Miniature planar coil transformer with shielding

Abstract

The present disclosure relates to a micro-planar coil transformer with shielding. A micro-planar coil transformer including one or more shields is disclosed. The one or more shields can block most common mode currents from passing from one side of the transformer to the other side. Reducing the common mode current passing through the transformer can result in a reduction in dipole radiation, which is a major component of electromagnetic interference (EMI) in some transformers.

Description

Technical Field

[0001] The present application relates to a miniature planar coil transformer. Background Art

[0002] For micro-planar coil transformers, a large portion of electromagnetic interference (EMI) can come from dipole radiation between the two sides of the transformer. EMI can have adverse effects on electronic components. Summary of the invention

[0003] A micro-planar coil transformer including one or more shields is disclosed. The one or more shields can block most common mode currents from passing from one side of the transformer to the other side. Reducing the common mode current passing through the transformer will result in a reduction in dipole radiation, which is a major component of electromagnetic interference (EMI) in some transformers.

[0004] According to aspects of the present disclosure, there is provided a micro planar coil transformer arranged on a substrate having an upper surface. The micro planar coil transformer includes: a first planar coil arranged in a first layer occupying a first area in a plane parallel to the upper surface, a second planar coil arranged in a second layer, and a shield arranged in an intermediate layer, the intermediate layer being between the first layer and the second layer. A projection on the first planar coil of an area surrounded by a perimeter of the shield covers a second area of ​​the coil that is smaller than the first area.

[0005] According to aspects of the present application, there is provided a micro-planar coil transformer arranged on a substrate having an upper surface. The micro-planar coil transformer comprises: a first side of the transformer, comprising a first planar coil arranged in a first layer and configured to be coupled to a first electrical ground; a second side of the transformer, comprising a second planar coil arranged in a second layer and configured to be coupled to a second electrical ground; a first shield arranged in a first intermediate layer and configured to be coupled to the first electrical ground, the first intermediate layer being between the first layer and the second layer; and a second shield arranged in a second intermediate layer and configured to be coupled to the second electrical ground, the second intermediate layer being between the first layer and the second layer.

[0006] According to aspects of the present disclosure, there is provided a micro planar coil transformer arranged on a substrate having an upper surface. The micro planar coil transformer includes: a first planar coil arranged in a first layer occupying a first area in a plane parallel to the upper surface; a second planar coil arranged in a second layer; and a shield arranged in an intermediate layer, the intermediate layer being between the first layer and the second layer. A projection on the first planar coil of an area surrounded by a perimeter of the shield surrounds a second area equal to the first area.

[0007] According to aspects of the present invention, there is provided a micro planar coil transformer comprising: a first planar coil arranged in a first layer; a second planar coil arranged in a second layer; and means for reducing dipole radiation between the first and second planar coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various aspects and embodiments of the present application will be described with reference to the following drawings. It should be understood that the drawings are not necessarily drawn to scale. Items appearing in multiple figures are represented by the same reference numerals in all the figures in which they appear.

[0009] Figure 1 is a side cross-sectional view of a micro planar coil transformer.

[0010] Figure 2 is an exploded top perspective view of a micro planar coil transformer.

[0011] Figure 3 is a schematic diagram of a circuit including a transformer;

[0012] Figure 4 is a top view of some components of a micro planar coil transformer.

[0013] Figure 5 is a top view of some components of a micro planar coil transformer.

[0014] Figure 6 is a top view of some components of a micro planar coil transformer.

[0015] Figure 7 is a side cross-sectional view of a micro planar coil transformer.

[0016] Figure 8 is a schematic diagram of a circuit including a transformer;

[0017] Fig. 9 is a side cross-sectional view of a micro planar coil transformer.

[0018] Fig.10 is a top view of some components of a micro planar coil transformer.

[0019] Fig.11 is a schematic diagram of a circuit including a transformer. DETAILED DESCRIPTION

[0020] According to aspects of the present application, a micro planar coil transformer includes a first planar coil disposed on a primary side of the transformer, the first planar coil being electromagnetically coupled to a second planar coil disposed on a secondary side of the transformer. The micro planar coil transformer is configured to exhibit reduced dipole radiation between the primary side and the secondary side of the transformer. One or more shields are included between the first and second planar coils to reduce dipole radiation. The shield can be a Faraday shield.

[0021] The present application relates to microdevices. One type of microdevice is a planar coil transformer. A transformer can be used to convert a first voltage level at a first portion of a circuit to a second voltage level at a second portion of the circuit. The transformer can transmit data and / or power signals. The transformer can be used to isolate signals between two portions of a circuit and thus can form part of an isolator in some embodiments. The transformer typically transmits an AC signal. In some cases, a DC-DC power converter can utilize a transformer, such as a microtransformer.

[0022] According to aspects of the present application, a transformer having a primary side and a secondary side is arranged. The primary side sends data and / or power signals, and the secondary side receives data and / or power signals. In some embodiments, data and / or power signals can be sent in two directions across the transformer.

[0023] In some embodiments, the primary side of the transformer is coupled to a circuit that generates a signal to be transmitted. In some embodiments, the secondary side of the transformer is coupled to an output. In a DC-DC converter utilizing a transformer, a rectifier may couple the secondary side to the output so that the signal from the secondary side is rectified before being output.

[0024] The micro planar coil transformer may include two or more micro planar coils. The first coil may be arranged on the primary side of the transformer, and the second coil may be arranged on the secondary side of the transformer. Each of the first coil and the second coil may be arranged on a substrate in a substantially planar configuration. The planar coil may be patterned on the substrate in a substantially spiral shape around a coil axis.

[0025] The primary side can transfer electromagnetic energy to the secondary side. A changing current applied to the first spiral coil causes a changing magnetic field arranged substantially along the coil axis of the first spiral coil, and the coils are arranged and electromagnetically coupled so that the changing magnetic field passes through the second spiral coil substantially along the coil axis of the second spiral coil, which induces a changing current in the second spiral coil on the secondary side.

[0026] Certain configurations of transformers can generate electromagnetic interference (EMI). High levels of EMI can interfere with the performance of electrical devices and can cause adverse effects on components. EMI can come from different source components, and various electrical phenomena can cause EMI, such as dipole radiation. In some micro transformers, the main component of EMI is dipole radiation. This is true for some integrated isolated DC-DC converters.

[0027] Dipole radiation may occur between the primary side and the secondary side of the transformer. Dipole radiation may be caused by common-mode current passing through an isolation barrier (e.g., an isolation layer) between the primary coil and the secondary coil of the transformer. Common-mode current may cross between the primary side and the secondary side due to parasitic capacitance between the two coils on different sides of the transformer. For example, if common-mode current flows from the primary side to the secondary side due to parasitic capacitance, it may flow back from the secondary side to the primary side in the form of dipole radiation, thus forming a current loop across the isolation layer. When the first coil and the second coil are arranged on two different substrates (e.g., two different printed circuit boards (PCBs)), dipole radiation may pass between the electrical ground / power planes of the two different substrates.

