A planar transformer and a power converter

Abstract

The present invention discloses a planar transformer and a power converter, wherein the planar transformer comprises, from bottom to top, a bottom layer of a secondary coil, a bottom shielding layer, a primary coil, a top layer of a shielding layer, and a top layer of a secondary coil, wherein both the top layer of a shielding layer and the bottom layer of a shielding layer comprise a shielding coil, wherein at least one of the shielding coils in the top layer of a shielding layer and the bottom layer of a shielding layer comprises an N1-turn clockwise coil and an N2-turn counterclockwise coil, or the top layer of a shielding layer and / or the bottom layer of a shielding layer further comprises a first auxiliary winding, wherein the top layer of a shielding layer or the bottom layer of a shielding layer comprises an N3-turn clockwise shielding coil and an N4-turn counterclockwise first auxiliary winding, wherein N4 is greater than 3, and the compensating common mode current of the planar transformer is adjusted by adjusting the ratio of N1 to N2 or the ratio of N3 to N4. The present invention provides a planar transformer and a power converter, which can reduce the common mode current caused by the primary winding, thereby reducing the interference of EMI common mode noise.

Description

Technical Field

[0001] The present invention relates to the technical field of transformers, and in particular to a planar transformer and a power converter. Background Art

[0002] 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.

[0003] Patent No. 201711390939.3 discloses a planar transformer, which is a primary type, in which the shielding winding is one turn and the auxiliary winding is three turns. The common mode current is adjusted by adjusting the number of turns inside the composite winding, but this solution has many PCB layers, complex processes and high costs. The primary winding has a high operating voltage, and a relatively large potential difference will be generated between it and the magnetic core, which may cause insulation breakdown between the magnetic core and the winding, reducing product reliability. Summary of the invention

[0004] 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 caused by the primary winding, thereby reducing the interference of EMI common mode noise.

[0005] The technical solution of the present invention is as follows:

[0006] A planar transformer comprises, from bottom to top, a bottom layer of a primary coil, a bottom shielding layer, a primary coil, a top layer of a primary coil, the top layer of a shielding layer and the bottom layer of a primary coil, the top layer of a shielding layer and the bottom layer of a primary coil each comprising a shielding coil, at least one of the top layer of a shielding layer and the bottom layer of a primary coil comprising N1 turns of a clockwise coil and N2 turns of a counterclockwise coil, or the top layer of a shielding layer and / or the bottom layer of a primary coil further comprises a first auxiliary winding, the top layer of a shielding layer and / or the bottom layer of a primary coil comprises N3 turns of a clockwise shielding coil and N4 turns of a counterclockwise first auxiliary winding, N4 being greater than 3, and the compensating common mode current of the planar transformer is adjusted by adjusting the ratio of N1 to N2 or the ratio of N3 to N4.

[0007] Wherein, the sum of N1 and N2 is less than 1.

[0008] Among them, the bottom-level secondary coil is wound clockwise or counterclockwise with the secondary static point potential as the starting end; the top-level secondary coil is connected in series or in parallel with the bottom-level secondary coil, and its winding direction is the same as that of the bottom-level secondary coil.

[0009] Among them, 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.

[0010] Among them, 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.

[0011] Among them, the top or / and bottom shielding layer also includes a second auxiliary winding, and the inner circle of the shielding coil of the top or / and bottom shielding layer is also provided with the second auxiliary winding, the number of turns of the second 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, or connected in series with the primary coil, or connected in series with the second auxiliary winding.

[0012] Among them, the inner circle of the N3 circles of clockwise shielding coil is provided with N4 circles of the counterclockwise first auxiliary winding, and the N3 is greater than 1.

[0013] The area of ​​the N3 clockwise shielding coil and the value of N3 can be changed to adjust the compensation common mode current of the transformer.

[0014] A power converter comprises the planar transformer mentioned above.

[0015] 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.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 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).

[0018] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A cross-sectional schematic diagram of a multilayer coil of a planar transformer provided in Embodiment 1 of the present invention;

[0021] Figure 2 A winding diagram of each layer of coils of a planar transformer provided in the first embodiment of the present invention;

[0022] Figure 3 A coil winding diagram of a top layer or bottom layer shielding layer of a planar transformer provided in the first embodiment of the present invention;

[0023] Figure 4 A winding diagram of a bottom shielding layer and a bottom level coil of a planar transformer provided in the first embodiment of the present invention;

[0024] Figure 5 A coil winding diagram of a top-level secondary coil and a top-layer shielding layer of a planar transformer provided in the first embodiment of the present invention;

[0025] Figure 6 A coil winding diagram of a top layer or bottom layer shielding layer of a planar transformer provided in the second embodiment of the present invention;

[0026] Figure 7 A three-dimensional diagram of a multilayer coil of a first planar transformer provided in Embodiment 3 of the present invention;

[0027] Figure 8 The winding diagram of each layer of coils of the first planar transformer provided in the third embodiment of the present invention;

[0028] Fig. 9 The winding diagram of each layer of coils of the second planar transformer provided in the third embodiment of the present invention;

[0029] Fig.10 A three-dimensional diagram of a multilayer coil of a third planar transformer provided in Embodiment 3 of the present invention;

[0030] Fig.11 The winding diagram of each layer of coils of the third planar transformer provided in the third embodiment of the present invention;

[0031] Fig.12 A schematic diagram of a transformer application according to an embodiment of the present invention;

[0032] Fig.13 This is a second schematic diagram of a transformer application according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention 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 invention and are not used to limit the present invention.

