Planar transformer and LLC converter

Abstract

The present disclosure relates to a planar transformer (1), in particular for a DC / DC converter, comprising: a magnetic core assembly (2) comprising at least one plate portion (3) and a plurality of legs (4) extending from the plate portion (3); a secondary side (50) having at least one secondary winding (5); and a primary side (60) having a plurality of primary windings (6); wherein the at least one secondary winding (5) and the plurality of primary windings (6) are stacked in a stacking direction (8) parallel to the extension direction (9) of the leg (4) into a plurality of layers (7), the plurality of primary windings (6) of different layers (7) are connected to one another, and the total surface area of the primary windings (6) of at least two layers (7) of the primary windings (6) is different. The disclosure also relates to an LLC converter (100, 200).

Description

Technical Field

[0001] The present disclosure relates to planar transformers, and in particular to planar transformers for use in DC / DC converters and LLC converters. Background Art

[0002] Planar transformers, DC / DC converters using the planar transformers, and LLC converters including such planar transformers are well known. Typically, during the use of the device, especially due to the compact size of the planar transformer, there are electromagnetic interference problems between the primary side and the secondary side. Specifically, disadvantageously, the planar transformer generates common-mode currents, which are caused by relatively high coupling capacitances, and this relatively high coupling capacitance is caused by the compact size of the planar transformer and the tightly stacked windings that are usually used. For example, the common-mode coupling capacitance may be five to ten times larger than that of a conventional wound transformer of the same type (in terms of usage and / or electrical characteristics). A common solution to these problems is to use a shielded winding between the primary and secondary windings to reduce or compensate / balance the common-mode currents and the noise and losses they generate.

[0003] For example, EP3696831A1 discloses a planar transformer having primary and secondary windings in winding layers and having charge balancing windings as shielding windings, which are arranged between the primary and secondary windings of the planar transformer according to the stacking direction to reduce or balance the common mode current. These charge balancing windings are complementary to the primary and secondary windings of the planar transformer.

[0004] CN211719418U also discloses a planar transformer having a plurality of additional shielding windings arranged between the primary and secondary windings along the stacking direction thereof.

[0005] However, these known solutions using shield windings bring a number of additional challenges. On the one hand, adding the shield winding layer significantly increases the distance between the primary and secondary windings, especially since these windings need to be electrically insulated from each other, thus reducing the inductive coupling efficiency of the planar transformer and thus also increasing its size. Furthermore, the current induced in the shield winding is a loss, since it does not participate in the core function of the transformer, namely the voltage transformation between the primary and secondary sides. Summary of the invention

[0006] One object of the present disclosure is to provide a planar transformer capable of compensating for common mode currents while being efficient and compact. Another object is to provide an LLC converter having these advantages.

[0007] In particular, a solution to these purposes can be achieved by a planar transformer provided by the present disclosure, which is particularly useful for DC / DC converters. The planar transformer includes a core assembly. The core assembly includes at least one plate portion and a plurality of legs extending from the plate portion. The planar transformer also includes a secondary side having at least one secondary winding and a primary side having a plurality of primary windings. Wherein, at least one secondary winding is stacked in layers with a plurality of primary windings along a stacking direction parallel to the extension direction of the legs of the core assembly. Multiple primary windings of different layers are connected to each other. Wherein, for at least two layers of primary windings, the total surface area of ​​the primary windings between them is different. For example, the total surface area of ​​one layer of primary windings is different from the total surface area of ​​the primary windings of another layer (or one or more other) of primary windings.

[0008] By using different total primary winding surface areas between at least two layers of the primary winding, the electrical coupling capacitance between the primary and the secondary is different with respect to the different layers of the primary winding, so that the common mode current capacity caused by the coupling capacitance is also compensated. In addition, due to the compensation of the common mode current, the middle point of the primary winding can be maintained at a substantially stable or quasi-stable potential. In this regard, the term "quasi-stable" refers to the stability of the potential at or near the switching frequency. In addition, the use of shielding layers is avoided, thereby saving space and reducing losses, that is, improving efficiency.

[0009] For ease of understanding, in this context, the term "a layer of winding" (layer winding) refers to all parts or segments of the coil of this layer. This includes parts or segments wound around different legs within this layer. In other words, within this layer, parts or segments wound around one leg and other parts or segments wound around another leg are collectively referred to as "a layer of winding". The term "winding layer", i.e. the winding layer of a planar transformer, refers to all its parts (coil parts) located in the same single plane, including parts at least partially wound on different legs. The winding layers are stacked (layered) parallel to the extension direction of the legs (also called the center axis), in particular, each layer (the extension plane of each layer) is perpendicular to the extension direction of the legs.

[0010] Furthermore, it should be noted that the terms "primary", "secondary", "primary side", "secondary side" and the corresponding windings are preferably only relative to the transformer, just to distinguish the two sides. However, it is well known that the input and output of the transformer can be switched, so that essentially, the above-mentioned "secondary side" will correspond to "input" and the "primary side" will correspond to "output".

[0011] Furthermore, the term "turns" will be used. Here, the term "turns" refers to at least a portion (of a primary winding) which has a curvature with a radius of the radial center of the leg in question. In other words, when referring to a winding or a winding portion having turns around a leg, the winding or winding portion has a curvature whose radial center, in a cross section perpendicular to the direction of extension of the leg, is located within the leg, in particular at the center of the leg. In other words, turns around a leg means that the winding or a portion of the winding is bent around the leg and preferably corresponds to the leg in shape. Along the basic extension of the winding or the winding portion, the winding may include a curvature inflection point, which is characterized by the fact that the winding basically switches (along its extension) from being wound on one leg to being wound on the other leg. In other words, the inflection point distinguishes a winding wound around one leg from a winding wound around the other leg.

[0012] Furthermore, the number of turns of a layer is preferably defined as the total number of turns of the winding around all legs in the layer. In particular, a full turn is defined as a winding that completely surrounds a leg, i.e., 360° around. A full turn can be formed by combining multiple layers of primary windings together. For example, one or more layers may include more than one full turn, but less than two full turns (or between two and three full turns, etc.), either individually or together. For example, four quarter turns may constitute a full turn, or a leg may be surrounded by five quarter turns, which defines one full turn and another quarter turn. With respect to the winding of a particular leg, in some embodiments, one or more full turns are divided into multiple winding layers, i.e., one layer, for example, includes a half turn around a first leg, while another layer, for example, includes another corresponding, i.e., another, half turn around the same first leg, but in a different plane / layer.

[0013] In some embodiments, the number of turns of each of the at least two layers of primary windings is different. Thus, different total surface areas are achieved by providing different numbers of turns between layers. However, in alternative embodiments, different surface areas can be achieved, for example, by different widths of the windings between layers.

[0014] Specifically, in some embodiments, the number of complete turns of each layer of the primary winding of at least two layers of primary winding is different.

[0015] Advantageously, the total number of turns of the layers in the at least two primary windings is respectively a non-integer rational number. In other words, the total number of turns of the layers can be a rational number that does not produce an integer (e.g., 10 / 4), while an example of an integer rational number is 10 / 5, which produces an integer rational number, namely 2.

