Electromagnetic components with planar and non-planar conductors

Abstract

An example electromagnetic component includes a thin conductor layer having traces extending circumferentially around the electromagnetic component and having widths extending radially around the electromagnetic component, the widths being selected such that the AC current distribution in the traces approximates the AC current distribution in a single trace having the same radial extent as the traces.

Description

[Technical field]

[0001] The devices and techniques described herein relate to electromagnetic components. [Background technology]

[0002] Electromagnetic components such as inductors and transformers may include one or more windings formed of electrical conductors. Some electromagnetic components have one or more magnetic cores. Summary of the Invention [Means for solving the problem]

[0003] Some aspects relate to an electromagnetic component that includes a thin conductor layer having traces extending circumferentially around the electromagnetic component and having a width extending radially around the electromagnetic component, the width being selected such that an AC current distribution in the traces approximates an AC current distribution in a single trace having the same radial extent as the traces.

[0004] The traces may include a first trace having a first width and a second trace having a second width, where the first trace may be an innermost trace of the thin conductor layer and the second width is greater than the first width.

[0005] The traces may include a third trace having a third width greater than the second width, the third trace being radially farther from a center of the electromagnetic component than the second trace.

[0006] The electromagnetic component may further include a magnetic core. The thin conductor layer may be disposed within a magnetic core. The magnetic core may include a center post and an outer rim, and the thin conductor layer may be between the center post and the outer rim.

[0007] The traces may be in series with each other. Some aspects include an electromagnetic component having traces extending circumferentially about the electromagnetic component, the electromagnetic component including a thin conductor layer having a width extending radially about the electromagnetic component, the traces including a first trace having a first width, the first trace being an innermost trace of the thin conductor layer, the first width being:

[0008]

number

[0009] where w1 is the first width and r win is the inner radius of the trace, and r wout is the outer radius of the traces and N is the quantity of traces.

[0010] The traces include a second trace having a second width greater than the first width, radially adjacent the first trace, and the second width being:

[0011]

number

[0012] where w2 is the width of the second trace. The traces include a third trace having a third width greater than the first width and radially adjacent to the second trace on the outside of the second trace, the third width being:

[0013]

number

[0014] where w3 is the width of the third trace. Some aspects include an electromagnetic component having N traces extending circumferentially around the electromagnetic component, a thin conductor layer having a width extending radially around the electromagnetic component, the traces including a first trace having a first width w1, the first trace being an innermost trace of the first layer, a second trace, and a third trace,

[0015]

number

[0016] where k is an index of the second and third traces equal to 2 or 3, respectively, and the second trace is radially adjacent to the first trace, and the third trace is radially adjacent to the second trace outside of the second trace.

[0017] The traces include at least one additional trace outside the third trace, the additional trace having a width w k >2*w1, where w k is a width of a trace having index k, and the trace index k is a number of traces starting with the innermost trace as index 1 and incrementing by 1 counting radially outward from the innermost trace.

[0018] In some embodiments,

[0019]

number

[0020] In the formula, r win is the inner radius of the trace, and r wout is the outer radius of the trace. Some aspects relate to a method of designing an electromagnetic component including a thin conductor layer having traces extending circumferentially around the electromagnetic component and having a width extending radially around the electromagnetic component, the method including obtaining a distribution of AC current density versus radial position of the electromagnetic component for a single trace having the same radial extent as the traces, integrating or summing the distribution over the radial position to obtain a total AC current, dividing the total AC current by a number N of traces to obtain an AC current per trace, and selecting a width for each of the N traces based on the distribution, such that the N traces have the determined per trace AC current.

[0021] Determining the width may include selecting a width for the first trace by integrating or summing along the radial distribution until a width is reached where the AC current in the first trace is equal to the determined AC current per trace.

[0022] The first trace may be the innermost trace or the outermost trace of the first layer. Some aspects relate to an electromagnetic component that includes a winding, the winding including a conductor including a first end and a second end and a plurality of turns connected in series between the first end and the second end, and a series turn capacitance corresponding to a first turn of the plurality of turns.

[0023] The series turn capacitance may be in series with the first turn and may be connected to the first turn at a location different from the first and second ends. A series turn capacitance may be connected in series between the first portion and the second portion of the first turn.

[0024] The plurality of turns may further include a second turn, the series turn capacitance being a first series turn capacitance, and the electromagnetic component may further include a second series turn capacitance corresponding to the second turn.

[0025] The series turn capacitance may include a stand-alone capacitor or an integrated capacitance. The series turn capacitance may include a stand-alone capacitor that is a discrete capacitor.

[0026] The windings may be formed in multiple layers, and the electromagnetic component may include vias between capacitor pads of the stand-alone capacitors that connect the inner layers of the multiple layers to another capacitance.

[0027] The series turn capacitance may include an integrated capacitance formed by an overlap between a first and second layer of conductors separated by a dielectric. The electromagnetic component may include a plurality of series turn capacitances formed by respective overlaps between first and second layers of conductors.

[0028] The first and second layers of conductor may be conductor layers of a printed circuit board. The first and second layers of the conductor may be electrode layers of a multilayer ceramic capacitor (MLCC) process or a low-temperature co-fired ceramic (LTCC) process.

[0029] An alternating current may flow through the winding between the first and second layers in a circumferential direction of the winding through a series turn capacitance. The capacitance value of the series turn capacitance may be selected to provide an impedance between 50% and 200% of the inductive impedance of the first turn.

[0030] The capacitance value of the series turn capacitance may be selected such that the impedance of the series turn capacitance cancels the impedance of the first turn. The series turn capacitance may include multiple series turn capacitances for the first turn.

[0031] Some aspects relate to an electromagnetic component that includes a winding including a thin conductor layer having a trace having at least a first turn and a second turn extending in a circumferential direction, the first turn having a first portion having a constant radius, the second turn having a second portion having a constant radius, and the trace further including a third portion that is a transition portion extending between the first portion and the second portion.