[0028] Common mode current may be caused by the difference in common mode voltage ripple amplitude between the two sides of the transformer. In an exemplary embodiment, the coil of the transformer has two terminals T1 and T2. In the exemplary embodiment, the first voltage signal V1 at the terminal T1 and the second voltage signal V2 at the terminal T2 are both half-sinusoidal curves and have the same sign. In the exemplary embodiment, the first voltage signal and the second voltage signal are 180 degrees out of phase. Due to their half-sinusoidal characteristics, the first voltage signal and the second voltage signal are not differential. The common mode voltage Vcom can be found as the average of the two signals, where Vcom=(V1+V2) / 2. In an exemplary embodiment, the common mode voltage ripple amplitude of the two terminals T1 and T2 of the coil is substantially greater than zero. The common mode voltage fluctuates at the even harmonics of the applied oscillation frequency.

[0029] The shields described herein may be applied to transformers having one or more coils and a common-mode voltage ripple amplitude substantially greater than zero. However, it should be understood that the above-described signals are merely one example of a set of voltage signals applied to a transformer that results in a common-mode voltage ripple amplitude greater than substantially zero. Other sets of signals that result in similar common-mode voltages and similar common-mode voltage ripples are also possible. Further, the shields described herein are not limited to application to transformers having such signals. In various embodiments, one or more shields are applied to a transformer that exhibits common-mode currents between the sides of the transformer, a transformer that exhibits dipole radiation between the sides of the transformer, and / or a transformer that exhibits EMI.

[0030] The common mode voltage of the two terminals TC1 and TC2 of the primary side coil Vcom1 can be obtained as the average value of the voltage VTC1 of the first terminal and the voltage VTC2 of the second terminal, where Vcom1 = (VTC1 + VTC2) / 2. In an exemplary embodiment, the signal applied to the primary side coil is a half-sine, 180 degree out-of-phase signal with the same sign as above, and the common mode voltage ripple amplitude of the primary side coil is substantially greater than zero.

[0031] The common mode voltage of the two terminals RC1 and RC2 of the secondary side coil Vcom2 can be found as the average of the voltage of the first terminal VRC1 and the voltage of the second terminal VRC2, where Vcom2 = (VRC1 + VRC2) / 2. In an exemplary embodiment, the common mode voltage ripple amplitude of the secondary side coil is substantially zero.

[0032] In some embodiments, in addition to having two terminals VT1 and VT2, the coil (e.g., the primary coil) may also be center-tapped. The coil may include two coil portions separated by a center tap. The voltage signal applied to the center tap may be a constant voltage VDD. In some embodiments, the center tap is held electrically grounded. The total common mode voltage Vcom of the center-tapped coil may be found to be the average of the common mode voltages of each of the two coil portions, so Vcom=(VT1+VT2) / 4+VDD / 2.

[0033] In some implementations, there is parasitic capacitance between the two coils on different sides of the transformer. Due to the parasitic capacitance, the difference between the common-mode voltage ripple amplitudes may introduce common-mode currents that flow through the isolation barrier from the primary side to the secondary side of the transformer. Typically, the currents are small enough not to cause safety issues, however, the currents can flow back to the primary side through dipole radiation, resulting in high levels of EMI.

[0034] As described above, in an exemplary embodiment, the common mode voltage ripple amplitude of the primary side coil is substantially greater than zero, and the common mode voltage ripple amplitude of the secondary side coil is substantially zero. The difference in ripple amplitude causes common mode current to pass between the two sides of the transformer, and thus also causes dipole radiation between the two sides of the transformer.

[0035] The inventors have recognized that shielding, such as a Faraday shield, can reduce or substantially eliminate dipole radiation encountered in a microtransformer.Accordingly, aspects of the present application provide a microtransformer having one or more shields between the primary and secondary coils of the transformer.

[0036] Figure 1A side cross-sectional view of a micro planar coil transformer 100 is shown. The micro planar coil transformer 100 is disposed on a substrate 110 having an upper surface 112 and includes a first coil layer 120, an intermediate layer 130, a first coil 140, a second coil 150, a shield 160, and a through-hole 170.

[0037] The micro planar coil transformer 100 includes a first coil 140. Figure 1 In the illustrative embodiment of , the first coil 140 is arranged in the first coil layer 120. Figure 1 In the embodiment, the first coil 140 is arranged above the substrate 110. In some embodiments, the first coil 140 is arranged on the primary side of the transformer.

[0038] The micro planar coil transformer 100 includes a second coil 150. The second coil 150 may be arranged on a second coil layer ( Figure 1 The second coil 150 is arranged above and above the first coil 140. In some embodiments, the second coil 150 is arranged on the secondary side of the transformer.

[0039] The first coil 140 and the second coil 150 are electromagnetically coupled. In an exemplary embodiment in which the first coil 140 is arranged on the primary side of the micro planar coil transformer 100 and the second coil 150 is arranged on the secondary side of the micro planar coil transformer 100, the first coil 140 may be a transmitting coil and the second coil 150 may be a receiving coil. The first coil 140 may transmit a signal received by the second coil 150 via electromagnetic energy. However, each coil may include a transmitting coil arranged on the primary side or a receiving coil arranged on the secondary side. For example, in some embodiments, a coil arranged in an upper layer, such as the second coil 150, may be arranged on the primary side as a transmitting coil, and a coil arranged in a lower layer, such as the first coil 140, may be arranged on the secondary side as a receiving coil.

[0040] exist Figure 1 , the first coil 140 and the second coil 150 are arranged around a first coil axis and a second coil axis, respectively. The coils are patterned in their respective layers so that the coil axes are arranged substantially perpendicular to the upper surface 112. The coil axes are substantially aligned with each other.

[0041] The transmitting coil is configured to transmit a signal to the receiving coil. When a varying current is applied to the transmitting coil, it induces a varying magnetic field. In the case of a close distance to the coil, the varying current flowing through the coil induces a varying magnetic field that is substantially aligned with the axis of the coil. The coil axes of the coil pair can be substantially aligned, and the coils can be arranged at a certain distance so that an acceptable portion of the varying magnetic field induced by the transmitting coil passes through the receiving coil. The varying magnetic field applied by the receiving coil induces a varying current in the receiving coil, which facilitates the transmission of power / data signals.

[0042] The micro planar coil transformer 100 includes a shield 160. The shield 160 is arranged between the first coil 140 and the second coil 150 along the direction of the coil axis. The shield may further be at least partially arranged between the first coil 140 and the second coil 150 along a direction substantially perpendicular to the coil axis.

