Planar transformers, power converters and circuit boards
By setting up multi-turn shielding coil segments and auxiliary windings in the shielding layer of the plane transformer, combined with the multi-layer structure, the problem of poor common mode current suppression effect in the prior art is solved, and low noise and low cost EMI performance improvement is achieved.
Patent Information
- Application Number
- CN202080013195.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-11-08
- Filing Date
- 2020-03-23
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2040-03-23
AI Technical Summary
Existing planar transformers are difficult to effectively reduce the common mode current between the primary coil and the secondary coil, resulting in large interference of EMI common mode noise.
A planar transformer is designed to provide a first shielding coil segment of N1 and a second shielding coil segment of N2 in the shielding layer, so that the two can jointly suppress common mode current, and combine the auxiliary winding and the multi-layer structure to adjust the shielding. Ratio of layer to auxiliary winding to optimize EMI performance.
The significant reduction in the common mode current sum is achieved, the EMI performance is improved, and the number of PCB board layers and cost of the planar transformer is reduced by flexibly adjusting the ratio of the shielding layer and auxiliary winding.
Smart Images
Figure CN113632184B_ABST
Abstract
Description
[0001] This application claims the priority of Chinese patent application No. 201911090375.0, and the entire contents of the patent application are incorporated into this application by reference. Technical Field
[0002] The present invention relates to the field of planar transformers, and in particular to a planar transformer, a power converter and a circuit board. Background Art
[0003] The common-mode current of the transformer has a great influence on EMI. In order to reduce the common-mode current caused by the primary coil as much as possible, usually, in traditional transformers, the common-mode current is adjusted by adjusting the number of turns of the transformer shield winding to reduce the interference of EMI common-mode noise.
[0004] Planar transformers are small in size and are increasingly used in switching power supplies. However, existing planar transformers often have difficulty in achieving good common-mode current suppression effects. Summary of the invention
[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide a planar transformer and a power converter to reduce the common mode current between the primary coil and the secondary coil, thereby reducing the interference of EMI common mode noise.
[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0007] A planar transformer comprises a secondary coil layer, a shielding layer and a primary coil layer located on a PCB board, wherein the secondary coil layer comprises at least part of the secondary coil, the secondary coil is provided with a secondary static point end, and the shielding layer is provided between the secondary coil layer and the primary coil layer; the shielding layer comprises a shielding coil, the shielding coil comprises a first shielding coil segment of N1 turns and a second shielding coil segment of N2 turns, the first shielding coil segment comprises a first shielding static point end and a first shielding free end, and the second shielding coil segment comprises a second shielding static point end and a second shielding free end; the winding direction of the first shielding coil segment is the same as the winding direction of the secondary coil, and the winding direction of the first shielding coil segment is opposite to the winding direction of the second shielding coil segment; the winding direction of the secondary coil refers to: the winding direction of the secondary coil with the secondary static point end as the starting end; the winding direction of the first shielding coil segment refers to: the winding direction of the first shielding coil segment with the first shielding static point end as the starting end; the winding direction of the second shielding coil segment refers to: the winding direction of the second shielding coil segment with the second shielding static point end as the starting end.
[0008] Preferably, when the number of turns of some secondary coils on the secondary coil layer is 1, N1+N2≤1.
[0009] Preferably, when the number of turns of some secondary coils on the secondary coil layer is 2, N1>1, and N1+N2≤2.
[0010] Preferably, it also includes another shielding layer; the secondary coil layer includes a first secondary coil layer and a second secondary coil layer; the first secondary coil layer and the second secondary coil layer respectively include a first secondary coil and a second secondary coil as part of the secondary coil; the first secondary coil and the second secondary coil are both not greater than 1 turn; the number of turns of the first secondary coil is equivalent to the number of turns of the second secondary coil; the shielding layer is located between the first secondary coil layer and the primary coil layer, and the other shielding layer is located between the second secondary coil layer and the primary coil layer; the other shielding layer includes another shielding coil, the other shielding coil includes a third shielding static point end and a third shielding free end, and the winding direction of the other shielding coil is the same as the winding direction of the secondary coil; the number of turns of the other shielding coil is equivalent to the number of turns of the second secondary coil; the winding direction of the other shielding coil refers to: taking the third shielding static point end as the starting end, the winding direction of the other shielding coil.
