Patent Description:
With the improvement of human requirements for smart living, the demand for data processing in society is growing. The global energy consumption in data processing averagely reaches hundreds of billions or even trillions of kilowatt-hour per year; and the area of a large data center may be tens of thousands of square meters. Therefore, high efficiency and high power density are the key indicators for the healthy development of this industry.

The key unit of the data center is the server which usually includes data processing chips on a motherboard including such as a central processing unit (CPU), chipsets, a memory, and their power supply and other necessary peripheral components. As the processing capacity of a server increases, the number and integration level of these processing chips also increase, which results in an increase in the volume and power consumption of the server. Therefore, the power supply for these chips (because it is on the same motherboard as the data processing chips, also referred to as the motherboard power supply), is expected to have higher efficiency, higher power density and smaller volume to support the energy saving and space reducing requirements of the entire server or even the entire data center. In order to meet the demand of high power density, the switching frequency of the power supply is also higher and higher. The switching frequency of the low-voltage and high-current power supply in the industry is basically <NUM> Megahertz (MHz).

The transformers for low-voltage and high-current applications are mostly implemented by a multi-layer printed circuit board (PCB). <FIG> is a side view of a transformer having a multi-layer PCB winding provided by the prior art. For example, as shown in <FIG>. , the winding is formed horizontally on the different layers of the PCB board, and the PCB board is usually sleeved on the magnetic columns of the core, so that the magnetic columns are vertical or nearly vertical to the PCB board, such that the magnetic columns are vertical or nearly vertical to the respective winding layers on the PCB board. And the thickness W of the winding is parallel to the length direction of the magnetic column; and the width H of the metal winding is vertical to the length of the magnetic column. Due to the PCB winding process, H and W generally satisfy the following relationship: H><NUM> W. In this PCB winding structure, the winding on different layers are connected by vias, since the layers are vertical to the magnetic columns, the vias are parallel to the magnetic columns. The winding on the inner layer is generally connected to that on the outer layer and the pins on the surface of the PCB (not shown) through vias. Generally, for the less than 5V voltage and larger than 50A current output applications, a transformer with at least ten-layers PCB is needed. And the height of a ten-layer PCB is about <NUM>. Thus the length of the via is long and the impedance of the via is large, so the loss caused by the via is large. <FIG> shows the top view of the winding on the right magnetic column of the core. In <FIG>, the winding on the same layer may be separated into several concentric circles with different diameters R1A, R2A,. Since the concentric circles have different diameters, they have different impedances. So there is a problem of uneven current distribution of the winding on one layer.

<FIG> is a structural schematic diagram of a transformer module. For convenience of description, in the schematic diagram, the shape of the winding, and the positional relationship between the winding and the magnetic core are specifically drawn, but the disclosure is not limited thereto. If multiple wiring layers need to be provided, an insulating layer and a new wiring layer can be sequentially added outside the wiring layer. With reference to <FIG>, the dimension of the winding parallel to the longitudinal direction of the magnetic column is defined as W, and the thickness of the winding which is the dimension of the winding vertical to the magnetic column of the magnetic core is H. When H and W satisfy the relationship: W><NUM>, we define this winding manner of the winding as a winding having a foil structure. For a winding in a foil structure, different portions of the winding have almost the same distance to the magnetic core, that is, the equivalent diameters of different portions e.g. R1B and R2B are almost the same. Thus equivalent impedance of different portions is almost the same. So the current distribution of the winding in a foil structure is almost even which reduces the winding loss greatly. Generally, the winding shown in <FIG> is made by a copper foil process that is the winding is made of copper foil by cutting or punching process. And in this structure, the output connectors of the winding, e.g. <NUM> and <NUM> are almost stretched out from the sides of the winding to connect to the circuits (not shown). The output connectors are always centralized, which means very few of the connectors (e.g. only two connectors for each winding in <FIG>) are used to connect to the circuit. The very few of the connectors stretching out from the sides of the winding makes the uneven current distribution on the joint part of the connectors and the other part of the winding. In addition, centralized output connectors always have long length. Thus the loss of the connectors is large.

<CIT> discloses a high-frequency transformer which is intended in particular for a welding or cutting machine. It has a transformer core and a primary and a secondary winding which are electrically isolated from one another. The transformer core consists of U-core elements each with an inner leg and an outer leg and a connecting section connecting these, whereby two U-core elements with their inner legs to each other are provided closely adjacent in a common plane, forming an E core layer. Two E core layers face one another closely and without gaps and form a transformer core layer. The transformer core has at least one transformer core layer. The inner legs of the at least one transformer core layer are jointly enclosed by the primary and secondary windings.

<CIT> discloses a low leakage, secondary circuit, a structure is provided for the power transformer in a high frequency power inverter system, or the like. The secondary circuit includes mutually insulated conductive strips which are placed in close proximity to one another, and which form the secondary winding of the power transformer, and which also form connections between the secondary winding and rectifying diodes included in the secondary circuit is minimized, thereby to minimize the leakage reactance in the circuit.

<CIT> discloses an axial double-split dry-type transformer coil structure with the same connection groups and a winding method. The axial double-split dry-type transformer coil structure comprises a first low-voltage coil, a second low-voltage coil and a group of high-voltage coils, wherein each of the first low-voltage coil and the second low-voltage coil is provided with two low-voltage coil sections, the two low-voltage coil sections of the first low-voltage coil and the two low-voltage coil sections of the second low-voltage coil are distributed in a cross mode, and two sections of leads for winding forming of the first low-voltage coil and the second low-voltage coil are leaded in and out from the upper end and the lower end respectively. The high-voltage coils are provided with multiple high-voltage coil sections distributed in the axial direction, the high-voltage coil sections are sequentially and mutually connected in series, and leads for winding forming of the high-voltage coils are leaded in and out from the upper end and the lower end respectively. The axial height of the first low-voltage coil and the axial height of the second low-voltage coil are both consistent to the axial height of the high-voltage coils.

<CIT> discloses a low-profile transformer or inductor for low voltages and large currents including a leg of a magnetically permeable core. A tube-type winding arrangement is made by use of a flat, flexible dielectric sheet, on one side of which a broad conductive area is affixed, and on the other side of which a plurality of mutually parallel elongated regions are affixed. The dielectric sheet is rolled into a tube defining a parting line which is perpendicular to the axes of elongation of the conductive strips. The discontinuous elongated strips are formed into a continuous winding by means of stitches. The stitches may be through vias extending through overlapping regions of the tube to interconnect ends of the strip conductors, or may be generated by an HDI conductor overlying the ends of the strip conductors, with through vias making connections to the ends of the strip conductors and to HDI conductors.

<CIT> discloses square toroid transformer assembled on a ceramic hybrid integrated circuit substrate. The primary and secondary windings of the transformer are provided on opposite arms of a square toroid ferrite core by providing first and second groups of spaced, parallel metal conductors on the surface of the ceramic substrate and adherent thereto, and an insulative layer over the first and second groups of conductors, leaving their respective end portions exposed. The square toroid ferrite core, coated with dielectric material, is attached to the insulative layer. Wire bonds in planes perpendicular to the longitudinal axes of the opposite arms each are wire bonded, respectively, to an inner end of one of the metal conductors and an outer end of an adjacent one. A large number of turns for both the primary winding and the secondary winding are achieved, resulting in high primary and secondary winding and inductances, while maintaining a uniform separation and high breakdown voltage between the primary and secondary wirings.

The present disclosure provides a transformer module and a power module, thereby achieving better distribution of windings.

In the following, only embodiment <NUM> is an embodiment of the present invention. The remaining examples serve illustrative purposes and do not form part of the present invention.