[0043] exist Figure 1 , the shield 160 is arranged in the intermediate layer 130. The intermediate layer 130 is arranged between the first coil 140 and the second coil 150. The intermediate layer may include an isolation layer that may be formed of an insulating or dielectric material. In some embodiments, the intermediate layer 130 may include polyimide.

[0044] exist Figure 1 , the shield 160 is arranged on a side of the intermediate layer 130 close to the first coil 140. In this arrangement, the shield 160 and the first coil 140 may be configured to be coupled to the same ground.

[0045] Dipole radiation may be transferred from one side of the micro planar coil transformer 100 to the other side of the transformer. Dipole radiation may be the result of common mode current flowing between the first coil 140 and the second coil 150. The shield 160 may be configured to reduce dipole radiation between the primary side and the secondary side of the transformer. The shield 160 may reduce dipole radiation by reducing or substantially eliminating common mode current flowing between the first coil 140 and the second coil 150. The shield 160 may be configured to couple to ground and the common mode current may be absorbed by ground coupling.

[0046] The microplanar coil transformer 100 includes a via 170 configured to electrically couple between two layers of the microplanar coil transformer 100. Figure 1 , a via 170 is coupled between the first coil layer 120 and a shield 160 disposed in the middle layer 130. The via 170 can couple the shield 160 to a ground that is coupled to an element on the primary side of the transformer or to an element in the first coil layer 120, such as a ground of the first coil 140.

[0047] The coils, shields, vias, and other elements may comprise a variety of materials. In some embodiments, the coils or shields comprise conductive materials, for example, metals such as copper, gold, or aluminum, or may comprise semiconductor materials, such as doped semiconductor materials. In some embodiments, each coil or shield is disposed in a metallization layer, or in more than one metallization layer.

[0048] The substrate 110 has an upper surface 112 . The upper surface 112 may be substantially flat. The upper surface of the substrate 110 is disposed between the substrate 110 and the first coil layer 120 .

[0049] According to aspects of the present application, a substrate such as substrate 110 may include various materials. In some embodiments, the substrate may include a semiconductor material. For example, the substrate may include a bulk or single crystal semiconductor substrate, such as a bulk or single crystal silicon substrate. In some embodiments, the substrate may include a deposited semiconductor substrate, such as polycrystalline silicon. In some embodiments, the substrate may include a silicon-on-insulator substrate or may include a buried oxide layer. Other semiconductor materials may be used as substrates. In some embodiments, a substrate such as substrate 110 may include a PCB.

[0050] Figure 2 An exploded top perspective view of a micro planar coil transformer 200 is shown. The micro planar coil transformer 200 may be a more detailed implementation of the micro planar coil transformer 100. The micro planar coil transformer 200 is disposed on a substrate 210 and includes an intermediate layer 230, a first coil 240, a second coil 250, and a shield 260.

[0051] The first coil 240 includes a first coil portion 242a, a second coil portion 242b, a first pad 244a, a second pad 244b, a center tap pad 246, and a middle portion 248. Figure 2 In the embodiment, two coil parts, a first coil part 242a and a second coil part 242b are arranged in series.

[0052] The first coil portion 242a and the second coil portion 242b are arranged as planar coils respectively. The first coil portion 242a and the second coil portion 242b are patterned as planar spirals with a plurality of turns. In certain embodiments, the coil or coil portion may only include a single turn. The first coil portion 242a and the second coil portion 242b are arranged around the coil axis substantially perpendicular to the upper surface 212 of the substrate 210 respectively.

[0053] The first coil 240 is coupled to the input and output pads. The first end of the first coil portion 242a is connected to the first pad 244a, and the first pad 244a is arranged outside the first coil portion 242a. The first end of the second coil portion is coupled to the second pad 244b, and the second pad 244b is arranged outside the second coil portion 242b. The signal can be applied to the first coil 240 via the first pad 244a and the second pad 244b.

[0054] The first coil portion 242a and the second coil portion are connected through the middle portion 248. The second end of the first coil portion 242a is connected to the middle portion 248 of the first coil 240. The second end of the second coil portion 242b is coupled to the middle portion 248. In this way, the first coil portion 242a is coupled to the second coil portion 242b through the middle portion 248.

[0055] The middle portion 248 may include a jumper, such as an overpass portion. The overpass portion is coupled from one end of the coil located inside the coil portion to a location outside the coil portion. The overpass portion may pass over or under at least one turn of the spiral coil, and may therefore be arranged in a layer above or below the layer of the first coil 240. The overpass portion may be at least partially arranged in the same layer as the first portion, and may be at least partially arranged in a layer different from the coil portion.

[0056] The middle portion 248 is coupled to the center tap pad 246. A signal may be applied to the first coil 240 via the center tap pad 246. For example, the center tap pad may be maintained at a constant voltage or may be grounded.

[0057] exist Figure 2 In the embodiment, the first coil 240 is arranged in an S-shaped coil shape. Other configurations are also possible, such as a C-coil shape. The S-shaped coil shape is arranged so that the current flowing through the first coil portion will spiral in a first rotational direction, and the current flowing through the second coil portion will spiral in a second rotational direction. The opposite rotational directions of the two portions of the S-shaped coil induce changing magnetic fields that are arranged in substantially anti-parallel directions.

[0058] Alternatively, the C-coil shape is arranged so that the current flowing through the first coil portion and the current flowing through the second coil portion will spiral in the same direction of rotation. The C-coil induces varying magnetic fields that are aligned in substantially parallel directions.

[0059] The second coil 250 includes a first coil portion 252 a , a second coil portion 252 b , a first pad 254 a , a second pad 254 b , and a middle portion 248 .

[0060] The second coil 250 differs from the first coil 240 in that the first pad 254a is arranged in the first coil portion 252a, and the second pad 254b is arranged in the second coil portion 242b. In some embodiments, when the second coil 250 is arranged in the second coil layer, the first pad 254a and the second pad 254b can be exposed or coupled to the through hole so that the end of the second coil 250 can be coupled to other circuit elements. Compared with manufacturing the second coil 250 with one or more overpass sections, this arrangement of pads can reduce manufacturing complexity or cost.

[0061] The second coil 250 differs from the first coil 240 in that the intermediate portion 258 does not include an overpass portion. Because the first pad 254a and the second pad 254b are disposed within the second coil 250, the intermediate portion can be coupled to the outermost turns of the coil 250 and thus does not need to pass over or under the layers of the second coil 250. This can reduce complexity and manufacturing costs.