[0032] The trace may further have a circumferentially extending third turn, the third turn having a fourth portion having a constant radius, and the trace further includes a fifth portion, the fifth portion being a second transition portion extending between the fourth portion.

[0033] The third portion and the fifth portion may be in the transition region. The transition region may have an area that is less than a quarter of the area of ​​the winding. The first end of the winding may extend below the transition region or above the transition region.

[0034] The first and second ends of the winding may extend through a back plate of the magnetic core. The first and second ends of the windings may be stacked such that the faces having the widest dimensions face each other.

[0035] The above summary is intended to be illustrative and not limiting. [Brief description of the drawings]

[0036] [Figure 1A] 1 shows examples of electromagnetic components having thin-layer conductors with one turn and three turns, respectively. [Figure 1B] 1 shows examples of electromagnetic components having thin-layer conductors with one turn and three turns, respectively. [Diagram 2]1C illustrates a plot of quality factors for an example planar electromagnetic component, such as the electromagnetic component illustrated in FIGS. 1A and 1B, having windings with different numbers of turns in a single layer of a fixed winding region. [Diagram 3] 1 shows an electromagnetic component having thin layer conductors of varying widths. [Figure 4] 1 shows plots of current density versus radial position for three different designs. [Figure 5A] 1 shows an example of a winding including a series turn capacitance formed by a stand-alone capacitor. [Figure 5B] 1 shows an example of a winding including a series turn capacitance formed by a stand-alone capacitor. [Figure 6A] 1 illustrates via placement between capacitor pads. [Figure 6B] 1 illustrates via placement between capacitor pads. [Figure 6C] 1 illustrates via placement between capacitor pads. [Figure 6D] 1 illustrates via placement between capacitor pads. [Figure 7] 1 shows a cross-sectional view of a structure including an integrated series turn capacitance between two layers of thin film conductors. [Figure 8A] 1 shows various views of a winding including an integrated series turn capacitance; [Figure 8B] 1 shows various views of a winding including an integrated series turn capacitance; [Figure 8C] 1 shows various views of a winding including an integrated series turn capacitance; [Figure 8D] 1 shows various views of a winding including an integrated series turn capacitance; [Figure 9] 1 shows a winding having transition regions between turns. [Figure 10A] 13 shows simulation results illustrating current crowding at the edge of the transition region. [Figure 10B] 13 shows simulation results illustrating current crowding at the edge of the transition region. [Figure 11A]It will be shown that the magnetic field due to the radial component of the trace in the transition region can be corrected by positioning the return trace above or below the transition region. [Figure 11B] It will be shown that the magnetic field due to the radial component of the trace in the transition region can be corrected by positioning the return trace above or below the transition region. [Figure 12] 13 shows simulation results illustrating the correction. [Figure 13A] 1 illustrates that improved performance is possible by stacking two planar conductors. [Figure 13B] 1 illustrates that improved performance is possible by stacking two planar conductors. [Figure 14] 1 illustrates a stacked lead design. [Figure 15] It is shown that the winding leads can extend through openings in the back plate of the magnetic core. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] In the drawings, identical or nearly identical components in different figures are labeled with like reference numbers. For clarity of illustration, not all components are labeled in the drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating various aspects of the methods and apparatus described herein.

[0038] The present inventors have developed several improvements to the electromagnetic components. Some electromagnetic components include thin layer conductors (also referred to herein as thin conductor layers). Thin layer conductors may have the advantage of being low profile and low cost to manufacture, as compared to alternative options such as magnet wire or Litz wire windings. Thin layer conductors can be formed by a variety of different processes, and in one example, can be formed from printed circuit boards (PCB traces).

[0039] FIG. 1A shows an example of an electromagnetic component having a winding (also called a coil) that includes a laminar conductor 2 having a single turn. Also shown in FIG. 1A are the winding leads 3, and a magnetic core 4. The magnetic core 4 in the example is a pot-shaped core having a center post 4a and an outer rim 4b. Optionally, the magnetic core 4 may have a back plate (not shown in FIG. 1A). Also shown in FIG. 1A are directions relative to the electromagnetic component, including a radial direction, extending radially from the center of an imaginary circle that approximates the outline of the electromagnetic component when viewed from above, a circumferential direction perpendicular to the radial direction at each circumferential location around the electromagnetic component, and a vertical (thickness) direction extending perpendicular to the radial and circumferential directions, as used in a polar coordinate system.

[0040] FIG. 1B shows an example of an electromagnetic component having a winding including a laminar conductor 2 having multiple turns, specifically, three turns in this example. Each turn corresponds to one revolution of the winding around the center of the winding. The winding in FIG. 1B gradually spirals from lead 3a toward the center and then returns just below the winding turns as return lead 3b. Also visible in FIG. 1B is the back plate 4c of the magnetic core 4. The winding turns and return lead 3b are electrically insulated from one another by a dielectric material (not shown).

[0041] Electromagnetic components with thin layer conductors can include a single conductor layer (as shown in Figures 1A and 1B), or multiple layers. Examples of electromagnetic components with multiple layers of thin layer conductors are discussed further below.

[0042] A laminar winding is a winding made of one or more laminar conductors. A laminar conductor is an electrical conductor in which the thickness of the winding is much smaller (e.g., at least 10 times smaller) than its width. For example, the laminar winding shown in FIG. 1A can be formed of a conductor foil with a thickness (in the vertical direction) much smaller than its width (in the radial direction). In the case of a laminar winding with multiple turns, the laminar winding has a thickness much smaller (e.g., at least 10 times smaller) than the width (radial extent) of all the turns of the laminar winding. For example, in FIG. 1B, the width of the laminar winding is the radial extent of the winding across all three traces, which in this case are three turns connected in series. Some examples of thin layer conductors or their applications include, but are not limited to, foil layers forming flat current loops (e.g., C-shaped, arc-shaped, rectangular, or any polygonal conductor), edge-wound conductors, printed circuit boards, multilayer self-resonant structures (U.S. Pat. Nos. 10,109,413 and 10,707,011, International Patent Application No. PCT / US2017 / 043377, U.S. Patent Application No. 16 / 994,448), inductively coupled current loops (International Patent Application No. PCT / US2021 / 15260), multilayer conductors with integrated capacitance (International Patent Application No. PCT / US2021 / 041387), and low frequency resonant structures (International Provisional Patent Application No. PCT / US2021 / 041387), as well as any of the previously mentioned patterned foil conductors.