[0016] In the above, in some specific examples, the total number of turns of the layers added together is an integer. For example, in the exemplary case of having four legs, one layer may include three half turns and one quarter turn of the primary winding with respect to the legs, and another layer may include another three half turns of the primary winding and one three quarter turn of the primary winding, so that each layer has non-integer rational numbers (7 / 4 and 9 / 4), and the sum is an integer, namely four (16 / 4).

[0017] In some embodiments, at least one layer of the primary winding includes at least one primary winding portion having one or more of the following configurations.

[0018] Therein, at least one primary winding section is preferably only indirectly connected to other primary winding sections of the same layer. In particular, at least one primary winding section of a layer is only connected to a primary winding section of the same layer via at least one primary winding section of another layer. In some embodiments, such a primary winding section can be partially or completely wound around one or more legs, respectively (and with respect to a layer).

[0019] Additionally or alternatively, at least one primary winding section is only electrically coupled between the primary side and the secondary side. In particular, this generates a capacitance (coupling capacitance), in particular without magnetic coupling. In other words, such a primary winding section generates or changes the coupling capacitance without interacting with other windings to achieve magnetic coupling, i.e. converting voltage / current between the primary side and the secondary side.

[0020] Preferably, the electrically coupled-only primary winding portions comprise a total number of turns accumulated over multiple layers, the total number of turns being a non-integer rational number.

[0021] Here, the term "electrically coupled only" refers to coupling as a capacitor. Structurally, for example, if all primary winding portions are wound on a leg over multiple layers, adding up to two and a quarter complete turns. The winding portions constituting two complete turns will be magnetically coupled, and the winding portions constituting the remaining quarter complete turn will only be electrically coupled, especially without affecting the magnetic coupling. Therefore, the only electrically coupled primary winding portions can therefore be capacitively coupled to the secondary side while keeping the magnetic coupling characteristics between the primary side and the secondary side substantially constant (relative to not including these portions). For example, in addition to the magnetically coupled primary winding portions, only electrically coupled primary winding portions can be added to certain layers. In addition, by arranging the only electrically coupled primary winding portions in certain layers, the use of shielding layers can be avoided. Therefore, the total thickness of the transformer in the stacking direction can be reduced, or common mode currents can be compensated without increasing the thickness of the transformer.

[0022] Furthermore, in some embodiments, at least one of the primary winding sections is less than a full turn. For example, one primary winding section of one layer may be a half turn around one leg. This primary winding section is not directly connected to other primary winding sections of the same layer, but may be connected, for example, to another primary winding section of a different layer, which also constitutes a half turn (the respective other half) around the same leg.

[0023] In some embodiments, when the primary side is connected to a voltage, at least one primary winding portion that is only electrically coupled does not carry a current associated with magnetic coupling. In other words, when the primary side is connected to a non-zero voltage, preferably no current flows through the at least one primary winding portion that is only electrically coupled. Wherein, the voltage preferably generates an electric field in the winding portion, but no current is induced therein. The above-mentioned electric field is coupled with the secondary side, thereby generating a capacitance therebetween. Specifically, when a voltage is applied, a current is caused to flow through other primary windings, more specifically, through other primary winding portions that are not only configured to be electrically coupled but also configured to be magnetically coupled. The current induces a magnetic field for transformer operation.

[0024] Preferably, in particular for the same core assembly, the total number of turns of the primary winding for all layers around a first leg is different from the total number of turns of the primary winding for all layers around a second leg. For example, the number of turns of the primary winding (and their respective primary winding parts) may be one full turn for one leg and two full turns for the other leg, or a non-integer rational number, on all layers. This leads to other advantages, since the induced magnetic field can be distributed between the legs. For example, this allows to distribute the magnetic field to the legs that can be cooled more effectively, so that for example a leg that is located closer to the outside, i.e. closer to e.g. a heat sink, may comprise more turns than for example a leg that is located closer to the inside, i.e. further away from said heat sink. Furthermore, the flexibility of the distribution of the windings / winding parts allows the primary winding to be adapted to a predetermined turns ratio when considering the secondary side winding.

[0025] In some embodiments, in at least one layer, at least one leg has no primary winding wound around it. For example, in the case of four layers, one leg may have one full turn in the first layer, one full turn in another layer, but no other primary windings or primary winding portions wound around it in the other two layers.

[0026] In particular, at least one leg may not have a complete turn of the primary winding wound around it in at least one layer. For example, as described above and will be shown in specific exemplary embodiments, one leg may include only a primary winding portion in one layer that does not constitute a complete turn around the leg, such as only a half turn. In other words, at least one leg may include only a partial turn of the primary winding wound around it in at least one layer.

[0027] In a preferred embodiment, at least one leg without a complete turn of the primary winding wound around it is a return leg for closing the magnetic circuit with the winding legs. These winding legs are at least one other leg of the same magnetic core, which includes at least one complete turn of the primary winding wound around it, i.e. are magnetically coupled. Furthermore, the aforementioned return leg may include one or more primary winding parts that are only electrically coupled in at least one layer.

[0028] With this exemplary arrangement of the primary winding and its primary winding parts, it is possible in particular to spread the primary winding between a plurality of layers for a predetermined fixed number of complete turns. In addition, in layers which, for example, comprise only less than a complete turn for one or more legs, additional primary winding parts which are only electrically coupled can be added. Thus, the capacitance of some layers is different from that of other layers, while saving space and increasing the efficiency of the transformer.

[0029] In some embodiments, the primary windings are elongated and meander-shaped. Additionally or alternatively, the secondary windings are preferably plate-shaped. In particular, the term "meander-shaped" refers to a view of the corresponding layer, i.e. a top view along the extension direction of the legs. The primary windings meander (i.e. along the winding path), bend or turn within the layer along their substantial extension direction. In particular, their cross-section perpendicular to their substantial extension is preferably rectangular, and since they are planar, their cross-sectional height is much smaller than their width or length.

[0030] Preferably, the planar transformer comprises two layers of secondary windings connected to each other, and sandwiches at least two layers of primary windings connected to each other. Preferably, the layers are arranged as: secondary, primary, primary, ..., secondary, where "..." represents further possible primary winding layers. In some examples, the planar transformer comprises two layers of secondary windings sandwiching four layers of primary windings.

[0031] Preferably, the respectively connected windings are connected to one another via through-holes extending in the stacking direction (parallel to the extension direction of the legs between the layers).

[0032] In some embodiments, the total secondary winding surface area of ​​all layers of the secondary winding is equal.

[0033] The present disclosure also relates to an LLC converter comprising a planar transformer according to any of the embodiments. Preferably, the LLC converter further comprises a resistive element and a capacitive element, in particular together as an RC circuit, directly connected to the midpoint of the primary winding of the planar transformer. Preferably, the RC circuit may be an RLC circuit (also comprising an inductor L).

[0034] In a preferred embodiment including an RC circuit, the RC circuit is configured to suppress or attenuate resonances in the transformer, especially higher-order resonances. Since the RC is directly connected to the midpoint of the primary winding, the primary winding is maintained at a substantially stable or quasi-stable potential, the RC is not loaded by the transformer, and therefore no loss of input voltage is generated. In addition, as described above, compensation of the common-mode current provides a stable or quasi-stable potential. In this regard, "quasi-stable" refers to resonances that are relatively small in terms of amplitude and higher in terms of frequency, and that are generated by the transformer at frequencies much higher than the switching frequency. However, these small higher-order resonances are suppressed by the RC circuit on the primary side. The RC circuit thus effectively acts as a high-pass filter.