[0062] The second coil 250 differs from the first coil 240 in that the middle portion 258 is not coupled to a center tap pad. In some embodiments, the middle portion can be center tapped, for example, by a through hole. In some embodiments, the second coil 250 can include a center tap pad coupled to the middle portion 258.

[0063] The first coil 240 and the second coil 250 are electromagnetically coupled. In some embodiments, the first coil 240 is arranged on the primary side of the micro-planar coil transformer 200, and the second coil 250 is arranged on the secondary side of the micro-planar coil transformer 200. In some embodiments, the first coil 240 is a transmitting coil, and the second coil 250 is a receiving coil.

[0064] The first coil portion 242a of the first coil 240 is electromagnetically coupled to the first coil portion 252a of the second coil 250. Similarly, the second coil portion 242b of the first coil 240 is electromagnetically coupled to the second coil portion 252b of the second coil 250. In some embodiments, each coil portion coupling can act as a separate transformer coupling, thereby forming two transformers arranged in series. Figure 2 2, each of the portions 242a, 242b, 252a and 252b are respectively arranged about a coil axis that is substantially perpendicular to the upper surface 212 of the substrate 210. The coil axes of each pair of coupled coil portions are substantially aligned.

[0065] The coil occupies an area on which the coil is arranged in a plane parallel to the upper surface of the substrate. The coil area may include the area of ​​any intermediate portion. Similarly, the coil portion occupies an area. The coils constituting a pair of coupled coils may occupy substantially the same area. The coil portions constituting a pair of coupled coil portions may occupy substantially the same area.

[0066] Shield 260 includes a first shield portion 262a, a second shield portion 262b, a shield pad 264, an intermediate portion 266, a first overpass opening 268a, and a second overpass opening 268b. In some embodiments, where the coil portion includes a planar spiral, the shield portion may have a substantially circular circumference. The shield portion may have a perimeter that forms other shapes.

[0067] Each shielding portion may be disposed between a pair of coupled coil portions. Figure 2 , the first shielding portion 262a is disposed between the coupled first coil portion 242a of the first coil 240 and the first coil portion 252a of the second coil 250. The second shielding portion 262b is disposed between the coupled second coil portion 242b of the first coil 240 and the second coil portion 252b of the second coil 250.

[0068] In some embodiments, the shield portions are coupled together. The intermediate portion 266 couples the first shield portion 262a to the second shield portion 262b. In some embodiments, the shield 260 does not include the intermediate portion 266, and the first shield portion 262a is not coupled to the second shield portion 262b through the intermediate portion.

[0069] According to aspects of the present application, the shield 260 has an external connector. Figure 2 In the embodiment, the middle portion 266 is coupled to the shielding pad 264. The shielding pad can be coupled to power or ground. Figure 2 260, shield pads 264 are coupled to middle portion 266 and are therefore arranged at substantially symmetrical positions of shield 260. Other arrangements are also possible. Shield 260 can be arranged such that shield 260 is not substantially symmetrically arranged. For example, shield pads 264 can be arranged at an outer position of shield 260 away from middle portion 266.

[0070] Shield coupling can be either symmetrical or asymmetrical. Each section of the transformer itself has significant inductance at high frequencies, so at these higher frequencies a symmetrical arrangement achieves equal shielding effectiveness for each of the paired coupled coil sections and can reduce EMI at odd harmonics of the applied oscillation frequency. A symmetrical connection can also reduce the resistance of the shield assembly because the maximum distance from any point on the shield to the shield pad is reduced. Reduced shield resistance can result in common mode currents being more effectively grounded.

[0071] In some embodiments, other arrangements of shield couplings are used. In some embodiments, the shield is coupled to a first shield pad at a first edge of the shield and coupled to a second shield pad across a mid-portion at a corresponding symmetrical second edge of the shield, thereby maintaining symmetry. In some embodiments, an asymmetrical connection may be used, for example to reduce complexity or cost at the expense of reduced shielding effectiveness.

[0072] The first and second overpass openings 268 a and 268 b are cutouts in the shield 260 that are configured to accommodate an overpass portion of the intermediate portion 248 of the first coil 240 within a perimeter of the shield 260 .

[0073] The overpass opening in the shield can be configured to reduce the number of layers in the transformer. When an overpass opening is provided in the shield, the overpass can be arranged in the same layer as the shield. This can allow two coils and the shield to be arranged in a total of three layers. If no overpass opening is provided in the shield, the same two coils and the shield would require at least four layers in total.

[0074] In some embodiments, the middle portion 258 of the second coil 250 includes an overpass portion, while the middle portion 248 of the first coil 240 does not include an overpass portion. In such an arrangement, the first overpass opening 268a and the second overpass opening 268b of the shield 260 are configured to accommodate the overpass portion of the middle portion 258 of the second coil 250 instead. In such an embodiment, because the second coil 250 is the upper coil, the overpass portion of the second coil 250 can be arranged to pass under the number of turns of the second coil 250. Since the shield 260 is arranged between the coils, the overpass portion of the second coil 250 is arranged in the same layer as the shield 260. Therefore, the transformer can also include only three metallization layers. In this alternative arrangement, the shield 260 can be arranged close to the second coil 250, and the isolation layer 230 can be arranged between the shield 260 and the first coil 240. In this arrangement, the shield 260 can be coupled to the same ground or power connection to which the second coil 250 is coupled. The perimeter of the shield encloses an area having a shielded area. The perimeter of the shield surrounds any shielded portion and any intermediate portion of the shield. The area enclosed by the perimeter of the shield includes the area occupied by the physical elements of the shield and the area of ​​any gaps between the physical elements of the shield within the perimeter. Gaps include overpass openings and other gaps, for example, gaps configured to reduce eddy currents, as described below.

[0075] In some embodiments, the area surrounded by the shield perimeter may occupy various areas relative to the coil, or may cover various areas of the coil. In some embodiments, for example, Figure 2In the shield 260, when the area surrounded by the perimeter of the shield is projected onto the coil below and / or above, such as the first coil 240 or the second coil 250, the projection of the area surrounded by the perimeter of the shield covers an area of ​​the coil that is substantially equal to the area occupied by the coil. This can be referred to as a "full shield" arrangement. Other arrangements are also possible. In some embodiments, the projection of the area surrounded by the perimeter of the shield covers an area of ​​the coil that is less than the area occupied by the coil. This can be referred to as a "partial shield" arrangement.

[0076] Similarly, the perimeter of the shield portion can surround an area having an area of ​​the shield portion. The perimeter of the shield portion separates the shield portion from any intermediate portions of the shield. Figure 2 In some embodiments, the perimeter of the first shielding portion 262a and the perimeter of the second shielding portion 262b are substantially circular. Figure 2 In the shielding portion 262a, when the area surrounded by the periphery of the shielding portion is projected onto the coil portion below and / or above, for example, the first coil portion 242a of the first coil 240 or the first coil portion 252a of the second coil 250, the projection of the area surrounded by the periphery of the shielding portion covers an area of ​​the coil portion that is substantially equal to the area occupied by the coil portion. Other arrangements are also possible. In some embodiments, the projection of the area surrounded by the periphery of the shielding portion covers an area of ​​the coil portion that is less than the area occupied by the coil portion.

