at their two ends 102 along their length, and the extension direction of the air gaps 103 is consistent with the length direction L of the core 100.

[0038] In some specific implementations, the core 100 can be made of a soft magnetic material, such as ferrite or amorphous / nanocrystalline soft magnetic material.

[0039] It should be noted that in this utility model, the number of winding arms of the iron core is not limited to two; it can also be three, four, five, or other numbers required by those skilled in the art. Each winding arm can be provided with a primary coil and a secondary coil.

[0040] like Figure 3 As shown, a primary coil 200 and a secondary coil 300 are wound on each winding arm 101 of the iron core 100. Furthermore, in the length direction L of the iron core 100, the secondary coil 300 is closer to the air gap 103 than the primary coil 200. In other words, the secondary coil 300 is positioned right next to the air gap 103, rather than the primary coil 200.

[0041] Because the permeability of the core material is thousands of times higher than that of the air gap, increasing the air gap significantly increases the magnetic reluctance at these locations. Based on the analysis of the transformer's magnetic flux lines, due to the high magnetic reluctance of the air gap, some magnetic flux lines bypass the main magnetic circuit and pass directly through the window area, forming closed magnetic loops. These closed magnetic fluxes couple only with the primary coil and not with the secondary coil, thus generating primary leakage inductance. In traditional transformers, the air gap is usually located on the winding arm, and the direction of the air gap's extension is consistent with the width direction of the core. Based on the same principle, this arrangement also creates secondary leakage inductance.

[0042] This invention ensures that the secondary magnetic flux is always coupled to the primary winding by placing the air gap 103 at the end of the iron core along its length, with the extension direction of the air gap 103 aligned with the length direction L of the iron core 100, and by arranging the secondary coil 300 immediately adjacent to the air gap 103. This arrangement effectively minimizes secondary leakage inductance. Simultaneously, the primary magnetic flux is not necessarily fully coupled to the secondary winding, thus maintaining the primary leakage inductance at the desired level.

[0043] like Figure 3 and Figure 4 As shown, in order to further ensure the electromagnetic performance of the transformer, in some more specific embodiments, the air gap 103 is located at the center position in the width direction W of the core 100.

[0044] Of course, in some other alternative implementations, the air gap may also be set at the center position in the width direction W of the core 100.

[0045] In some specific embodiments, in order to further improve electromagnetic performance, at least one soft magnetic material sheet 104 arranged parallel to the length direction L of the iron core 100 may be provided in the air gap 103 to divide the air gap 103 into several sub-air gaps 1031.

[0046] For example, in such Figure 3 and Figure 4 In the illustrated embodiment, for example, two parallel soft magnetic material sheets 104 can be disposed within the air gap 103, thereby dividing the air gap 103 into three sub-air gaps 1031.

[0047] In some other specific implementations, such as Figure 5 As shown, the iron core 100 has an air gap 103 at each of its two ends 102 along its length. Although the electromagnetic performance of this single air gap configuration is slightly inferior to that of the previously described configuration with multiple sub-air gaps 1031, the single air gap configuration is simpler to manufacture, thus further reducing costs.

[0048] In some specific embodiments, the width of the air gap 103 can be 0.5 to 2 mm. For example, when the iron core 100 has an air gap 103 at each of its two ends 102 along its length, the width of the single air gap can be 0.5 to 2 mm. When the air gap has multiple sub-air gaps 1031, the total width of the air gap covering the multiple sub-air gaps and the soft magnetic material sheet between the sub-air gaps is 0.5 to 2 mm.

[0049] In some specific implementation methods, such as Figure 5 As shown, in the primary coil 200 wound on the iron core, at least one primary coil is wound on the iron core with at least two layers, and the number of turns of the outer layer 201 of the primary coil away from the iron core is less than or equal to the number of turns of the inner layer 202 of the primary coil relatively close to the iron core. Figure 5 Each square in the diagram represents the cross-section of one turn of the coil. Although Figure 5 In the example shown, the number of turns of the primary coil outer layer 201, which is farther from the iron core, is less than the number of turns of the primary coil inner layer 202, which is relatively closer to the iron core. However, this figure is only an exemplary display, and it is also possible for the number of turns of the primary coil outer layer 201, which is farther from the iron core, to be equal to the number of turns of the primary coil inner layer 202, which is relatively closer to the iron core.

[0050] Of course, in some other alternative implementations, the number of turns of the outer layer 201 of the primary coil, which is farther from the iron core, can be greater than the number of turns of the inner layer 202 of the primary coil, which is relatively closer to the iron core. However, this winding method would require more wires, which is relatively disadvantageous for saving costs.

[0051] In such Figure 5 In the example shown, the primary coil 200 is wound with two layers on the iron core. Of course, in some other specific embodiments, the primary coil 200 can also be wound with more than two layers of coil on the iron core, such as three or four layers. However, considering the heat dissipation problem, the number of layers should not be too many.

[0052] In other specific implementations, the primary coil can also be wound on the iron core in one layer, but this method requires a longer iron core while keeping the number of turns the same, which increases the size of the transformer.