[0034] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below for illustration.

[0035] Embodiment 1

[0036] See also Figure 1 The present embodiment provides a planar transformer, which is a sub-primary structure, and includes, from bottom to top, a bottom layer of a primary coil 1, a bottom layer of a shielding layer 2, a primary coil 3, a top layer of a shielding layer 4, and a top layer of a secondary coil 5. According to different output power specifications, the top layer of a shielding layer 4 and the bottom layer of a shielding layer 2 can be connected in series or in parallel. There is an intermediate layer between the bottom layer and the top layer of the secondary coils, and the intermediate layer can be a multi-layer structure. The planar transformer as a whole can be a 6-14 layer structure, such as Figure 2 This is a schematic diagram of a 6-layer structure.

[0037] 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 .

[0038] 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.

[0039] 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 3 As shown, the ratio of the clockwise coil to the counterclockwise coil is 0.7 / 0.3 or 0.6 / 0.4.

[0040] As an embodiment, the top shielding layer 4 includes N1 clockwise coil and N2 counterclockwise coil, such as Figure 4 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.

[0041] As an embodiment, the bottom shielding layer 4 includes N1 clockwise coil and N2 counterclockwise coil, such as Figure 5 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 .

[0042] 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.

[0043] 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.

[0044] Embodiment 2

[0045] See also Figure 6 This embodiment provides a planar transformer, which is different from the first embodiment in that the top shielding layer 4 and / or the bottom shielding layer 2 also includes a first auxiliary winding 22, and the top shielding layer 4 and / or the bottom shielding layer 2 includes N3 turns of clockwise shielding coil 21 and N4 turns of counterclockwise first auxiliary winding 22, N4 is greater than 3, and the best EMI performance is achieved by adjusting the forward and reverse ratio of the shielding layer and the first auxiliary winding 22 and the copper platinum area of ​​the shielding layer. According to different output specifications, the ratio can be 2 / 6 or 1.5 / 6, or other ratios.

[0046] In this embodiment, the inner circle of the N3 circles of clockwise shielding coil 21 is provided with N4 circles of counterclockwise first auxiliary winding 22, wherein N3 is greater than 1.

[0047] The area of ​​the clockwise shielding coil of the N3 circle and the value of N3 can be changed to adjust the compensation common mode current of the transformer.

[0048] like Figure 6 The area of ​​the shielding coil 21, that is, the width of the copper foil coil can be adjusted according to the actual area of ​​the PCB board, making full use of its copper foil area, and combining the ratio of N3 and N4 to obtain the best EMI performance.

[0049] Embodiment 3

[0050] 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.

[0051] like Figure 7 , Figure 8 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 .

[0052] or Figure 1 , Fig. 9 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 .

[0053] or Fig.10 , Fig.11 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 .

[0054] The number of turns of the second auxiliary winding 23 is less than 3.

[0055] 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.

[0056] like Fig.12 and Fig.13 As shown, The marked ones are primary and secondary static points. The output has two applications. Fig.12 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.13 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.

[0057] 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.

[0058] Embodiment 4

[0059] 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.

[0060] The planar transformer includes, from bottom to top, a bottom layer of secondary coils, a bottom shielding layer, a primary coil, a top layer of shielding layer and a top layer of secondary coils. The top layer of shielding layer and the bottom layer of shielding layer both include shielding coils. At least one of the shielding coils in the top layer of shielding layer and the bottom layer of shielding layer includes N1 turns of clockwise coils and N2 turns of counterclockwise coils, or the top layer of shielding layer or the bottom layer of shielding layer also includes a first auxiliary winding. The top layer of shielding layer or the bottom layer of shielding layer includes N3 turns of clockwise shielding coils and N4 turns of counterclockwise first auxiliary windings. N4 is greater than 3. The compensation common mode current of the planar transformer is adjusted by adjusting the ratio of N1 to N2 or the ratio of N3 to N4.

[0061] 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).

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. 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 turns of clockwise coils and N2 turns of counterclockwise coils, or the top-level shielding layer and / or the bottom-level shielding layer also include a first auxiliary winding, the top-level shielding layer and / or the bottom-level shielding layer include N3 turns of clockwise shielding coils and N4 turns of counterclockwise first auxiliary windings, N3 is greater than 1, and N4 is greater than 3, and the compensating common-mode current of the planar transformer is adjusted by adjusting the ratio of N1 to N2, the ratio of N3 to N4, or the area of ​​the N3 turns of clockwise shielding coils; The sum of N1 and N2 is less than 1, the ratio of N1 to N2 is 0.7 / 0.3 or 0.6 / 0.4, and the ratio of N3 to N4 is 2 / 6 or 1.5 / 6.

2. A planar transformer according to claim 1, 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.

3. A planar transformer according to claim 2, 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.

4. A planar transformer according to claim 2, 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.

5. A planar transformer according to claim 3 or 4, characterized in that: The top or / and bottom shielding layer also includes a second auxiliary winding, and the inner circle of the shielding coil of the top or / and bottom shielding layer is also provided with the second auxiliary winding, the number of turns of the second 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, or connected in series with the primary coil, or connected in series with the second auxiliary winding.

6. A power converter, characterized in that: A planar transformer comprising any one of claims 1 to 5.

7. A power converter according to claim 6, 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.

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