[0077] Figure 3 An exemplary schematic diagram of a circuit 300 is shown. The circuit 300 includes a transformer. The circuit 300 may be a circuit schematic implementation of the micro planar coil transformer 200. The circuit 300 includes a primary side 310, a secondary side 320, a first coil 330, a second coil 340, a shield 350, and an isolation layer 360.

[0078] The primary side 310 is coupled to a primary side ground 312, and the secondary side 320 is coupled to a secondary side ground 322. Figure 3 , the primary side ground 312 and the secondary side ground 322 are not coupled.

[0079] Secondary side 320 includes output 324. Output 324 provides an output signal from circuit 300.

[0080] The first coil 330 includes a first coil portion 332a and a second coil portion 332b, and the first coil 330 is coupled to a first terminal 334a, a second terminal 344b, and a center tap 336. The first terminal 332a and the second terminal 332b include input terminals of the first coil 330. In some embodiments, each of the first terminal 332a and the second terminal 332b is directly or indirectly coupled to the primary side ground 312.

[0081] The first coil is coupled to a center tap 336. The center tap 336 is disposed between the first coil portion 332a and the second coil portion 332b.

[0082] The second coil 340 includes a first coil portion 342a and a second coil portion 342b, and the second coil is coupled to a first terminal 344a and a second terminal 344b. The first terminal 342a and the second terminal 342b include output terminals of the second coil 340. In some embodiments, each of the first terminal 342a and the second terminal 342b is directly or indirectly coupled to the secondary side ground 322 and the output 324. In some embodiments, a transformer includes a rectifier disposed between the second coil and one or more of the output terminal and the secondary side ground.

[0083] exist Figure 3 In some embodiments, the second coil 340 is coupled to a center tap, such as a center tap disposed between the first coil portion 342a and the second coil portion 342b.

[0084] An input signal may be applied to each of the first terminal 332a and the second terminal 332b. In some embodiments, the signals are independent or non-differential, such as half-sine 180 degree out-of-phase signals with the same sign as described above. When such a signal is applied to the first terminal 332a and the second terminal 332b, the common mode voltage ripple amplitude of the first coil 330 is substantially greater than zero. The center tap 336 may be maintained at a constant voltage or maintained at ground.

[0085] In some embodiments, the common mode voltage ripple amplitude of the second coil 340 is substantially zero. In some embodiments, the common mode voltage ripple amplitude of the second coil 340 is substantially greater than zero and less than the common mode voltage ripple amplitude of the first coil 330.

[0086] Due to the parasitic capacitance between the first coil 330 and the second coil 340 transformer, the ripple amplitude difference between the first coil 330 and the second coil 340 will introduce a common mode current that crosses from the primary side 310 to the secondary side 320 of the circuit 300, and the common mode current will flow back to the primary side 310 through dipole radiation, potentially causing unacceptable EMI levels.

[0087] However, the shield 350 disposed in the isolation layer 360 is configured to reduce dipole radiation between the primary side 310 and the secondary side 320 . The shield 350 may include a Faraday shield, and is disposed between the first coil 330 and the second coil 340 .

[0088] The shield 350 is configured to block the electric field between the first coil 330 and the second coil 340. Therefore, most or substantially all common mode current is blocked by the shield and absorbed by the power or ground (e.g., primary side ground 312) coupled to the shield 350. Therefore, most or substantially all common mode current flows only in the loop 370 of the primary side 310 and does not cross the isolation layer 360. The loop 370 is completely on the primary side 310, so the substantially zero common mode current from the loop 370 will pass through the isolation layer 360 and will not cause dipole radiation and will not cause EMI.

[0089] In some embodiments, the common mode voltage ripple amplitude of the second coil 340 is substantially greater than zero. Therefore, some common mode current can make the isolation layer 360 through the shield 350 from the secondary side 320 through the loop 380. Some dipole radiation can be generated from the loop 370, but the dipole radiation is reduced or substantially eliminated.

[0090] Figure 4 A top view of some components of the micro planar coil transformer 400 is shown. The components of the micro planar coil transformer 400 include a first coil 440 and a shield 460. The first coil 440 and the shield 460 may be mainly arranged in different layers of the micro planar coil transformer 400.

[0091] The first coil 440 includes a first coil portion 442a, a second coil portion 442b, a first pad 444a, a second pad 444b, a center tap pad 446, and an intermediate portion 448 including a first overpass portion 448a and a second overpass portion 448b.

[0092] exist Figure 4 442a, the overpass portion intersects the turns of the coil portions. The first overpass portion 448a is arranged in the same layer as the shield 460, and couples an end of the first coil portion 442a within the first coil portion 442a to the second coil portion 442b, across the turns of the first coil portion 442a. Similarly, the second overpass portion 448b is arranged in the same layer as the shield 460, and couples an end of the second coil portion 442b located within the second coil portion 442b to the first coil portion 442a, across the turns of the second coil portion 442b.

[0093] Alternatively, the overpass portion can connect the ends of the coil to the coil pads. In such an arrangement, the overpass portion can cross from the first coil portion 442a to the first pad 444a and cross from the second coil portion 442b to the second pad 444b. In this arrangement, the middle portion 448 does not include the overpass portion, but is entirely arranged in the layer of the first coil. The overpass opening in the shield is arranged to accommodate an alternative position of the overpass portion.

[0094] Shield 460 includes first shield portion 462a, second shield portion 462b, shield pad 464, middle portion 466, first overpass opening 468a and second overpass opening 468b. First overpass portion 448a is disposed within first overpass opening 468a and second overpass portion 448b is disposed within second overpass opening 468b.

[0095] Overpass portions in the shield and their corresponding overpass openings may reduce the shielding effectiveness. Thus, when an overpass covers a portion of the coil, that portion of the coil is therefore not covered by the shield, which may reduce the shielding effectiveness or provide a source of noise. Overpasses or underpasses in the non-shielded layer may increase the shielding effectiveness at the expense of requiring additional layers. In some localized shielding arrangements, the overpass portion may instead pass over the portion of the coil not covered by the shield perimeter. In some embodiments, the shielded area may include the area occupied by the overpass portion.

[0096] In some embodiments, other shield couplings may be used. For example, in some embodiments, the shield may be coupled to the center tap. In such embodiments, portions of the shield may be used as an overpass portion of the coil. Thus, separate shield pads and center tap pads are not required. Such an arrangement may reduce manufacturing cost and complexity, but may reduce shielding effectiveness in some embodiments.

