CN111628631A

CN111628631A - Gate driver, gradient driver system, method for manufacturing driver power supply

Info

Publication number: CN111628631A
Application number: CN201910152224.7A
Authority: CN
Inventors: 王汝锡; 刘小虎; K·麦纳里; J·A·萨贝德; 陶峰峰
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2019-02-28
Filing date: 2019-02-28
Publication date: 2020-09-04

Abstract

The invention provides a gate driver circuit. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power supply circuit includes a coreless transformer and a resonant converter coupled to the coreless transformer. A method of manufacturing an isolated gate driver power supply circuit for a gate driver circuit and a gradient driver system for a Magnetic Resonance Imaging (MRI) system are also provided.

Description

Gate driver, gradient driver system, method for manufacturing driver power supply

Technical Field

The subject matter disclosed herein relates to gate drivers, and more particularly to gate drivers for magnetic resonance imaging systems, gradient driver systems, and methods of manufacturing isolated gate driver power supply circuits for gate driver circuits.

Background

Typically, a Magnetic Resonance Imaging (MRI) system includes multiple subsystems spread throughout different rooms (e.g., equipment room, scanning room, control room, etc.) of a medical facility. Some of these subsystems include circuitry that utilizes ferrite/magnetic components that, if present in the scan chamber, can interfere with the magnetic field in the scan chamber. However, there is a tendency to reduce the footprint of the MRI system and to move some of the components into the scanning room.

Disclosure of Invention

The following outlines certain embodiments commensurate with the scope of the initially claimed subject matter. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible forms of the disclosure. Indeed, the disclosed technology may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

According to a first embodiment, a gate driver circuit is provided. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power supply circuit includes a coreless transformer and a resonant converter coupled to the coreless transformer.

According to a second embodiment, a gradient driver system for a magnetic resonance imaging system is provided. The gradient driver system includes a gate driver circuit. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power circuit includes an air-core transformer that includes a plurality of windings magnetically coupled together. The isolated gate driver power circuit also includes a resonant converter coupled to the air-core transformer. The resonant converter is configured to compensate for leakage inductance of the air-core transformer.

According to a third embodiment, a method of manufacturing an isolated gate driver power supply circuit for a gate driver circuit is provided. The method includes coupling a coreless transformer to the resonant converter, wherein the coreless transformer includes a primary winding and a secondary resistance joined by an interconnect line. The method also includes coupling a power source to the coreless transformer. The method also includes coupling a rectifier to the resonant converter.

Drawings

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic diagram of an embodiment of a gradient driver system in which a gate driver is disposed within a scan chamber;

FIG. 2 is a block diagram of an embodiment of the gate driver of FIG. 1;

FIG. 3 is a schematic diagram of an embodiment of the isolated power supply of FIG. 2;

FIG. 4 is a schematic diagram of an embodiment of an air-core transformer;

FIG. 5 is a schematic diagram of an embodiment of a circuit model and an analytical model for an air-core transformer with resonance;

FIG. 6 is a graphical representation of a gain curve and an input impedance curve for the air-core transformer of FIG. 5;

FIG. 7 is a schematic diagram of an air-core transformer with three windings and a modeled embodiment;

FIG. 8 is a schematic diagram of an embodiment of the air-core transformer of FIG. 7 with resonance;

FIG. 9 is a schematic diagram of an embodiment of a rectifier (e.g., a full bridge rectifier) of an isolated power supply;

FIG. 10 is a schematic diagram of an embodiment of a rectifier (e.g., a half-bridge rectifier) of an isolated power supply;

FIG. 11 is a schematic diagram of an embodiment of a rectifier (e.g., a center-tapped rectifier) of an isolated power supply;

FIG. 12 is a schematic diagram of an embodiment of a rectifier to isolate a power supply (e.g., two full bridge rectifiers coupled to respective windings);

FIG. 13 is a schematic diagram of an embodiment of an isolated gate driver power supply;

FIG. 14 is a graphical representation of gate voltage versus load for an isolated gate driver power supply;

FIG. 15 is a schematic diagram of an embodiment of an air-core transformer in which the windings (e.g., spirals) are integrated into a printed circuit board;

FIG. 16 is a schematic diagram of an embodiment of an air-core transformer in which the windings (e.g., spiral) and interconnections are integrated into a printed circuit board;

FIG. 17 is a schematic diagram of an embodiment of an air-core transformer in which the windings (e.g., spiral shapes) are integrated into a printed circuit board;

FIG. 18 is a schematic diagram of an embodiment of an air-core transformer with cylindrical windings (e.g., with non-intersecting interconnected windings or wires);

FIG. 19 is a schematic diagram of an embodiment of an air-core transformer with cylindrical windings (e.g., with interleaved interconnected windings or wires);

FIG. 20 is a schematic diagram of an embodiment of an air-core transformer with cylindrical windings (e.g., with spacers for securing interconnecting windings or wires);

fig. 21 is a schematic diagram of an embodiment of an air-core transformer (e.g., with interconnected windings or wires integrated into a printed circuit board) soldered to a printed circuit board.

