A power adapter

Abstract

The application discloses a power adapter, comprising a planar transformer, the planar transformer comprises a magnetic core and a circuit board with coils, the circuit board is installed in the magnetic core, the magnetic core has a center column, the center column is arranged in the circuit board, the coils comprise a primary coil and a secondary coil, the number of turns of the secondary coil is Ns, the number of turns of the primary coil is Np, Np / Ns>=4, Ns>=3, the current density of the coil is J>=10A / mm 2 In the application, Np / Ns>=4, the number of turns of the secondary coil is set to be >=3, and the current density of the coil is J>=10A / mm 2 In the case of the same power, the number of turns N of the coil is increased, the effective area of the magnetic core can be reduced, the area of the circuit board can be reduced, and then the volume of the circuit board and the magnetic core is reduced, the volume of the planar transformer can be designed to be smaller, and then the volume of the power adapter is smaller.

Description

Technical Field

[0001] This invention relates to power adapters used in electronic devices. Background Technology

[0002] With the explosive growth of smartphones and laptops, there is a growing demand for smaller and lighter power adapters for greater convenience. As a key component of any power adapter, the size of the transformer is crucial. Planar transformers offer advantages such as low height, small size, good consistency, ease of mass production, low leakage inductance, good heat dissipation, and good electromagnetic compatibility, making them a widely used type of transformer. There are various types of planar transformers, among which PCB planar transformers are the most widely used due to their robust structure and ease of manufacturing.

[0003] However, existing PCB planar transformers use a single-piece structure, with the secondary coil typically having 1 or 2 turns, and are generally in the range of six to a dozen layers, sometimes approaching twenty layers. As the power requirements of existing power adapters increase, the larger the PCB planar transformer becomes, the larger the power adapter becomes, and the more complex the routing becomes, with many blind and buried vias. Therefore, the manufacturing cost and time of the PCB are very long. In addition, there are voltage withstand requirements for the primary and secondary windings. The PCB lamination structure design affects the distribution of parasitic capacitance, making efficiency optimization and EMI results more complex, resulting in very long testing and design times. Summary of the Invention

[0004] The features and advantages of the present invention are set forth in part in the description which follows, or may be apparent from the description, or may be learned by practicing the invention.

[0005] The purpose of this invention is to provide a power adapter that, while maintaining the same power output, allows for a smaller planar transformer and thus a smaller power adapter.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A power adapter includes a planar transformer, the planar transformer including a magnetic core and a circuit board with a coil, the circuit board being mounted in the magnetic core, the magnetic core having a central post passing through the circuit board, the coil including a primary coil and a secondary coil, the secondary coil having Ns turns, the primary coil having Np turns, Np / Ns≥4, Ns≥3, and the current density of the coil J≥10A / mm². 2 .

[0007] The primary coil and the secondary coil are located on a circuit board. The primary coil has multiple layers and is connected to each other. The secondary coil has multiple layers and is connected to each other.

[0008] The circuit board has multiple boards stacked together, including at least one board with a primary coil and at least one board with a secondary coil.

[0009] There are at least two circuit boards with primary coils, and the circuit boards with primary coils and circuit boards with secondary coils are arranged alternately, with the circuit boards with primary coils connected to each other.

[0010] There are at least two circuit boards with secondary coils, with circuit boards with primary coils and circuit boards with secondary coils arranged alternately, and the circuit boards with secondary coils are connected to each other.

[0011] Each circuit board includes a trace section and a connection section located on one side of the trace section. The magnetic core covers the trace section, and the connection section is exposed on the side of the magnetic core. The connection sections of two adjacent circuit boards are located on both sides of the magnetic core, and electronic components are disposed on the upper surface and / or lower surface of the connection section.

[0012] A buffer heat sink is provided between the upper surface of the circuit board and the magnetic core, and a buffer heat sink is provided between the lower surface of the circuit board and the magnetic core.

[0013] A buffer heat sink is provided between the topmost circuit board and the magnetic core, and a buffer heat sink is provided between the bottommost circuit board and the magnetic core.

[0014] The circuit board also includes a power supply coil for an auxiliary power supply, which includes an auxiliary coil for the primary circuit and an auxiliary coil for the secondary circuit. The voltage of the auxiliary coil for the primary circuit is proportional to the voltage of the power input, and / or the voltage of the auxiliary coil for the secondary circuit is proportional to the voltage of the power input.

[0015] The primary coil and the auxiliary coil of the primary circuit are set on separate circuit boards, and the secondary coil and the auxiliary coil of the secondary circuit are set on separate circuit boards.

[0016] The auxiliary coils of the primary circuit and the secondary circuit are located on the same circuit board.

[0017] The circuit board also includes an insulating layer. Both the coil and the insulating layer have multiple layers. An insulating layer is provided between two adjacent coil layers. The top and bottom layers of the circuit board are insulating layers that cover the coil.

[0018] The multiple circuit boards are encapsulated into a single unit using insulating potting compound.

[0019] The multiple circuit boards and the magnetic core are encapsulated into a single unit using insulating potting compound.

[0020] The circuit board has multiple pieces, which are stacked together. At least one circuit board has both a primary coil and a secondary coil. The primary coil and the secondary coil on the at least one circuit board have multiple layers, and the primary coils are connected to each other, and the secondary coils are connected to each other.

[0021] The primary coil has multiple layers, the secondary coil has multiple layers, and the primary coil has at least two circuit loops and / or the secondary coil has at least two circuit loops.

[0022] This invention ensures that Np / Ns ≥ 4, the number of turns in the secondary coil is Ns ≥ 3, and the current density of the coil is J ≥ 10 A / mm². 2 Once the adapter's operating conditions are determined, the ratio n of the primary coil turns to the secondary coil turns is constant. As the number of turns Ns in the secondary coil increases (from 1,2 to 3,4,5…), the number of turns Np in the primary coil also increases significantly. Therefore, the number of turns N in the planar transformer increases. With the power adapter's power remaining constant (e.g., 100W) and the magnetic flux density B remaining constant, according to the formula B = LI / NA, we assume the product of LI remains constant, and the product of NA also remains constant or increases slightly (i.e., ensuring B is not greater than Bsat, where Bsat is the saturation magnetic flux density of the selected core material). Because the total number of coil turns N increases, the effective area A of the core can decrease, meaning the cross-sectional area of ​​the central post decreases. Since the cross-sectional area of ​​the central post decreases, the circular through-holes on the circuit board also decrease. Furthermore, since the coil is arranged around the central post, the area occupied by the coil on the circuit board also decreases, thus reducing the circuit board area. Consequently, the volume of the circuit board and the core decreases. This reduction in the volume of the circuit board and the core leads to a reduction in the volume of the planar transformer, and consequently, a reduction in the volume of the power adapter. When the number of turns of the secondary coil Np / Ns≥4 and Ns≥3, the voltage of the auxiliary coil of the primary circuit is proportional to the voltage of the power supply input, or / and the voltage of the auxiliary coil of the secondary circuit is proportional to the voltage of the power supply input. This reduces the window area of ​​the transformer occupied by the auxiliary coil, while increasing the effective window utilization coefficient of the primary and secondary coils. This makes the transformer structure simple, reduces costs and reduces leakage inductance. Attached Figure Description

[0023] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings:

[0024] Figure 1 This is a structural diagram of a planar transformer with electronic components mounted on a second circuit board, as shown in the first embodiment of the present invention.

[0025] Figure 2The explosion of the planar transformer with electronic components on the second circuit board in the first embodiment of the present invention. Figure 1 ;

[0026] Figure 3 The explosion of the planar transformer with electronic components on the second circuit board in the first embodiment of the present invention. Figure 2 ;

[0027] Figure 4 This is an exploded view of the circuit board in the first embodiment of the present invention;

[0028] Figure 5 This is a side view of a planar transformer with electronic components mounted on a second circuit board, as shown in the first embodiment of the present invention.

[0029] Figure 6 for Figure 1 A structural diagram viewed from top to bottom;

[0030] Figure 7 This is a structural diagram of a planar transformer with electronic components mounted on the first and second circuit boards in the second embodiment of the present invention.