[0011] Preferably, the width of the first shielding coil segment and the width of the second shielding coil segment are respectively equivalent to the width of the secondary coil, and the first shielding coil segment and the second shielding coil segment are on the same surrounding ring.
[0012] Preferably, N1>N2.
[0013] Preferably, the shielding layer further includes an auxiliary winding, the auxiliary winding is further provided with an auxiliary static point end and an auxiliary dynamic point end, the auxiliary winding is located radially inward of the shielding coil; the number of turns of the auxiliary winding is equivalent to the number of turns of the secondary coil; the winding direction of the auxiliary winding is the same as the winding direction of the secondary coil, and the winding direction of the auxiliary winding refers to: taking the auxiliary static point end as the starting end, the winding direction of the auxiliary winding; or,
[0014] The other shielding layer also includes an auxiliary winding, which is also provided with an auxiliary static point end and an auxiliary moving point end, and the auxiliary winding is located radially inward of the other shielding coil; the number of turns of the auxiliary winding and the number of turns of the other shielding coil are respectively equivalent to the number of turns of the secondary coil; the winding direction of the auxiliary winding is the same as the winding direction of the secondary coil, and the winding direction of the auxiliary winding refers to: with the auxiliary static point end as the starting end, the winding direction of the auxiliary winding.
[0015] Preferably, when the number of turns of some secondary coils on the secondary coil layer is 1, 0.8≤N1+N2<1.
[0016] Preferably, when the number of turns of some secondary coils on the secondary coil layer is 2, N1>1, and 1.8≤N1+N2<2.
[0017] The present application also provides a planar transformer, which includes, from bottom to top, a bottom layer secondary coil, a bottom shielding layer, a primary coil, a top layer shielding layer and a top layer secondary coil. The top layer shielding layer and the bottom layer shielding layer both include shielding coils. At least one shielding coil in the top layer shielding layer and the bottom layer shielding layer includes N1 clockwise coils and N2 counterclockwise coils. The compensating common-mode current of the planar transformer is adjusted by adjusting the ratio of N1 and N2.
[0018] Preferably, the sum of N1 and N2 is less than 1.
[0019] Preferably, the bottom-layer secondary coil is wound clockwise or counterclockwise with the secondary static point potential as the starting end; the top-layer secondary coil is connected in series or in parallel with the bottom-layer secondary coil, and its winding direction is the same as that of the bottom-layer secondary coil.
[0020] Preferably, the shielding coil of the bottom shielding layer includes N1 clockwise coils and N2 counterclockwise coils, and the shielding coil of the top shielding layer is a one-turn coil with the primary static point potential as the starting end, and its winding direction is the same as that of the bottom layer secondary coil.
[0021] Preferably, the shielding coil of the top shielding layer includes N1 clockwise coils and N2 counterclockwise coils, and the shielding coil of the bottom shielding layer is a one-turn coil with the primary static point potential as the starting end, and its winding direction is the same as that of the bottom layer secondary coil.
[0022] Preferably, the top or / and bottom shielding layer also includes an auxiliary winding, and the inner circle of the shielding coil of the top or / and bottom shielding layer is also provided with the auxiliary winding, the number of turns of the auxiliary winding is less than 3, one end of the shielding coil of the top or bottom shielding layer is connected to the primary static point, and the other end of the shielding coil of the top or bottom shielding layer is suspended.
[0023] The present application also provides a power converter, comprising any one of the planar transformers described above, or any one of the planar transformers described above.
[0024] Preferably, when the output voltage of the power converter is between 5V and 24V, the number of layers of the PCB board of the planar transformer is 6-14.
[0025] The present application also provides a circuit board with a power conversion function, comprising any of the planar transformers described above.
[0026] Preferably, the planar transformer is formed on the circuit board by a circuit board manufacturing process; or, the planar transformer is electrically connected and mounted on the circuit board.
[0027] Compared with the prior art, the beneficial effects of the present invention are:
[0028] By adopting the above-mentioned scheme of this embodiment, that is, setting the first shielding coil segment of N1 circle and the second shielding coil segment of N2 circle as shielding coils in the shielding wire layer, the two can work together to suppress the common mode current, and finally cooperate to make the total common mode current very small.
[0029] The planar transformer designed in the present invention is suitable for an adapter or charger with an output voltage of 5V-24V, or a power converter, adapter or charger that outputs a fixed voltage (5V / 12V / 15V / 19V / 20V / 24V) within this voltage range, or a variable voltage (5V-9V / 5V-11V / 5V-12V / 5V-15V / 5V-20V).