[0035] Preferably, the other end of the RC circuit, ie the end not connected to the midpoint, is preferably connected to a stable potential midpoint between the input capacitors of the LLC.

[0036] Preferably, the resistance element and the capacitance element of the RC circuit are discrete elements. Further preferably, the inductance of the RLC circuit is also a discrete element.

[0037] The present disclosure also relates to an LLC converter. The LLC converter of this embodiment includes a planar transformer, which includes a core assembly, which includes at least one plate portion and a plurality of legs extending from the plate portion. In addition, the planar transformer includes a secondary side having a plurality of secondary windings and a primary side having a plurality of primary windings. Wherein, at least one secondary winding and a plurality of primary windings are stacked into a plurality of layers along a stacking direction parallel to the extension direction of the legs, and a plurality of primary windings of different layers are connected to each other, especially through through-holes. Further, the primary side is connected to the input of the LLC converter and includes a center tap of the primary winding, and the secondary side is connected to the output of the LLC converter and includes a center tap of the secondary winding. Wherein, the primary and / or secondary center taps are directly connected to the RC circuit. Preferably, the primary and secondary center taps are connected to the midpoints of the primary winding and the secondary winding, respectively. Preferably here, the total surface area of ​​the primary windings of all layers of the primary winding is equal. Further preferably, the total surface area of ​​the secondary windings of all layers of the secondary winding is equal.

[0038] Preferably, as mentioned above, the RC circuit of this embodiment is an RLC circuit. Further preferably, any of its components are discrete.

[0039] Preferably, the layers of the primary winding are symmetrical, in particular symmetrical with respect to the center tap. In other words, for example all layers of the primary winding have the same number of turns around the same leg, or for example the layers of the primary winding are mirrored symmetrically with respect to the center tap. For example, in the latter case, the shape of the primary winding in one layer on one side of the center tap will be equal to the shape of the primary winding in another layer on the other side of the center tap, but not necessarily equal to the shape of another layer of the primary winding on the same side of the center tap.

[0040] Preferably, the primary winding is meander-shaped, as described above. Additionally or alternatively, the secondary winding is preferably plate-shaped.

[0041] Preferably, the magnetic core component of the aforementioned embodiment is formed of ferrite. Preferably, the plate portion and the legs of the magnetic core component are formed integrally with each other, in particular, are integrated with each other.

[0042] Preferably, the primary winding and / or the secondary winding are formed from copper.

[0043] Preferably, the primary winding and / or the secondary winding are printed on a printed circuit board. Further preferably, each of the above layers is a printed circuit board.

[0044] Preferably, in some embodiments, the magnetic core component is a so-called "matrix core", which comprises a substantially rectangular, in particular square, plate portion and four legs extending therefrom. Preferably, when viewed in a cross section perpendicular to the direction in which the legs extend, the legs are arranged equidistant from each other, in particular each distributed at the corners of the square core component.

[0045] Preferably, the magnetic core assembly comprises two plate parts, which sandwich the primary winding layer and the secondary winding layer in the stacking direction, and the legs extend from the plate parts through the winding layers. Wherein, along the stacking direction, a gap may be provided between the leg connected to the first plate part and the leg connected to the second plate part. The gap may be an air gap, or may be filled with a material, such as a resin or a part of a printed circuit board.

[0046] The aforementioned LLC converter may be an example of a DC / DC converter in or for which a planar transformer is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] More details, advantages and features of the preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, wherein:

[0048] Figures 1a-1f shows a schematic cross-sectional view of layers of a planar transformer according to a first embodiment of the present disclosure;

[0049] Figure 2a-2fshows a schematic cross-sectional view of layers of a planar transformer according to a first embodiment of the present disclosure;

[0050] Figure 3 shows a circuit diagram of a first embodiment of an LLC converter according to the present disclosure;

[0051] Figure 4 Another circuit diagram of a first embodiment of an LLC converter according to the present disclosure is shown;

[0052] Figure 5a-5d shows a schematic cross-sectional view of layers of a planar transformer according to a third embodiment of the present disclosure;

[0053] Figure 6a-6f shows a schematic cross-sectional view of layers of a planar transformer according to a fourth embodiment of the present disclosure;

[0054] Figure 7 A circuit diagram showing a second embodiment of an LLC converter according to the present disclosure; and

[0055] Figures 8a-8d A schematic configuration example of a magnetic core component of a planar transformer according to the present disclosure is shown.

[0056] List of reference numerals:

[0057] 1 Planar transformer 2 Core assembly 3 Plate

[0058] 4 Legs 5 Secondary Winding 6 Primary Winding

[0059] 7 Layer 8 Stacking direction 9 Leg extension direction

[0060] 10 Primary winding layer (primary layer) 11 Secondary winding layer (secondary layer) 12 Primary winding section

[0062] 13 through hole 14 first interlayer through hole 15 second interlayer through hole

[0063] 16 Primary starting point connection belt (starting point) 17 Primary end point connection belt (end point) 18 Primary midpoint connection belt (midpoint)

[0065] 19 Primary midpoint connection strap (midpoint) 20 Secondary midpoint connection strap (secondary midpoint) 21 Secondary terminal connection

[0067] 22 Secondary layer interconnection via 23 Width 24 Third layer via

[0069] 25 heat sink 26 fourth interlayer through hole 27 fifth interlayer through hole

[0070] 28 Sixth interlayer via hole 29 Seventh interlayer via hole 30 Gap

[0071] 31 Tab 50 Secondary side 60 Primary side

[0072] 100 LLC Converter 101 Voltage Doubler 102 Resistor

[0073] 103 Capacitor 104 RC Circuit 105 Input Capacitor

[0074] 106 Output capacitor S1-S6 switch C_res resonant capacitor

[0075] L_res resonant inductor C3, C4 coupling capacitor I_C3(t) common mode current

[0076] I_C4(t) Common mode current 200 LLC converter 201 Push-pull stage

[0077] 202 Resistor 203 Capacitor 204 RC Circuit

[0078] 205 Input capacitor 206 Primary center tap 207 Secondary center tap

[0079] 208 Output capacitor Np1 Number of primary windings Np2 Number of primary windings

[0080] Ns1 Number of secondary windings Ns2 Number of secondary windings P# Primary winding section reference number DETAILED DESCRIPTION

[0082] Figures 1a-1f FIG. 1 is a schematic cross-sectional view of a layer 7 of a planar transformer 1 according to a first embodiment of the present disclosure. Figures 1a-1f .

[0083] First, before explaining the planar transformer 1, the Figures 1a-1f An overview of what is shown in .

[0084] Figures 1a-1f Each of the diagrams shows a layer 7 of a planar transformer 1 (hereinafter referred to as "transformer 1"). The layers 7 are stacked on top of each other along a stacking direction 8 to form the planar transformer 1, but for easier understanding, the layers 7 are stacked on top of each other along a stacking direction 8 to form the planar transformer 1. Figures 1a-1f Shown in expanded form.

[0085] Figures 1a to 1d The layers 7 are respectively layers 7 including the primary winding 6 (hereinafter referred to as “primary winding layer 10 ” or “primary layer 10 ”). Figure 1e and 1f The layers 7 are layers 7 including the secondary winding 5 (hereinafter referred to as "secondary winding layer 11" or "secondary layer 11") respectively.