[0031] Figure 8 This is an exploded view of a planar transformer with electronic components mounted on the first and second circuit boards in the second embodiment of the present invention.

[0032] Figure 9 This is a structural diagram of the circuit board in the second embodiment of the present invention;

[0033] Figure 10 This is a side view of a planar transformer with electronic components mounted on the first and second circuit boards in the second embodiment of the present invention.

[0034] Figure 11 This is an exploded view of the planar transformer in the third embodiment of the present invention;

[0035] Figure 12 This is a side view of the planar transformer in the third embodiment of the present invention;

[0036] Figure 13 This is an exploded view of the planar transformer in the fourth embodiment of the present invention;

[0037] Figure 14 This is a side view of the planar transformer in the fourth embodiment of the present invention;

[0038] Figure 15 This is an exploded view of the planar transformer in the fifth embodiment of the present invention;

[0039] Figure 16 This is a side view of the planar transformer in the fifth embodiment of the present invention;

[0040] Figure 17 This is an exploded view of the planar transformer in the sixth embodiment of the present invention;

[0041] Figure 18 This is a side view of the planar transformer in the sixth embodiment of the present invention;

[0042] Figure 19 The circuit structure diagram shows two first circuit boards connected in series, and another two first circuit boards connected in series and then in parallel.

[0043] Figure 20 The circuit structure diagram shows two first circuit boards connected in parallel, and another two first circuit boards connected in parallel and then connected in series.

[0044] Figure 21 The circuit diagram shows the circuit structure when the terminal E of the auxiliary coil of the primary circuit and the terminal F of the secondary coil have the same polarity and the number of turns of the secondary coil is 2.

[0045] Figure 22 The circuit diagram shows the circuit structure when the terminal E of the auxiliary coil of the primary circuit and the terminal F of the secondary coil have the same polarity and the number of turns of the secondary coil is 4.

[0046] Figure 23 This is a circuit diagram showing the circuit structure when the endpoint B of the auxiliary coil of the primary circuit in an embodiment of the present invention has the same polarity as the endpoint A of the primary coil, and the number of turns of the secondary coil is 2.

[0047] Figure 24 The circuit diagram shows the circuit structure when the terminal B of the auxiliary coil and the terminal A of the primary coil are of the same polarity in the primary circuit of the present invention, and the number of turns of the secondary coil is 4.

[0048] Figure 25 This is a structural diagram of a planar transformer on a circuit board according to the seventh embodiment of the present invention;

[0049] Figure 26 This is a structural diagram of the horizontal planar transformer in the eighth embodiment of the present invention;

[0050] Figure 27 This is an exploded view of the horizontal planar transformer in the eighth embodiment of the present invention;

[0051] Figure 28 This is a structural diagram of a planar transformer without electronic components on the circuit board according to the ninth embodiment of the present invention;

[0052] Figure 29 This is an exploded view of a planar transformer with no electronic components on the circuit board according to the ninth embodiment of the present invention;

[0053] Figure 30 This is an exploded view of the planar transformer in the tenth embodiment of the present invention;

[0054] Figure 31 This is an exploded view of the planar transformer in the eleventh embodiment of the present invention. Detailed Implementation

[0055] like Figures 1 to 4 As shown, the power adapter proposed in this embodiment of the invention includes a planar transformer 100, which includes a magnetic core 110 and a circuit board. Figure 2 and Figure 3 In the middle, those labeled 121 and 122 are circuit boards. There are one or more circuit boards. The circuit boards are installed in the magnetic core 110. The magnetic core has a central post 1111, which is inserted through the circuit board.

[0056] like Figure 2 and Figure 3 As shown, in this embodiment, the magnetic core is composed of two parts spliced ​​together. The two parts of the magnetic core are the first part 111 and the second part 112. The central column 1111 is located on the first part 111. The central column 1111 is cylindrical in shape, but it can also be square, rectangular, elliptical, etc. The cross-sectional shape of the first part 111 is E-shaped, and the shape of the second part 112 is plate-shaped, but it can also be E-shaped.

[0057] refer to Figure 3 The circuit board has a circular through hole 123, and the central post 1111 passes through the circular through hole 123 of the circuit board.

[0058] Most existing adapters use step-down transformers, so the secondary coil current is several times larger than the primary coil current. In order to reduce secondary copper losses, the number of turns Ns of the secondary coil of this type of PCB planar transformer is selected as 1 or 2 (the larger the number of turns, the greater the resistance of the wire, and the copper loss is proportional to the resistance and the square of the current).

[0059] In this invention, the coil includes a primary coil and a secondary coil. The number of turns in the secondary coil is Ns, and the number of turns in the primary coil is Np. Np / Ns ≥ 4, for example, Np / Ns = 4, 5, 6, 7, 8, 9, 10, 11, 12, etc., and can also be Np / Ns ≥ 5, Np / Ns ≥ 6, Np / Ns ≥ 7, Np / Ns ≥ 8, Np / Ns ≥ 9, Np / Ns ≥ 10, Np / Ns ≥ 11, Np / Ns ≥ 12, etc.; Ns ≥ 3, for example, Ns = 3, 4, 5, 6, 7, 8, etc., and can also be Ns ≥ 4, Ns ≥ 5, Ns ≥ 6, Ns ≥ 7, Ns ≥ 8, etc.; the current density of the coil J ≥ 10 A / mm². 2

J=I / (wd*T), where I is the average current of the coil, Wd is the width of the coil trace, and T is the thickness of the coil trace (copper foil).

[0060] Because traditional wire-wound transformers have relatively low manufacturing costs, some have attempted to increase the number of secondary coil turns, such as setting Ns=4. However, due to the poor heat dissipation of the wires in wire-wound transformers, the current density J of the coil cannot be too high, limiting the improvement in the transformer's energy storage capacity and making it difficult to reduce its size. Some might apply the experience of wire-wound transformers to planar transformers, simply changing the core structure from EE to EI, merely transforming a thicker transformer into a thinner one. This doesn't break free from established thinking; a large effective core area is still used. While the transformer is made thinner, the core volume remains large. Therefore, increasing the coil current is a limiting condition of this patent, setting the coil current density J≥10A / mm². 2 J≥13A / mm 2 J≥15A / mm 2 wait.

[0061] With a constant ratio of the number of turns Np in the primary coil to the number of turns Ns in the secondary coil, and when Np / Ns ≥ 4, the current density J of the coil is set to ≥ 10 A / mm². 2 For example, J = 10 A / mm 2 13A / mm 2 15A / mm 2 18A / mm 2 20A / mm 2 25A / mm 2 30A / mm 2 35A / mm 2 40A / mm 2 Of course, J≥13A / mm is also possible. 2 J≥15A / mm 2 J≥18A / mm 2 J≥20A / mm 2 J≥25A / mm 2 J≥30A / mm 2 J≥35A / mm 2 J≥40A / mm 2As the number of turns Ns in the secondary coil increases from 1 or 2 to 3, 4, 5, etc., the number of turns Np in the primary coil also increases significantly. Therefore, the number of turns N in the planar transformer increases significantly. With the power adapter power remaining constant (e.g., 100W) and the magnetic flux density B remaining constant, according to the formula B = LI / NA (where B is the magnetic flux density of the core, L is the inductance of the core coil, I is the current flowing through the coil, N is the number of turns in the core coil, and A is the effective area of ​​the core), assuming the product of LI and NA remains constant, the effective area A of the core can decrease as the number of turns N increases. This means the cross-sectional area of ​​the central column decreases. Since the cross-sectional area of ​​the central column decreases, the circular through-holes on the circuit board also decrease. Furthermore, since the coil is arranged around the central column, the area occupied by the coil on the circuit board also decreases. Therefore, the area of ​​the circuit board also decreases accordingly, leading to a reduction in the volume of the circuit board and the core. This reduction in the volume of the circuit board and the core results in a reduction in the volume of the planar transformer, and consequently, a reduction in the volume of the power adapter. Therefore, in this invention, Np / Ns ≥ 4, and the current density of the coil is set to J ≥ 10 A / mm². 2 The number of turns Ns in the secondary coil is set to ≥3. With the same power output, increasing the number of turns N reduces the effective area of ​​the magnetic core, thus reducing the circuit board area and consequently the size of the circuit board and magnetic core. This allows for a smaller planar transformer design, and consequently, a smaller power adapter. Increasing the current density in the coil reduces the width Wd of the coil conductor, allowing for a smaller transformer window area, further reducing the transformer's size and consequently, the power adapter's size.