Detailed Description

One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present disclosure, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

The present disclosure relates to gate drivers (e.g., as part of a gradient driver system) that can be reliably and safely used in a scan room of a Magnetic Resonance Imaging (MRI) system without affecting image quality. The gate driver includes an isolated gate driver power circuit that includes a coreless transformer (e.g., an air-core transformer). Thus, the gate driver does not include any ferromagnetic material and is frequency compatible with MRI functionality. In certain embodiments, the coreless transformer includes a primary winding and a secondary winding arranged concentrically to provide acceptable magnetic coupling, sufficient insulation, and minimal sensitivity to switching voltage rate of change (dv/dt). In some embodiments, the isolated gate driver power supply circuit may include a resonant converter coupled to a coreless transformer to compensate for leakage inductance and generate a load-independent output voltage. The isolated gate driver power supply circuit may more effectively reduce conducted interference as well as radiated interference due to soft switching and resonant operation with stable and synchronized operation. In general, gate drivers provide high power efficiency and load insensitivity at a lower cost.

Fig. 1 is a schematic diagram of an embodiment of a gradient driver (e.g., gradient amplifier) system 10 in which a gate driver 12 is disposed within a scan chamber 14. The gradient driver system 10 includes a controller or control board 16 coupled to a plurality of gate drivers 12 via an interface board 18. The gate driver 12 is an electronic circuit that couples control electronics (e.g., controller 16) to the power semiconductor devices to implement control functions (such as turning the power devices on/off). As described in more detail below, the gate drivers 12 each include an isolated gate power supply that includes a coreless transformer (e.g., an air-core transformer). The gate driver 12 is coupled to a power stage 20. Power stage 20 includes power semiconductor devices (e.g., Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), Insulated Gate Bipolar Transistors (IGBTs), or other semiconductor power devices). The number of gate drivers 12 coupled to the power stage 20 to control the switching of the semiconductor power devices may vary. Additionally, a Direct Current (DC) power supply 22 is coupled to the power stage 20. The power stage 20 is coupled to a filter (e.g., a power supply filter) that filters the power supply line to remove ripple signals. As depicted, the gate driver 12, as well as the power stage 20 and filter 26, are located within the scan chamber 14 due to their structure. The gate driver 12 is configured to be reliably and safely utilized in the presence of high magnetic fields within the scan chamber.

Fig. 2 is a block diagram of an embodiment of the gate driver 12 (or gate driver board) of fig. 1. The gate driver 12 includes

control logic

28, 30 coupled to

drivers

32, 34 for controlling the upper and lower gates of the upper and lower power semiconductor devices, respectively, to turn the devices on and off. The

control logic

28, 30 is coupled to fiber optics 36, 38, respectively. The gate driver 12 also includes an isolated power supply (e.g., an isolated gate power supply) that provides voltage levels (e.g., secondary voltages) and power to the control logic to drive (e.g., charge and discharge) the gates of the power semiconductor devices. The power supplies 40, 42 are isolated by high voltage to avoid shorting the power stages. As depicted, the gate driver 12 may include a sensor 44 (e.g., a temperature sensor, a VBUS sensor, etc.) and provide feedback to the controller 16 via fiber optics, isolation wires, differential wires, or other means.

Fig. 3 is a schematic diagram of an embodiment of the isolated power supplies 40, 42 of fig. 2. As depicted, each

isolated power supply

40, 42 includes a coreless transformer 46 (e.g., an air-core transformer) lacking ferromagnetic material that includes a first coil 48 (e.g., a primary Radio Frequency (RF) coil) magnetically coupled (e.g., inductively coupled) to a second coil 50 (e.g., a secondary RF coil). In some embodiments, the transformer 46 may include a different number of windings or coils. As disclosed below, the

coils

48, 50 may be arranged concentrically to provide acceptable magnetic coupling, sufficient insulation, and minimal sensitivity to switching voltage rate of change (dv/dt). As depicted, the transformer 46 (and in particular the coil 48) is coupled to an oscillator 52 and a power amplifier 54. The oscillator 52 converts power from DC to AC. The power amplifier 54 amplifies the power supplied to the load. As depicted, the transformer 46 is coupled to a rectifier 56 and an additional circuit 58. The rectifier 56 converts AC to DC.