[0086] As can be seen from FIG. 1 , the primary winding 6 is of a meandering shape.

[0087] The secondary winding layer 11 sandwiches the primary winding layer 10 along the stacking direction 8, so that they are arranged along the stacking direction 8 as follows: the secondary winding layer 11 ( Figure 1e , hereinafter referred to as "first layer 1e"), primary winding layer 10 ( Figure 1a , hereinafter referred to as "second layer 1a"), primary winding layer 10 ( Figure 1c , hereinafter referred to as "third layer 1c"), primary winding layer 10 ( Figure 1b , hereinafter referred to as "fourth layer 1b"), primary winding layer 10 ( Figure 1d , hereinafter referred to as "fifth layer 1d"), secondary winding layer 11 ( Figure 1f , hereinafter referred to as “sixth layer 1f”).

[0088] Now, the transformer 1 will be explained.

[0089] The transformer 1 comprises at least one secondary winding 5 and a plurality of primary windings 6. Here and hereinafter, the term "winding" refers to a coil forming the primary or secondary side of the transformer 1, the number of which corresponds to its total number of turns.

[0090] The primary winding 6 is part of the primary side 60 ( Figure 1a-1d ), and the secondary winding 5 is part of the secondary side 50 ( Figure 1e and 1f ).

[0091] For example, the transformer 1 of the present embodiment includes four primary windings 6 (four primary winding layers 10) and two secondary windings 5 ​​(two secondary winding layers 11). The transformer 1 may preferably include only one secondary winding 5. The transformer 1 may preferably include at least two primary windings 6, and preferably no more than eight primary windings 6, each including two to eight primary winding layers 10.

[0092] From Figure 1, especially Figure 1e As can be seen from the figure, the transformer 1 includes a magnetic core assembly 2 (which can also be Figures 8a-8d ). The magnetic core component 2 includes at least one plate portion 3 and a plurality of legs 4 extending from the plate portion 3. The leg extension direction 9 of the legs 4 is parallel to the aforementioned stacking direction 8. In this example, the magnetic core component 2 includes two plate portions 3, which sandwich the layer 7 in the stacking direction. Figure 1e and 1f The core component 2 comprises four legs 4. The legs 4 extend through all layers 7 along their extension direction 9.

[0093] The aforementioned primary winding 6 generally (explained further below) induces a magnetic flux in the leg 4, which is indicated by the known symbols for magnetic flux ● and X. As can be seen from FIG. 1 , the magnetic flux of one leg 4 is in the same direction parallel to the stacking direction 8 of all layers 7 of this leg 4.

[0094] A plurality of primary windings 6 of different primary layers 10 are connected to each other. In other words, the primary windings 6 of one primary layer 10 are connected to the primary windings 6 of another primary layer 10. Here, the primary windings 6 are interconnected in the entire primary layer 10 by vias 13, 14, 15 and 24. The connection scheme will be further explained below. First, the structure of the primary windings 6 will be further explained.

[0095] In the transformer 1, for at least two layers 7 of the primary winding 6, their total surface areas of the primary winding 6 are different. Figure 1a-1d It can be clearly seen that in this example the primary winding 6 is different between all primary layers 10 and their surface areas are correspondingly different.

[0096] As is evident from Figure 1, the width 23 of the primary windings 6 is the same for all primary windings 6, their width 23 being defined perpendicularly to their basic extension within a layer 10 and perpendicularly to their thickness in the stacking direction 8. Their thickness in the stacking direction 8 is also the same. Their total surface area therefore corresponds to their length along their basic extension, respectively, within a layer 10. In other words, therefore, the length of the primary windings 6 is different for different primary layers 10.

[0097] Thereby, the coupling capacitance generated between the primary side 60 and the secondary side 50 is adapted to compensate for the common mode current generated in the primary winding 6 and the secondary winding 5 .

[0098] In this embodiment, for at least two layers 10 (primary layers 10) of the primary winding 6, the number of turns of each layer 10 of the primary winding 6 is different between them. In order to calculate or determine the number of turns, Figure 1a-1d A dotted grid is included that divides the primary winding 6 into primary winding sections 12. Each square of the dotted grid divides the primary winding 6 into primary winding sections 12 of a quarter turn. In addition, the primary winding sections 12 are denoted by the reference numeral P#, "#" being the number of penetrations from the starting point 16 to the end point 17. The "P-1 / 2" of the layer 1a extends electrically away from the starting point 16, i.e. not in the direction toward the end point 17, so that it has a negative reference. A reference with an integer "P1 / 2" or a multiple thereof (e.g. "P15 / 2") indicates that the primary winding section 12 has half of a quarter turn, i.e. one eighth turn (half of a square of the dotted grid).

[0099] In the aforementioned embodiment, the end point 17 is in the fourth layer 1b and is not currently in the fifth layer 1d. This is advantageous because the end point 17 of the primary winding 6 generally has a high voltage and has a strong influence on the coupling capacitance of the secondary winding 5. However, alternatively, the end point 17 may be in the fifth layer 1d. In other words, the configuration of the fourth layer 1b and the fifth layer 1d may be appropriately exchanged so that the fifth layer 1d shown is exchanged with the fourth layer 1b, and vice versa, i.e., their stacking order is exchanged.

[0100] The number of turns of a layer 7 is defined as the total number of turns of the windings 5, 6 (secondary or primary) around all legs 4 of this layer. One turn of a winding 5, 6 is defined as follows. If a winding 5, 6 or a corresponding winding portion 12 comprises a bend around this leg 4, i.e. a curvature with a radius pointing to the center of the leg 4 in a cross section of the leg 4, one turn is defined relative to one of the legs 4, wherein a winding 5, 6 is defined as comprising one turn (or partial turn) around a particular leg 4, e.g., in layer 1a, the winding portions 12 numbered P0 and P2 are each a quarter turn around the first leg 4 located to the upper left thereof (counting clockwise from the upper left), and e.g., the winding portions 12 numbered P3 and P4 are each a quarter turn around the second leg 4 (upper right corner). A full turn is defined as the partial turns adding up to one for a particular leg 4. Therein, the inflection point along the extension of the primary winding 6 indicates the switch between a winding section 12 rotating around one leg 4 and a winding section 12 rotating around the other leg 4 .

[0101] For example, in layer 1a, the primary winding 6 includes primary winding sections 12: P-1 / 2, P0-P8, and P11 / 2, P12, P13 / 2. Together, layer 1a includes ten quarter-turn primary winding sections 12 (P0-P8, P12) and three eighth-turn winding sections 12, making the total number of turns of the second layer 1a 23 / 8 (or 2.875).

[0102] On the other hand, layer 1d includes, for example, four quarter-turn primary winding sections 12 (P16-P18, P22) and four eighth-turn primary winding sections 12 (P15 / 2, P19 / 2, P21 / 2, P23 / 2), thus including a total of one and a half turns (1 1 / 2 or 1.5).

[0103] Thus, the total number of turns of at least two layers 7, in particular the primary layer 10, is a non-integer rational number, as described above for the example of layers 1a, 1d. This configuration significantly reduces the total common mode current by compensating for the common mode current between the primary windings 6.