[0062] Given a constant switching frequency, according to the formula B = LI / NA, those skilled in the art often believe that increasing the number of coil turns helps increase the inductance. However, if the core material is already close to its energy storage limit, increasing the number of coil turns will cause the core to saturate, and the inductance will actually plummet rather than increase. Therefore, increasing the number of coil turns requires increasing the size of the core, which in turn increases the size and volume of the transformer to ensure that the core does not saturate. In this invention, under the same power conditions, Np / Ns ≥ 4, the number of turns of the secondary coil Ns ≥ 3, and the current density of the coil J ≥ 10 A / mm². 2 By keeping the product of LI and NA constant, increasing the number of coil turns N reduces the effective area A of the magnetic core, thus reducing the size of the circuit board and the magnetic core. This reduction in the size of the circuit board and the magnetic core leads to a smaller planar transformer, which in turn reduces the size of the power adapter, overcoming existing technological biases. (The inductance of the magnetic core coil is proportional to the square of the number of turns; increasing the number of turns causes a dramatic increase in inductance. To keep LI constant, the inductance can be adjusted by changing the air gap in the magnetic core. The inductance is very sensitive to changes in the air gap; even a slight increase in the air gap will significantly reduce the inductance.)

[0063] In addition, according to the formula B = LI / NA, when designing a transformer, it is essential to prevent the magnetic material from approaching its energy storage limit, that is, B cannot be greater than Bsat (Bsat is the saturation magnetic induction intensity of the selected core material).

[0064] For example, when designing a 100W adapter, given the input and output voltages, input and output currents, and efficiency requirements, and the topology determined, the number of turns in the primary coil (NP), the number of turns in the secondary coil (Ns), and the turns ratio of the primary to secondary coils (n = Np / Ns) are also fixed. When n < 4, the total number of turns N is relatively small. For example, when n = 3 and Ns = 2, the number of turns in the primary coil is 6, the number of turns in the secondary coil is 2, and the total number of turns is 8. Even if the number of turns in the secondary coil (Ns) is doubled to 4, the number of turns in the primary coil becomes 12, and the total number of turns becomes 16, but the number of coil layers on the circuit board will not be too many. Therefore, when n < 4, although the design is complex, some people may still try to increase the number of turns in the secondary coil to improve the transformer's storage capacity. Moreover, those skilled in the art often tend to believe that increasing the number of coil turns will saturate the magnetic core, so increasing the number of coil turns requires increasing the size of the magnetic core; otherwise, a small magnetic core with high power will be disastrous. Therefore, when n increases further, those skilled in the art are more inclined not to increase the number of turns in the secondary coil (Ns). Therefore, in this invention, under the same power conditions, Np / Ns is set to ≥ 4 and the number of turns in the secondary coil Ns is set to ≥ 3. The product of L1 and NA is kept constant. Increasing the number of coil turns N reduces the effective area A of the magnetic core, thus reducing the volume of the circuit board and the magnetic core. This reduction in the volume of the circuit board and the magnetic core leads to a reduction in the volume of the planar transformer, which in turn reduces the volume of the power adapter, overcoming existing technical biases. (Alternatively, the product of L1 can be kept constant, and the product of NA can be slightly increased, or N can be increased while adjusting L and A so that the value of B = L1 / NA remains constant or is smaller, ensuring that B is not greater than Bsat, while A decreases.)

[0065] For example, the primary coil has 12 turns and the secondary coil has 2 turns. In this invention, the primary coil has 18 turns and the secondary coil has 3 turns; the primary coil has 24 turns and the secondary coil has 4 turns. Although increasing the number of coil turns N increases the number of coil layers (e.g., from 8 layers to 16 layers), the coil traces on the circuit board are very thin. While increasing the number of coil layers makes the circuit board thicker, the increase in volume due to the increased thickness is far less than the decrease in volume of the circuit board and the magnetic core. Therefore, the increased circuit board thickness has a very small impact on the volume of the planar transformer.

[0066] In addition, the magnetic loss of a planar transformer is related to its volume. The larger the volume of the planar transformer, the greater its magnetic loss. Therefore, reducing the volume of the planar transformer is beneficial to reducing magnetic loss.

[0067] like Figure 4As shown, each circuit board includes an insulating layer 1212 and a coil 1213, and both the insulating layer 1212 and the coil 1213 in each circuit board have multiple layers. An insulating layer 1212 is provided between two adjacent coils 1213, and the top and bottom layers of the circuit board are insulating layers 1212 that cover the coils. That is, in a circuit board with a primary coil, an insulating layer is provided between two adjacent primary coils, and the top and bottom layers of the circuit board with a primary coil are insulating layers that cover the primary coils; in a circuit board with a secondary coil, an insulating layer is provided between two adjacent secondary coils, and the top and bottom layers of the circuit board with a secondary coil are insulating layers that cover the secondary coils.

[0068] Since adjacent coils on the same circuit board need to be connected, but there is an insulating layer between them, connection holes 1214 are made on the insulating layer between adjacent coils to facilitate the connection. Connection points are also set on the coils at locations corresponding to the through holes. To seal the coils and connection holes 1214, the top and bottom layers of the circuit board are set as insulating layers 1212, which cover the coils and connection holes 1214. This method of using outer layer insulation to seal inner layer circuits is applicable to circuit boards with primary coils and circuit boards with secondary coils in this invention. The purpose of sealing the coils and their connection holes with insulating layers is to electrically isolate the circuit board with the primary coil from the circuit board with the secondary coil, or to electrically isolate two adjacent circuit boards with primary coils, or to isolate the circuit board from the magnetic core, thus achieving the high voltage withstand requirements of the primary and secondary windings. In this way, the circuit board with the primary coil does not need to be covered with pressure-resistant tape or filled with insulating glue to meet the pressure withstand requirements.

[0069] Current planar transformers use a single-piece structure, with the secondary coil typically having 1 or 2 turns. To complete the routing, insulation, and shielding of the primary coil, secondary coil, and auxiliary power supply coil, and to meet EMI requirements, the PCB board needs at least six to more than ten layers. If the number of secondary turns is to be increased to 3 or 4 or even more, the PCB board would need to be made to more than ten to dozens of layers, which is too difficult to achieve the required specifications. Under current technology, the cost is very high, making it not the preferred method. In this invention, the preferred approach is to use multiple circuit boards.

[0070] like Figure 2 , Figure 3 , Figure 5 and Figure 6As shown, the circuit board has multiple boards stacked together. At least one board has a primary coil and at least one board has a secondary coil. That is, the coils on at least one board are all primary coils. Each board with a primary coil includes multiple layers of primary coils and multiple layers of insulating layers. The coils on at least one board are all secondary coils. Each board with a secondary coil includes multiple layers of secondary coils and multiple layers of insulating layers. The primary coils and secondary coils are disposed on different boards.

[0071] In other embodiments, insulating sheets can be provided on the upper and lower surfaces of the circuit board, or insulating potting compound can be used to replace the insulating layer, which can also meet the withstand voltage requirements.

[0072] There are at least two circuit boards with primary coils, and the circuit boards with primary coils and circuit boards with secondary coils are alternately arranged. The circuit boards with primary coils are connected to each other, and there is a gap between adjacent circuit boards. In one embodiment, there are three circuit boards: two circuit boards with primary coils (hereinafter referred to as first circuit board 121) and one circuit board with secondary coils (hereinafter referred to as second circuit board 122). The three circuit boards are stacked vertically, with the first circuit board 121 as the top layer, the second circuit board 122 as the middle layer, and the first circuit board 121 as the bottom layer, forming an alternating arrangement of the first circuit board 121 and the second circuit board 122. The top first circuit board 121 is connected to the bottom first circuit board 121, that is, the circuit boards with primary coils are connected to each other.