For most of the transformers for low-voltage and high-current applications, in the prior art, the transformer adopts a PCB winding structure. In the structure, the plane where the PCB board is located is vertical to the magnetic column, and the winding surrounding the magnetic column is formed by means of the trace on the PCB wiring layer. However, the PCB winding structure will cause the equivalent diameters of the inner and outer sides of the trace of the metal winding of the wiring layer to be inconsistent, resulting in the equivalent impedance of the inner side of the winding being smaller than the equivalent impedance of the outer side of the winding, so that there is a problem of uneven distribution of the windings. Thus, when the transformer is used, the corresponding current may be unevenly distributed.

While for most of the transformers with the foil winding structure in the prior art, the centralized output connectors of the winding are almost stretched out from the sides of the winding to connect to the circuits, which results in the uneven current distribution on the joint part of the connectors and the other part of the winding. And since the centralized output connectors stretch out from sides of the windings, they always have long length. Thus the loss of the connectors is large.

In order to solve these technical problems, the present disclosure provides a transformer module and a power module.

In one example, the windings in a foil structure are formed in the wiring layer by, for example, electroplating, electroless plating, spray coating, dipping, electrophoresis, electrostatic spraying, chemical vapor deposition, physical vapor deposition, evaporation or printing. A plurality of wiring layers may be disposed on the surface of the magnetic columns of the magnetic core, and an insulating layer is disposed between the adjacent wiring layers. The windings between the different wiring layers may be connected through connectors, e.g. vias, passing through the insulating layer.

<FIG> is a perspective view of a magnetic core in a transformer module provided by an example; <FIG> is a perspective view of the transformer after forming a second metal winding on the magnetic core shown in <FIG>; <FIG> is a perspective view of an example after forming a first metal winding (bottom up) on the transformer module shown in <FIG>; <FIG> is a perspective view by forming the ends (for example, a surface-mounted pin) on the transformer module shown in <FIG>, and <FIG> is an electrical schematic diagram corresponding to the pins of the transformer module shown in <FIG>. Referring to <FIG>, the transformer module includes a magnetic core <NUM>, a first metal winding <NUM> (as shown in <FIG>, the first metal winding is, for example, a secondary winding S2 of the transformer module) and a second metal winding <NUM> (as shown in <FIG>, the second metal winding is, for example, the primary winding P of the transformer module).

Optionally, the magnetic core is hollow square shaped/hollow box shaped, ring shaped, an I-shaped or C-shaped. For example, the magnetic core <NUM> shown in <FIG> is a hollow square shaped magnetic core. This disclosure does not limit the shape of the magnetic core.

The number of turns of the first metal winding (e.g. the secondary winding S2) may be one turn or plural turns. For example, the number of turns of the first winding <NUM> shown in <FIG> is one turn.

Optionally, the number of turns of the second metal winding (e.g. the primary winding P) may be one turn or plural turns. For example, as shown in <FIG>, the number of turns of the second winding <NUM> is plural turns which forms a spiral type winding around a plurality of magnetic columns of the hollow square shaped magnetic core, wherein the thick black line shown in <FIG> is an insulating layer exposed between the turns of the metal winding, so is the thick black lines shown in the following figures.

Specifically, the first wiring layer, the first insulating layer, and the second wiring layer are sequentially disposed from the outside to the inside on the magnetic core. As shown in <FIG>, the metal winding <NUM> is formed in the second wiring layer by e.g. an etching process or a copper foil winding process such that the second winding <NUM> winds around the four magnetic columns of the magnetic core <NUM> in a foil structure. After the second winding <NUM> in the second wiring layer is formed covering the magnetic core <NUM>, a first insulating layer is disposed outside the second wiring layer, and then a first wiring layer is disposed outside the first insulating layer, wherein the first insulating layer is used for the insulation between the first wiring layer and the second wiring layer. And therefore, the second wiring layer is at least partially covered by the first insulating layer and at least partially covered by the first wiring layer. As shown in <FIG>, the first metal winding <NUM> e.g. a one-turn winding is formed in the first wiring layer and winds around all the magnetic columns of the magnetic core <NUM> in a foil structure. The first winding <NUM> wraps around the magnetic core <NUM> and also at least partially covers the second winding <NUM>. Therefore, the second winding is also at least partially covered by the first winding, and the first insulating layer is also at least partially covered by the first winding. The cover described in the present disclosure may be contact cover or non-contact cover, such as projection cover. As described above, the "cover" in "the first insulating layer is at least partially covered by the first metal winding" means contact cover. The "cover" in "the second metal winding is at least partially covered by the first insulating layer" also refers to contact cover. The "cover" in "the second metal winding is at least partially covered by the first metal winding" means non-contact cover, that is, projection cover.

Specifically, in an example, an initial insulating layer may be selectively attached to the surface of the magnetic core by spraying or deposition, and the initial insulating layer has the function of enhancing the bonding force and protecting the magnetic core, but the present invention is not limited to this, alternatively, the initial insulating layer may be or may not be provided. A second wiring layer may be a metal layer e.g. a copper layer and disposed on the core by electroplating or electroless plating process; and then a metal protective layer, such as a tin layer or a gold layer, is disposed on the surface of the second wiring layer by electroplating or electroless plating; then the metal protective layer is patterned by a writing process to expose a portion of the second wiring layer which needs to be etched; and then the portion of the second wiring layer which needs to be etched are etched under the protection of the metal protective layer to form a second metal winding; finally, the protective layer is removed and the second winding, e.g. the primary winding P comes into being as <FIG> shows. Then, the first insulating layer is selectively attached to the second metal winding by spraying or deposition, and the first insulating layer has the function of enhancing the bonding force and protecting the magnetic core. And a similar process is adopted. A first wiring layer is provided on the surface by plating or electroless plating, the first wiring layer may be a copper layer; then a metal protective layer is electroplated or electroless plated on the surface of the first wiring layer, such as a tin layer or a gold layer; and then the metal protective layer is patterned by a writing process to expose a portion of the first wiring layer which needs to be etched; and then the portion of the first wiring layer are etched under the protection of the metal protective layer to form a first metal winding; finally, the protective layer is removed to expose the first metal winding, e.g. the secondary winding S2. However, the present invention is not limited thereto, and other winding forming processes are also applicable. For example, the first and second winding may be the copper foils made by e.g. a punching or cut process to wind around the columns of the core.

In this example, it can be seen that the second winding <NUM> is a spiral winding with plural turns surrounding all the columns of the hollow square shaped (or hollow-square shaped) magnetic core. The first winding <NUM> has one turn and also wraps all the magnetic columns of the hollow square shaped magnetic core. As a matter of fact, the second winding <NUM> may wind some columns of the core, e.g. one or two columns of the core, even a part of one magnetic column of the core. So does the first winding <NUM>. As shown in <FIG>, a gap splits the winding <NUM> and forms two ends <NUM>, <NUM> of the winding on the bottom surface of the magnetic core by etching, cutting process etc..

Further, in conjunction with <FIG>, in this example, the second metal winding <NUM> also has a first end and a second end, which are covered by an insulating layer and the first winding <NUM> and connected to the third output pin P1 and the fourth output pin P2 (shown in <FIG>) by a first connector e.g. a via and a second connector e.g. a via (not shown) respectively for electrical connection with an external circuit. And both the first connector and the second connector just pass through the first insulating layer. Thus, the length of the connectors is very short, and the loss the connectors are small. Generally, there are multiple first and second connectors distributed on the corresponding pads. Then the current distribution is more even. The first metal winding <NUM> is, for example, a secondary winding of the transformer, and the second metal winding <NUM> is, for example, a primary winding of the transformer. And in this example, the two output pins P1 and P2 are both the surface-mounted pins. Actually, they may be other types of pins, such as, DIP pins, pins made by coils etc..