[0104] More specifically, the primary winding portion 12 provides at least two capacitors that (capacitively) connect the primary side 60 to the secondary side 50 using voltages of opposite polarity to cancel the common mode currents that are generated. This will be further explained below with respect to the midpoint 18 of the primary winding.

[0105] Now, the connection scheme of the windings 5, 6 will be explained.

[0106] As described above, the primary windings 6 are interconnected through the through holes 13, 14, 15, and 24. Specifically, the primary windings 6 are connected to each other in series through the through holes 13, 14, 15, and 24.

[0107] The through-hole 13 extends through all the primary layers 10 and connects the primary connection straps 16, 17, 18 and 19 of the primary winding 6, and is therefore referred to as "through-hole 13". Here, the through-holes 13 of the second layer 1a and the fourth layer 1b respectively connect them to the outside. Among them, the primary connection strap 16 of the second layer 1a is the primary starting connection strap 16 ("starting point"), to which the input voltage is connected (for example, the high side of the input voltage). The primary connection strap 17 of the fourth layer 1b is the primary terminal connection strap 17 ("terminal point"), which is also connected to the input voltage (for example, the low side of the input voltage). The current flows from the primary starting connection strap 16 (hereinafter referred to as "starting point 16") via the primary windings 6 of all the primary layers 10 to the primary terminal connection strap 17 (hereinafter referred to as "terminal point 17"). These are connected to the external input voltage using the through-hole 13.

[0108] Furthermore, the second layer 1a is connected to the third layer 1c using vias 14 and 15. The vias 14 and 15 interconnect the two layers 10 (1a and 1c), and are therefore referred to as "first interlayer via 14" and "second interlayer via 15".

[0109] Thus, based on the P# designation of the primary winding portions 12, P8 is connected to P9 through the first interlayer via 14. Within the third layer 1c, the zigzag shape of the primary winding 6 is further followed through the primary winding portions 12P9-P16. The primary layer 10 includes a midpoint connection strip 18 (hereinafter referred to as "midpoint 18"), which allows connection to the midpoint of the primary winding 6. Furthermore, in between, the third layer 1c is interconnected with the second layer 1a through the second interlayer via 15, which connects the primary winding portions 12P11 / 2 and P13 / 2 of each of the second layer 1a and the third layer 1c to each other.

[0110] The midpoint 18 of the third layer 1c is connected to the midpoint connection strip 19 ("midpoint 19") of the fifth layer 1d using the through hole 13. Via their connection, the midpoints 18, 19 form the common midpoint of the series connection of all primary windings 6. Similar to the second layer 1a and the third layer 1c described above, the primary winding portions 12 of the fifth layer 1d and the fourth layer 1b are interconnected through the third inter-layer through hole 24 to reach the end point 17 in the fourth layer 1b. The midpoints 18 and 19 directly connected to each other will be collectively referred to as "midpoints 18, 19" (also see "MP" in the figure) hereinafter.

[0111] Here, the voltage polarity is defined as positive from the starting point 16 to the midpoints 18 and 19, and negative from the midpoints 18 and 19 to the end point 17. However, this definition is arbitrary as long as the polarities on both sides of the midpoints 18 and 19 are opposite to each other. In other words, negative can be defined as from the starting point 16 to the midpoints 18 and 19, and positive can be defined as from the midpoints 18 and 19 to the end point 17.

[0112] As can be seen from Figure 1 and the foregoing exemplary description, the transformer 1 comprises at least one primary winding section 12 which is only indirectly connected (i.e. via at least one primary winding section 12 of another layer 7) to other primary winding sections 12 of the same layer 7. For example, the winding sections 12 denoted as P11 / 2, P12, P13 / 2 are indirectly connected to the winding sections denoted as P-1 / 2-P8 in the second layer 1a only via the primary winding sections 12 of the third layer 1c, i.e. P9-P11 / 2, P13 / 2-P16.

[0113] Typically, when voltage is input, the primary winding parts 12, i.e. in particular those primary winding parts providing one or more complete turns of the legs 4 on one or more layers 7, induce a magnetic field in the legs 4 through the flow of current, i.e. magnetic / inductive coupling as well as electrical coupling.

[0114] For example, considering the first leg 4 (upper left), two complete turns are formed, namely through the following primary winding sections 12: P1, P2, P15, P16 (first turn), P17, P18, P31, P32 (second turn). In addition, since these primary winding sections 12 are arranged between the starting point 16 and the end point 17 along their elongation and current path, these primary winding sections 12 carry current and therefore contribute to magnetism.

[0115] In addition, regarding the following remaining primary winding portions 12 of the first leg 4, they only contribute to electrical properties, but not to magnetic / inductive properties: P-1 / 2 and P0 of the second layer 1a and P16, P15 / 2 of the fifth layer 1d. These primary winding portions 12 generate coupling capacitance, but do not contribute to magnetic / inductive properties because they do not carry current when voltage is input. In other words, since they are not arranged between the starting point 16 and the end point 17 along their extension or current path, they do not carry current.

[0116] Generally, for the primary winding portion 12 that does not carry current but only contributes / couples electrically, the closer it is arranged to the start point 16 or the end point 17, the stronger its contribution / coupling is, and thus has a higher impact on the coupling capacitance and the common mode current.

[0117] In addition, the total number of turns of the primary winding 6 of all layers 7 (all primary layers 10) around the first leg 4 is different from the total number of turns of the primary winding 6 of all layers 7 around the second leg 4. In other words, the respective legs 4 comprise a different total number of turns. In particular, the number of complete turns, i.e. comprising only the magnetically coupled primary winding portion 6, is different between at least two legs 4.

[0118] For example, as described above, the first leg 4 (upper left) includes a total of thirteen quarter turns (twelve quarter turns and two eighth turns P-1 / 2, P15 / 2), in particular two complete turns, while the second leg 4 (upper right) includes six quarter turns (P3, P4, P5, P19 / 2, P20, P21 / 2, P19 / 2, P21 / 2), in particular no complete turns. In this regard, it should be noted that the second leg 4 (upper right) is a return leg for closing the magnetic circuit. Therefore, the respective primary winding sections 12 are used to compensate for the common mode current without having a non-negligible influence on the magnetic characteristics.

[0119] Furthermore, the second leg 4 (upper right) is included in the third layer 1c, and the fourth leg 4 (lower left) is included in the fifth layer 1d, without the primary winding 6 being wound around them.

[0120] The secondary layer 11 comprises a secondary winding 5. Here, the secondary winding 5 is plate-shaped, and each leg 4 defines a complete turn. The two secondary layers 11 are connected to each other in parallel via secondary layer interconnection through-holes 22. Similar to the through-holes 13, these secondary layer interconnection through-holes 22 also extend parallel to the stacking direction 8, passing through all layers 7 of the transformer 1. In addition, the secondary layer 11 is connected to the outside, i.e. the output, via a secondary terminal connection 21. Among them, the secondary midpoint connection band 20 (hereinafter referred to as "secondary midpoint 20") is also connected to the secondary winding 5 (at Figure 1e , 1f The secondary layer 11 is further connected to a heat sink 25.

[0121] As will be explained in more detail below Figure 1e and 1f and Figure 3 As shown in the comparison of FIG. 1 , the secondary terminal connection 21 connects the secondary layer 11 to the RTN, which corresponds to Figure 3 V_out_rtn in the circuit is the output voltage. In addition, the switches S5 and S6 are located on the secondary layer 11 with their source, drain and / or gate, respectively. Figure 3 Each of the switches S5 and S6 shown in the figure may include one or more switches, that is, may be composed of a plurality of switches connected in parallel or in series.