[0073] There are at least two circuit boards with secondary coils, and circuit boards with primary coils and circuit boards with secondary coils are alternately arranged. The circuit boards with secondary coils are connected to each other, and there is a gap between adjacent circuit boards. In one embodiment, there are three circuit boards: two circuit boards with secondary coils (hereinafter referred to as the second circuit board) and one circuit board with primary coils (hereinafter referred to as the first circuit board). The three circuit boards are stacked vertically, with the second circuit board on the top layer, the first circuit board in the middle layer, and the second circuit board on the bottom layer, forming an alternating arrangement of the first and second circuit boards. The uppermost second circuit board is connected to the lowermost second circuit board, that is, the circuit boards with secondary coils are connected to each other.

[0074] In one embodiment, the circuit board comprises four boards: two boards with primary coils (hereinafter referred to as the first circuit board) and two boards with secondary coils (hereinafter referred to as the second circuit board). The four circuit boards are stacked vertically, with the first circuit board on top, the second circuit board on the second layer, the first circuit board on the third layer, and the second circuit board on the bottom, forming an alternating arrangement of the first and second circuit boards. The top-layer first circuit board is connected to the third-layer first circuit board, and the second-layer second circuit board is connected to the bottom-layer second circuit board. That is, the circuit boards with primary coils are connected to each other, and the circuit boards with secondary coils are connected to each other. The positions of the first and second circuit boards can be interchanged.

[0075] In one embodiment, the circuit board comprises five boards: three boards with primary coils (hereinafter referred to as the first circuit board) and two boards with secondary coils (hereinafter referred to as the second circuit board). The five circuit boards are stacked vertically, with the first circuit board at the top, the second circuit board at the second, the first circuit board at the third, the second circuit board at the fourth, and the first circuit board at the bottom, forming an alternating arrangement of the first and second circuit boards. The top, third, and bottom first circuit boards are sequentially connected, and the second circuit boards at the second and fourth layers are connected. Similarly, the positions of the first and second circuit boards can be interchanged; of course, the circuit board may also have six boards.

[0076] The circuit boards with primary coils and those with secondary coils can also be arranged in other ways. For example, if there are four circuit boards, the top two layers are circuit boards with primary coils, which are connected to each other, and the bottom two layers are circuit boards with secondary coils, which are also connected to each other; alternatively, the top layer can be a circuit board with a primary coil, the middle two layers can be circuit boards with secondary coils, and the bottom layer can be a circuit board with a primary coil, with the top and bottom layers connected to each other, and the middle two layers connected to each other.

[0077] In embodiments of the present invention, multiple circuit boards are provided, and the primary coil and secondary coil are separately arranged on different circuit boards. At least one circuit board contains the primary coil, and at least one circuit board contains the secondary coil. When Np / Ns≥4, the number of turns Ns of the secondary coil is set to ≥3, and the current density J of the coil is set to ≥10A / mm². 2As the number of turns Ns in the secondary coil increases, the number of turns NP in the primary coil also increases. Therefore, the number of turns N in the planar transformer increases. With the power adapter power remaining constant, the effective area A of the magnetic core can be reduced due to the increased number of turns N, resulting in a smaller circuit board area and consequently a smaller circuit board and magnetic core volume. This reduction in circuit board and magnetic core volume leads to a smaller planar transformer volume, which in turn reduces the overall size of the power adapter. Therefore, for the same power output, the planar transformer can be designed to be smaller, resulting in a smaller power adapter.

[0078] In this embodiment of the invention, the power adapter has a power of 65W and an output voltage of 5-20V.

[0079] like Figures 7 to 10 As shown, each circuit board includes a trace portion 1201 and a connecting portion 1202 located on one side of the trace portion 1201. The trace portion 1201 is the part used to carry the coil, and the connecting portion 1202 is the part used to connect circuit boards with primary coils or circuit boards with secondary coils. After installation, the trace portion 1201 is almost entirely covered by the magnetic core, while the connecting portion 1202 is exposed on the side of the magnetic core 110. When multiple circuit boards are stacked on top of each other, the connection part 1202 of two adjacent circuit boards is located on both sides of the magnetic core 110 (e.g., the connection part of the first layer circuit board is located on the left side of the magnetic core, the connection part of the second layer circuit board is located on the right side of the magnetic core, the connection part of the third layer circuit board is located on the left side of the magnetic core, and so on). This leaves space on the upper and lower surfaces of the connection part, so that electronic components 140 can be placed on the upper and lower surfaces of the connection part. At the same time, it also makes the two adjacent connection parts 1202 on the same side of the magnetic core 110 have a large distance between them, forming a gap, in which electronic components 140 can be placed, making full use of the space of the planar transformer and reducing its volume.

[0080] In one embodiment, the circuit board has three pieces, with circuit boards with primary coils and circuit boards with secondary coils arranged alternately. That is, the top layer is the circuit board with primary coils, the middle layer is the circuit board with secondary coils, and the bottom layer is the circuit board with primary coils. The connection part 1202 of the two circuit boards with primary coils is exposed on the left side of the magnetic core 110, and the connection part 1202 of the circuit board with secondary coils is exposed on the right side of the magnetic core 110. In this way, there is a large gap between two adjacent circuit boards with primary coils, which allows electronic components 140 to be placed. The electronic components 140 are placed on the upper and lower surfaces of the connection part of the circuit board with secondary coils.

[0081] In one embodiment, the circuit board has four pieces, with circuit boards with primary coils and circuit boards with secondary coils alternating. Specifically, the top layer is a circuit board with primary coils, the second layer is a circuit board with secondary coils, the third layer is a circuit board with primary coils, and the bottom layer is a circuit board with secondary coils. The connection portion of two circuit boards with primary coils is exposed on the left side of the magnetic core, and the connection portion of two circuit boards with secondary coils is exposed on the right side of the magnetic core. This creates a large gap between the connection portions of adjacent circuit boards with primary coils, allowing for the placement of electronic components 140. The electronic components 140 are disposed on the upper and lower surfaces of the connection portions of the circuit boards with secondary coils. Of course, if the circuit board has four pieces, the top two layers are circuit boards with primary coils, and the bottom two layers are circuit boards with secondary coils. The connection parts of the topmost primary coil circuit board and the third secondary coil circuit board are exposed on the left side of the magnetic core, with a large gap between them to allow for the placement of electronic components; the connection parts of the second primary coil circuit board and the bottom secondary coil circuit board are exposed on the right side of the magnetic core, with a large gap between them to allow for the placement of electronic components. Alternatively, the top and bottom layers can be circuit boards with primary coils, and the middle two layers can be circuit boards with secondary coils. Similarly, the positions of the primary coil circuit boards and the secondary coil circuit boards can be interchanged.

[0082] In this invention, electronic components are provided on a circuit board with a primary coil, or on a circuit board with a secondary coil, or on a circuit board with a primary coil, or on a circuit board with a secondary coil.

[0083] Figure 1 , Figure 2 , Figure 3 and Figure 5 In the circuit, electronic components are mounted on a circuit board with a secondary coil (hereinafter referred to as the second circuit board).

[0084] Multiple circuit boards are encapsulated together as a single unit using insulating potting compound. These circuit boards can also be encapsulated together with a magnetic core. The potting compound enhances the insulation strength between the circuit board with the primary coil and the circuit board with the secondary coil, and also facilitates heat conduction and dissipation in the transformer.

[0085] The circuit board also includes a power supply coil for an auxiliary power supply, which includes an auxiliary coil for the primary circuit and an auxiliary coil for the secondary circuit. The voltage of the auxiliary coil for the primary circuit is proportional to the voltage of the power input.

[0086] like Figure 11 and Figure 12 As shown, a buffer heat sink 130 is provided between the magnetic core and the circuit board. The buffer heat sink 130 can eliminate the vibration noise generated when the planar transformer is working, and can also play a role in heat dissipation. Preferably, the buffer heat sink is a silicone sheet.