[0030] According to the different voltage output ranges of the power conversion circuit, the ratio of the clockwise coil / counterclockwise coil of the shielding layer can be flexibly designed to vary between 0.1 / 0.9 and 0.9 / 0.1. The ratio of the clockwise / counterclockwise coil of the shielding layer to the auxiliary winding varies from 0.1 to 1.5 / 1. By selecting a suitable ratio combination, the best EMI performance can be achieved, and the number of PCB layers of the planar transformer can be reduced. This is conducive to reducing the cost of the planar transformer.
[0031] Other beneficial effects of the present invention will be explained in the specific implementation manner through the introduction of specific technical features and technical solutions. Through the introduction of these technical features and technical solutions, those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The preferred embodiments according to the present invention will be described below with reference to the accompanying drawings.
[0033] Figure 1 A cross-sectional schematic diagram of a multilayer coil of a planar transformer provided in Embodiments 1 and 3 of the present invention;
[0034] Figure 2 A winding diagram of each layer of coils of a planar transformer provided in the first embodiment of the present invention;
[0035] Figure 3 The diagram of the winding of each layer of coils of a planar transformer according to the second embodiment of the present invention;
[0036] Figure 4 The diagram of the winding of each layer of coils of a planar transformer according to the second embodiment of the present invention;
[0037] Figure 5 A winding diagram of each layer of coils of a planar transformer provided in the third embodiment of the present invention;
[0038] Figure 6 A coil winding diagram of a top layer or bottom layer shielding layer of a planar transformer provided in the third embodiment of the present invention;
[0039] Figure 7 A winding diagram of a bottom shielding layer and a bottom level coil of a planar transformer provided in the third embodiment of the present invention;
[0040] Figure 8 A coil winding diagram of a top-level secondary coil and a top-layer shielding layer of a planar transformer provided in the third embodiment of the present invention;
[0041] Fig. 9 A three-dimensional diagram of a multilayer coil of a first planar transformer provided in Embodiment 4 of the present invention;
[0042] Fig.10 The winding diagram of each layer of coils of the first planar transformer provided in the fourth embodiment of the present invention;
[0043] Fig.11 The winding diagram of each layer of coils of the second planar transformer provided in the fourth embodiment of the present invention;
[0044] Fig.12 A three-dimensional diagram of a multilayer coil of a third planar transformer provided in the fourth embodiment of the present invention;
[0045] Fig.13 The winding diagram of each layer of coils of the third planar transformer provided in the fourth embodiment of the present invention;
[0046] Fig.14 A schematic diagram of a transformer application according to an embodiment of the present invention;
[0047] Fig.15 This is a second schematic diagram of a transformer application according to an embodiment of the present invention. DETAILED DESCRIPTION
[0048] Embodiment 1
[0049] like Figure 1 and 2As shown, an embodiment of the planar transformer of the present invention is a secondary-primary-secondary structure, which includes, from bottom to top, a secondary coil layer 1, a shielding layer 2, multiple primary coil layers 3, a shielding layer 4 and a secondary coil layer 5, all of which are located on a PCB board. At least part of the secondary coil is provided on the secondary coil layer 1 and the secondary coil layer 5. The two parts of the secondary coil constitute the secondary coil. The secondary coil is provided with a secondary static point end 12 and a secondary static point end 52. The shielding layer 4 is provided between the secondary coil layer 5 and the primary coil layer 3, and the shielding layer 2 is provided between the secondary coil layer 1 and the primary coil layer 3.
[0050] The secondary coil layer 1 includes a secondary coil 11, the secondary coil layer 5 includes a secondary coil 51, the shielding layer 2 includes a shielding coil 21, the shielding layer 4 includes a shielding coil 41, and the primary coil layer 3 includes a primary coil 31. Figure 2 It can be seen that when looking down at the surface of the secondary coil 11, the secondary coil 11 takes the secondary static point end 12 as the starting end and wraps around the magnetic core clockwise to the end point 13, and then connects to the end point 53 of the secondary coil 51. The secondary coil 51 continues to wrap around the magnetic core clockwise from the end point 53 to the secondary static point end 52. In other words, the winding direction of the secondary coil refers to the direction in which the secondary coil wraps around the magnetic core of the planar transformer (after assembly, the magnetic core is located at the position 14) with the secondary static point end 12 as the starting end. In this embodiment, the secondary coil 11 and the secondary coil 51 are connected in series to form the entire secondary coil. The number of turns of the secondary coil 11 and the secondary coil 51 is equivalent, that is, the same or nearly the same, for example, the difference in the number of turns between the two does not exceed 0.2 turns. In this embodiment, the number of turns of the secondary coil 11 and the secondary coil 51 are both 1 turn or close to 1 turn. Thus, when the planar transformer is applied to a high power density power converter (such as an adapter or a charger), the current of the secondary coil is relatively large and the width of the secondary coil is also relatively large, which can meet the requirements.