Figure 4 is a schematic diagram of an embodiment of an air-core transformer 46. As depicted, the coils 48, 50 (e.g., litz wire) are wound on a single body 60 (e.g., a plastic bobbin) and magnetically coupled together. In certain embodiments, the

coils

48, 50 may be wound on separate bodies and then coupled together. The

coils

48, 50 are disposed in a concentric arrangement, with a portion of the coil 48 disposed within the coil 50. The concentric arrangement improves coupling between the

coils

48, 50. Two different layers of

coils

48, 50 are provided on the

ends

60, 62 of the body 60. The number of turns in each of the

coils

48, 50 may vary. As depicted, insulation layers 64 of different thicknesses are disposed between the

coils

48, 50. The insulating layer 64 may include an insulating paper 66 and an insulating film 68 (e.g., a polyimide film).

To reduce the influence of leakage inductance on load regulation, the transformer 46 is provided with a resonance. Fig. 5 is a schematic diagram of an embodiment of a circuit model 70 and an analytical model 72 of an air-core transformer 76 with resonance. As depicted, L_aAnd L_pFirst and

second coils

48 and 50, respectively, are shown. As depicted, the transformer 76 is coupled to a resonant converter 78 (e.g., a resonant inverter). In particular, the resonant converter 78 includes

respective capacitors

80, 82 coupled in series with the

coils

48, 50. For example, capacitor 80(C1 and C)_p) Coupled in series with coil 48, and capacitor 82(C2 and C)_s) Coupled in series with the coil 50.

Capacitors

80, 82 compensate for leakage inductance. The transformer 76 is coupled to an AC power source 84.

Models

70, 72 represent the resistance of

coils

48, 50 as R1 and R, respectively, for coil 48_pAnd R2 and R for coil 50_s。

In addition, resonant converter 82 tunes transformer 76 to operate at a frequency with the output being a fixed voltage with no load (represented by numeral 84). In other words, the transformer 76 is insensitive to the output voltage (e.g., does affect the voltage gain). For example, the voltage gain (G) for the transformers in the

models

70, 72 shown in equation 1_v) It is desirable to make the difference in switching frequency Δ (ω) equal to 0 (i.e., without affecting the voltage gain):

wherein

Δ(ω)＝ω⁴·L_p·C_p·L_s·C_s·(k_ps ²-1)+ω²·(L_p·C_p+L_s·C_s)-1 (2)

Z_p(ω)＝R_p+i·X_pω (3)

And is

The equation for determining the frequencies ω L and ω H to achieve Δ (ω) ═ 0 is:

and

in the above equation, M_psRepresenting the mutual inductance, L, between the

coils

48, 50_pAnd L_sRepresenting the respective inductances, C, of the

coils

48, 50_pAnd C_sRepresenting the respective capacitances, R, of the

coils

48, 50_acDenotes the total resistance, R_p(ω) represents the resistance of the coil 48, Xp represents the reactance at a given frequency, Z_p(ω) represents the impedance at a given frequency, and k_psRepresenting the coupling coefficient between the

coils

48, 50. Fig. 6 illustrates how a fixed frequency (e.g., resonant frequency) is selected for resonant converter 78 to tune transformer 76. Fig. 6 is a graphical representation of a gain curve 88 and an input impedance curve 90 for the air-core transformer 76 of fig. 5. The resonant frequency 92 (in this case f _ H, where f _ H ═ ω) is selected at the frequency at which the gain curves converge together such that the output is a fixed voltage for the load_HAnd/2 pi). Operating at the resonant frequency 92, the transformer 70 (and the isolated gate driver power supply) will have an output voltage that is insensitive to load variations, as described above. This enables the gate driver power supply together with the transformer 76 with resonance to switch with zero voltage andsoft handoff is therefore utilized to minimize handoff losses and reduce conducted and radiated interference to the MRI system while providing stable and synchronized operation. Any change in voltage can be compensated for via a linear regulator.