[0043] Thin film conductors (also referred to herein as electrical conductors or simply conductors) can be made of any conductive material or combination of materials, including, but not limited to, one or more metals, such as silver, copper, aluminum, gold, and titanium, as well as non-metallic materials, such as graphite. The conductive material can have an electrical conductivity greater than 1 MS / m, optionally greater than 200 kS / m. Thin film conductors can have any physical form, including, but not limited to, a solid material, a foil, a conductor laminated on a substrate, a printed circuit board trace, an electrode layer in a multilayer ceramic capacitor (MLCC) process, an electrode layer in a low temperature co-fired ceramic (LTCC) process, an integrated circuit trace, or any combination thereof.

[0044] Layers of thin film conductors, or thin film conductors of different traces (e.g., turns), can be separated by any non-conductive material (dielectric material) or combination of materials, including, but not limited to, one or more of air, FR4, PLA, ABS, polyimide, PTFE, polypropylene, Rogers Substrate, plastic, glass, alumina, ceramic, a dielectric or ceramic layer of a multilayer ceramic capacitor (MLCC) process, or a dielectric or ceramic layer of a low temperature co-fired ceramic (LTCC) process.

[0045] 1A and 1B, the laminated conductor may be positioned between a center post and an outer rim within the winding region of the magnetic core. However, the techniques and apparatus described herein are not limited to a particular type of magnetic core, as some magnetic cores may not have a center post and / or an outer rim, and in some cases, the magnetic core may be omitted.

[0046] When a magnetic core is present, the magnetic core may be made entirely or in part of one or more ferromagnetic materials having a relative magnetic permeability greater than 1, optionally greater than 10. The magnetic core material may include, but is not limited to, one or more of iron, various steel alloys, cobalt, ferrites including manganese-zinc (MnZn) and / or nickel-zinc (NiZn) ferrites, nano-granular materials such as Co-Zr-O, and powder core materials consisting of a powder of a ferromagnetic material mixed with an organic or inorganic binder. However, the techniques and devices described herein are not limited with respect to the magnetic core of a particular material. The shape of the magnetic core may be, by way of example, a pot core, a sheet (I-core), a sheet with a center post, a sheet with an outer rim, a RM core, a P core, a PH core, a PM core, a PQ core, an E core, an EP core, or an EQ core. However, the techniques and devices described herein are not limited to a particular magnetic core shape. The electromagnetic component may include one or more of a magnetic core with an air gap in the magnetic flux path or a magnetic core without an air gap. In some embodiments, for example in the case of open-faced pot cores commonly used in wireless power transfer, an air gap in the magnetic flux path may be important.

[0047] Variable trace width based on AC current distribution Electromagnetic components having thin-film conductors can have high performance (i.e., low losses or high quality factor) if the winding consists of a single turn of thin-film conductor - a thin-film conductor wrapped once around a central mandrel (e.g., the center post in the magnetic core of FIG. 1A) - or if the winding consists of multiple turns, each having a radial width less than the skin depth of the conductor at the operating frequency.

[0048] FIG. 2 shows the quality factor of an example of a planar electromagnetic component having windings with different numbers of turns in a single layer of the fixed winding region, such as that shown in FIGS. 1A and 1B. In FIG. 2, the curve entitled "Equal Trace Width" shows the quality factor as a function of the number of turns (or width of each turn) for the example electromagnetic component of FIGS. 1A and 1B, where each turn has the same width (i.e., in the radial direction of FIG. 1B). The quality factor represents the performance of the electromagnetic component, and the higher the quality factor, the better the performance and the lower the losses of the electromagnetic component. It can be seen that a single turn winding (such as the example of FIG. 1A) has a quality factor Q of over 900, but adding a second turn or trace to the winding reduces the quality factor to about 250 (73.4% drop in Q). The performance, or quality factor, is lowest (85% drop in Q) between 7 and 10 turns, and increases as the number of turns increases beyond 10. The quality factor versus number of turns plotted in FIG. 2 is based on an example planar electromagnetic component design, and the specific values ​​of the quality factor and number of turns depend on the electromagnetic component design, but the trends of quality factor as a function of number of turns described herein are similar for different designs. The remaining curves in Figure 2 are discussed below.

[0049] Many applications for electromagnetic components (e.g., inductors, transformers, wireless charging coils) may specify that the number of turns be neither too few (e.g., less than 5) nor too many (e.g., more than 20). The specification for a particular number of turns in some applications may correspond to a number of turns for which the quality factor of the electromagnetic component with the thin-film conductor is a minimum (e.g., 7 turns in FIG. 2), or another number of turns that results in a low Q, which may make the thin-film conductor unsuitable or not as effective as desired.

[0050] The inventors have developed techniques for designing electromagnetic components with thin-layer conductors that have good quality factors independent of the number of turns. Such techniques involve varying the radial width of each trace. That is, different traces in the same layer or plane can have different radial widths. The radial width of the traces can be a function of radial distance from a center point. In particular, the radial width of each trace can be selected to approximate the AC current distribution in a single trace having the same radial extent as the traces of the winding. The apparatus and techniques described herein are applicable to windings with any number of traces or turns greater than or equal to two.