[0122] refer to Figure 2a-2f , a second embodiment of the transformer 1 will be described. The terms, especially the abbreviations, defined above with respect to the first embodiment will also be used hereinafter.

[0123] In the second embodiment, another example is shown for arranging and connecting the primary winding 6 within and between the primary layers 10. The configuration of the secondary layer 11 is the same as that of the first embodiment.

[0124] In the transformer 1 of FIG. 2 , corresponding to the first embodiment, Figure 2a-2f In other words, they are arranged such that their arrangement along the stacking direction 8 is: the secondary winding layer 11 ( Figure 2e , hereinafter referred to as "first layer 2e"), primary winding layer 10 ( Figure 2a , hereinafter referred to as "second layer 2a"), the primary winding layer 10 ( Figure 2c , hereinafter referred to as "third layer 2c"), primary winding layer 10 ( Figure 2b , hereinafter referred to as "fourth layer 2b"), the primary winding layer 10 ( Figure 2d , hereinafter referred to as "fifth layer 2d"), secondary winding layer 11 ( Figure 2f , hereinafter referred to as "sixth layer 2f"). The starting point 16 is correspondingly in the second layer 2a, the end point 17 is correspondingly in the fourth layer 2b, and the midpoints 18 and 19 are in the third layer 2c and the fifth layer 2d.

[0125] Here, the first leg 4 (upper left) has two complete turns of the primary winding 6 wound around it. The third leg 4 (lower right) also has two complete turns of the primary winding 6 wound around it. For example, for the third leg 4, the primary winding portions 12 denoted as P7, P8, P9 and P10 interconnected by the first inter-layer vias 14 form a first complete turn. In addition, the primary winding portions 12 denoted as P23 / 2, P24, P25, P26 of the fourth layer 2b and the primary winding portion 12 denoted as P23 / 2 of the fifth layer 2d, which are interconnected by the third inter-layer vias 24, form a second complete turn.

[0126] Furthermore, the second leg 4 (upper right) does not have a complete turn of the primary winding 6 wound around it, but comprises six quarter-turn primary winding portions 12 which, however, do not correspond complementarily to each other to form a complete turn. The same is true for the fourth leg 4 (lower left).

[0127] Here, all primary winding parts 12 carry current and thus contribute / couple magnetic and electrical properties. When considering multiple layers 7, by arranging the primary winding parts 12, especially arranging P23 / 2, P24 asymmetrically, it is advantageous to compensate for common mode currents while further optimizing the magnetic field distribution characteristics. With regard to the above explanations of Figures 1 and 2, Embodiment 1 and Embodiment 2, it should be emphasized that additional primary winding parts 12 can be appropriately added or removed therein. Specifically, especially in, for example Figure 2a In the free space where the fourth leg 4 (lower left) of the second layer 2a in FIG. 1 is located, a further primary winding portion 12 can preferably be added, which is preferably only electrically coupled, i.e., it does not carry current. Of course, depending on the number of turns required for the transformer 1, further magnetically coupled primary winding portions 12, i.e., further current-carrying primary winding portions 12 and / or the number of turns of the primary winding 6 are preferably added.

[0128] Now, refer to Figure 3 and Figure 4 , the LLC converter 100 of the present disclosure will be described. Figure 3 shows a circuit diagram of a first embodiment of an LLC converter 100 according to the present disclosure; Figure 4 Another circuit diagram of a first embodiment of an LLC converter 100 according to the present disclosure is shown.

[0129] For the precise circuit configuration of LLC converter 100, in particular Figure 3 , Figure 3 Its connection scheme and configuration are shown in detail.

[0130] In particular, LLC converter 100 (hereinafter referred to as "converter 100") includes a planar transformer 1 of embodiment 1 or 2 of planar transformer 1. The primary side 60 of transformer 1 is connected to the input side of converter 100 (represented by V_in+ (high side) and V_in_rtn (low side, "rtn" stands for "return")) and switches S1-S4. In addition, on the input side, converter 100 includes a resonant inductor L_res and a resonant capacitor C_res.

[0131] In addition, Figure 3 In FIG. 1 , a start point 16 , an end point 17 and midpoints 18 , 19 of the transformer 1 are shown.

[0132] At the secondary side 50 , the converter 100 comprises a voltage doubler 101 before the output, which comprises switches S5 and S6 . The outputs are represented by V_out+ and V_out_rtn . Furthermore, the secondary midpoint 20 of the secondary winding 5 is connected to the midpoint of the voltage doubler 101 between the output capacitors 106 .

[0133] Figure 3 The secondary side 50 shown corresponds to Figure 1e , Figure 1f and Figure 2e , Figure 2f The secondary layer 11.

[0134] Furthermore, the converter 100 comprises an RC circuit 104 connected to the midpoints 18, 19 of the primary winding 6. The RC circuit 104 comprises a resistive element 102 and a capacitor 103, both of which are preferably discrete components. The other end of the RC circuit 104 is connected to a stable potential between the input capacitors 105. Therefore, the potential across the RC circuit 104 remains stable.

[0135] The RC circuit 104 is configured to suppress or attenuate resonances in the transformer, especially high-order resonances. Since the RC circuit 104 is directly connected to the midpoints 18, 19 of the primary winding 6, which are maintained at a substantially stable or quasi-stable potential, the RC circuit 104 does not act as a load via the transformer 1, and therefore does not generate any input voltage loss. In addition, as described above, the compensation of the common-mode current provides a stable or quasi-stable potential. In this regard, "quasi-stable" refers to resonances generated by the transformer 1 at frequencies much higher than the switching frequency that are relatively small in terms of amplitude. These small resonances are suppressed by the RC circuit 104 of the primary side 60. The RC circuit 104 therefore effectively acts as a high-pass filter.

[0136] Therefore, the RC circuit 104 works in conjunction with the common mode current compensation of the transformer 1 to further improve the efficiency of the converter 100, especially in contrast to a non-disclosed converter that does not have a transformer that compensates for the common mode current. In this case, the RC circuit can act as a high pass filter, but will further increase the losses of such a converter.

[0137] For explanation purposes, Figure 4 Including coupling capacitors C3, C4, and schematic connections shown in dashed lines. Coupling capacitors C3, C4 are lumped coupling capacitors between the primary side 60 and the secondary side 50. Coupling capacitors C3, C4 are parasitic, that is, not discrete components. In order to demonstrate the common mode currents i_C3 (t), i_C4 (t), the primary side 60 and the secondary side 50 are shown as short-circuited.