[0051] The shielding layer 4 includes a shielding coil 41, which includes a first shielding coil segment 411 with N1 turns and a second shielding coil segment 412 with N2 turns. When the number of turns of the secondary coil 51 is 1, 0<N1<1, 0<N2<1, N1+N2≤1; the first shielding coil segment 411 is provided with a first shielding static point end 413 and a first shielding free end 416 (the free end is not connected to any circuit), and the second shielding coil segment 412 is provided with a second shielding static point end 414 and a second shielding free end 416 (the free end is not connected to any circuit). Looking down at the shielding coil 41 and the secondary coil from the same direction, the winding direction of the first shielding coil segment 411 is the same as that of the secondary coil, and the winding direction of the first shielding coil segment 411 is opposite to that of the second shielding coil segment 412; the winding direction of the first shielding coil segment 411 refers to: from the first shielding static point end 413 as the starting end to the first shielding free end 416, the first shielding coil segment 411 is wrapped around the magnetic core of the planar transformer; the winding direction of the second shielding coil segment 412 refers to: from the second shielding static point end 414 as the starting end to the second shielding free end 415, the second shielding coil segment 412 is wrapped around the magnetic core. The first shielding static point end 413 and the second shielding static point end 414 are used to connect to the same or different static point ends on the primary coil side (the static point end on the primary coil side includes the common end of the primary coil and the capacitor, and the primary side ground end, such as Fig.14 Or the two primary coils shown in 15 Location), preferably, the first shielding static point terminal 413 and the second shielding static point terminal 414 can be connected to the same static point terminal on the primary coil side.
[0052] The primary coil layer includes a plurality of sub-primary coil layers 3 , each of which includes a sub-primary coil 31 , and all the sub-primary coils 31 are connected in series to form a primary coil.
[0053] Theoretically, if Figure 3 As shown, when the shielding coil 41 in the shielding layer 4 adopts the shielding coil 21 in the shielding layer 2, that is, the number of turns of the shielding coil 41, the shielding coil 21, the secondary coil 51 and the secondary coil 11 are all equivalent, that is, the same or nearly the same (for example, the difference between the number of turns of the shielding coil 21 and the number of turns of the secondary coil 11 does not exceed 0.2 turns), and the winding directions of the four are the same, then the combination of the shielding coils of the shielding layer 4 and the shielding layer 2 can make the sum of the common-mode currents between the primary coil and the secondary coil in the entire planar transformer 0, that is, there is no common-mode current conduction interference to the outside. However, in the actual manufacturing process of the planar transformer, such as Figure 3The shielding coil 41 and the shielding coil 21 shown cannot reduce the sum of the common-mode current to a small value. After research, it is found that by adopting the above solution of this embodiment, that is, providing the first shielding coil segment 411 of N1 circle and the second shielding coil segment 412 of N2 circle as the shielding coil 41 in the shielding layer 4, the two can work together to suppress the common-mode current, and finally cooperate to make the sum of the common-mode current very small, for example, 0 or close to 0.
[0054] After further research, it is found that in most cases, in the manufactured planar transformer, the number of turns N2 of the second shielding coil segment 412 is often required to be set smaller than the number of turns N1 of the first shielding coil segment 411, that is, N2<N1, so that the total common mode current of the entire planar transformer can be very small. Therefore, in order to achieve this purpose, in a more preferred embodiment, the number of turns N2 of the second shielding coil segment 412 is set smaller than the number of turns N1 of the first shielding coil segment 411. For example, N1:N2=0.7 / 0.3 or 0.6 / 0.4.
[0055] In a more preferred embodiment, the width of the first shielding coil segment 411 and the width of the second shielding coil segment 412 are respectively equivalent to the width of the secondary coil (that is, the percentage difference between the widths of the two does not exceed 10%), and the first shielding coil segment 411 and the second shielding coil segment 412 are on the same surrounding ring. In this way, the area of the shielding layer can be smaller while ensuring the effect of suppressing common-mode current, thereby making the area of the planar transformer smaller.