[0051] Electromagnetic components having trace widths selected according to such techniques can achieve high quality factors. For example, as shown in Figure 2, such techniques can result in a quality factor of around 900, independent of the number of turns ("equal AC currents"). This technique can be useful in a variety of applications by introducing a degree of freedom in the design of electromagnetic components having thin-layer conductors.

[0052] In some embodiments, when the radial width of each turn is chosen (e.g., optimally) using the techniques described herein, the performance of the planar electromagnetic component can be improved or the losses in its windings can be reduced by making the order of magnitude as large as possible or larger. An example of such an electromagnetic component having three traces in one layer is shown in FIG. 3. FIG. 3 illustrates that the inner traces can be made smaller in width than the outer traces to approximate the radial AC current distribution in a single trace having the same radial extent as the winding traces. The reason for the smaller width of the inner traces can be seen from FIG. 4, which shows that in a single turn winding, the current tends to concentrate near the inner edge.

[0053] Traditionally, the radial width of each turn in a multi-turn planar coil can be selected by making the direct current (DC) resistance of each turn equal, with the radially outer turns usually being selected to be proportionately wider, even though they have a longer average turn length. Although this strategy ("Equal DC ESR" in Figure 2) can yield better performance than a design in which all traces have equal radial widths ("Equal Trace Width" in Figure 2), the resulting performance of such a multi-turn winding is as low as 37% of a single-turn winding (63% reduction in Q).

[0054] As mentioned above, the inventors have developed a technique for selecting the radial width of each turn of a multi-turn planar coil to result in a coil with a good quality factor independent of the number of turns. As shown in FIG. 2, a planar coil with a single turn winding provides a significantly better quality factor compared to a planar coil with a multi-turn winding. A single turn winding has no radial breaks in the conductive material of the planar coil winding, and the radial AC current distribution in the winding is naturally adjusted so that the majority of the generated magnetic field lines are parallel to the planar winding, thereby reducing winding losses. In contrast, a multi-turn winding, whether the width of each turn is selected to be equal or to provide equal DC equivalent series resistance (ESR), has radial breaks in the conductive material of the winding that disrupt the natural adjustment of the current distribution, resulting in current crowding at the edges of each turn, leading to significant winding losses. The current crowding problem is also exacerbated because the current in each turn - with equal width or equal direct current (DC) ESR - results in an alternating current (AC) current distribution that is not parallel to the winding. As mentioned above, an effective strategy to achieve a multi-turn planar coil with a high quality factor is to select the width of each turn such that the relative AC current distribution in the multi-turn coil mimics the AC current distribution of a single-turn coil. In other words, the width of each turn of a multi-turn winding having N turns (N-turn winding) can be chosen by simulating or calculating the AC current distribution of a single-turn winding with similar inner and outer radii, and dividing the single-turn winding into N sub-rings of different widths, each with equal total AC current based on the simulated or calculated single-turn AC current distribution.

[0055] Use the following steps to find the inner radius r win and outer radius r wout A trace width can be chosen that will have equal AC current in each turn of an N-turn winding having r winis the inner radius of the innermost turn, and r wout is the outer radius of the outermost turn. In this example, the winding has a radius of r win and a circle of radius r wout The coils are located in an annular region (winding region) defined by the area between the circles.

[0056] (1) Inner radius r win and outer radius r wout It is possible to obtain a relationship between current density and radial position for a single trace having a radius of 20.25 mm. In some embodiments, such a relationship (e.g., a curve) can be obtained by simulation or calculation. An example of such a simulated relationship is shown by the solid line in FIG. 4 for an inner radius of 20.25 mm and an outer radius of 41.75 mm.

[0057] (2) Select the desired number of turns / traces N. Step 2 can be performed during the design process of the electromagnetic component and can be performed before or after step 1. The number of turns / traces N is typically determined by a particular application and can be a given parameter for the design of the electromagnetic component. N is typically selected during the design of the larger system in which the electromagnetic component is used. For example, a power converter to obtain a desired current ripple will require a particular inductance and a particular number of turns N will be selected to achieve such inductance. The traces can be designed to be connected in any configuration, such as in series or parallel.

[0058] (3) From step 1, the total AC current in the current density versus position relationship can be determined by integrating or summing the relationship determined in step 1 over radial position across the radial extent of the electromagnetic component. This step can be performed before step 2 or after step 2.

[0059] (4) The total AC current determined in step 3 is divided by the desired number of traces, N. This gives the AC current per trace according to the current distribution in step 1. (5) The width of each trace may be determined such that the AC current for each trace, integrated or summed over the width with the relationship from step 1, equals the AC current for each trace determined in step 4. For example, the width of the first trace (e.g., starting with the innermost or outermost trace) may be calculated first. The width may be calculated by integrating or summing along the relationship or curve determined in step 1 until the AC current for the trace equals the AC current determined in step 4. The widths of the remaining traces may be calculated similarly. These widths may be calculated in various orders, such as from the inner radius to the outer radius, from the outer radius to the inner radius, etc.

[0060] The AC current distribution as a function of radial position in a winding with an inner radius of 20.25 mm and an outer radius of 41.75 mm is compared in FIG. 4 for 1) a single turn coil, 2) a multi-turn coil with equal trace widths for each turn, and 3) a multi-turn coil mimicking the AC current distribution of the single turn coil. The single turn coil has a continuous AC current distribution with higher current densities at the inner and outer edges of the winding. For the multi-turn coil with equal trace widths for each turn, the AC current distribution is significantly different from that of the single turn winding; the current density is significantly higher at the inner edge of each turn than at the outer edge, resulting in significantly higher winding losses. The technique described makes the total AC current in each turn equal based on the single turn AC current distribution, but the multi-turn coil has an AC current distribution that closely follows the AC current distribution of the single turn winding, with slightly higher current densities at the edges of each turn. Although there are increased losses compared to a single turn coil due to the slightly higher current density at the edges of each turn, the increase in losses is minimal and the quality factor is nearly equal to that of a single turn winding.