[0138] As in Figure 4As can be seen in FIG. 1 and as explained in relation to the embodiment of the transformer 1 , the electrical coupling of the secondary winding 5 to the primary winding 6 between the starting point 16 and the midpoints 18, 19 is weaker than the electrical coupling to the primary winding 6 between the midpoints 18, 19 and the end point 17. Therefore, by providing the above-mentioned electrically coupled primary winding portion 12 generally closer to the starting point 16, it is possible to compensate for the common mode currents i_C3(t) and i_C4(t), which flow in opposite directions and add together to form the total common mode current. This can be derived as follows:

[0139] V C3 =n*(V out / 2)-(V out / 2)=(n-1)*(V out / 2), and

[0140] V C4＝ -n*(V out / 2)-(V out / 2)=-(n+1)*(V out / 2)

[0141] Where V C# is the voltage of the coupling capacitor C# (C4, C3), Vout is the output voltage, and n is the turns ratio between the secondary winding 5 and the primary winding, the primary winding being located between the starting point 16 and the midpoints 18, 19 (Np1), or between the midpoints 18, 19 and the end point 17 (Np2). It can be concluded that, when considering their absolute values, for a given n, V C4 will be greater than V C3 Therefore, the coupling of the primary winding 6 between the starting point 16 and the midpoints 18 , 19 is weaker than the coupling of the primary winding between the midpoints 18 , 19 and the end point 17 .

[0142] As shown in comparison with FIG. 1 , with respect to the midpoints 18, 19 and in consideration of magnetic coupling requirements, the layer 7 disposed near the top (i.e., near the start point 16) has more turns of the primary winding portion 12 than near the bottom (i.e., near the end point 17). For example, the second layer 1a disposed closest to the start point 16 has the primary winding portion 12 with the highest number of turns in the two primary layers 10 above the midpoints 18, 19 (i.e., the second layer 1a and the third layer 1c). In addition, the fourth layer 1b has the primary winding portion 12 with the highest number of turns in the two primary layers 10 below the midpoints 18, 19 (i.e., the fourth layer 1b and the fifth layer 1d). Therefore, in consideration of magnetic requirements, the primary winding portion 12 is moved closer to the start point 16, rather than providing the primary winding portion 12 with the highest number of turns for the third layer 1c or the fifth layer 1d.

[0143] refer to Figure 5a-5d , a third embodiment of the planar transformer 1 is described. Figure 5a-5dA schematic cross-sectional view of a layer 10 of a planar transformer 1 according to a third embodiment of the present disclosure is shown.

[0144] Here, the secondary layer 11 shown in Figures 1 (1e, 1f) and 2 (2e, 2f) is omitted, but preferably includes the same structure. In other words, only the primary layer 10 is shown herein. In addition, the transformer 1 of the present embodiment includes the aforementioned magnetic core component 2, which includes at least one plate portion 3 and a plurality of legs 4. In the present embodiment, the magnetic core component 2 includes four legs 4.

[0145] Furthermore, the stacking along the stacking direction 8 of the layers 7 is as follows: the secondary winding layers 11 (for example Figure 1e , hereinafter referred to as the "first layer 1e"), the primary winding layer 10 ( Figure 5c , hereinafter referred to as "second layer 5c"), primary winding layer 10 ( Figure 5a , hereinafter referred to as the "third layer 5a"), the primary winding layer 10 ( Figure 5b , hereinafter referred to as "fourth layer 5b"), the primary winding layer 10 ( Figure 5d , hereinafter referred to as the "fifth layer 5d"), the secondary winding layer 11 (eg Figure 1f , hereinafter referred to as “sixth layer 1f”).

[0146] As can be seen from Figure 5, in this embodiment, the transformer 1 comprises four primary layers 10, each of which has the same surface area of ​​the primary winding 6. As in the first and second embodiments, the primary windings 6 of the primary layers 10 are interconnected between layers through through holes 13, 14 and 24.

[0147] In this embodiment, the primary windings 6 are arranged symmetrically with respect to their midpoints 18, 19. Here, the midpoints 18, 19 are interconnected using a through hole 13 between the second layer 5c and the fifth layer 5d, thereby defining a common midpoint 18, 19. Each of the first leg 4 (upper left) and the third leg 4 (lower right) comprises two and a half turns wound around them on all primary layers 10.

[0148] With reference to Fig. 6, a fourth embodiment of the planar transformer 1 is described. Figure 6a-6f A schematic cross-sectional view of a layer 10 of a planar transformer 1 according to a fourth embodiment of the present disclosure is shown.

[0149] The transformer 1 of this embodiment includes the aforementioned magnetic core component 2, and the magnetic core component 2 includes at least one plate portion 3 and a plurality of legs 4. In this embodiment, the magnetic core component 2 includes four legs 4.

[0150] Furthermore, the stacking along the stacking direction 8 of the layers 7 is as follows: the secondary winding layers 11 (for example Figure 6e , hereinafter referred to as the "first layer 6e"), the primary winding layer 10 ( Figure 6a , hereinafter referred to as "second layer 6a"), the primary winding layer 10 ( Figure 6c , hereinafter referred to as "third layer 6c"), the primary winding layer 10 ( Figure 6d , hereinafter referred to as "fourth layer 6d"), the primary winding layer 10 ( Figure 6b , hereinafter referred to as the "fifth layer 6b"), the secondary winding layer 11 (eg Figure 6f , hereinafter referred to as the “sixth layer 6f”).

[0151] The secondary winding layer 11, in particular its connection scheme is Figure 7 As shown in the following, reference will be made to Figure 7 Provide explanation.

[0152] The primary winding of the second layer 6 a and the primary winding of the fifth layer 6 b are symmetrical.

[0153] The second layer 6a comprises a starting point 16. Further, the primary layers 10 are interconnected by vias in the order: 14, 15, 24, 26, 27, 28 and 29, the latter connected to a terminal point 17 in the third layer 6c, the primary winding sections 12 being listed in sequence by reference numerals P1-P32.

[0154] Also in this embodiment, as in the third embodiment, the transformer 1 comprises four primary layers 10, each of which has the same surface area of ​​the primary winding 6. Each primary layer 10 comprises eight quarter turns of the primary winding 6.

[0155] The first leg 4 (upper left) includes two complete turns in total, consisting of P3, P4 and P5 and P6 (first complete turn) and P15, P16 and P17 and P2 (second complete turn). The second leg 4 (upper right) also includes two complete turns in total, consisting of P7, P8 and P13, P14 (first complete turn) and P9-P12 (second complete turn). The remaining small gap 30 between P9 and P12 is closed by a tab 31 in the third layer 6c, which is connected to P9 by a second interlayer via 15.

[0156] The fifth layer 6 b includes the midpoint 18 of all the primary layers 10 .

[0157] refer to Figure 7 , explaining the second embodiment of the LLC converter 200 of the present disclosure. Figure 7 FIG. 2 shows a circuit diagram of a second embodiment of an LLC converter 200 according to the present disclosure. Figure 4 As shown in Figure 7 A short circuit between the primary side 60 and the secondary side 50 is schematically shown to demonstrate the common mode current flow.

[0158] LLC converter 200 (hereinafter referred to as “converter 200 ”) includes planar transformer 1 according to the third or fourth embodiment. In other words, converter 200 includes planar transformer 1 having primary layers 10 having the same surface area of ​​primary winding 6 .

[0159] Here, the converter 200 includes a primary center tap 206 leading to the midpoint 18, 19 of the third embodiment or to the midpoint 18 of the fourth embodiment. The primary center tap 206 is directly connected to the RC circuit 204, which includes a resistor element 202 and a capacitor 203 as discrete components. The primary center tap 206 is connected to the midpoint between the input capacitors 205. The primary side 60 and the input side of the converter 200 correspond to Figure 3 Converter 1.