The transformer module is connected to an external circuit (such as a switch module) by the first output pin V0, the second output pin D2, the third output pin P1, and the fourth output pin P2, wherein in this example these pins are all surface-mounted pins and they may be other types of pins, such as DIP pins etc. For example, if the first winding is the copper foil made by punching or cut process, then the pins may also be made by the copper foil. That is to say, the pins and the first winding are integrated. The first surface-mounted pin V0, the second surface-mounted pin D2, the third surface-mounted pin P1, and the fourth surface-mounted pin P2 are all located on the first side (for example, the bottom surface) of the transformer module. In this example, the first side of the transformer module is the outer surface of the first wiring layer. The first side may also be a surface in parallel with the outer surface of the first wiring layer, wherein the surface in parallel with the outer surface may be close to the outer surface and the distance between two surfaces are small, for example, not more than <NUM>, which facilitates external assembly and connection. However, the invention is not limited thereto.

The first pin V0, the second pin D2, the third pin P1 or the fourth pin P2 may have various shapes, such as a square shape or a circle shape. In some examples, the first pin V0, the second pin D2, the third pin P1 or the fourth pin P2 may be surface-mounted pins. In <FIG>, D2 and V0 may be big hollow square shape pads or circle shape pads without P1 and P2 pins, while P1 and P2 are small rectangular shape pads.

Optionally, in the above example, the first surface-mounted pin V0, the second surface-mounted pin D2, the third surface-mounted pin P1, and the fourth surface-mounted pin P2 may be located on the different sides of the transformer module, for example, V0 and D2 can be located on the first side of the transformer module, while P1 and P2 can located on the second side of the transformer module, wherein the first side and the second side are different sides.

In the prior art shown in <FIG>, for a multilayer PCB transformer, the winding has different radii of different parts of the same layer winding, so that the impedance of the inner ring of the same layer winding is smaller than the impedance of the outer ring, so the current distribution on the same layer winding is not uniform, and the loss of the winding is correspondingly larger. And the windings in different layers are connected to each other through vias. But in the traditional PCB process, the diameters of these vias are big, usually larger than <NUM> microns. The distance between two vias is typically greater than <NUM> microns for structure and pattern considerations. In this example, since the traditional PCB board is no longer disposed, the first via and the second via may be directly formed in the first insulating layer by laser drilling or the like, so that the first via and the second via have smaller diameter, which can increase the number of via and further reduce the impedance of via. However, the invention is not limited thereto.

The vias may be hollow generally. However, by adjusting the electroplating agent the vias may also be filled with metal, e.g. copper for winding loss reduction.

Further, as described above, in a PCB winding structure, the windings in different layers may connect to each other through vias. Generally, such vias are long and have large impedance, and the winding loss caused by the vias is large. In this example, since the insulating layer such as the first insulating layer has a thickness less than <NUM> which is much smaller than the insulating layer of the PCB winding structure, the first via and/or the second via are short and the impedance is small, so that the loss of the winding caused by the vias can be reduced greatly.

Further, in the prior art, the pins of the secondary winding of the transformer of the multi-layer PCB structure can only be led out on the surface of the PCB, and the pins of the secondary winding of the inner layer can only be led to the surface of the PCB through the vias, thus causing that the current is concentrated and the winding loss is excessive. In some examples, the metal winding as the secondary side may be evenly foil winded around the magnetic core, and a plurality of sets of corresponding surface-mounted pins may be uniformly distributed on the first side of the magnetic core, thus the current is evenly distributed on the whole winding. Based on this, the winding loss can be reduced.

Further, the power of the transformer module provided by some examples is easy to expand, and all the magnetic column can be covered with a winding to improve the power of the transformer module. The magnetic module can be lengthened and the winding can be widened to increase the power of the transformer module.

As described in this example, the transformer winding is in a foil structure, the equivalent diameters of each part of the winding are similar, thus the equivalent impedances of each part are similar, thereby an almost even current distribution of the winding is achieved. The inner winding connects to the output pins by the connector passing through the insulation layer between the wiring layers that inner winding and the outer winding lay on which reduces the length of the connector greatly when compared with the prior art in <FIG>. So the loss of the connector is reduced greatly. Furthermore, as shown in <FIG>, the connectors or the pinouts may be plurals and distributed which can further improve the even current distribution of the winding. So the loss of the winding reduces greatly.

As shown in <FIG>, the first metal winding is a copper foil wound around the magnetic core in a foil structure continuously, the winding covers four magnetic core columns, and the two ends of the winding are respectively connected to the two pins V0 and D2, these two pins are connected to external circuits such as switch devices, etc., wherein the number of each of pins V0 and D2 is one, as shown in <FIG>. The structure shown in <FIG> is slightly different from 3D. In <FIG>, the metal winding continuously winds on part of the magnetic columns of the hollow square shaped core, such as three magnetic columns. The two ends of the winding are still connected to the two pins V0 and D2, and the number of each of the pins V0 and D2 is also one. Taking <FIG> as an example, from the side of the transformer, a is the inner length of the winding, and b is the outer length of the winding. Therefore, it can be considered that the average length of the winding W=(a+b)/<NUM>, and d is the average length of the pins on the winding, n is the ratio of the pin length to the winding length, n=d/W. Since the windings are connected to the external circuit through the pins, the length of d will affect the uniformity of the current distribution on the winding. For the average length of a certain winding, as d increases, the current distribution will become more uniform and the winding loss will become smaller and smaller. As shown in <FIG>, the abscissa in <FIG> is n, and the ordinate P is the winding loss, as n increases, the corresponding winding loss is greatly reduced. Preferably, when d≥ <NUM>/2W, the winding loss is small and tends to be stable. In <FIG>, n=<NUM>, that is, the length of the pin is almost equal to the average length of the winding, so the pin structure in <FIG> can make the current distribution on the winding more uniform, and correspondingly the winding loss is smaller. In this application, the magnetic core is not limited to the hollow square shape, and is also applicable to the magnetic cores of the T-shape, UU-shape and UI-shape.

Similarly, for the plurality of pins of the secondary winding, as shown in <FIG> which is similar to <FIG>, both of them include a hollow square shaped magnetic core, and a continuous winding wound on three magnetic columns. Different from <FIG>, the winding of <FIG> includes a plurality of first pins V0 and a plurality of second pins D2, that is, the numbers of the first pin V0 and the numbers of the second pin D2 are both greater than or equal to <NUM>. As shown in <FIG>, the total length of the pin includes three parameters: d1, d2, and d3, and the total length of the pin is d=d1+d2+d3. In <FIG>, if V0 or D2 is only a single pin, the length of the V0 or D2 pin is small, that is, the ratio of the length of the pin to the average length of the winding n is relatively small, so that the corresponding winding loss is still not small. However, for a plurality of pins of V0 or D2, for example, three pins as shown in the figure, the length of the pin is greatly increased, and the ratio n of the length of the pin to the average length of the winding becomes larger, which will cause current distribution on the winding more even. It can be understood that the first pin V0 and the second pin D2 in the figure can be various shapes such as a square shape or a circle shape, for example, when the pin is a circle shape, the length of the pin can be the diameter of the circle. Furthermore, the distribution of the plurality of first pins V0 and the plurality of second pins D2 is more uniform, the current distribution in the winding is more uniform, and correspondingly, the winding loss is smaller. In general, preferably, when the total length d of the first pins V0 or the second pins D2 is greater than or equal to <NUM>/<NUM> of the winding length W, the winding loss is small and tends to be stable; the more the number of the first pinsV0 or the second pins D2, the smaller the winding loss; the more uniform the distribution of the first pins V0 or the second pins D2, the smaller the winding loss.

In the present example of <FIG>, only one schematic of the transformer module in a foil structure is shown, that is, the winding in the foil winding structure covers the four magnetic columns of the magnetic core. In fact, the winding in the foil winding structure can cover one magnetic column or a plurality of magnetic columns. This application does not limit this.