[0097] The inventors have recognized that in some transformer configurations, a shield covering less than the entire area of ​​the coil can further reduce or substantially eliminate dipole radiation. For example, when the common-mode voltage ripple amplitude of the coil on both the primary and secondary sides is substantially greater than zero, a shield that does not completely cover the coil can be used. In such a configuration, only a single shield can be used.

[0098] exist Figure 4 In the figure, when the area surrounded by the periphery of the shield 460 is projected onto the lower or upper coil (e.g., the first coil 440), the projection of the area surrounded by the periphery of the shield 460 covers the area of ​​the first coil 440, which is smaller than the area occupied by the first coil 440.

[0099] Similarly, when the area surrounded by the periphery of the shielding portion, such as the shielding portion 462a, is projected onto the first coil portion below and / or above (e.g., the first coil portion 462a), the projection of the area surrounded by the shielding portion 462a covers an area of ​​the coil portion 442a that is smaller than the area occupied by the coil portion 442a.

[0100] In some embodiments, the common mode voltage ripple amplitude of the first coil is substantially greater than zero, and the common mode voltage ripple amplitude of the second coil is substantially greater than zero and less than the common mode voltage ripple amplitude of the first coil.

[0101] The inventors have recognized that if the common mode current is reduced or substantially eliminated by matching the common mode voltage ripple amplitude, the dipole radiation can be reduced. As described above, there is a parasitic capacitance between the first and second coils. If the voltage applied to the capacitor plates is the same, then no current will flow through the capacitor. Similarly, if the common mode voltage ripple amplitude is matched on the first and second coils, the common mode current will not flow. Therefore, the common mode current can be eliminated, and therefore no dipole radiation will cross between the sides.

[0102] The inventors have recognized that the area of ​​the partial shield covering the coils can be configured so that the exposed common mode voltage ripple amplitude of the primary side and the exposed common mode voltage ripple amplitude of the secondary side closely match or substantially match each other. The partial shield that can cover a percentage A of the transmit coil can absorb percentage A of the common mode voltage ripple amplitude and expose the receive coil to percentage B of the common mode voltage ripple amplitude of the transmit coil, where percentage B is substantially equal to percentage A subtracted from 100%.

[0103] The first coil may occupy a first area in a plane parallel to the upper surface of the substrate. The coupled second coil may substantially occupy the first area. A projection of an area surrounded by the shielded perimeter in the plane onto the first coil may cover a second area of ​​the coil that is smaller than the first area.

[0104] In some embodiments, the area ratio, including the ratio of the second area to the first area, is related to or is at least partially based on the ripple ratio, which is the ratio of the second common-mode voltage ripple amplitude of the second coil to the first common-mode voltage ripple amplitude of the first coil. For example, if the ripple ratio is less than 1, the shield and the coil can be patterned to have an area ratio less than 1. In some embodiments, the area ratio and the ripple ratio include substantially complementary percentages. The sum of the complementary percentages is 1, i.e., 100%. Therefore, the first ratio and the second ratio substantially add up to 1, or to 100%. Therefore, the shield can be patterned to have an area ratio relative to the coil that is substantially equal to the ripple ratio subtracted from a value of 1 or from 100%.

[0105] The inventors have recognized that for some transformers, the ripple ratio is related to the coupling factor k of the first coil and the second coil. Therefore, in some embodiments, the area ratio can be related to or at least partially based on the coupling factor of the coils. In some embodiments, the ripple ratio is directly proportional to the coupling factor of the first coil and the second coil. In some embodiments, the ripple ratio can be substantially equal to the coupling factor. Therefore, in some embodiments, the area ratio and the coupling factor substantially add up to 1, or to 100%. Therefore, the shield can be configured to have an area ratio substantially equal to the coupling factor subtracted from a value of 1 or from 100%.

[0106] The coupling factor k of the transformer is affected by coil diameter, distance between coils, coil alignment, bond wire inductance, etc. The coupling factor k is not substantially affected by the circuits coupled to the transformer, such as drive or rectification circuits.

[0107] The same principles may additionally or alternatively be applied to the shield portion and the coil portion as they are applied herein to the shield and the coil.

[0108] The inventors have recognized that it is beneficial to block only the electric field and allow the magnetic field to substantially pass through the shield. In some embodiments, for example Figure 4 In the shield 460, the shield can be configured to substantially block the electric field from passing through the shield. The shield can be configured to reduce or substantially eliminate the amount of magnetic field blocked by the shield so that the magnetic field passes substantially completely through the shield.

[0109] The shield applied to the helical coil can be arranged to have a circumference of an entire circle and cover the entire coil, or can be arranged to have other perimeter shapes that only partially cover the coil. Shields configured to substantially block electric fields and substantially block the passage of magnetic fields are not arranged purely in a circle. Shields, such as shield 460 or shield 1060 described below, can be divided into many narrow strips. Such shields can include multiple high aspect ratio segments that are configured to reduce eddy currents in the shield. Multiple high aspect ratio segments can be patterned to form an overall circular or other shape of the shield.

[0110] Eddy currents are closed loops of electrical current that may be induced in a shield or other electrical conductor perpendicular to the changing magnetic field passing through it. The physical space through which the changing magnetic field passes determines the size of the eddy current loop. The magnitude of the current is proportional to the size of the loop. Larger currents correspond to larger energy losses from the magnetic field, thereby reducing the efficiency of the transformer. Therefore, reducing the size of the loop, such as by using high aspect ratio segments, will allow more of the magnetic field to pass through the shield and will reduce or substantially eliminate the efficiency-reducing effects of eddy currents.

[0111] In some embodiments, non-shielding techniques can be used to at least partially eliminate the ripple on one or more sides of the transformer. Thus, a single full shield can be used to block the common mode voltage ripple amplitude on the other side of the transformer, so that the ripple on each side is removed separately.

[0112] Figure 5A top view of some components of the micro-planar coil transformer 500 is shown. The components of the micro-planar coil transformer 500 include a first coil 540 and a second coil 570. The first coil 540 includes a first coil portion 542a and a second coil portion 542b, which are coupled together through an intermediate portion 548. The first coil 540 is coupled to pads 544a and 544b. The intermediate portion 548 is coupled to a center tap pad 546. The second coil 570 includes a first coil portion 572a and a second coil portion 572b, which are not coupled through an intermediate portion. The first coil portion 572a is coupled to pads 574a and 574b. The second coil portion 572b is coupled to pads 574c and 574d. The first coil 540 and the second coil 570 can be arranged on the primary side of the transformer respectively and can be arranged in the lower layer.