[0087] In one embodiment, the circuit board comprises three pieces: two circuit boards with primary coils and one circuit board with secondary coils. These three circuit boards are stacked vertically, with the top layer being the circuit board with primary coils (hereinafter referred to as the first circuit board 121), the middle layer being the circuit board with secondary coils (hereinafter referred to as the second circuit board), and the bottom layer being the circuit board with primary coils. A silicone sheet 130 is disposed between the top layer, the first circuit board 121, and the first portion 111 of the magnetic core, and a silicone sheet 130 is disposed between the bottom layer, the first circuit board 121, and the second portion 112 of the magnetic core.

[0088] The transformer loss P is the sum of copper loss P1 and iron loss P2 (also called core loss), i.e., P = P1 + P2. According to the copper loss formula P1 = ρL / S (ρ is the resistivity of copper, L is the length of the coil, and S is the cross-sectional area of ​​the coil's copper sheath, which is the product of the coil trace width Wd and the coil copper sheath thickness T), as the number of coil turns N increases, the total coil length increases, thus increasing the coil resistance and consequently the transformer's copper loss. In this case, the copper sheath thickness T can be increased to increase the coil's cross-sectional area and prevent the copper loss from increasing further. According to the iron loss formula P2 = Pv * Ve (Pv is the core loss per unit volume, Ve is the core volume), as the number of coil turns N increases, the effective area A of the core decreases, thus reducing the core volume and consequently the iron loss. Therefore, in this invention, Np / Ns≥4, the number of turns Ns of the secondary coil is set to ≥3, and the cross-sectional area S of the conductor is increased by increasing the copper foil thickness of the coil. This reduces the iron loss of the transformer while reducing the volume of the planar transformer, without increasing the copper loss, thus reducing the total power loss of the transformer.

[0089] In other embodiments, copper loss can also be reduced by adding at least one circuit board with a primary coil or a circuit board with a secondary coil without changing the coil width and copper thickness.

[0090] The primary coil has multiple layers, the secondary coil has multiple layers, and the primary coil has at least two circuit loops and / or the secondary coil has at least two circuit loops.

[0091] like Figure 13 and 14As shown, in one embodiment, the circuit board has five boards stacked one on top of the other. There are four boards with primary coils (hereinafter referred to as first circuit board 121) and one board with secondary coils (hereinafter referred to as second circuit board 122). The top two layers are first circuit boards 121, the middle layer is second circuit board 122, and the bottom two layers are first circuit boards 121. Of the four first circuit boards 121, the two boards in the top two layers are connected in series, and the two boards in the bottom two layers are connected in series and then in parallel. (Reference) Figure 19 In this embodiment, Lp1, Lp2, Lp11, and Lp22 are all a set of primary coils, that is, the primary coils contain four sets of primary coils, and each set of primary coils includes one or more primary coils. Figure 19 In this circuit, there are two circuit loops for the primary coil. Lp1 and Lp2 form the circuit loop LpA for the first primary coil, and Lp11 and Lp22 form the circuit loop LpB for the second primary coil. Lp1 and Lp2 are connected in series, and Lp11 and Lp22 are connected in series and then in parallel. Alternatively, the two first circuit boards 121 on the top two layers can be connected in parallel, and the two first circuit boards 121 on the bottom two layers can be connected in parallel and then in series. Figure 20 In this circuit, there are two circuit loops for the primary coil. Lp1 and Lp2 form the first primary coil circuit loop LpA, and Lp11 and Lp22 form the second primary coil circuit loop LpB. Lp1 and Lp11 are connected in parallel, and Lp2 and Lp22 are connected in parallel and then in series. For example... Figure 19 and Figure 20 In the diagram, Np1 = Np11, Np2 = Np22, LpA:NpA = Np1 + Np2 = 28Ts, LpB:NpB = Np11 + Np22 = 28Ts. Np1 is the number of turns in Lp1, Np2 is the number of turns in Lp2, Np11 is the number of turns in Lp11, Np22 is the number of turns in Lp22, NpA is the number of turns in the circuit loop LpA of the first primary coil, and NpB is the number of turns in the circuit loop LpB of the second primary coil. Therefore, as the number of coil turns N increases, without changing the coil width and copper foil thickness, according to Pcu = I... 2*R, by increasing the number of circuit boards and using the above circuit connection, the current flowing through each group of coils is only half of what it was before, and the resistance of each group of coils is less than twice the previous resistance. This results in copper losses on each group of coils being less than half of what they were before (for example, the number of turns is doubled, but the average length per turn is smaller, so the length increases by less than double, the current is halved, and the copper losses are less than half of what they were before). Therefore, the coil's heat dissipation is better, and the temperature will be lower. Furthermore, since the losses on each group of coils are less than half of what they were before, the copper foil thickness can be reduced, resulting in smaller gaps between coils, smaller coil trace widths, and lower leakage inductance. (LpA circuit loop: Vbuk->Lp1->Lp2->Q10->current limiting resistor->ground; LpB circuit loop: Vbuk->Lp11->Lp22->Q10->current limiting resistor->ground.)

[0092] By increasing the circuit loop of the primary coil from one to two, heat dissipation on each coil group is improved and the coil trace width can be reduced, the transformer window area can be smaller, the volume of the magnetic core can be smaller (only increasing the total thickness of the PCB board slightly), and the power adapter can be smaller.

[0093] Similarly, secondary coils can also be connected in series and parallel to increase the circuit loop, thereby reducing copper losses, increasing heat dissipation, and reducing the core size. (Reference) Figure 19 In this embodiment, Ls1, Ls2, Ls11, and Ls22 are all a group of secondary coils, that is, the secondary coils contain four groups of secondary coils, and each group of secondary coils includes one or more layers of secondary coils. Figure 19 In this circuit, there are two circuit loops for the secondary coil. Ls1 and Ls2 form the circuit loop LsA for the first secondary coil, and Ls11 and Ls22 form the circuit loop LsB for the second secondary coil. Ls1 and Ls2 are connected in series, and Ls11 and Ls22 are connected in series and then in parallel. Figure 20 In this circuit, the secondary coil has two circuit loops: Ls1 and Ls2 form the first secondary coil circuit loop LsA, and Ls11 and Ls22 form the second secondary coil circuit loop LsB. Ls1 and Ls11 are connected in parallel, and Ls2 and Ls22 are connected in parallel and then in series. For example... Figure 19 and Figure 20 In the circuit diagram, Ns1 = Ns11, Ns2 = Ns22, LsA:NsA = Ns1 + Ns2 = 4Ts, LsB:NsB = Ns11 + Ns22 = 4Ts. Ns1 is the number of turns of Ls1, Ns2 is the number of turns of Ls2, Ns11 is the number of turns of Ls11, Ns22 is the number of turns of Ls22, NsA is the number of turns of the circuit loop LsA of the first primary coil, and NsB is the number of turns of the circuit loop LpB of the second primary coil.

[0094] like Figure 15 and Figure 16 As shown, in one embodiment, the circuit board has six pieces, which are stacked one on top of the other. There are four circuit boards with primary coils (hereinafter referred to as first circuit boards 121) and two circuit boards with secondary coils (hereinafter referred to as second circuit boards 122). The top two layers are the first circuit boards 121, the middle two layers are the second circuit boards 122, and the bottom two layers are the first circuit boards 121. Of the four first circuit boards 121, the two first circuit boards 121 in the top two layers are connected in series, and the two first circuit boards 121 in the bottom two layers are connected in series and then in parallel. Alternatively, the two first circuit boards 121 in the top two layers can be connected in parallel, and the two first circuit boards 121 in the bottom two layers can be connected in parallel and then in series. Therefore, as the number of coil turns N increases, without changing the coil width and copper thickness, according to Pcu = I... 2 By increasing the number of circuit boards and using the circuit connections described above, the current flowing through each group of coils is reduced to half of what it was before, and the resistance of each group of coils is less than twice the previous resistance. This results in copper losses on each group of coils being less than half of what they were before (for example, the number of turns is doubled, but the average length per turn is smaller, so the length increases by less than double, the current is halved, and the copper losses are less than half of what they were before). Therefore, heat dissipation on each group of coils is better, and the temperature will be lower.