[0056] Assuming that the first shielding coil segment 411 and the second shielding coil segment 412 are respectively located on two different surrounding rings (for example, the second shielding coil segment 412 is outside the first shielding coil segment 411), when the width of the first shielding coil segment 411 and the second shielding coil segment 412 needs to be greater than a certain width, the shielding layer 4 needs a larger area to accommodate the first shielding coil segment 411 and the second shielding coil segment 412. In a more preferred embodiment, N1+N2 is close to 1, for example, 0.8≤N1+N2<1, that is, the free end 416 of the first shielding coil segment 411 and the free end 415 of the second shielding coil segment 412 are close, so that the gap of the shielding layer is smaller, which is more conducive to suppressing common mode current.
[0057] When the number of turns of the secondary coil 51 is 2, 1<N1<2 (i.e., the number of turns of the first shielding coil segment 411 is greater than 1 turn and less than 2 turns), 0<N2<1 (i.e., the number of turns of the second shielding coil segment 412 is greater than 0 and less than 1 turn), and N1+N2≤2; wherein, the second shielding coil segment 412 can be arranged on the surrounding ring close to the inner side of the first shielding coil segment 411, or on the surrounding ring close to the outer side of the first shielding coil segment 411. Preferably, 1.8≤N1+N2<2, i.e., the free end 416 of the first shielding coil segment 411 and the free end 415 of the second shielding coil segment 412 are close, so that the gap of the shielding layer is smaller, which is more conducive to suppressing the common mode current.
[0058] In other embodiments, the secondary coil 51 and the secondary coil 11 may also be connected in parallel to form the entire secondary coil.
[0059] In a more preferred embodiment, Figure 2 As shown, the shielding layer 4 is also provided with an auxiliary winding 42, on which an auxiliary static point end and an auxiliary dynamic point end are provided, and the auxiliary winding 42 is located radially inside the shielding coil; the number of turns of the auxiliary winding 42 is equivalent to the number of turns of the secondary coil, for example, the difference between the number of turns of the two does not exceed 0.2 turns, wherein, when the secondary coil 11 and the secondary coil 51 are connected in series, the number of turns of the secondary coil is the sum of the number of turns of the secondary coil 11 and the secondary coil 51 (for example, in this embodiment, the number of turns of the auxiliary winding 42 is 2, and the total number of turns of the secondary coil is also 2); the winding direction of the auxiliary winding 42 is the same as the winding direction of the secondary coil, and the winding direction of the auxiliary winding 42 refers to: the winding direction of the auxiliary winding 42 with the auxiliary static point end as the starting end. By placing the auxiliary winding 42 in the shielding layer 4, the layer specifically for placing the auxiliary winding 42 can be omitted, thereby achieving the purpose of reducing the number of layers of the planar transformer.
[0060] Of course, the planar transformer may also adopt a primary-secondary-primary structure, that is, including a primary coil layer, a shielding layer, a secondary coil layer, a shielding layer and a primary coil layer in sequence from bottom to top, and the purpose of the present invention may also be achieved.
[0061] Embodiment 2
[0062] Figure 4 is another preferred embodiment of the planar transformer of the present invention, which Figure 2 The embodiments of the present invention are generally the same, and the main differences include: Figure 4 As shown, the shielding layer 4 of this embodiment adopts Figure 2 The shielding coil of the shielding layer 2 in the present embodiment is Figure 2 The shielding coils in the middle shielding layer 4 (ie, the first shielding coil segment 411 and the second shielding coil segment 412 ) In addition, the shielding layer 4 of this embodiment does not have an auxiliary winding, while the shielding layer 2 has an auxiliary winding 21 .
[0063] Embodiment 3
[0064] See also Figure 1 , the present embodiment provides a planar transformer, which is a secondary-primary structure, and includes, from bottom to top, a bottom-level coil 1, a bottom-level shielding layer 2, a primary coil 3, a top-level shielding layer 4, and a top-level coil 5. According to different output power specifications, the top-level shielding layer 4 and the bottom-level shielding layer 2 can be connected in series or in parallel. There is an intermediate layer between the bottom-level coil and the top-level coil, and the intermediate layer can be a multi-layer structure. The planar transformer as a whole can have a 6-14-layer structure, such as Figure 5 This is a schematic diagram of a 6-layer structure.