[0113] Separate signals are applied to the first coil 540 and the second coil 570 through their respective pads. The oscillation direction of the applied signal may be substantially unfavorable, so that the common mode ripples of the first coil 540 and the second coil 570 are also unfavorable. Therefore, the total common mode ripples of the two primary side coils can be substantially matched and substantially cancel each other, and as a result, the common mode voltage ripple amplitude of the primary side can be substantially zero.

[0114] In some embodiments, the center tap pad 546 includes two separate pads. The first pad is coupled to the first coil portion 542a, and the second pad is coupled to the second coil portion 542b, and there is no connection via any intermediate portion between the first pad and the second pad. Such an arrangement can cause the matching between the first coil 540 and the second coil 570 to increase. Since the shape of each coil and pad arrangement of the first coil 540 and the second coil 570 is more similar than in a single pad configuration, increased matching may occur in two pad configurations. In some embodiments, in two pad configurations, the shape of each coil and the pad arrangement for the first coil 540 and the second coil 570 are substantially the same. This arrangement requires additional bonding wires for the second pad to connect.

[0115] Figure 6 A top view of some components of the micro planar coil transformer 600 is shown. The components of the micro planar coil transformer 500 and the components of the micro planar coil transformer 600 may form the same transformer. The components of the micro planar coil transformer 600 include a third coil 650 and a shield 660.

[0116] The third coil 650 includes a first coil portion 652a, a second coil portion 652b, a first pad 654a, a second pad 654b, and a middle portion 658 including a first overpass portion 658a and a second overpass portion 658b. The third coil 650 may be disposed on the secondary side of the transformer and may be disposed in an upper layer.

[0117] The shield 660 includes a first shield portion 662a, a second shield portion 662b, a shield pad 664, a middle portion 666, a first overpass opening 668a, and a second overpass opening 668b.

[0118] In some embodiments, the third coil 650 can be electromagnetically coupled to the first coil 540 and the second coil 570. As described above, according to the non-shielding technology, the common mode voltage ripple amplitude of the primary side including the coils 540 and 570 can be substantially zero. Therefore, the shield 660 is a single full shield for blocking the common mode voltage ripple amplitude of the secondary side including the third coil 650, thereby eliminating the ripples of the ripples on both sides.

[0119] Shielding can be used with back-to-back transformers. Figure 7 A cross-sectional side view of a micro planar coil transformer 700 is shown. The micro planar coil transformer 700 comprises a back-to-back transformer. The micro planar coil transformer 700 is arranged on a substrate 710 having an upper surface 712 and comprises a lower layer 714, a lower coil layer 720, intermediate layers 730, 732, 734 and 736, an upper coil layer 722, a first coil 740, a second coil 750, a coil coupling 752, a third coil 760, a fourth coil 770, a first shield 780, a second shield 790, a first through hole 782 and a second through hole 792. Portions 784 and 794 of the coils may be exposed to provide coupling points.

[0120] The shield may be arranged closer to the first coil 740 and the fourth coil 770 so that the common mode current does not pass through the isolation layer. The first shield 780 and the second shield 790 may be arranged above the intermediate layers 730, 732, and 734 and below the intermediate layer 736 so that the first shield and the second shield are arranged closer to the first coil 740 and the fourth coil 770 than the second coil 750 and the third coil 760. Having the shields 780 and 790 arranged closer to the coils 740 and 770 can reduce the distance into the isolation layer, which is the distance that any current loop from the coils 740 and 770 propagates.

[0121] Figure 8An exemplary schematic diagram of a circuit 800 is shown. The circuit 800 includes a back-to-back transformer. The circuit 800 can be a circuit schematic implementation of the micro-planar coil transformer 700. The circuit 800 includes a first transformer 810 having a primary side 812a and a secondary side 812b, a second transformer 820 having a primary side 822a and a secondary side 822b. The circuit 800 includes a first coil 840 having a first terminal 844a and a second terminal 844b, a second coil 850 having a first terminal 854a and a second terminal 854b, a third coil 860 having a first terminal 864a and a second terminal 864b, and a fourth coil 870 having a first terminal 874a and a second terminal 874b. The circuit 800 includes a first shield 880 coupled to the primary side ground 814 and a second shield coupled to the secondary side ground 824.

[0122] In a back-to-back transformer, to prevent the flow of common mode current, each transformer pair of coupled coils may be arranged with a shield between them. In some embodiments, each shield includes all shields, and the shields are arranged in the same layer. In some embodiments, the shields may include identical shields.

[0123] In some embodiments, a back-to-back transformer can include one or more partial shields. For example, back-to-back micro-planar coil transformers, such as micro-planar coil transformer 700, can include partial shields. Figure 7 In the embodiment of the present invention, the micro-planar coil transformer 700 includes a first shield 780 and a second shield 790, each of which may include a full shield. However, the back-to-back micro-planar coil transformers may alternatively include a single shield, which may include a partial shield. For example, in some embodiments, the micro-planar coil transformer 700 includes only one of the first shield 780 and the second shield 790. Figure 4 The partial shield arrangement technique described above can be used to arrange a shield included in a back-to-back micro-planar coil transformer. For example, the area of ​​the partial shield can be patterned in relation to or at least partially based on the area of ​​the first coil 740. This arrangement can be in the form of a shield of about Figure 4 Dipole radiation is reduced in a similar manner as described. This arrangement may require the same number of layers as the two full shielding arrangements of the micro planar coil transformer 700.

[0124] Each coil of the back-to-back transformer may include one or more coil sections, as described above with reference to Figure 2 described.

[0125] Some embodiments may include two shields. Fig. 9A cross-sectional side view of a micro planar coil transformer 900 is shown. The micro planar coil transformer 900 includes two shields. The micro planar coil transformer 900 is arranged on a substrate 910 having an upper surface 912 and includes a lower layer 914, a lower coil layer 920, intermediate layers 930, 932, 934 and 936, an upper coil layer 922, a first coil 940, a second coil 950, a first shield 960, a second shield 970 and a through hole 982. Portions 984 and 994 of the coils may be exposed to provide coupling points.

[0126] Fig.10 Some components of the micro planar coil transformer 1000 are shown. The components of the micro planar coil transformer 1000 may include components of the micro planar coil transformer 900. The micro planar coil transformer 1000 includes a first coil 1040 and a shield 1060.

[0127] The first coil 1040 includes a first coil portion 1042 a , a second coil portion 1042 b , a first pad 1044 a , a second pad 1044 b , a center tap pad 1046 , and a middle portion 1048 .