[0061] The effectiveness of the techniques described herein can be seen in Figure 2, where the quality factor of multi-turn coils with equal AC current ("equal AC current") remains fairly constant from 1 to 50 turns, and only decreases slightly up to 100 turns. Meanwhile, the quality factor of multi-turn coils with equal width or DC ESR is significantly lower than the quality factor of a similar single-turn coil.

[0062] The radial gap between adjacent turns may be determined by the fabrication process. In some embodiments, the radial gap can be as small as possible. This is in contrast to the literature, which states that the spacing must ultimately be the width of each turn / trace, which reduces performance as the copper area is reduced by at least a factor of two. Using the smallest possible radial gap between traces allows for a larger copper area and a better utilization of the winding area. The gap cannot be made infinitesimal, which would reduce the width of each turn. Thus, in some embodiments, the radial gap between adjacent turns / traces is less than the width of the turn / trace and greater than zero. The exact location of the gap with respect to the microcut is not critical, as long as the gap surrounds the microcut.

[0063] Characterizing the Final Coil Design The following description applies to coils with N different turns / traces in a single layer. These N different traces can be connected in parallel or in series or in any combination of series and parallel, and traces in different layers can be connected in parallel or in series or in any combination of series and parallel. N traces connected in series result in a coil with N turns.

[0064] For each layer with N traces, the traces are numbered k=1 to N, where k=1 represents the innermost turn and k=N represents the outermost turn. The inner radius of the planar coil is r win and the outer radius is r wout It is displayed by.

[0065] A planar coil designed according to the above method can be characterized as follows: For a coil with N traces in a layer, Table 1 shows the width w of the kth trace for designing a winding according to the techniques described herein. k (In this case, k = 1 to N-1). The width of the outermost trace, w Nis determined by the total available width and the widths of the other N-1 turns.

[0066] [Table 1]

[0067] Add capacitance into the winding. A conventional coil is constructed from one or more turns of conductive material wound into an induced current loop with two ends (terminations). The coil can be optionally placed on a magnetic core. In a conventional coil, one or more capacitors can be connected to the two ends of the winding. The one or more capacitors connected to the two ends of the winding can provide a resonant capacitance.

[0068] In some embodiments, the resonant capacitance can be distributed among multiple capacitances connected in series with each turn of the coil. The capacitance connected in series with the turns of the coil is also referred to herein as the series turn capacitance. The capacitance value of the series turn capacitance can be selected to cancel or nearly cancel the inductive impedance of the turn with which the capacitor is connected in series. However, the techniques and apparatus described herein are not limited to strict cancellation. Partial cancellation, or additional cancellation, may be useful (e.g., capacitive reactance is 50%-200% of the inductive reactance of the turn). In wireless power transfer, or other resonant power conversion applications, the series turn capacitance value can be chosen to resonate with the inductance of the turn, resulting in a resonance that is used for wireless power transfer or power conversion.

[0069] Distributing some or all of the resonant capacitance among multiple capacitances in series with the turns of the series resonant coil may reduce losses in the circuit, windings, and leads. By distributing the resonant capacitance among one or more turns as a series turn capacitance, the voltage (potential difference) between each turn or between the turn and the return current path is reduced, thereby reducing or eliminating excitation of parasitic capacitance. In some embodiments, lower voltage rated capacitive devices can be used for the capacitance in series with each turn, as opposed to providing a single resonant capacitance for the entire coil. Series turn capacitance may allow for improved power operation by distributing heat generation more evenly within the coil.

[0070] Experimental results show that using series turn capacitance increases the Q. An 18cm 4 turn coil with capacitor leads (conventional design) has a measured quality factor of 150. Adding a series turn capacitor at each turn increases the quality factor to 850.

[0071] In some embodiments, every turn of the coil can include series turn capacitance and provide superior performance, however, the apparatus and techniques described herein are not limited in this respect, as series turn capacitance can be provided for any one or more turns of the coil.

[0072] The inclusion of one or more series turn capacitances may apply to resonant coils constructed with any type of conductor, including, but not limited to, Litz wire, PCB traces, foils, magnet wire, conductors stacked on substrate layers, inductively coupled current loops, multi-layer self-resonant structures, electrode layers of multi-layer ceramic capacitor (MLCC) processes, electrode layers of low temperature co-fired ceramic (LTCC) processes, integrated circuit traces, etc. The conductors may be planar or non-planar. Examples of non-planar coils include solenoid and barrel wound coils. The coils or windings may be placed on a magnetic core, but placing them on a magnetic core is optional.

[0073] The series turn capacitance can be provided by a wide variety of capacitive devices, such as, for example, a stand-alone capacitor or an integrated capacitor. The stand-alone capacitor can be formed by any of a wide variety of devices. Stand-alone capacitors are devices that have a predominantly capacitive (negative reactive) impedance at a desired operating frequency, and they can have an inductive (positive reactive) impedance that is less than the capacitive impedance at the operating frequency, and optionally, an impedance that is less than 20% of the capacitive impedance at the operating frequency. In some embodiments, one or more stand-alone capacitors are discrete capacitors. Stand-alone capacitors can have individual packaging that can be galvanically connected (e.g., by soldering) to an electrical conductor. Stand-alone capacitors can include, but are not limited to, one or more of ceramic capacitors, multilayer ceramic capacitors (MLCCs), film capacitors, mica capacitors, PTFE capacitors, tantalum capacitors, tantalum-polymer capacitors, thin film capacitors, electric double layer capacitors, polymer capacitors, electrolytic capacitors, niobium oxide capacitors, silicon capacitors, tunable capacitors, and any combination, network, or array of devices.

[0074] An example of a coil including a series turn capacitance formed by a stand-alone capacitor is shown in Figures 5A and 5B. Figure 5A shows a three-turn winding formed from thin conductor layers, with each turn including a series turn capacitance 51 formed by one or more stand-alone capacitors. In this example, the single series turn capacitance 51 is located 50% of the way through each turn and 180 degrees away from the two ends 3. However, the series turn capacitance 51 need not be located in this position, nor need it be limited to only one series turn capacitance per turn.