In some embodiments, the air-core transformer may include more than two windings or coils. Fig. 7 is a schematic diagram of an air-core transformer 94 with three windings and its modeling. Fig. 7 depicts a model 95 of a transformer 94, an inductance matrix 93, and the transformer 94. In particular, the transformer 94 includes a primary winding or coil 96, a secondary winding or coil 98, and a tertiary winding or coil 100. The respective inductances for the

coils

96, 98, 100 and between the

coils

96, 98, 100 are respectively represented by L₁₁、L₁₂、L₁₃、L₂₂、L₂₃And L₃₃And (4) showing. The leakage inductances of the

coils

96, 98, and 100 are respectively represented by L_l1、L_l2And L_l3And (4) showing. The magnetizing inductance of the coil 96 is defined by L_m1And (4) showing. The coupling coefficient between the coils is represented by K₁₂、K₁₃And K₂₃And (4) showing. In other embodiments, the transformer 94 may include a different number of coils or windings.

As mentioned above, the air-core transformer may include a resonance. Fig. 8 is a schematic diagram of the air-core transformer 94 of fig. 7 with resonance. As depicted, the transformer 94 is coupled to a resonant converter 102 (e.g., a resonant inverter). In particular, the resonant converter 102 includes

respective capacitors

104, 106, 108 coupled in series with the

coils

96, 98, 100. For example, capacitor 104(C1) is coupled in series with coil 96, capacitor 106(C2) is coupled in series with coil 98, and capacitor 108(C3) is coupled in series with coil 100.

Capacitors

104, 106, 108 compensate for leakage inductance. In addition, resonant converter 102 tunes transformer 94 to operate at a frequency where the output is a fixed voltage with no load. This enables the gate driver power supply along with the resonant transformer 94 to utilize zero voltage switching and thus soft switching to minimize switching losses and reduce conducted and radiated interference to the MRI system while providing stable and synchronous operation.

The isolated power supplies 40, 42 of fig. 2 may also each include a rectifier for converting AC to DC and outputting power from the power supplies 40, 42. Fig. 9 to 12 are schematic diagrams of rectifiers. Fig. 9, 10 and 11 show a full bridge rectifier 110, a half bridge rectifier 112, and a center tapped rectifier 114 coupled to a coil or winding 116 (e.g., a secondary winding) of an air-core transformer. As depicted, the winding 116 is coupled in series with a capacitor 118(C2) of the resonant converter. The

rectifiers

110, 112, 114 are coupled to an equivalent load resistance 120(R _ ld). Fig. 12 shows respective full-

bridge rectifiers

110, 122 coupled to respective coils or windings of an air-core transformer. For example, winding 116 (e.g., a secondary winding) is coupled to full-bridge rectifier 110 and winding 124 (e.g., a tertiary winding) is coupled to full-bridge rectifier 122. In fig. 12, the

windings

116, 124 are each coupled in series with a

capacitor

118, 126 of the resonant converter. As depicted, the

rectifiers

116, 122 are coupled to an equivalent load resistance 120(R _ ld).

Fig. 13 is a schematic diagram of an embodiment of an isolated gate driver power supply 128 for a gate driver. The isolated gate driver power supply 128 includes an air-core transformer 130 coupled to a resonant converter 132 (e.g., a resonant inverter). In particular, the air-core transformer includes three coils or

windings

96, 98, 100 coupled in series with capacitors 104(C1), 106(C2), and 108(C3), respectively, of the resonant converter 132. The

windings

96, 98, 100 function as a primary winding, a secondary winding and a tertiary winding, respectively. As described above, resonant converter 132 provides tuning for transformer 130 to compensate for leakage inductance. The full bridge circuit 134 is coupled to the transformer 130 and provides AC power to the transformer 130. Full-

bridge rectifiers

110, 122 are coupled to the

windings

98, 100, respectively. The

rectifiers

110, 122 convert AC to DC and provide power to the load 136.

Fig. 14 is a graphical representation of gate voltage versus load for an isolated gate driver power supply (e.g., as shown in fig. 13). The x-axis 140 and y-axis 142 represent the load and gate voltages, respectively. The graphical representation 138 shows that the gate voltage output of the isolated gate driver power supply remains relatively consistent (e.g., at 80% or greater efficiency) when the load exhibits such a behavior, as shown by curve 144. In other words, the voltage drop for isolating the gate driver power supply is minimal as the load increases.

As noted above, with the utilization of air-core transformers, it is desirable to increase the coupling coefficient while reducing the capacitive coupling between the primary and secondary windings. Fig. 15-21 provide alternative embodiments for both increasing the coupling coefficient and decreasing the capacitive coupling. These embodiments disclose different techniques for fixing the interconnection winding position between a primary winding (e.g., primary side) and a secondary winding (e.g., secondary side) of a transformer.