[0095] like Figure 17 and Figure 18 As shown, in one embodiment, the circuit board has six pieces, stacked one on top of the other. There are four circuit boards with primary coils (hereinafter referred to as first circuit boards 121) and two circuit boards with secondary coils (hereinafter referred to as second circuit boards 122). The top layer is the second circuit board 122, the middle four layers are the first circuit boards 121, and the bottom layer is the second circuit board 122. In the four layers of first circuit boards 121, the two first circuit boards 121 in the top two layers are connected in series, and the two first circuit boards 121 in the bottom two layers are connected in series and then in parallel. Alternatively, the two first circuit boards 121 in the top two layers can be connected in parallel, and the two first circuit boards 121 in the bottom two layers can be connected in parallel and then in series. Therefore, as the number of coil turns N increases, without changing the coil width and copper thickness, according to Pcu = I... 2 By increasing the number of circuit boards and using the circuit connections described above, the current flowing through each group of coils is reduced to half of what it was before, and the resistance of each group of coils is less than twice the previous resistance. This results in copper losses on each group of coils being less than half of what they were before (for example, the number of turns is doubled, but the average length per turn is smaller, so the length increases by less than double, the current is halved, and the copper losses are less than half of what they were before). Therefore, heat dissipation on each group of coils is better, and the temperature will be lower.

[0096] like Figure 21 and Figure 22Current planar transformers, due to their smaller secondary coil turns (1 to 2 turns), employ a common polarity between the lower endpoint E of the primary circuit's auxiliary coil Lpa and the lower endpoint F of the secondary coil Ls. The auxiliary power supply coils consist of the primary circuit's auxiliary coil Lpa and the secondary circuit's auxiliary coil Lsa (see reference). Figure 21 and Figure 22 That is, a circuit board with a primary coil has an auxiliary coil for the primary circuit, and a circuit board with a secondary coil has an auxiliary coil for the secondary circuit.

[0097] The following explanation uses the auxiliary coil Lpa of the primary circuit as an example.

[0098] like Figure 21 and Figure 22 In the diagram, the lower endpoint E of the auxiliary coil Lpa in the primary circuit has a hollow circle, and the lower endpoint F of the secondary coil Ls also has a hollow circle. These hollow circles (indicating the same polarity) indicate that the lower endpoint E of the auxiliary coil Lpa and the lower endpoint F of the secondary coil Ls have the same polarity. For example... Figure 21 In this circuit, the primary coil has 10-14 turns, the secondary coil has 2 turns, and the auxiliary coil of the primary circuit has 2-4 turns. The auxiliary coil of the primary circuit usually uses two sets of coils: one set with 2 turns (when the power supply output is 9V-24V) and the other set with 4 turns (when the power supply output is 5V).

[0099] 1. When the power adapter outputs 5V, the maximum voltage of the auxiliary coil in the primary circuit is: If the number of turns of the auxiliary coil in the primary circuit is 2, the maximum power output is 5V. However, many power controllers require a minimum voltage of 8V, so the number of turns of the auxiliary coil in the primary circuit must be 4 to meet the requirement.

[0100] 2. When the power adapter outputs 9V-24V, the maximum voltage of the auxiliary coil in the primary circuit is: if the auxiliary coil of the primary circuit has 2 turns, the maximum power output is 9-24V.

[0101] When the secondary coil turns Ns≥3 and Np / Ns≥4 are used in the embodiments of the present invention, for example... Figure 22 The primary coil has 20-28 turns, the secondary coil has 4 turns, and the auxiliary coil of the primary circuit has 4-8 turns. In order to reduce the power consumption of the controller power supply, the auxiliary coil of the primary circuit generally uses two sets of coils: one set with 4 turns (when the power supply output is 9V-24V) and the other set with 8 turns (when the power supply output is 5V).

[0102] 1. When the power adapter outputs 5V, ignoring the forward voltage of the secondary rectifier diode, the maximum voltage of the auxiliary coil in the primary circuit is: If the number of turns of the auxiliary coil in the primary circuit is 4, the maximum power output is 5V. This cannot meet the minimum voltage requirement of 8V required by the power controller. Therefore, the number of turns of the auxiliary coil in the primary circuit must be 8 to meet the requirement.

[0103] 2. When the power adapter outputs 9V-24V, the maximum voltage of the auxiliary coil in the primary circuit is: the auxiliary coil of the primary circuit has 4 turns, and ignoring the conduction voltage of the secondary rectifier diode, the maximum power output is 9-24V.

[0104] When Np / Ns≥4, the number of turns of the secondary coil is set to Ns≥3, and the current density of the coil is set to J≥10A / mm². 2 The lower endpoint E of the auxiliary coil in the primary circuit has the same polarity as the lower endpoint F of the secondary coil. The total number of turns in the auxiliary coil of the primary circuit is 12. This excessive number of turns occupies a large portion of the transformer's window area, reducing the effective window utilization coefficient of both the primary and secondary coils. Since the transformer's energy is primarily transferred from the primary coil to the secondary coil, and the main energy is concentrated in these two coils, a larger auxiliary coil will complicate the transformer's structure, increase cost, and raise leakage inductance. Furthermore, a higher number of turns in the auxiliary coil leads to greater losses and requires a larger transformer window area, resulting in a larger transformer size.

[0105] Therefore, in this invention, in order to reduce the window area of ​​the transformer occupied by the auxiliary coil of the primary circuit, the effective window utilization coefficient of the primary and secondary coils is increased. When Np / Ns≥4, the number of turns of the secondary coil Ns≥3, and the current density of the coil J≥10A / mm² is set. 2 Set the upper terminal B of the auxiliary coil Lpa in the primary circuit to have the same polarity as the upper terminal A of the primary coil Lp. At this point, the voltage Vcc of the auxiliary coil in the primary circuit is independent of the secondary coil voltage Vo (i.e., independent of the output voltage 5-20V), but proportional to the primary coil voltage Vbuk (i.e., proportional to the power input voltage 85Vac-265Vac). Figure 23 and Figure 24 It can be seen that there is a hollow circle at the upper end B of the auxiliary coil of the primary circuit, and there is also a hollow circle at the upper end A of the primary coil. There is a hollow circle at the lower end F of the secondary coil. Through the hollow circles (marked as the same polarity terminals), it can be known that the endpoint B of the auxiliary coil Lpa and the endpoint A of the primary coil Lp of the primary circuit are of the same polarity. That is, the endpoint A of the transformer coil connected to Vbuk and the endpoint B of the transformer coil connected to the positive terminal of the rectifier diode connected to Vcc are the same polarity terminals.

[0106] For example Figure 23 When the number of secondary coil turns is not increased (i.e., the number of secondary coil turns is 1 to 2), if the number of primary coil turns is 11 and the number of secondary coil turns is 2, the number of auxiliary coil turns in the primary circuit is set to 1. Since the load current of the auxiliary power supply is extremely small, the highest pulse voltage of the auxiliary coil is taken as the maximum value of the auxiliary power supply.

[0107] 1. When the input voltage is 85V:

[0108] Maximum output voltage = 85 * 2^0.5 * Npaux / Np = 85 * 2^0.5 * 1 / 11 = 10.928V (Npaux is the number of turns of the auxiliary coil Lpa in the primary circuit, and Np is the number of turns of the primary coil Lp).

[0109] 2. When the input voltage is 265V:

[0110] The maximum output voltage is 265*2^0.5*Npaux / Np=265*2^0.5*1 / 11=34.07V.

[0111] Regardless of whether the input voltage is 85V or 265V, it meets the minimum voltage requirement of 8V for the power controller.

[0112] When the secondary coil turns Ns≥3 and Np / Ns≥4 are used in the embodiments of the present invention, for example... Figure 24 If the primary coil has 22 turns and the secondary coil has 4 turns, the auxiliary coil of the primary circuit has 1-3 turns. In order to reduce the power consumption of the controller power supply, the auxiliary coil of the primary circuit will generally use two sets of coils. One set of coils is set to 2 turns (when the input voltage is low, such as 85-190V), and the other set of coils is set to 1 turn (when the input voltage is high, such as 190-265V).