[0160] Due to the configuration of the planar transformer 1 according to the third or fourth embodiment, the number of primary windings Np1 between the starting point 16 and the center tap 206 (i.e., the midpoints 18, 19) is equal to the number of primary windings Np2 between the center tap 206 and the end point 17. The number of primary windings Np1, Np2 corresponds to the number of complete turns of the primary winding 6 on both sides of the midpoints 18, 19.

[0161] The secondary side 50 of the present transformer 1 corresponds to Figure 6e and 6f In contrast, in this embodiment, the secondary side 50 further includes a secondary center tap 207 connected to the midpoint 20 of the secondary winding 5. The secondary layer interconnects the through holes 22 (compare Figure 6e , 6f ), the midpoint 20 is at the same potential as RTN (ie, V_out_rtn). The secondary center tap 207 is also connected to the midpoint between the output capacitors 208. The number of secondary windings Ns1 is equal to Ns2.

[0162] The secondary side 50 thus constitutes a push-pull stage 201 including switches S5 and S6. As in other embodiments, switches S5, S6 may each include or consist of a plurality of switches connected in series or in parallel.

[0163] On the other hand, preferably, the present embodiment optionally includes full-wave rectification instead of the push-pull stage 210 .

[0164] The symmetrical configuration of the primary winding 6 and the symmetrical arrangement of the secondary winding 5 shown in Figures 5 and 6 result in compensation of the common mode currents, since i_C3(t) and i_C4(t) are equal but of opposite polarity. For this reason, the RC circuit 204 also has the advantages described above with respect to the RC circuit 104, in particular providing no loss or very low loss damping.

[0165] Instead of the RC circuit 204 being connected on the primary side 60, the RC circuit 204 may be connected to the secondary center tap 207. Furthermore, both the primary side 60 and the secondary side 50 may include such an RC circuit 204.

[0166] Figures 8a to 8d A schematic configuration example of a core component 2 of a planar transformer 1 according to the present disclosure is shown. Figure 8b Shows Figure 8a Side view of Figure 8d Shows Figure 8c Side view of.

[0167] In particular, Figure 8a and 8b The configuration of the magnetic core assembly 2 as described above with respect to FIG. 1 is shown. Figure 8c and 8d An alternative configuration of the magnetic core assembly 2 is shown. Figure 8a , 8b and for example Figure 1e and 1f As shown in comparison with , the legs 4 may alternatively be arranged at the corners of the plate portion 3 .

[0168] Figure 8a , 8b An advantage of the configuration is that the windings 5, 6 can be covered, which provides an enclosure for the windings 5, 6 and can capture stray magnetic fields.

[0169] Figure 8c , 8d The advantages of this configuration are that the legs 4 can be cooled more effectively and the magnetic core assembly 2 has a more compact size.

[0170] The above two configurations can preferably be combined with the above embodiments. In particular, any of the above configurations of the primary side 60 and their respective primary winding layers 10 can preferably be combined with any of the above configurations of the secondary side 50 and their respective secondary winding layers 11 .

[0171] Therefore, by compensating for the common mode current, the present disclosure provides a planar transformer and LLC converter with high efficiency while having a compact size.

[0172] In addition to the above written description, explicit reference is made to FIGS. 1 to 8 , in which the drawings show in detail circuit diagrams and configuration examples of the present disclosure.

Claims

1. A planar transformer (1) for use in a DC / DC converter, characterized in that: include: A magnetic core assembly (2) comprising at least one plate portion (3) and a plurality of legs (4) extending from the plate portion (3); a secondary side (50) having at least one secondary winding (5); and A primary side (60) having a plurality of primary windings (6); wherein The at least one secondary winding (5) and the plurality of primary windings (6) are stacked into a plurality of layers (7) along a stacking direction (8) parallel to an extension direction (9) of the legs (4), The plurality of primary windings (6) of different layers (7) are connected to each other, and The total surface area of ​​the primary winding (6) is different between at least two layers (7) of the primary winding (6).

2. The planar transformer (1) according to claim 1, characterized in that The number of turns of the layer (7) is defined as the total number of turns of the windings (5, 6) around all legs (4) in the layer (7), wherein the number of turns of the primary winding (6) of each layer (7) of at least two layers (7) of the primary winding (6) is different.

3. The planar transformer (1) according to claim 2, characterized in that The total number of turns of the layers (7) in at least two layers (7) of the primary winding (6) is respectively a non-integer rational number.

4. The planar transformer (1) according to claim 3, characterized in that The total number of turns of each layer (7) in the plurality of layers (7) is an integer.

5. The planar transformer (1) according to claim 1, characterized in that At least one layer (7) of the primary winding (6) comprises at least one primary winding portion (12) which is electrically coupled to other primary winding portions (12) of the same layer (7) only indirectly via at least one primary winding portion (12) of other layers (7).

6. The planar transformer (1) according to claim 5, characterized in that At least one of the primary winding portions (12) is less than one complete turn.

7. The planar transformer (1) according to claim 1, characterized in that At least one layer (7) of the primary winding (6) comprises at least one primary winding portion (12), which is only electrically coupled between the primary side (60) and the secondary side (50), and when the primary side (60) is connected to a voltage, the at least one primary winding portion (12) which is only electrically coupled does not carry current.

8. The planar transformer (1) according to claim 2, characterized in that The total number of turns of the primary winding (6) of all layers (7) around the first leg (4) is different from the total number of turns of the primary winding (6) of all layers (7) around the second leg (4).

9. The planar transformer (1) according to claim 1, characterized in that In at least one layer (7), at least one of the legs (4) does not comprise a primary winding (6) wound around it.

10. The planar transformer (1) according to claim 1, characterized in that The primary winding (6) is elongated and meander-shaped, and / or the secondary winding (5) is plate-shaped.

11. The planar transformer (1) according to claim 1, characterized in that It comprises two layers (7) of a secondary winding (5) connected to each other and sandwiches at least two layers (7) of a primary winding (6) connected to each other.

12. The planar transformer (1) according to claim 11, characterized in that The respectively connected windings are connected to each other via through holes (13, 14, 15, 24, 26-29) extending between the layers (7) in the stacking direction (8).

13. The planar transformer (1) according to claim 1, characterized in that The direction of the magnetic flux in one leg (4) parallel to the extension direction (9) of the leg (4) is the same for all layers (7) of the primary winding (6).

14. An LLC converter (100), characterized in that: Comprising a planar transformer (1) according to any one of the preceding claims.

15. An LLC converter (200), characterized in that: The invention comprises a planar transformer (1), wherein the planar transformer (1) comprises: A magnetic core assembly (2) comprising at least one plate portion (3) and a plurality of legs (4) extending from the plate portion (3); A secondary side (50) having a plurality of secondary windings (5); as well as A primary side (60) having a plurality of primary windings (6); wherein at least one of the secondary windings (5) and the plurality of primary windings (6) are stacked into a plurality of layers (7) along a stacking direction (8) parallel to an extension direction (9) of the legs (4), The plurality of primary windings (6) of different layers (7) are connected to each other; The primary side (60) is connected to the input of the LLC converter (200) and comprises a center tap (206) of the primary winding (6). wherein the secondary side (50) is connected to the output of the LLC converter (200) and comprises a center tap (207) of the secondary winding (5), and Wherein, the primary and / or secondary center taps (206, 207) are directly connected to the RC circuit (204).

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