Further, the transformer module provided by some examples is easy to expand, and all the magnetic columns can be covered with a winding to improve the power of the transformer module. The magnetic columns can be lengthened and the winding can be widened to increase the power of the transformer module.

On the basis of example <NUM>, example <NUM> of the present disclosure further provides a transformer module, wherein the magnetic core of the transformer module further includes a second insulating layer and a third wiring layer beneath the second wiring layer, so the second insulating layer is at least partially covered by the second winding.

The transformer module further includes: a third winding on the third wiring layer and winds around the magnetic core in a foil structure, wherein the third winding is also at least partially covered by the second insulating layer; and a fifth surface-mounted pin which is located on the first side of the transformer module for electrically connecting the covered third winding.

<FIG> shows another example. Specifically, <FIG> shows a transformer with a primary winding P and center-tapped secondary windings S1 and S2. The primary winding P has two ends connected to the pins P1 and P2. One secondary winding S1 has two ends connected to the pins D1 and V0 while the other secondary winding S2 has two ends connected to the pins V0 and D2. S1 and S2 are connected in series on the common end which connects to the pin V0. <FIG> is the bottom view of the corresponding transformer of <FIG>. <FIG> is the bottom view of the transformer with winding S1. Referring to <FIG>, unlike the example shown in <FIG>, the third wiring layer is further added in this example, that is, the first wiring layer, the first insulating layer, the second wiring layer, the second insulating layer and the third wiring layer are respectively disposed from the outside to the inside on the magnetic core. The first wiring layer, the second wiring layer, and the third wiring layer are respectively used to form the first metal winding S2, the second metal winding P, and the third metal winding S1 which forms a "sandwich" transformer structure S1-P-S2. Assuming that the third winding <NUM> has, for example, one turn, as shown in <FIG>, and the third winding <NUM> wraps four magnetic columns of the hollow square shaped magnetic core, and forms two ends <NUM> and <NUM> on the bottom side of the magnetic core by the process e.g. etching, cutting, or the like etc..

<FIG> shows the bottom view of the transformer with the second insulating layer, the second wiring layer, the first insulating layer, the first wiring layer, winding outside the third wiring layer in sequence. So the third winding is at least partially covered by the second insulating layer. The two ends of the third winding <NUM> include a first end <NUM> connected to the fifth pin D <NUM> of the outermost layer through a third connector e.g. a via (not shown) for the electrical connection to an external circuit wherein pin D <NUM> may locate on the first side (for example, the bottom surface). The second end <NUM> of the third winding <NUM> is usually connected to one end of the first wiring layer winding, and is connected to the first surface-mounted pin V0 through the fourth connector e.g. a via (not shown), which is not limited in the present invention. That is to say, the two ends <NUM>, <NUM> pass through the second insulating layer, the second wiring layer and the first insulating layer. The first winding and the second winding are connected to the external pin in the same manner as the foregoing example, and the first winding connects the first surface-mounted pin V0 and the second surface-mounted pin D2, and the second winding connects the third surface-mounted pin P1 and the fourth surface-mounted pin P2.

Specifically, a base insulating layer may be selectively attached to the surface of the magnetic core by spraying or deposition, which is used for insulation, strengthening the bonding force, and protecting the magnetic core, but the invention is not limited to this, and the base insulating layer may not be disposed. And a third wiring layer, for example a copper layer, may be disposed on the surface of the magnetic core or the base insulating layer by electroplating or electroless plating; and then a metal protective layer, such as a tin layer or a gold layer, may be disposed on the surface of the third wiring layer by electroplating or electroless plating; then the metal protective layer is patterned by a writing process to expose a portion of the third wiring layer to be etched; and then patterns of the third wiring layer are etched under the protection of the protective layer to form a third winding; finally, the protective layer is removed to expose the third winding, that is, the secondary winding S1. Then, the second insulating layer is attached to the third metal winding by spraying or deposition, and then a second wiring layer, e.g. a copper layer is provided on the second insulating layer by electroplating or electroless plating; then a metal protective layer, such as a tin layer or a gold layer, is electroplated or electrolessly plated on the surface of the second wiring layer; and then the metal protective layer is patterned by a writing process to expose a portion of the second wiring layer to be etched; and then patterns of the second wiring layer are etched under the protection of the metal protective layer to form a second winding; finally, the protective layer is removed to expose the second metal winding, that is, as the primary winding P. Then, the first insulating layer is attached to the second metal winding by spraying or deposition, and then a first wiring layer, e.g. a copper layer is provided on the first insulating layer by electroplating or electroless plating; then a metal protective layer, such as a tin layer or a gold layer, is electroplated or electrolessly plated on the surface of the first wiring layer; and then the metal protective layer is pattern defined by a writing process to expose a portion of the first wiring layer to be etched; and then patterns of the first wiring layer are etched under the protection of the metal protective layer to form a first winding; finally, the protective layer is removed to expose the first winding, that is, as the secondary winding S2. However, the invention is not limited thereto, and other winding forming processes are also applicable.

An optional method, as shown in <FIG>, the fifth surface-mounted pins D1 have plural pins, locating between the first surface-mounted pin V0 and the second surface-mounted pin D2. Further, the second surface-mounted pin D2 further includes a plurality of teeth <NUM>, which are alternately arranged with the plurality of fifth surface-mounted D1 pins. Optionally, the plurality of teeth <NUM> are evenly alternately arranged with the plurality of fifth surface-mounted pins D1. The plurality of fifth surface-mounted pins and plurality of second surface-mounted pins are used to connect multiple sets of switches and help to reduce impedance and improve integration. The more even distribution the pins D <NUM>, D2 has, the more even current distribution of current the transformer has. And the smaller impedance the transformer has. Optionally, the surface-mounted pins may be columnar or spherical, etc., and the invention is not limited thereto.

Alternatively, <FIG> is a bottom view of another transformer module provided by an example. In contrast to <FIG>, the fifth pin D1 is located between the first pin V0 and the second pin D2. The magnetic core may include a through hole <NUM>, the fifth pin D1 partially surrounds the through hole <NUM>, for example, the fifth pin D1 has a C-shape. From the bottom view of the transformer module, the first pin V0 is a hollow square shaped pin surrounding the through hole <NUM>, and the second surface-mounted pin D2 is C-shaped partially surrounding the through hole <NUM>. However, the present invention is not limited thereto. By adjusting the positions of the third pin P1 and the fourth pin P2, the first, second, and fifth pins may also form other shapes such as the hollow square shape surrounding the through hole. Shapes such as C-shape, hollow square-shape can increase the connection strength with external modules and are suitable for connecting multiple modules.

<FIG> are schematic diagrams of a power module provided by an example with corresponding ends marking on them. <FIG> are respectively cross-sectional views of power modules of <FIG>. With reference to <FIG>, the power module includes: a transformer module <NUM> as in various examples; and a switch module <NUM>, the switch module <NUM> and the first side (for example, the bottom surface having a pin) of the transformer module <NUM> are in contact and electrically connected to the first pin V0 and the second pin D2.

As shown in <FIG> and <FIG>, the power switch <NUM> is electrical connected to the first pin V0. <FIG> shows that the switch module may also include at least one full bridge circuit formed by four power switches (such as MOSFETs), and the full bridge circuit is electrically connected to the first pin V0 and the second pin D2. Optionally, the switch module <NUM> may include a board <NUM> and at least one power switch <NUM> which is embedded or molded in the board <NUM> as shown in <FIG>. And the power switches may be disposed on the board <NUM> (not shown). According to the practical application of the circuit topology, different types of power switches can be selectively electrically connected to the first pin and/or the second pin, the present invention is not limited to this, and the power switch can also be connected to other pins. Take <FIG> as an example, SR <NUM> may be connected between the first pin Vo and the output pin GND or between the second pin D2 and the output pin VOUT according to different topology. Each power switch shown in the figures can be connected in parallel by multiple power switches according to the output power of the actual transformer. As shown in <FIG>, the power switch may be located on the lower surface of the transformer module, or the power switch may also be located on the upper surface of the transformer module, which is not limited in the present disclosure.