[0065] The bottom-level secondary coil 1 is wound clockwise or counterclockwise with the secondary static point potential as the starting end; the winding direction of the top-level secondary coil 5 is the same as that of the bottom-level secondary coil 1 .
[0066] Wherein, the top shielding layer 4 and the bottom shielding layer 2 both include shielding coils 21, and at least one shielding coil 21 in the top shielding layer 4 and the bottom shielding layer 2 includes N1 clockwise coils and N2 counterclockwise coils, and the sum of N1 and N2 is less than 1.
[0067] As an embodiment, the shielding coils 21 of the top shielding layer 4 and the bottom shielding layer 2 both include N1 turns of clockwise coils and N2 turns of counterclockwise coils, and the sum of N1 and N2 is less than 1. The best EMI performance can be achieved by adjusting the ratio of the clockwise coils to the counterclockwise coils of the top shielding layer 4 and the bottom shielding layer 2, such as Figure 6 As shown, the ratio of the clockwise coil to the counterclockwise coil is 0.7 / 0.3 or 0.6 / 0.4.
[0068] As an embodiment, the top shielding layer 4 includes N1 clockwise coil and N2 counterclockwise coil, such as Figure 7 As shown, the shielding coil 21 of the bottom shielding layer 2 is a one-turn coil, with the primary static point potential as the starting end, and the winding direction of the bottom shielding layer 2 is the same as that of the bottom secondary coil 1.
[0069] As an embodiment, the bottom shielding layer 4 includes N1 clockwise coil and N2 counterclockwise coil, such as Figure 8 As shown, the shielding coil 21 of the top shielding layer 4 is a one-turn coil, with the primary static point potential as the starting end, and the winding direction of the top shielding layer 4 is the same as that of the top-level coil 5 .
[0070] The coil of the top-level secondary coil 5 or the bottom-level secondary coil 1 is a full turn, preferably 1 or 2 turns, and a wide copper foil is used as the coil, which can pass a large current and is suitable for an adapter.
[0071] For adapters or chargers with output voltages of 5-20v, 5-9v, and 5-11v, the total number of layers of the PCB board is 6 to 14.
[0072] Embodiment 4
[0073] This embodiment provides a planar transformer. Based on the first embodiment, an auxiliary winding is added to the inner circle of the shielding coil and designed on the same layer to reduce the total plate thickness and reduce the cost.
[0074] like Fig. 9 , Fig.10 As shown, the bottom shielding layer 2 further includes a second auxiliary winding 23 , which is arranged in the inner circle of the shielding coil of the bottom shielding layer 2 .
[0075] or Figure 1 , Fig.11 As shown, the top shielding layer 4 further includes a second auxiliary winding 23 , which is arranged in the inner circle of the shielding coil of the top shielding layer 4 .
[0076] or Fig.12 , Fig.13 As shown, both the bottom shielding layer 2 and the top shielding layer 4 include a second auxiliary winding 23 , and the second auxiliary winding 23 is arranged in the inner turns of the shielding coils of the bottom shielding layer 2 and the top shielding layer 4 .
[0077] The number of turns of the second auxiliary winding 23 is less than 3.
[0078] One end of the shielding coil of the top shielding layer 4 or the bottom shielding layer 2 is connected to the primary static point, and the other end of the shielding coil of the top shielding layer 4 or the bottom shielding layer 2 is suspended, or connected in series with the primary coil 3, or connected in series with the second auxiliary winding 23.
[0079] like Fig.14 and Fig.15 As shown, The marked ones are primary and secondary static points. The output has two applications. Fig.14 The figure shows that the anode of the output diode is connected to the transformer, and the cathode is connected to the positive terminal of the output capacitor. Fig.15 As shown, the cathode of the output diode is connected to the transformer, and the anode is connected to the negative electrode of the output capacitor. In actual application, in order to facilitate PCB wiring, the starting end of the shielding layer can be connected to one of the two static points of the input according to the actual application situation.
[0080] The planar transformer designed by the present invention can flexibly design the ratio of the clockwise coil / counterclockwise coil of the shielding layer according to the different voltage output ranges of the power conversion circuit, and can be changed between 0.1 / 0.9 and 0.9 / 0.1. The ratio of the clockwise / counterclockwise coil of the shielding layer to the auxiliary winding changes from 1 / 10 to 1.5 / 1. By selecting a suitable ratio combination, the best EMI performance can be achieved, and the number of PCB board layers of the planar transformer can be reduced. This is conducive to reducing the cost of the planar transformer.