[0113] 1. When the input voltage is 85V:

[0114] Maximum output voltage = 85 * 2^0.5 * Npaux / Np = 85 * 2^0.5 * 2 / 22 = 10.928V.

[0115] 2. When the input voltage is 265V:

[0116] Maximum output voltage = 265 * 2^0.5 * Npaux / Np = 265 * 2^0.5 * 1 / 22 = 17.035V.

[0117] Regardless of whether the input voltage is 85V or 265V, setting the total number of turns of the auxiliary coil in the primary circuit to 3 can meet the minimum voltage requirement of 8V for the power controller, significantly reducing the total number of turns in the auxiliary coil. Therefore, when the number of turns in the secondary coil Ns≥3 and Np / Ns≥4, the voltage of the auxiliary coil in the primary circuit is set to be proportional to the voltage of the primary coil (i.e., proportional to the power input voltage 85Vac-265Vac). This reduces the transformer window area occupied by the auxiliary coil in the primary circuit, while increasing the effective window utilization coefficient of both the primary and secondary coils. This simplifies the transformer structure, reduces cost, and minimizes leakage inductance.

[0118] Similarly, when the number of turns of the secondary coil is not increased (i.e., the number of turns of the secondary coil is 1 to 2), if the number of turns of the primary coil is 12 and the number of turns of the secondary coil is 2, the number of turns of the auxiliary coil of the primary circuit is set to 1.

[0119] 1. When the input voltage is 85V:

[0120] Maximum output voltage = 85 * 2^0.5 * Npaux / Np = 85 * 2^0.5 * 1 / 12 = 10.015V (Npaux is the number of turns in the auxiliary coil, and Np is the number of turns in the primary coil).

[0121] 2. When the input voltage is 265V:

[0122] The maximum output voltage is 265*2^0.5*Npaux / Np=265*2^0.5*1 / 12=31.22V.

[0123] Regardless of whether the input voltage is 85V or 265V, it meets the minimum voltage requirement of 8V for the power controller.

[0124] When the secondary coil turns Ns≥3 and Np / Ns≥4 are used in the embodiments of the present invention, if the primary coil turns are 18, the secondary coil turns are 3, and the auxiliary coil turns of the primary circuit are 1-3, in order to reduce the power consumption of the controller power supply, the auxiliary coil of the primary circuit will generally use two sets of coils, one set with 2 turns (when the input voltage is low, such as 85-190V) and the other set with 1 turn (when the input voltage is high, such as 190-265V).

[0125] 1. When the input voltage is 85V:

[0126] Maximum output voltage = 85 * 2^0.5 * Npaux / Np = 85 * 2^0.5 * 2 / 18 = 13.354V.

[0127] 2. When the input voltage is 265V:

[0128] Maximum output voltage = 265 * 2^0.5 * Npaux / Np = 265 * 2^0.5 * 1 / 18 = 20.817V.

[0129] Regardless of whether the input voltage is 85V or 265V, setting the total number of turns in the auxiliary coil to 3 will meet the minimum voltage requirement of 8V for the power controller, significantly reducing the total number of turns in the auxiliary coil. Therefore, when Np / Ns≥4, setting the number of turns in the secondary coil Ns≥3 results in a current density J≥10A / mm². 2 By setting the voltage of the auxiliary coil in the primary circuit to be proportional to the voltage of the primary coil (i.e., proportional to the input voltage of the power supply, 85Vac-265Vac), the window area of ​​the transformer occupied by the auxiliary coil is reduced, while the window area of ​​the transformer that can be occupied by the primary and secondary coils is increased, resulting in a simpler transformer structure, reduced cost, and lower leakage inductance.

[0130] Similarly, the number of turns in the secondary coil can also be 5.

[0131] Alternatively, the voltage of the auxiliary coil Lsa in the secondary circuit can be set to be proportional to the voltage of the primary coil Lp (i.e., proportional to the power input voltage of 85Vac-265Vac, such as...). Figure 23 and Figure 24 In the circuit, there is a hollow circle at the upper end C of the auxiliary coil Lsa of the secondary circuit, and there is also a hollow circle at the upper end A of the primary coil Lp. The hollow circles indicate that the endpoint C of the auxiliary coil of the secondary circuit and the endpoint A of the primary coil are of the same polarity. This reduces the window area of ​​the transformer occupied by the auxiliary coil and increases the effective window utilization coefficient of the primary and secondary coils. In this invention, the voltage Vcc of the auxiliary coil of the primary circuit can be set to be proportional to the voltage Vbuk of the primary coil (i.e., proportional to the power input voltage of 85Vac-265Vac); or the voltage VOSUB of the auxiliary coil of the secondary circuit can be set to be proportional to the voltage Vbuk of the primary coil (i.e., proportional to the power input voltage of 85Vac-265Vac); or the voltage of the auxiliary coil of the primary circuit can be proportional to the voltage of the primary coil (i.e., proportional to the power input voltage of 85Vac-265Vac), while the voltage of the auxiliary coil of the secondary circuit can be proportional to the voltage of the primary coil (i.e., proportional to the power input voltage of 85Vac-265Vac).

[0132] In this embodiment, the circuit board with the primary coil (hereinafter referred to as the first circuit board) includes the primary coil and the auxiliary coil of the primary circuit, and may also include the shielding coil and the compensation coil; the circuit board with the secondary coil (hereinafter referred to as the second circuit board) includes the secondary coil and the auxiliary coil of the secondary circuit, and may also include the shielding coil and the compensation coil, that is, the primary coil and the auxiliary coil of the primary circuit are disposed on the same circuit board, and the secondary coil and the auxiliary coil of the secondary circuit are disposed on the same circuit board.

[0133] like Figure 25 As shown, in another embodiment, the primary coil and the secondary coil are located on a single circuit board. When Np / Ns ≥ 4, the number of turns of the secondary coil is set to Ns ≥ 3, and the current density of the coil is set to J ≥ 10 A / mm². 2 As the number of turns NS of the secondary coil increases, the number of turns NP of the primary coil also increases, thus increasing the number of turns N of the planar transformer. With the power adapter power remaining constant, the increased number of turns N allows for a reduction in the effective area A of the magnetic core, leading to a decrease in the via area and overall circuit board area. This, in turn, reduces the volume of the circuit board and the magnetic core, resulting in a smaller planar transformer and consequently a smaller power adapter. In this embodiment, a buffer heat sink is provided between the upper surface of the circuit board and the first part of the magnetic core, and another buffer heat sink is provided between the lower surface of the circuit board and the second part of the magnetic core.

[0134] like Figure 26 and Figure 27 As shown, this is a horizontal planar transformer structure. A circuit board with a primary coil (hereinafter referred to as the first circuit board 121) has a primary terminal lead 32, and a circuit board with a secondary coil (hereinafter referred to as the second circuit board 122) has a secondary terminal lead 33. The primary terminal lead 32 and the secondary terminal lead 33 are used to connect other components. The circuit boards with primary coils are connected by connecting posts 31.

[0135] like Figure 28 and Figure 29 As shown, this embodiment is a pure transformer structure without any electronic components. The circuit board with the primary coil (hereinafter referred to as the first circuit board 121) is provided with a primary pin pad 41, and the circuit board with the secondary coil (hereinafter referred to as the second circuit board 122) is provided with a secondary pin pad 42. The primary pin pad 41 and the secondary pin pad 42 are used to connect other components.

[0136] In this embodiment of the invention, except Figure 28 and Figure 29 Apart from that, all other components are vertical planar transformer structures. The transformer is connected to other components through primary pin pad 41 and secondary pin pad 42.