Wherein, the power switch can be a diode, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT) and the like.

Specifically, the bare die of one or more parallel power switches SR can be directly integrated into a board by an embedded process to form the switch module, but the disclosure is not limited thereto. The power switch can be placed just below the pins of the transformer module for easy connection to the pins. Referring to <FIG>, in this example, although the numbers of the first pin V0 and the second pin D2 are both one, if the size of the power switch or the size of the external connection pin of the switch module is smaller than the size of the transformer module, a plurality of parallel SRs can be connected to the pins, and the SRs can be evenly distributed or unevenly distributed on the pins. The example shown in <FIG> can also be similarly set. Referring to <FIG>, in this example, the plurality of fifth pins D1 and the teeth of the plurality of second pins D2 can be used to connect a plurality of power switches. <FIG> is a bottom view of the switch module provided by an example. As shown in <FIG>, the lower surface of the board may form an output pin, such as VOUT, GND, and the like. Then the corresponding transformer module is welded to the board to form a power module, as shown in <FIG>.

Alternatively, one or more parallel SRs are firstly welded to the surface of the board, then the switch module is formed by a molding process, the other surface of the board forms a pad corresponding to the transformer module, and the transformer module is welded on the corresponding surface of the board to form the power module.

Further, the power module further includes a capacitor module disposed on the board and disposed adjacent to the transformer module. As shown in <FIG> and the like, the capacitor module can be electrically connected to the second pin D2. In another example, as shown in <FIG>, the capacitor module can be electrically connected to the first pin V0, and the invention is not limited thereto. The power module may further include an LLC power unit, a controller, etc., so that the power module is used as an LLC converter. Specifically, <FIG> is a cross-sectional view of a power module provided by an example, as shown in <FIG>, Co is the output capacitor. In <FIG>, Co is placed on the switch module and beside the transformer. When the core of the transformer is a square or circle shape, Co may be place inside the through hole of the core, e.g. the hole of the core in <FIG>. Furthermore, Co may be placed on the board of the switch module or even embedded inside the board of the switch module.

It should be noted that the above power module is not limited to the LLC converter, and is also applicable to any circuit including a transformer module, such as a flyback converter, a full bridge circuit, and the like.

On the basis of the example <NUM>, the present disclosure further provides a power module, wherein the power module includes a transformer module similar to the example <NUM>, and the second insulating layer and the third wiring layer are sequentially disposed on the magnetic core, and the second insulating layer is at least partially covered by the second metal winding. The transformer module further includes: a third metal winding formed in the third wiring layer winded around the magnetic core in a foil structure, wherein the third winding is at least partially covered by the second insulating layer; and a fifth pin, the fifth pin is located on a first side (e.g., a bottom surface) of the transformer module, and a first end of the third winding is electrically connected to the fifth pin D1 through the third connector, such as via, the second end of the third winding is electrically connected to the first pin V0, and the rest is not described herein.

<FIG> is an electrical schematic diagram of a power module provided with plurality of ends marking on it by an example. As shown in <FIG>, the secondary windings S <NUM> and S2 of the center-tapped transformer are connected to a first power switch, a second power switch and a cap respectively. And after the transformer module and the switch module are stacked, the switch module is further electrically connected to the fifth pin.

Further, as shown in <FIG>, the power module further includes a first power switch (SR) and a second power switch (SR), wherein the first end of the first power switch is electrically connected to the second pin D2, the first end of the second power switch is electrically connected to the fifth pin D1, and the second end of the first SR and the second end of the second SR are electrically connected, but the invention is not limited thereto, and each of the illustrated power switches may actually be equivalently connected in parallel by a plurality of power switches depending on the power level of the device.

Further, the power module further includes a capacitor module, for example, as an LC resonant capacitor or an output capacitor, and the present invention is not limited thereto. Further, the capacitor module is disposed on the board and adjacent to the transformer module, and the capacitor module is electrically connected to the first pin V0, as shown in <FIG>, and Co is an output capacitor. In some other examples, the capacitor may also be located adjacent to the same side of the switch device SR on the carrier board; or the capacitor may also be embedded in the carrier board; or the capacitor may be placed in the through hole of the transformer, when the transformer core of <FIG> is a hollow square shape, etc.; even if the capacitor is placed on the upper surface of the magnetic core, the power switch SR is placed on the lower surface of the magnetic core. Wherein, the power module may further include an LLC primary power unit, a controller, etc., such that the power module functions as an LLC converter.

It can be seen that the power module is easy to be modular produced. First, multiple power switches SRs are integrated on one board to form multiple switch modules. Then, multiple transformer modules are surface mounted to the corresponding switch modules, thus multiple power modules with a common board come into being, wherein each power module has one switch module and one transformer module stacked on the switch module. And finally separate the power modules by e.g. cutting process, so that independent multiple power modules can be produced at one time, but the invention is not limited thereto.

Further, the power switches are directly connected to the plurality of output Pins of the transformer module, and the connection loss is small; the primary and secondary circuits of the transformer module are directly coupled to each other, the AC impedance of the windings is small, and the AC loss is small, but the present invention is not limited to this.

In some examples including example <NUM> and example <NUM>, the correspondence of the surface-mounted pins is (but not limited to):.

However, in some other examples, such as in the embodiment <NUM>, for the convenience of description, the electrical connection points corresponding to the pins are not the same as the corresponding electrical connection points in the foregoing examples, the present disclosure is not limited to this.

In the above examples that do not form part of the present invention, respective windings of the transformer are located in the same wiring layer. <FIG> is a cross-sectional view of the transformer module of <FIG> taken along line AA', from which it can be seen that the windings are respectively located in the first, second, and third wiring layers, wherein the first, second and third wiring layers are arranged in order from the outside to the inside. In <FIG>, the connecting via between the first end of the winding S <NUM> in the third wiring layer and the second pin D <NUM> is represented by a dash line while the via between the second end of the winding S1 and V0 is represented by a shadow area, because the via connecting the first end of the winding and D1 is not in the cross section along AA'. And <FIG> shows that one winding is substantially on one wiring layer.

According to the present invention, the windings are placed in a staggered manner, that is to say that different parts of the same winding are located in different wiring layers, for example in two wiring layers. A cross-sectional view of such a winding arrangement is shown in <FIG>. As shown in <FIG>, <NUM> is a magnetic core; a first metal winding wound around the magnetic core <NUM> in a foil structure includes a first winding segment <NUM> formed in the first wiring layer and a second winding segment <NUM> formed in the second wiring layer, the first end of the first winding segment is electrically connected to the first end of the second winding segment through a via, and the second end of the first winding segment is electrically connected to the first pin V0 through a via, the second end of the second winding segment is connected to the second pin D1; the second metal winding also winds around the magnetic core <NUM> in a foil structure, and includes a third winding segment <NUM> disposed on the first wiring layer and a fourth winding segment <NUM> formed in the second wiring layer, the first end of the third winding segment is connected to the first end of the fourth winding segment through a via, and the second end of the fourth winding segment forms a third pin D2. As shown in the figure, the second end of the third winding segment is connected to the first pin V0 through a via. Thus, the first and second windings form a connection structure of the transformer secondary windings S <NUM>, S2 as shown in <FIG>. The winding P of the transformer in <FIG> is the third metal winding <NUM> on the third wiring layer in <FIG>, and the third wiring layer and the second insulating layer may be sequentially located between the first insulating layer and the second wiring layer. The secondary windings S1, S2 in <FIG> are arranged by a staggered arrangement method, which greatly improves the symmetry between the two windings compared to the arrangement mode of the same winding being located in the same winding layer as shown in the <FIG>, and the current sharing effect of the current flowing through the first SR, the second SR during the working process of the circuit is significantly improved. In addition to the winding of <FIG>, this way of staggered layer arrangement can be used in the winding of <FIG>, that is to say, and the first and second metal windings, such as winding P and winding S2 in <FIG> may also become the windings lay on different wiring layer just as the windings shown in <FIG>.