[0081] Embodiment 5
[0082] This embodiment provides a power converter, which uses any one of the planar transformers described in the above embodiments. When the output voltage of the power converter is between 5V and 24V, the PCB board of the planar transformer is designed with 6 to 14 layers.
[0083] The planar transformer includes, from bottom to top, a bottom layer secondary coil, a bottom shielding layer, a primary coil, a top layer shielding layer and a top layer secondary coil. The top layer shielding layer and the bottom layer shielding layer both include shielding coils. At least one shielding coil in the top layer shielding layer and the bottom layer shielding layer includes N1 clockwise coils and N2 counterclockwise coils. The compensating common-mode current of the planar transformer is adjusted by adjusting the ratio of N1 and N2.
[0084] The planar transformer designed in the present invention is suitable for an adapter or charger with an output voltage of 5V to 24V, or a power converter, adapter or charger that outputs a fixed voltage (5V / 12V / 15V / 19V / 20V / 24V) within this voltage range, or a variable voltage (5V-9V / 5V-11V / 5V-12V / 5V-15V / 5V-20V).
[0085] The present invention also provides a circuit board with a power conversion function, which includes a planar transformer of any of the above-mentioned embodiments. As a non-limiting example, the circuit board of the present invention can be either a mainboard of a power adapter or a circuit board in other electrical and electronic products, as long as the circuit board carries the planar transformer of the utility model. The planar transformer is formed on the circuit board through a circuit board manufacturing process; or, the planar transformer is electrically connected and mounted on the circuit board, for example, by soldering or plugging the planar transformer on the circuit board through pins.
[0086] Those skilled in the art will appreciate that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.
[0087] It should be understood that the above-mentioned embodiments are merely illustrative and not restrictive. Without departing from the basic principles of the present invention, various obvious or equivalent modifications or substitutions that can be made by those skilled in the art to the above-mentioned details will all be included in the scope of the claims of the present invention.
Claims
1. A planar transformer, characterized in that: The invention comprises a secondary coil layer, a shielding layer and a primary coil layer located on a PCB board, wherein the secondary coil layer comprises at least a part of a secondary coil, the secondary coil is provided with a secondary static point end, and the shielding layer is provided between the secondary coil layer and the primary coil layer; The shielding layer includes a shielding coil, the shielding coil includes a first shielding coil segment of N1 turns and a second shielding coil segment of N2 turns, the first shielding coil segment includes a first shielding static point end and a first shielding free end, and the second shielding coil segment includes a second shielding static point end and a second shielding free end; The winding direction of the first shielding coil segment is the same as the winding direction of the secondary coil, and the winding direction of the first shielding coil segment is opposite to the winding direction of the second shielding coil segment; The winding direction of the secondary coil refers to: the winding direction of the secondary coil with the secondary static point end as the starting end; the winding direction of the first shielding coil segment refers to: the winding direction of the first shielding coil segment with the first shielding static point end as the starting end; the winding direction of the second shielding coil segment refers to: the winding direction of the second shielding coil segment with the second shielding static point end as the starting end.
2. The planar transformer according to claim 1, characterized in that: When the number of turns of the partial secondary coil on the secondary coil layer is 1, N1+N2≤1.
3. The planar transformer according to claim 1, characterized in that: When the number of turns of the partial secondary coil on the secondary coil layer is 2, N1>1, and N1+N2≤2.
4. The planar transformer according to claim 1, characterized in that: Also comprising another shielding layer; The secondary coil layer includes a first secondary coil layer and a second secondary coil layer; the first secondary coil layer and the second secondary coil layer respectively include a first secondary coil and a second secondary coil as a part of the secondary coil; the first secondary coil and the second secondary coil are both no more than 1 turn; the number of turns of the first secondary coil is equal to the number of turns of the second secondary coil; The shielding layer is located between the first secondary coil layer and the primary coil layer, and the other shielding layer is located between the second secondary coil layer and the primary coil layer; The other shielding layer comprises another shielding coil, the other shielding coil comprises a third shielding static point end and a third shielding free end, the winding direction of the other shielding coil is the same as the winding direction of the secondary coil; the number of turns of the other shielding coil is equal to the number of turns of the second secondary coil; The winding direction of the other shielding coil refers to: the winding direction of the other shielding coil with the third shielding static point end as the starting end.