[0137] like Figure 30As shown, in this embodiment, the primary coil and the auxiliary coil of the primary circuit are separately disposed on different circuit boards. The primary coil is disposed on the circuit board with the primary coil (hereinafter referred to as the first circuit board 121), while the auxiliary coil of the primary circuit is disposed on the third circuit board 124. This separate disposal simplifies the structure of the first circuit board 121, making it more concise. In this embodiment, the secondary coil and the auxiliary coil of the secondary circuit are separately disposed on different circuit boards. The secondary coil is disposed on the circuit board with the secondary coil (hereinafter referred to as the second circuit board 122), while the auxiliary coil of the secondary circuit is disposed on the fourth circuit board 125. This separate disposal simplifies the structure of the second circuit board 125, making it more concise. The third circuit board 124 may also include a shielding coil and a compensation coil, and the fourth circuit board 125 may also include a shielding coil and a compensation coil.

[0138] like Figure 31 As shown, in this embodiment, the primary coil and the auxiliary coil of the primary circuit are separately arranged on different circuit boards, and the secondary coil and the auxiliary coil of the secondary circuit are separately arranged on different circuit boards. The primary coil is arranged on the circuit board with the primary coil (hereinafter referred to as the first circuit board 121), the secondary coil is arranged on the circuit board with the secondary coil (hereinafter referred to as the second circuit board 122), and the auxiliary coil of the primary circuit and the auxiliary coil of the secondary circuit are arranged on the fifth circuit board 126. The separate arrangement simplifies the structure of the first circuit board 121 and the second circuit board 122, making the first circuit board 121 and the second circuit board 122 more concise. The fifth circuit board 126 may also include a shielding coil and a compensation coil.

[0139] In another embodiment, the circuit board comprises multiple boards stacked on top of each other. At least one board simultaneously carries both primary and secondary coils. The primary and secondary coils on this board have multiple layers, with the primary coils connected to each other and the secondary coils connected to each other. For example, the circuit board may have three boards, one of which carries both primary and secondary coils. This board has multiple layers of primary and secondary coils, with the primary coils connected to each other and the secondary coils connected to each other. The other two boards can be one board with a primary coil and one board with a secondary coil, or two boards with primary coils and two boards with secondary coils. Alternatively, two boards or all three boards can simultaneously carry both primary and secondary coils. Primary coils on different boards are connected, and secondary coils on different boards are connected.

[0140] In this invention, Np / Ns ≥ 4, the number of turns in the secondary coil Ns ≥ 3, and the current density of the coil J ≥ 10 A / mm². 2With the same power output, increasing the number of coil turns N reduces the effective area of ​​the magnetic core, thus reducing the area of ​​the vias and the overall circuit board area. This leads to a smaller circuit board and magnetic core volume, allowing for a smaller planar transformer design and consequently a smaller power adapter. This structural design significantly reduces transformer size; for example, a 45W transformer core can be made to handle 65W, 75W, and 90W. By using multiple circuit boards, the number of coil layers per board is significantly reduced compared to a single board. Previously, a single board had twenty layers, resulting in high manufacturing time and cost. Now, with multiple boards, each with six layers, manufacturing time and cost are greatly reduced, saving development time and inventory costs. Furthermore, the voltage withstand requirement of the planar transformer can be adjusted by changing the distance between adjacent boards, making voltage withstand requirements more flexible. Additionally, by using multiple circuit boards, different turns ratios for the primary and secondary coils can be achieved simply by changing the circuit boards. By setting the voltage of the auxiliary coil to be proportional to the voltage of the primary coil, the window area of ​​the transformer occupied by the auxiliary power supply coil is reduced, while the window area of ​​the transformer that can be occupied by the primary and secondary coils is increased, resulting in a simpler transformer structure, reduced cost, and lower leakage inductance.

[0141] In summary, this invention reduces the core volume by increasing the number of turns in the secondary coil to decrease the effective area of ​​the core pillar; it also reduces the number of turns in the auxiliary coil by changing the power supply connection method; it further reduces the core volume by increasing the current density of the coil to decrease the area of ​​the transformer window; it further reduces the core volume by increasing the circuit loop of the primary and secondary coils through series-parallel connection of the primary and secondary coils to improve heat dissipation and reduce the transformer window area; it also minimizes the size of the power adapter by placing components in the gaps between multiple PCB boards; and it minimizes the size of the power adapter by increasing thermal conductivity through insulating potting compound.

[0142] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. Those skilled in the art can implement the present invention in various modifications without departing from its scope and spirit. For example, a feature shown or described in one embodiment can be used in another embodiment to obtain yet another embodiment. The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A power adapter, characterized in that, The device includes a planar transformer comprising a magnetic core and a circuit board with coils, the circuit board being mounted in the magnetic core, the magnetic core having a central post, the coils being arranged around the central post, the central post being inserted into the circuit board, the coils comprising a primary coil and a secondary coil, the secondary coil having Ns turns, the primary coil having Np turns, Np / Ns≥4, Ns≥3, and the current density of the coil J≥10A / mm². The circuit board has a circular through hole, and the central post passes through the circular through hole of the circuit board; the circuit board also includes a power supply coil for an auxiliary power supply, the power supply coil for the auxiliary power supply includes an auxiliary coil for the primary circuit and an auxiliary coil for the secondary circuit, the voltage of the auxiliary coil for the primary circuit is proportional to the voltage of the power input and / or the voltage of the auxiliary coil for the secondary circuit is proportional to the voltage of the power input.

2. The power adapter according to claim 1, characterized in that, The primary coil and the secondary coil are located on a circuit board. The primary coil has multiple layers and is connected to each other. The secondary coil has multiple layers and is connected to each other.

3. The power adapter according to claim 1, characterized in that, The circuit board has multiple boards stacked together, including at least one board with a primary coil and at least one board with a secondary coil.

4. The power adapter according to claim 3, characterized in that, There are at least two circuit boards with primary coils, and the circuit boards with primary coils and circuit boards with secondary coils are arranged alternately, with the circuit boards with primary coils connected to each other.

5. The power adapter according to claim 3, characterized in that, There are at least two circuit boards with secondary coils, with circuit boards with primary coils and circuit boards with secondary coils arranged alternately, and the circuit boards with secondary coils are connected to each other.

6. The power adapter according to claim 3, characterized in that, Each circuit board includes a trace section and a connection section located on one side of the trace section. The magnetic core covers the trace section, and the connection section is exposed on the side of the magnetic core. The connection sections of two adjacent circuit boards are located on both sides of the magnetic core, and electronic components are disposed on the upper surface and / or lower surface of the connection section.

7. The power adapter according to claim 2, characterized in that, A buffer heat sink is provided between the upper surface of the circuit board and the magnetic core, and a buffer heat sink is provided between the lower surface of the circuit board and the magnetic core.

8. The power adapter according to claim 3, characterized in that, A buffer heat sink is provided between the topmost circuit board and the magnetic core, and a buffer heat sink is provided between the bottommost circuit board and the magnetic core.

9. The power adapter according to claim 1, characterized in that, The primary coil and the auxiliary coil of the primary circuit are set on separate circuit boards, and the secondary coil and the auxiliary coil of the secondary circuit are set on separate circuit boards.

10. The power adapter according to claim 9, characterized in that, The auxiliary coils of the primary circuit and the secondary circuit are located on the same circuit board.

11. The power adapter according to claim 1, characterized in that, The circuit board also includes an insulating layer. Both the coil and the insulating layer have multiple layers. An insulating layer is provided between two adjacent coil layers. The top and bottom layers of the circuit board are insulating layers that cover the coil.

12. The power adapter according to claim 3, characterized in that, The multiple circuit boards are encapsulated into a single unit using insulating potting compound.

13. The power adapter according to claim 3 or 12, characterized in that, The multiple circuit boards and the magnetic core are encapsulated into a single unit using insulating potting compound.

14. The power adapter according to claim 1, characterized in that, The circuit board has multiple pieces, which are stacked together. At least one circuit board has both a primary coil and a secondary coil. The primary coil and the secondary coil on the at least one circuit board have multiple layers, and the primary coils are connected to each other, and the secondary coils are connected to each other.

15. The power adapter according to claim 1, characterized in that, The primary coil has multiple layers, the secondary coil has multiple layers, and the primary coil has at least two circuit loops and / or the secondary coil has at least two circuit loops.

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