The design of the pins can be similar to other embodiments in the present disclosure, for example, there are a plurality of third pins D2, the second pin D1 includes a plurality of teeth, and the plurality of teeth and the plurality of third pins D2 are alternately arranged; or the numbers of the second and third pins are both plural, and the plurality of second pins and the plurality of third pins are alternately arranged and so on, as shown in <FIG> is a bottom view of the transformer in an embodiment of the present application, including a first pin V0, a second pin D1, and a third pin D2, wherein the first pin V0 is located between the second pin D1 and the third pin D2, the length of each pin is almost equal to the average length of the winding; the first, second and third pins can be either a hollow square shape or a plurality of pins being distributed on a part of the windings as shown in <FIG>. And the plurality of pins are symmetrically arranged, the present application is not limited to this.

The corresponding power module may include a switch module, and the switch module is in contact with the first side of the transformer module. The switch module can include a board and at least one power switch. Similar to <FIG>, the switch module includes a plurality of first SRs and a plurality of second SRs; a first end of the first SR is connected to the first pin D1, and a first end of the second SR is connected to the third pin D2, a second end of the first SR is electrically connected to a second end of the second SR. According to different pins of the transformer, the plurality of first SRs (i.e., SR1 in <FIG>) and the plurality of second SRs (i.e., SR2 in 9E) can be separated into two rows as shown in <FIG> is a schematic illustration of a portion of the transformer and the switching elements disposed thereon, taken along the dashed line in <FIG>. The portion of the transformer module includes three pins D1, D2 and V0. The pin V0 is located between D1 and D2. There is a switch module on the transformer module, and the switch module includes a plurality of SR1s and a plurality of SR2s. The plurality of SR1s and the plurality of SR2s are separated into two rows. The switch module is in contact with one side of the transformer. In addition, the power switches can also be arranged in the same row, wherein SR1 and SR2 are arranged in a staggered manner, and the present application is not limited thereto. Of course, the switch module can also include a carrier board, and the switch can be placed on the carrier board or embedded in the carrier board.

Further, the power module may further include a capacitor module disposed on the board and disposed adjacent to the transformer module, and the capacitor module is electrically connected to the first pin or the second pin. The present disclosure is not limited to this. For example, the capacitor may be located below the carrier board, as shown in <FIG>, the capacitor Co is located below the power switch. And the capacitor Co can also be buried in the carrier board or placed on the other side of the transformer opposite the switch module, such as the upper side of the transformer module in <FIG>; And the capacitor Co can also be placed in the through hole of the magnetic core. In short, the location of the capacitor module is varied.

In the circuit diagram shown, for example, in <FIG>, if the secondary windings S <NUM> and/or S2 are separately segment formed to lead the connection ends on different sides of the transformer module, the positions of the first SR and/or the second SR are not necessary limited to the bottom surface of the transformer module, but are electrically connected in series in the corresponding metal windings by pins S1', D1, and/or S2', D2 in <FIG>, devices may be flexibly disposed on multiple surfaces, which is beneficial to optimize the spatial distribution. This portion will be further described in Examples <NUM> to <NUM>.

In the previously described examples, the windings of the transformer are formed by electroplating, and the pins are led out through via holes, but the disclosure is not limited thereto. As shown in <FIG>, the winding of the transformer is a winding layer formed by electroplating or electroless plating, and the pins D1 and V0 are connected to the inner layer winding through via holes, but the invention is not limited thereto.

In fact, the winding of the transformer can also be formed by metal foil in a foil structure, such as copper foil. <FIG> is a cross-sectional view of a transformer in an example that serves an illustrative purpose and does not form a part of the present invention. As described in the example <NUM>, the transformer module includes a first metal winding <NUM>, a second metal winding <NUM>, and a third metal winding <NUM> from the outside to the inside. The initial insulating layer is located between the third metal winding and the magnetic core, and the second insulating layer is located between the third and second metal windings, and the first insulating layer is located between the second and first metal windings. Wherein the second metal winding <NUM> can be used as the primary winding P, the third wiring layer metal winding <NUM> can be used as the secondary winding S1, and the first wiring layer metal winding <NUM> can be used as the secondary winding S2 to form the "sandwich" structure of the secondary windings sandwiching the primary winding. The third metal winding <NUM> is a whole copper layer covering the magnetic core column <NUM>, so the magnetic core column <NUM> is at least partially covered by the initial insulating layer and the third metal winding <NUM>, and similarly, the third metal winding <NUM> is also at least partially covered by the second insulating layer and a second metal winding <NUM>, and the second metal winding <NUM> is at least partially covered by the first insulating layer and the first metal winding <NUM>.

Similar to the example <NUM>, the third metal winding <NUM> includes two ends, which are a first end and a second end, wherein the first end is connected to the fifth pin of the outermost layer, for example, the pin D1, for electrical connection to the outside. The second end of the third metal winding <NUM> is typically connected to one end of the first metal winding <NUM> and is commonly connected to the first pin of the outermost layer, such as pin V0. The first and second ends of the third winding pass through the second insulating layer, the second winding layer, the first insulating layer and the first winding layer. Different from the example <NUM>, the first end of the third metal winding <NUM> and the second end of the third metal winding <NUM> are not led out by via holes. <FIG> illustrate one approach of making metal winding using one-piece metal foil.

First, a whole piece of metal foil, such as a copper foil, is cut into a structure as shown in <FIG> (i.e., an expansion view of the third metal winding). A "⊥"-shape structure as shown in the figure is cut on the two parallel sides of the copper foil, and the structure is used to form the pins <NUM>, <NUM> of the winding; then, the copper foil is folded according to the dot dash lines in the figure. The folded shape is as shown in <FIG>. Then, a long strip of copper foil as the second metal winding of the transformer is used to wind around the surface of the third metal winding, and the respective erected pins <NUM>, <NUM> of the third metal winding are avoided during the winding process, as shown in <FIG>; finally, a first metal winding is fabricated using a process similar to that of fabricating the third metal winding. A whole piece of copper foil is cut and folded into a first metal winding as shown in <FIG>, and holes <NUM> corresponding to the pins <NUM>, <NUM> of the third metal winding are cut at one end of the first metal winding to let the pins of the third metal winding protrude from the holes (in the figure, there are two holes <NUM> for the pins <NUM>, <NUM> passing through, in fact, the two holes can be opened into one hole); finally, an insulation treatment is performed on the pin of the first end of the third metal winding, and then is bended and then lays on the surface of the first metal winding to form a fifth pin D1, the pin of the second end of the third wiring layer metal winding is bended and then lays on the surface of the first wiring layer metal winding for connecting to form a first pin V0, as shown in <FIG>.

In some examples, there may be a plurality of first, fifth, and second pins, and the plurality of first pins V0 are located between the fifth pins D1 and the second pins D2, and the first, second, and fifth pins are separately arranged in a row, as shown in <FIG>, and the application is not limited thereto.