[0053] Similarly, in some specific implementations, such as Figure 5 As shown, in the secondary coil 300 wound on the iron core, at least one secondary coil is wound with at least two layers on the iron core, and the number of turns of the outer layer 301 of the secondary coil away from the iron core is less than or equal to the number of turns of the inner layer 302 of the secondary coil relatively close to the iron core.

[0054] Of course, in some other optional specific embodiments, the number of turns of the outer layer 301 of the secondary coil away from the iron core can also be greater than the number of turns of the inner layer 302 of the secondary coil that is relatively closer to the iron core. However, this winding method will require more wires, which is relatively disadvantageous for saving costs.

[0055] In such Figure 5 In the example shown, the secondary coil 300 is wound with two layers on the iron core. Of course, in some other specific embodiments, the secondary coil 300 can also be wound with more than two layers of coil on the iron core, such as three or four layers. However, considering the heat dissipation problem, the number of layers should not be too many.

[0056] In other specific implementations, the secondary coil can also be wound on the iron core in one layer, but this method requires a longer iron core while keeping the number of turns the same, which increases the size of the transformer.

[0057] like Figure 3 and Figure 6 As shown, in some specific embodiments, a baffle 400 is provided between adjacent primary coil 200 and secondary coil 300. In some more specific embodiments, the baffle 400 can be made of plastic to prevent interference between the primary and secondary coils. Plastic baffles have the advantages of interference resistance, low cost, and good manufacturability.

[0058] like Figure 7 As shown, in some specific embodiments, the core 100 is further surrounded by a shielding shell 500. In some more specific embodiments, the shielding shell may be made of aluminum, which encloses the entire assembly, providing electromagnetic shielding and aiding in heat dissipation.

[0059] As shown above, since center-tapped transformers are more prone to significant fluctuations in secondary-side voltage, the transformer described in this invention is suitable for center-tapped transformers, i.e., the secondary coil of the transformer has a center tap P.

[0060] However, this does not mean that the transformer described in this utility model can only be constructed as a center-tapped transformer. In other embodiments, the secondary coil of the transformer described in this utility model may not have a center tap, but the transformer still has the beneficial effect of eliminating secondary leakage inductance as much as possible while retaining a large primary leakage inductance.

[0061] In another embodiment, this utility model also provides an on-board charger system, which includes the transformer as described above.

[0062] The on-board charger system described in this utility model has stable performance due to the use of the aforementioned transformer.

[0063] Since this utility model only relates to the improvement of the transformer and not to the improvement of other components and systems of the on-board charger system, the specific system structure and working principle of the on-board charger system will not be described in detail here.

[0064] It should be noted that the transformer described in this utility model is not limited to use in on-board charger systems, but can also be applied to other charger systems.

[0065] It should be noted that the prior art within the scope of protection of this utility model is not limited to the embodiments given in this utility model. All prior art that does not contradict the solution of this utility model, including but not limited to prior patent documents, prior publications, prior public uses, etc., can be included in the scope of protection of this utility model.

[0066] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0067] It should also be noted that the embodiments listed above are merely specific embodiments of this utility model. Obviously, this utility model is not limited to the above embodiments, and any similar changes or modifications made thereto that can be directly derived or easily conceived by those skilled in the art from the content disclosed in this utility model should fall within the protection scope of this utility model.

Claims

1. A transformer comprising a core (100) having at least two parallel winding arms (101) extending along the length of the core, each winding arm having an alternately arranged primary coil (200) and a secondary coil (300) wound thereon; characterized in that: An air gap (103) is provided at each of the two ends (102) along the length direction (L) of the iron core, and the extension direction of the air gap is consistent with the length direction of the iron core; Along the length of the iron core, the secondary coil is closer to the air gap than the primary coil.

2. The transformer as described in claim 1, characterized in that, The air gap is located at the center of the iron core in the width direction (W).

3. The transformer as described in claim 1, characterized in that, The width of the air gap is 0.5 to 2 mm.

4. The transformer as described in claim 1, characterized in that, Each of the two ends along the length of the iron core is provided with an air gap.

5. The transformer as described in claim 1, characterized in that, The air gap is provided with at least one soft magnetic material sheet (104) arranged parallel to the length direction of the iron core to divide the air gap into several sub-air gaps (1031).

6. The transformer as described in claim 1, characterized in that, At least one primary coil is wound in at least two layers on the iron core, and the number of turns of the outer layer (201) of the primary coil away from the iron core is less than or equal to the number of turns of the inner layer (202) of the primary coil relatively close to the iron core.

7. The transformer as described in claim 1, characterized in that, At least one secondary coil is wound on the iron core in at least two layers, and the number of turns of the outer layer (301) of the secondary coil away from the iron core is less than or equal to the number of turns of the inner layer (302) of the secondary coil relatively close to the iron core.

8. The transformer as described in claim 1, characterized in that, The secondary coil of the transformer has a center tap (P).

9. The transformer as described in claim 1, characterized in that, A baffle (400) is provided between adjacent primary and secondary coils.

10. The transformer as described in claim 1, characterized in that, The core is surrounded by a shielding shell (500).

11. An on-board charger system, characterized in that, It includes the transformer as described in any one of claims 1-10.

Images