[0075] In some embodiments, providing more than one series turn capacitance per turn may improve heat distribution. When more than one series turn capacitance is included per turn, one or more series capacitances may be separated by a portion of the conductor. FIG. 5B shows an example where each turn includes two series turn capacitances 51 located 180 degrees apart from each other. However, the number of series turn capacitances per turn is not limited to two, as any number of series turn capacitances may be included. The series turn capacitances do not have to be 180 degrees apart from each other and may be anywhere within the turn.

[0076] Standalone Capacitor Connection and Placement In multi-layer structures, a challenge arises in connecting series turn capacitances that are stand-alone capacitors (e.g., discrete capacitors) to turns on inner layers. Using vias to connect to inner layers may result in sacrificing conductor area in other layers. The inventors have recognized that an efficient way to use space is to position the vias in the middle of the gap between the capacitor pads to which the stand-alone capacitors are soldered.

[0077] 6A-6D show a 4 layer PCB with a 4 turn coil on layers 1 and 2. The layer numbering is: top layer=1, inner upper layer=2, inner lower layer=3, bottom layer=4. In particular, FIG. 6A shows a top view of the top layer, FIG. 6B shows a blown up portion of FIG. 6A showing the area around and between the capacitor pads 61, FIG. 6C shows a bottom view of the bottom layer, and FIG. 6D shows a blown up portion of FIG. 6C showing the area around and between the capacitor pads 61. In this example, layers 1 and 2 are 4 turn copper windings, and layer 4 is for the return trace. The capacitor pads 61 on layer 1 are made with a large gap between the pads so that layer 2 is accessible for connection to a stand-alone capacitor. In between these pads is a through via 62 connected to layer 2, and the capacitor pad 61 is placed on the bottom layer (layer 4) where the via 62 is shorted to the capacitor pad. This provides a way to access inner layers using a through-via process, which may be less expensive than a blind or nested via process. Beneficially, via 62 does not cut the conductive area from the top layer (layer 1). In this example, layer 3 may be a blank layer. However, in other embodiments, layer 3 may include a coil layer.

[0078] Integrated series turn capacitance In some embodiments, the series turn capacitance can be formed in an integrated manner. In a multi-layer structure with thin conductors, one or more series turn capacitances can be formed by two layers of thin conductors of the multi-layer structure separated by a dielectric. FIG. 7 illustrates a structure including an integrated series turn capacitance between two layers. As can be seen, conductor A of layer 1 partially overlaps (vertically) with conductor B of layer 2 to form a capacitance between them. Conductor B partially overlaps with conductor C of layer 1 to form a capacitance between them. Conductor C partially overlaps with conductor D of layer 2 to form a capacitance between them. An alternating current (AC) flows through conductors A-D and their integrated series turn capacitance along the direction of the arrows shown in FIG. 7. That is, the AC current flows back and forth between the conductors of layer 1 and layer 2 through the integrated capacitance. The capacitance is proportional to the area of ​​overlap between the conductors of different layers. Thus, the capacitance can be selected by varying the overlap area.

[0079] 8A-8D show a perspective view (FIG. 8A), a top view (FIG. 8B), a top view of the bottom layer (layer 2) (FIG. 8C), and a top view of the top layer (layer 1) (FIG. 8D) of an example of a coil with integrated series turn capacitance as shown in FIG. 7. The conductors in layers 1 and 2 run circumferentially with gaps separating adjacent conductors on the same layer (e.g., A, C), and the conductors on different layers overlap each other to form the series turn capacitance. With this design, an AC current flows back and forth between the two layers as it makes a circuit around the coil, so that a "turn" utilizes the conductors on both layers. In this example, the coil is shown with two turns that are electrically isolated from each other. However, this is only one example, and the coil with integrated series turn capacitance can be formed with any number of turns or turns. Additionally, while an example is shown with two layers, in other examples, the coil with integrated series turn capacitance can be formed in three or more layers. For example, in a three-layer structure, capacitances can be formed between layer 1 and layer 2, then between layer 2 and layer 3, then between layer 3 and layer 2, then between layer 2 and layer 1, and so on around the coil. Additionally, while an example having eight series turn capacitances on the inner turn and twelve series turn capacitances on the outer turn is shown in FIGS. 8A-8D, the apparatus and techniques described herein are not limited in this respect as the number of series turn capacitances on a turn can be zero or more, and the number of series turn capacitances can be the same or different for different turns. Additionally, in some embodiments, the electromagnetic components can have different types of series turn capacitances. For example, one or more series turn capacitances can be formed by integrated series turn capacitances, and one or more series turn capacitances can be formed by stand-alone capacitors.

[0080] Concentric Turn Electromagnetic components with laminar windings are often made with winding turns in a helical configuration with a continuously varying radius of the winding, as shown in FIG. 1B. The inventors have recognized and appreciated that it is possible to enhance the performance of laminar windings by using concentric turns with transition regions between turns of different radii. The turns can be circular and have a constant radius outside of the transition region, as shown in FIG. 9 for a three-turn winding. Within the transition region 91, the traces connecting adjacent turns extend from one radial location corresponding to the first turn to a second radial location corresponding to the second turn. Within the transition region 91, the traces extend in a direction that has a radial component that transitions from one radius to another radius. In some embodiments, the transition region 91 is an area of ​​the winding (in a top view) that has traces that transition from one radius to another radius, but that is less than one-quarter of the total area of ​​the winding (which is the area between the inner radius of the innermost turn to the outer radius of the outermost turn).