In this example, at least one of the connectors, the corresponding metal winding, and the corresponding pin are in one piece, and the connector passes through the insulation layer to connect with the pin. As described above, the "corresponding" means contact each other. For example, the pins of the third metal winding are bent on the surface of the first winding after passing through the insulating layer between the third winding and the second winding, and the insulating layer between the second winding and the first winding.

Taking the insulation of the third metal winding <NUM> as an example. The insulation requirement of the third metal winding includes an initial insulating layer on the inner side and a second insulating layer on the outer side thereof. The initial insulating layer is used for insulation from the magnetic core column <NUM>, and the second insulating layer is used for insulation from the second metal winding <NUM>. The thickness requirement of the insulating layer depends on the interlayer withstand voltage and the interlayer distributed capacitance. For example, in this case, the thickness of the insulating layer is required to be <NUM>. In addition, the insulating layer shall be windable, to avoid peeling from the metal layer during bending.

In response to these requirements, and how to effectively process insulating layers between different metal wiring layers and between a wiring layer and a magnetic core column, the present application provides a new method of manufacturing an insulating layer. In the first step, a surface roughening treatment is performed on the cut metal copper, such as the third metal winding shown in <FIG>, including mechanical grinding or chemical roughening and browning, in which brown oxidation treatment is optimal. The purpose of surface roughening is to increase the contact surface area between the metal layer and the insulating material, thereby increasing the adhesion of the insulating material, and ensuring that delamination and peeling between the metal layer and the insulating material do not occur during subsequent bending. In the second step, the base insulating layer <NUM> by the first insulating process is formed on the metal layer <NUM> after the surface roughening, as shown in <FIG>. Insulation modes include electro-deposition, spraying or printing etc. Among them, the electro-deposition mode is preferred, which has the lowest requirement on the shape of the metal layer, and is more reliable for the insulation of some parts that are difficult to process, such as the corners of the metal layer, and the adhesion performance is also better. For example, the electro-deposition can be acrylic electric coating, which is composed of polyacrylic resin and polyurethane hardener. The portion <NUM> where the connecters and pins are required can be avoided by covering and shielding in advance. In the third step, the additional insulating layer <NUM> by the second insulating process is formed after the base insulating layer, as shown in <FIG>. The thickness of the insulating layer that can be made by the mode of electro-deposition is relatively limited, and typically, the thickness is between <NUM> and <NUM>. Therefore, when the thickness of the insulating layer is required to be greater than <NUM>, an additional insulating layer may be required. The additional insulating layer may be formed by, for example, providing an insulating glue1008, as shown in <FIG>. Wherein, the additional insulating layer is not limited to insulating glue, and may also be fabricated by a photoresist film, local dispensing, and the like. In order to avoid cracking of the insulating layer while bending the metal layer, partial insulating layer may be performed as shown in <FIG> is a schematic cross-sectional view of the metal layer before being bent, and <FIG> is a schematic cross-sectional view of the metal layer after being bent. As shown in the <FIG>, there is no insulating material in the corner portion that need to be bent. The second insulation process increases the total thickness of the insulating layer. Wherein, this step is not essential. In the case where the thickness requirement is not high, the base insulating layer may meet the requirements. Finally, optionally, an adhesive layer may be coated after the insulating layer to achieve bonding and fixing between the plurality of metal wiring layers.

The manufacturing process of a metal winding is summarized as shown in <FIG>. Step S1, cutting a metal copper foil to form the connector and the pin; step S1. <NUM>: roughening the surface of at least one of the first mental copper foil and the second metal copper foil; step S2. <NUM>: a first insulation process is performed on the surface of the at least one of the first metal copper foil and the second metal copper foil to form an inner base insulating layer; step S2. <NUM>: a second insulation process is performed on the surface of inner base insulating layer of the metal copper foil to form an outer additional insulating layer; step S2. <NUM>: coating an adhesive layer on the surface of at least one of the first metal copper foil and the second metal copper foil; step S3: bending the first metal copper foil to form a first metal winding to cover on the magnetic core. Step S4: the second metal copper foil is at least partially covered on the surface of the first metal winding to form the second metal winding, and the pins of the first metal winding pass through the second metal winding. Step S5: cutting the third metal copper foil to form hole or gap, and bending the third metal copper foil to at least partially cover the second metal winding to form a third metal winding, and the pins of the first metal winding pass through the hole or gap.

Wherein, step S1. <NUM>, step S2. <NUM>, and step S2. <NUM> are all optional steps. It should be noted that the present application does not limit the order before the foregoing steps. For example, step S2. <NUM> and step S2. <NUM> may be performed before step S1, or may be performed after step S1. In some examples, the second metal copper foil in step S4 may be a long strip copper foil, which is wound on the surface of the first metal winding as the second metal winding, and forming a hole or a gap during the winding process to let the pins of the first metal winding pass through.

The corresponding power module can be referred to the power module in embodiment <NUM>, and details are not described herein again.

In the circuit diagram shown, for example, in <FIG>, if the secondary windings S1 and/or S2 are separately segmented to lead out the connection ends on different sides of the transformer module, the positions of the first SR and/or the second SR are not necessarily limited to the bottom surface of the transformer module, but they are electrically connected in series in the corresponding metal windings by the pins S1', D1, and/or S2', D2 in <FIG>, which can be flexibly arranged on multiple surfaces. It is beneficial to optimize the spatial distribution. This section will be further described in examples <NUM> to <NUM>.

<FIG> are respectively structural schematic diagrams of the transformer module provided by an example that serves an illustrative purpose and does not form a part of the present invention. <FIG> is a cross-sectional view of the transformer module provided by an example that serves an illustrative purpose and does not form a part of the present invention taken along the line AB shown in <FIG>. <FIG> is a cross-sectional view of a transformer module provided by an example that serves an illustrative purpose and does not form a part of the present invention taken along the line AB of <FIG>, and the broken lines in <FIG> indicate the omitted portion. Specifically, with reference to <FIG> and <FIG>, the transformer module includes:.

Optionally, with reference to <FIG> and <FIG>, the transformer module further includes:
a second metal winding winds around the magnetic core <NUM> in a foil structure includes a third winding segment <NUM> formed in the first wiring layer and a fourth winding segment <NUM> formed in the second wiring layer, and the first end of the third winding segment <NUM> is connected to the fifth pin D2 through the via <NUM>, the second end of the third winding segment <NUM> is electrically connected to the second pin V0, and the first end of the fourth winding segment <NUM> forms a sixth pin S2', the second end of the fourth winding <NUM> is electrically connected to the fourth pin GND, and the fifth pin D2 and the sixth pin S2' are both located on the first side of the transformer module. In an application example, the third metal winding <NUM> can be used as the primary winding P, the first metal winding can be used as the secondary winding S1, and the second metal winding can be used as the secondary winding S2, for example corresponding to <FIG>.

Optionally, after the corresponding electronic device, such as a switch, is electrically connected to the fifth pin D2 and the sixth pin S2', the third winding segment <NUM> formed in the first wiring layer and the fourth winding segments <NUM> formed in the second wiring layer are electrically connected in series.

Optionally, the transformer module may include the first metal winding and the second metal winding, and the third metal winding as well as the corresponding wiring layer and the insulating layer between the adjacent layers are not highlighted, and the first winding and the second winding are respectively used as the primary winding P and the secondary winding S1 of the transformer module, for example, corresponding to <FIG>. This disclosure is not limited to this.

Optionally, the vias may be located at about middle points of the first metal winding <NUM> and the second metal winding <NUM>. For example, assuming that both the first winding and the second winding have one turn, the first winding segment <NUM>, the second winding segment <NUM>, the third winding segment <NUM> and the fourth winding segment <NUM> are about half turn winding around the magnetic core <NUM>, but the present disclosure is not limited thereto, and the number of turns of the first metal winding and the third metal winding are not limited to one.