[0128] The shield 1060 includes a first shield portion 1062a, a second shield portion 1062b, a shield pad 1064, a middle portion 1066, a first overpass opening 1068a, and a second overpass opening 1068b. The shield 1060 may include Fig. 9 Each of the first shield 960 and the second shield 970 in the transformer. A transformer with two shields can have two full shields. The first full shield can prevent common mode current from passing through the isolation layer from the primary side, while the second full shield can prevent common mode current from passing through the isolation layer from the secondary side.

[0129] Fig.11 An exemplary schematic diagram of a circuit 1100 is shown. The circuit 1100 includes a transformer with a double shield. The circuit 1100 can be a circuit schematic implementation of the micro planar coil transformer 900. The circuit 1100 includes: a primary side 1110, which includes a first coil 1130; and a first shield 1150, which is coupled to the primary side ground 1112; a secondary side 1120, which includes a second coil 1140; a second shield 1160 coupled to the secondary side ground 1160; and an isolation layer 1170. The first coil 1130 has a first terminal 1134a, a second terminal 1134b, and a center tap 1136. The second coil 1140 has a first terminal 1144a and a second terminal 1144b coupled to the output 1124.

[0130] Circuit 1100 includes two full shields. First shield 1150 and second shield 1160 are configured to block the electric field between first coil 1130 and second coil 1140. Therefore, most or substantially all common mode currents are blocked by the shields and absorbed by primary side ground 1112 and secondary side ground 1122. In this way, most or substantially all common mode currents flow only in loop 1180 and loop 1190. The current in loop 1080 flows only on primary side 1110 and may be absorbed by primary side ground. The current in loop 1190 flows only on secondary side 1120 and may be absorbed by secondary side ground 1122. The current in each loop will not pass through isolation layer 1170. Since loop 1180 is completely on primary side 1110, if loop 1190 is completely on secondary side 1110, substantially zero common mode current will pass through the isolation layer and will not cause dipole radiation or cause EMI.

[0131] Double shielding arrangements require additional layers compared to single shielding arrangements. For example, if the overpass section is arranged in a shielded layer, at least four layers are required. Some arrangements of double shielding require 5 or more layers.

[0132] Each coil of the double shield transformer may include one or more coil sections, as described above with reference to Figure 2 described.

[0133] A method for manufacturing a micro-planar coil transformer may include the following steps: forming Figure 1 , 7 and any one of the layers described in 9; and patterning each coil and shield. For example, a substrate may be provided. A bottom layer may be formed on the substrate. A first coil layer including a first coil may be formed on a base layer or on a substrate. In the above arrangement, the first coil may be patterned in the first coil layer. One or more intermediate layers including one or more shields may be formed on the first coil layer. One or more shields may be constructed in one or more intermediate layers in the above arrangement. In the above arrangement, a second coil may be patterned above the intermediate layer. The second coil may be formed in a second coil layer.

[0134] A method of operating a micro-planar coil transformer may include the following steps: applying a signal set to the terminals of a first coil arranged on the primary side of the transformer so that the first coil has a first common-mode voltage ripple amplitude substantially greater than zero, and a second coil arranged on the secondary side of the transformer electromagnetically coupled to the first coil has a second common-mode voltage ripple amplitude greater than or equal to zero and less than the first common-mode voltage ripple amplitude. The method may include reducing dipole radiation between the first coil and the second coil. The method may include using a shield to block the common-mode current between the first coil and the second coil. The method may include using a full shield to block substantially all common-mode current. The method may include exposing the second coil to a portion of the first common-mode voltage ripple amplitude using a partial shield, wherein the portion is substantially equal to the second common-mode voltage ripple amplitude. In some embodiments, the ratio of the portion to the first common-mode voltage ripple amplitude is substantially equal to the coupling factor of the first and second coils.

[0135] Although shielding in this application may generally be described with respect to a micro-planar coil transformer including a center-tapped coil consisting of two coil sections, aspects of this application may be applied to other transformers. For example, in some embodiments, shielding described in this application may be applied to other transformers that exhibit dipole radiation. In some embodiments, shielding may be applied to other transformers that exhibit common-mode current crossing between the primary side and the secondary side. In some embodiments, shielding may be applied to transformers that exhibit common-mode voltage ripple amplitude differences between the primary side and the secondary side.

[0136] Therefore, having described several aspects and embodiments of the present application technology, it should be understood that a person of ordinary skill in the art will readily think of various changes, modifications and improvements. Such changes, modifications and improvements are intended to be within the spirit and scope of the technology described in this application. Therefore, it should be understood that the foregoing embodiments are given only by way of example, and within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced in a manner different from that specifically described. In addition, if these features, systems, articles, materials and / or methods are not mutually contradictory, any combination of two or more features, systems, articles, materials and / or methods described herein is included within the scope of the present disclosure.

[0137] Moreover, as described, some aspects may be embodied as one or more methods. The actions performed as part of the method may be ordered in any suitable manner. Thus, embodiments may be constructed in which the actions are performed in a sequence different from that shown, and even if shown as sequential actions in an illustrative embodiment, the actions may include performing some actions simultaneously.

[0138] In some embodiments, the terms "about," "substantially," and "approximately" may be used to indicate within ±20% of a target value, in some embodiments within ±10% of a target value, in some embodiments within ±5% of a target value, and in some embodiments within ±2% of a target value. The terms "about" and "approximately" may include the target value.

Claims

1. A micro planar coil transformer arranged on a substrate having an upper surface, comprising: a first planar coil arranged in a first layer and occupying a first area in a plane parallel to the upper surface; a second planar coil disposed in the second layer; and a shield disposed in an intermediate layer, the intermediate layer being between the first layer and the second layer; wherein a projection of an area enclosed by the perimeter of the shield onto the first planar coil covers a second area of ​​the coil that is smaller than the first area, The ratio of the second area to the first area and the ratio of the second common mode voltage ripple amplitude of the second planar coil to the first common mode voltage ripple amplitude of the first planar coil are substantially complementary percentages, and the second common mode voltage ripple amplitude is smaller than the first common mode voltage ripple amplitude.

2. The micro planar coil transformer of claim 1, wherein a ratio of the second common-mode voltage ripple amplitude to the first common-mode voltage ripple amplitude is substantially equal to a coupling coefficient of the first planar coil and the second planar coil.

3. The micro planar coil transformer of claim 1, comprising only three metallization layers, the three metallization layers comprising the first layer, the second layer and the middle layer.

4. The micro planar coil transformer of claim 1, comprising an overpass portion of the first planar coil disposed in the middle layer.

5. The micro planar coil transformer of claim 1, wherein the first planar coil is electromagnetically coupled to the second planar coil, and wherein the micro planar coil transformer further comprises: a third planar coil disposed in the second layer and coupled to the second planar coil; and A fourth planar coil is electromagnetically coupled to the third planar coil and is arranged in the first layer.

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