[0081] Such a configuration has many advantages. It allows for more efficient use of the available winding space, thereby reducing conduction losses. Also, as shown in FIG. 9, the inner edge of the planar windings nearly follows the center post of the magnetic core, which provides magnetic field lines that are nearly parallel to the plane of the multi-turn winding, which in turn reduces eddy currents induced in the windings, further reducing losses dissipated within the windings. In addition, in a helical winding, the current flow has a small radial component at all circumferential positions, whereas in a winding with concentric turns, the current flow has a radial component only inside the transition region of the winding turns. Furthermore, as discussed below, the concentration of radial current flow in a small area also allows the effects of such radial currents to be cancelled, leading to further performance improvements.

[0082] Current in the transition region A single turn coil has one dimensional current flow (circumferential). A multi-turn coil can have a transition region from one turn to another, which results in current flow in a second dimension (radial). This current flow in the second dimension results in current concentration at the edges of the conductor at the transition region, as shown in the simulation results shown in top and bottom views in Figures 10A and 10B.

[0083] In some embodiments, the magnetic field due to the radial component of the trace in the transition region can be corrected by positioning the return trace above or below the transition region, as shown in Figure 11A (perspective view) and Figure 11B (top view). Figure 12 shows simulation results illustrating the reduced current density compared to Figures 10A and 10B.

[0084] Full coverage provides better current distribution but results in higher parasitic capacitance. Power loss at operating frequencies can be controlled by adding capacitance so that each turn resonates with the inductance of the corresponding turn. However, parasitic capacitance can lead to increased harmonic currents, which can affect circuit performance. Partial coverage can approach full coverage in terms of performance, with smaller or controllable parasitic capacitance. Parasitic capacitance can be controlled to provide higher impedance at higher harmonics, reducing harmonic currents.

[0085] Two traces with opposite currents The performance of electromagnetic components can be improved by carefully arranging planar conductors relative to each other. In areas where two planar conductors have currents flowing in opposite directions, better performance can be achieved by stacking the two planar conductors (with the faces with the larger dimensions adjacent to each other) as shown in FIG. 13B, rather than placing them side-by-side as shown in FIG. 13A. Stacking planar conductors with opposite currents as shown in FIG. 13B results in better current distribution compared to placing them side-by-side. When two conductors are stacked (FIG. 13B), the two conductors do not necessarily have to have the same width. If one conductor is narrower than the other, the current of the wider conductor will flow mainly in the overlapping area.

[0086] This is useful when designing how the coil will be connected to the power electronics circuit. For example, the lead design in Figure 9 can lead to additional losses because there are two side-by-side winding leads with currents flowing in opposite directions. Therefore, the lead currents will be concentrated on the inner edges of those two leads.

[0087] The lead design of Figure 14 reduces losses because the two leads 3 are stacked so that they overlap each other (with their widest dimensions facing each other as opposed to the narrowest dimensions of the previous example), allowing the lead current to utilize the entire width of the lead.

[0088] In other embodiments, the winding leads 3 may extend through openings in the back plate of the magnetic core, as shown in Figure 15. Alternatively, each lead extending through an opening in the back plate can be replaced with an array of one or more pins or wires.

[0089] Various aspects of the apparatus and methods described herein may be used alone or in combination, or in various configurations not described in the description of the embodiments above, and are not limited in application to the details and configurations of components illustrated in the above description or drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0090] Ordinal expressions such as "first," "second," "third," and the like used in the claims to modify claim elements do not in themselves imply a priority, precedence, or ordering of one claim element over another, or a temporal order in which the acts of a method are performed, but are used solely for the purpose of indicating a claim element having a certain name and distinguishing the claim element from another claim element having the same name (which is the same except for the ordinal expression).

[0091] Terms such as "substantially," "approximately," and "about" indicate that a parameter is within 10%, and in some cases less than 5%, of a stated value. Also, the phraseology and terminology used herein is for the purpose of description and not of limitation. The words "including," "comprising," "having," "having," "using," and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof, as well as additional items.

Claims

1. An electromagnetic component, A thin conductor layer having traces extending circumferentially around the electromagnetic component and having a width extending radially around the electromagnetic component, the width being selected so that the AC current distribution in the traces approximates the AC current distribution in a single trace having the same radial extent as the traces. An electromagnetic component comprising:

2. 2. The electromagnetic component according to claim 1, the traces include a first trace having a first width and a second trace having a second width; The electromagnetic component, wherein the first trace is an innermost trace of a thin conductor layer and the second width is greater than the first width.

3. 3. The electromagnetic component according to claim 2, the traces include a third trace having a third width greater than the second width; An electromagnetic component wherein the third trace is radially farther from the center of the electromagnetic component than the second trace.

4. The electromagnetic component according to any one of claims 1 to 3 further comprises: Includes a magnetic core, The thin conductor layer is disposed within the magnetic core, making it an electromagnetic component.

5. 5. The electromagnetic component according to claim 4, The magnetic core includes a center post and an outer rim. The thin conductor layer is an electromagnetic component disposed between the center post and the outer rim.

6. The electromagnetic component according to any one of claims 1 to 3, The traces are in series with each other, electromagnetic components.

7. An electromagnetic component, a thin conductor layer having traces extending circumferentially around the electromagnetic component and having widths extending radially around the electromagnetic component, the traces being first traces having a first width, the first trace being an innermost trace of the thin conductor layer; The first width is [Equation 1] and w in the formula １ is the first width, and r ｗｉｎ is the inner radius of the trace, and r ｗｏｕｔ is the outer radius of the traces and N is chosen to be the quantity of traces.

8. Electromagnetic component 7, wherein The trace further a second trace having a second width greater than the first width; the second trace is radially adjacent to the first trace; The second width is [Equation 2] and w in the formula ２ is selected to be the width of the second trace.

9. Electromagnetic component 8, wherein The trace further a third trace having a third width greater than the first width; the third trace is radially adjacent to and outside the second trace; The third width is [Equation 3] and w in the formula ３ is selected to be the width of the third trace.