Optionally, the first side and the second side of the transformer module are opposite sides. For example, the first side of the transformer module may be the upper surface of the transformer module, and the second side of the transformer module may be the lower surface of the transformer module. Alternatively, the first side of the transformer module can be one side of the transformer module and the second side of the transformer module can be a different side of the transformer module. The specific positions of the first side and the second side are not limited in the present disclosure.

Optionally, the magnetic core is hollow square shaped, ring-shaped, I-shaped or C-shaped.

Optionally, the number of turns of the first metal winding is one turn, the number of turns of the third metal winding is a plurality of turns to form a spiral type winding around the magnetic core, and the number of turns of the second metal winding is one turn.

The distribution of the first pin D1, the fifth pin D2, the third pin S1', and the sixth pin S2' of the transformer module will be described below:
As an alternative, <FIG> is a top view of a transformer module provided by an example that serves an illustrative purpose and does not form a part of the present invention. As shown in <FIG>, the number of the first pin D1 is plural, and the number of the fifth pin D2 is plural. And the plurality of first pins D1 and fifth pins D2 are alternately arranged, and the plurality of first pins D1 and the plurality of fifth pins D2 are located between the third pin S1' and the sixth pin S2'.

As another alternative, <FIG> is a top view of a transformer module provided by another example that serves an illustrative purpose and does not form a part of the present invention. As shown in <FIG>, the first D1, the fifth pin D2, the third pin S1' and the sixth pin S2'are both hollow square shaped, wherein the first pin D1 and the fifth pin D2 are both located between the third pin S1' and the sixth pin S2'. When the output pins of the second winding are disposed on the first side, the pin located on the first side, such as the first pin D1, the fifth pin D2, may also be other shapes such as C-shaped, which are not limited in this disclosure.

<FIG> is a bottom view of a transformer module provided by an example. As shown in <FIG>, an output PIN, such as VOUT, GND, etc., may be formed on a lower surface of the transformer module. In <FIG>, the pin VOUT is placed between two GND pins. <FIG> is a bottom view of a transformer module provided by another example. As shown in <FIG>, an output PIN, such as VOUT, GND, etc., may be formed on the lower surface of the transformer module. In <FIG>, the multiple pins VOUT are distributed almost evenly in the one big pin GND.

An example further provides a transformer module, since a transformer winding with a foil winded structure is coated on a transformer magnetic column, so that the equivalent diameters of respective parts of the winding having the foil winded structure are similar to each other, and the equivalent impedances are similar, thereby achieving the effect of even winding distribution.

<FIG> is a cross-sectional view of a power module provided by another example. As shown in <FIG>, the power module includes:.

Optionally, the switch module <NUM> includes a board <NUM> and at least two power switches (SR) <NUM>. As shown in <FIG>, the switch module <NUM> includes power switches (SR) <NUM>, which are disposed in the board <NUM> by the molding, embedded process etc.. At least one first SR is electrically connected to the first pin D1 and the third pin S1', and at least one second SR is electrically connected to the fifth pin D2 and a sixth pin S2'. Wherein, the power switch may be located on the lower surface of the transformer module, or the power switch may be located on the upper surface of the transformer module, which is not limited in this disclosure.

Specifically, the switch module is formed by directly integrating bare dies of one or more parallel SRs in a board by an embedded process. Pads corresponding to the transformer module's pins are formed on the lower surface of the board, and the switch module and the transformer module are soldered together to form a power module.

Alternatively, one or more parallel SRs are first welded to the surface of the board, and then the switch module is formed by a molding process, and a pad corresponding to the transformer module is formed on the other surface of the board, and the transformer module is welded on the surface of the board to form the power module.

Further, the power module further includes: a capacitor module, wherein the capacitor module is in contact with the second side of the transformer module and is electrically connected to the second pin and the fourth pin. Specifically, the power module may further include an LLC primary power unit, a controller, etc., so that the power module functions as an LLC converter. Alternatively, the capacitor module includes an output capacitor Co. The capacitor module may be placed on the switch module and beside the transformer. When the core of the transformer is a square or circle shape, the capacitor module may be place inside the through hole of the core, e.g. the hole of the core in <FIG>. Furthermore, the capacitor module may be placed on the board of the switch module or even embedded inside the board of the switch module. Furthermore, the capacitor module may be placed on one side of the transformer module e.g. the topside of the transformer module while the switch module is placed on the other side of the transformer module e.g. the bottom side of the transformer module or the adjacent sides of the top side of the transformer.

Alternatively, the power module may only include a primary power unit, a resonant unit, a controller, and an output capacitor.

<FIG> is a top view of a power module provided by another example that serves an illustrative purpose and does not form a part of the present invention. As shown in <FIG>, the power module includes:.

Wherein, the SR may be a diode, a MOSFET or an IGBT or the like. The first SR and the second SR may be respectively encapsulated as switch modules, or may be integrated into a switch module. The disclosure is not limited to this.

In the example <NUM> to the example <NUM>, the first metal winding and the second metal winding S1 and/or S2 in the circuit diagram shown in <FIG> may be separately segmented formed to lead out connection ends on different sides of the transformer module.

In some examples, such as Example <NUM> to Example <NUM>, the correspondence of the surface-mounted pins is (but not limited to):.

However, in the example <NUM> to the example <NUM>, for the convenience of description, the electrical connection points corresponding to the surface-mounted pins are different from the corresponding electrical connection points in the example <NUM> to the example <NUM>, the present disclosure is not limited to this.

The transformer module of the foregoing examples may also lead the two ends of the third metal winding to the pins and may be led out to the first side, the second side or the other side, and the present disclosure is not limited thereto. The shape of the pin is not limited to the square-shape, C-shape, or other shapes shown in the figures, and can be flexibly changed according to the actual application.

Each of the metal windings of the transformer module of the foregoing examples can flexibly correspond to the primary winding and the secondary winding of different types of transformers, and can be used, for example, for the ordinary transformer of <FIG> or for the secondary tapped transformer of FIG. 4E (related to the two secondary windings in series), and can also be used for transformers with multiple independent secondary winding, etc., the disclosure is not limited to this.

Claim 1:
A power module, comprising:
a transformer, comprising:
a magnetic core (<NUM>, <NUM>) comprising at least one magnetic column, a first wiring layer, a first insulating layer and a second wiring layer, the first wiring layer, the first insulating layer and the second wiring layer being sequentially disposed on the magnetic core (<NUM>, <NUM>) from inside to outside;
a first metal winding, wound around the magnetic core (<NUM>, <NUM>) in a foil structure, comprising a first winding segment (<NUM>) formed in the first wiring layer and a second winding segment (<NUM>) formed in the second wiring layer, wherein a first end of the first winding segment (<NUM>) is electrically connected to a first end of the second winding segment (<NUM>) through a first connector, a second end of the first winding segment (<NUM>) is electrically connected to a first pin (V0) through a second connector, and a second end of the second winding segment (<NUM>) electrically connects to a second pin (D1);
a second metal winding, wound around the magnetic core (<NUM>, <NUM>) in the foil structure, comprising a third winding segment (<NUM>) formed in the first wiring layer and a fourth winding segment (<NUM>) formed in the second wiring layer, a first end of the third winding segment (<NUM>) is electrically connected to a first end of the fourth winding segment (<NUM>) through a third connector, a second end of the third winding segment (<NUM>) is electrically connected to the first pin (V0) through a fourth connector and a second end of the fourth winding segment (<NUM>) electrically connects to a third pin (D2); wherein the first connector, the second connector, the third connector and the fourth connector each pass through the first insulating layer;
wherein with the foil structure, a dimension of a winding parallel to a longitudinal direction of the magnetic column is W, a thickness of the winding which is a dimension of the winding vertical to the magnetic column is H, and H and W satisfy a relationship: W><NUM>.