5. The planar transformer according to claim 1, characterized in that: The width of the first shielding coil segment and the width of the second shielding coil segment are respectively equivalent to the width of the secondary coil, and the first shielding coil segment and the second shielding coil segment are on the same surrounding ring.
6. The planar transformer according to claim 1, characterized in that: N1>N2.
7. The planar transformer according to claim 1, characterized in that: The shielding layer also includes an auxiliary winding, which is also provided with an auxiliary static point end and an auxiliary dynamic point end, and the auxiliary winding is located radially inward of the shielding coil; the number of turns of the auxiliary winding is equivalent to the number of turns of the secondary coil; the winding direction of the auxiliary winding is the same as the winding direction of the secondary coil, and the winding direction of the auxiliary winding refers to: taking the auxiliary static point end as the starting end, the winding direction of the auxiliary winding; or, The other shielding layer also includes an auxiliary winding, which is also provided with an auxiliary static point end and an auxiliary moving point end, and the auxiliary winding is located radially inward of the other shielding coil; the number of turns of the auxiliary winding and the number of turns of the other shielding coil are respectively equivalent to the number of turns of the secondary coil; the winding direction of the auxiliary winding is the same as the winding direction of the secondary coil, and the winding direction of the auxiliary winding refers to: with the auxiliary static point end as the starting end, the winding direction of the auxiliary winding.
8. The planar transformer according to claim 5, characterized in that: When the number of turns of the partial secondary coil on the secondary coil layer is 1, 0.8≤N1+N2<1.
9. The planar transformer according to claim 5, characterized in that: When the number of turns of the partial secondary coil on the secondary coil layer is 2, N1>1, and 1.8≤N1+N2<2.
10. A planar transformer, characterized in that: From bottom to top, it includes a bottom-level coil, a bottom shielding layer, a primary coil, a top-level shielding layer and a top-level coil. The top-level shielding layer and the bottom-level shielding layer both include shielding coils. At least one shielding coil in the top-level shielding layer and the bottom-level shielding layer includes N1 clockwise coils and N2 counterclockwise coils. The compensating common-mode current of the planar transformer is adjusted by adjusting the ratio of N1 and N2.
11. A planar transformer according to claim 10, characterized in that: The sum of N1 and N2 is less than 1.
12. A planar transformer according to claim 11, characterized in that: The bottom-layer secondary coil is wound clockwise or counterclockwise with the secondary static point potential as the starting end; the top-layer secondary coil is connected in series or in parallel with the bottom-layer secondary coil, and its winding direction is the same as that of the bottom-layer secondary coil.
13. A planar transformer according to claim 12, characterized in that: The shielding coil of the bottom shielding layer includes N1 clockwise coils and N2 counterclockwise coils. The shielding coil of the top shielding layer is a one-turn coil with the primary static point potential as the starting end, and its winding direction is the same as that of the bottom layer secondary coil.
14. A planar transformer according to claim 12, characterized in that: The shielding coil of the top shielding layer includes N1 clockwise coils and N2 counterclockwise coils. The shielding coil of the bottom shielding layer is a one-turn coil with the primary static point potential as the starting end, and its winding direction is the same as that of the bottom layer secondary coil.
15. A planar transformer according to claim 13 or 14, characterized in that: The top layer and / or bottom layer shielding layer also includes an auxiliary winding, and the inner circle of the shielding coil of the top layer and / or bottom layer shielding layer is also provided with the auxiliary winding, the number of turns of the auxiliary winding is less than 3, one end of the shielding coil of the top layer or bottom layer shielding layer is connected to the primary static point, and the other end of the shielding coil of the top layer or bottom layer shielding layer is suspended.
16. A power converter, characterized in that: It includes the planar transformer described in any one of claims 1 to 9, or the planar transformer described in any one of claims 10 to 15.
17. A power converter according to claim 16, characterized in that: When the output voltage of the power converter is between 5V and 24V, the number of layers of the PCB board of the planar transformer is 6-14.
18. A circuit board with a power conversion function, characterized in that: Comprising a planar transformer as described in any one of claims 1-15.
19. The circuit board according to claim 18, characterized in that The planar transformer is formed on the circuit board by a circuit board manufacturing process; or, The planar transformer is electrically connected and mounted on the circuit board.