10. An electromagnetic component, a thin conductor layer having N traces extending circumferentially around the electromagnetic component and having a width extending radially around the electromagnetic component, the traces having a first width w １ a first trace having a first width, the first trace being an innermost trace of a first layer; The trace is [Equation 4] a second trace having a width of 1000; and a third trace having a width of 1000; where k is an index of the second trace and the third trace equal to 2 or 3, respectively, the second trace being radially adjacent to the first trace, and the third trace being radially adjacent to the second trace outside the second trace. Electromagnetic components including.

11. 11. The electromagnetic component according to claim 10, The trace further at least one additional trace outside the third trace; The third trace is of width w ｋ >2*w １ and The w in the formula ｋ is the width of the trace with index k, The trace index k is the number of traces, starting with the innermost trace as index 1 and incrementing by 1 counting radially outward from the innermost trace, electromagnetic component.

12. 12. The electromagnetic component according to claim 10 or 11, [Equation 5] So, r in the formula ｗｉｎ is the inner radius of the trace, and r ｗｏｕｔ where is the outer radius of the trace, the electromagnetic component.

13. 1. A method for designing an electromagnetic component, comprising: the electromagnetic component includes a thin conductor layer having traces extending circumferentially around the electromagnetic component and having a width extending radially around the electromagnetic component; The method is: obtaining a distribution of AC current density versus radial position of the electromagnetic component for a single trace having the same radial extent as the trace; integrating or summing the distribution over radial position to obtain a total AC current; Dividing the total AC current by the number of traces N to obtain the AC current per trace; selecting a width for each of the N traces, whereby the N traces are obtained with the determined AC current per trace based on the distribution; A method comprising:

14. 14. The method of claim 13, The method, wherein determining the width includes selecting a width for the first trace by integrating or summing along the distribution along a radius until a width is reached where the AC current in the first trace equals the determined AC current per trace.

15. 15. The method of claim 14, The method, wherein the first trace is an innermost trace or an outermost trace of the first layer.

16. An electromagnetic component, a winding including a conductor having a first end and a second end and a plurality of turns connected in series between the first end and the second end; a series turn capacitance corresponding to a first turn of the plurality of turns; An electromagnetic component comprising:

17. 17. The electromagnetic component according to claim 16, The electromagnetic component, wherein the series turn capacitance is in series with the first turn and is connected to the first turn at a location different from the first end and the second end.

18. 18. The electromagnetic component according to claim 16 or 17, The series turn capacitance is connected in series between the first portion and the second portion of the first turn.

19. 18. The electromagnetic component according to claim 16 or 17, the plurality of turns further includes a second turn; the series turn capacitance is a first series turn capacitance; The electromagnetic component further includes a second series turn capacitance corresponding to the second turn.

20. 18. The electromagnetic component according to claim 16 or 17, A series turn capacitance is an electromagnetic component that includes a stand-alone capacitor or an integrated capacitance.

21. 21. The electromagnetic component according to claim 20, Series turn capacitance is an electromagnetic component that includes stand-alone capacitors, which are discrete capacitors.

22. 21. The electromagnetic component according to claim 20, The windings are formed in multiple layers; the electromagnetic component includes a via between capacitor pads of the stand-alone capacitor; A via is an electromagnetic component that connects the inner layers of multiple layers to another capacitance.

23. 21. The electromagnetic component according to claim 20, A series turn capacitance is an electromagnetic component that includes an integrated capacitance formed by an overlap between a first and second layer of conductor separated by a dielectric.

24. 24. The electromagnetic component of claim 23, The electromagnetic component includes a plurality of series turn capacitances formed by respective overlaps between first and second layers of conductors.

25. 23. The electromagnetic component of claim 22, The electromagnetic component, wherein the first and second layers of conductor are conductor layers of a printed circuit board.

26. 23. The electromagnetic component of claim 22, The electromagnetic component, wherein the first and second layers of the conductor are electrode layers of a multilayer ceramic capacitor (MLCC) process or a low temperature co-fired ceramic (LTCC) process.

27. 23. The electromagnetic component of claim 22, An electromagnetic component in which alternating current flows through a winding between a first and second layer in the circumferential direction of the winding through a series turn capacitance.

28. 18. The electromagnetic component according to claim 16 or 17, An electromagnetic component, wherein the capacitance value of the series turn capacitance is selected to provide an impedance between 50% and 200% of the inductive impedance of the first turn.

29. 18. The electromagnetic component according to claim 16 or 17, An electromagnetic component, wherein the capacitance value of the series turn capacitance is selected so that the impedance of the series turn capacitance cancels the impedance of the first turn.

30. 18. The electromagnetic component according to claim 16 or 17, The electromagnetic component, wherein the series turn capacitance includes a plurality of series turn capacitances relative to the first turn.

31. An electromagnetic component, a winding including a thin conductor layer having a trace with at least a first turn and a second turn extending circumferentially; the first turn has a first portion with a constant radius; the second turn has a second portion with a constant radius; The trace further includes a third portion that is a transition portion extending between the first portion and the second portion.

32. 32. The electromagnetic component of claim 31 , the trace further includes a third circumferentially extending turn; the third turn has a fourth portion having a constant radius; The trace further includes a fifth portion that is a second transition portion extending between the fourth portion.

33. 33. The electromagnetic component of claim 32, The electromagnetic component, wherein the third portion and the fifth portion are in a transition region.

34. 34. The electromagnetic component of claim 33, The transition region has an area that is less than one-quarter of the area of the winding.

35. The electromagnetic component according to any one of claims 31 to 34, The electromagnetic component, wherein the first end of the winding extends below the transition region or above the transition region.

36. The electromagnetic component according to any one of claims 31 to 34, The electromagnetic component, wherein the first end and the second end of the winding extend through a back plate of the magnetic core.

37. The electromagnetic component according to any one of claims 31 to 34, An electromagnetic component in which the first and second ends of the windings are stacked with their widest dimensions facing each other.

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