In some embodiments, the components of the gate driver may be easily integrated into a Printed Circuit Board (PCB). Fig. 15 and 16 are schematic diagrams of the primary side 146 and the secondary side 150 of an air-core transformer 148 integrated (e.g., printed) into or onto a PCB152, wherein the primary side 146 and the secondary side 150 comprise spiral windings. As depicted in fig. 15, the interconnecting windings 154 linking the primary side 146 and the secondary side 150 are discrete from the PCB 152. As depicted in fig. 16, the interconnected windings 154 are integrated (e.g., printed) into the PCB152 and are interleaved to increase coupling between the windings. Fig. 17 is a schematic diagram of an air-core transformer 148 in which the windings (e.g., having a ring shape) of the primary side 146 and the secondary side 150 are integrated into a PCB 152. As depicted in fig. 17, the interconnect winding 154 is discrete from the PCB 152.

Fig. 18-21 are schematic diagrams of a primary side 146 and a secondary side 150 having cylindrical windings. The cylindrical windings of the primary side 146 and the secondary side 150 may be disposed around a plastic bobbin or any other structure that does not include ferromagnetic material. As depicted in fig. 18, the interconnecting windings 154 disposed around the primary side 146 and the secondary side 150 do not cross. As depicted in fig. 19, the interconnected windings 154 are interleaved to increase coupling between the cylindrical windings. In certain embodiments, as depicted in fig. 20, spacers 156 may be used to fix the position of the interconnected windings relative to the cylindrical windings. In certain embodiments, as depicted in fig. 21, the primary side 146 and the secondary side 150 may be soldered to a PCB152 while the interconnect windings 154 (e.g., crossing interconnect windings) are integrated into or on the PCB 152.

Technical effects of the disclosed embodiments include providing a gate driver that can be reliably and safely used in a scan room of a Magnetic Resonance Imaging (MRI) system without affecting image quality. The gate driver includes an isolated gate driver power circuit that includes a coreless transformer (e.g., an air-core transformer). In some embodiments, the isolated gate driver power supply circuit may include a resonant converter coupled to a coreless transformer to compensate for leakage inductance. In addition, the resonant converter tunes the transformer to enable the isolated gate driver power circuit to generate an output independent of the load. The isolated gate driver power supply circuit may more effectively reduce conducted and radiated interference due to soft switching and resonant operation with stable and synchronized operation. Overall, the gate driver provides high power efficiency and load insensitivity at lower cost.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A gate driver circuit, comprising:

an isolated gate driver power supply circuit comprising:

a coreless transformer; and

a resonant converter coupled to the coreless transformer.

2. The gate driver circuit of claim 1, wherein the coreless transformer includes a plurality of windings, the plurality of windings being magnetically coupled together.

3. A gate driver circuit as claimed in claim 2, wherein the plurality of windings comprises a primary winding magnetically coupled to a secondary winding.

4. A gate driver circuit as claimed in claim 3, wherein the primary winding and the secondary winding are arranged concentrically with respect to each other.

5. A gate driver circuit as claimed in claim 4, wherein the resonant converter comprises a plurality of capacitors and the plurality of capacitors comprises a first capacitor and a second capacitor, the first and second capacitors being coupled in series to the primary winding and the secondary winding respectively.

6. A gate driver circuit as claimed in claim 5, wherein the resonant converter is configured to compensate for leakage inductance of the coreless transformer.

7. A gate driver circuit as claimed in claim 6, wherein the resonant converter is configured to enable the isolated gate driver power supply circuit to generate a load independent output voltage.

8. A gate driver circuit as claimed in claim 7, wherein the resonant converter is configured to achieve zero voltage switching by the isolated gate driver power supply circuit.

9. The gate driver circuit of claim 1, wherein the gate driver circuit is configured to be disposed within and used within a scan room having a magnetic resonance imaging system.

10. The gate driver circuit of claim 1, wherein the isolated gate driver power supply circuit comprises: a power supply configured to provide power to the isolated gate driver power supply circuit; and a rectifier configured to provide a power output from the isolated gate driver power supply.

11. A gradient driver system for a Magnetic Resonance Imaging (MRI) system, comprising:

a gate driver circuit, comprising:

an isolated gate driver power supply circuit comprising:

an air-core transformer comprising a plurality of windings that are magnetically coupled together; and

a resonant converter coupled to the air-core transformer, wherein the resonant converter is configured to compensate for a leakage inductance of the air-core converter.

12. The gradient driver system of claim 11, wherein the plurality of windings comprises a primary winding that is magnetically coupled to a secondary winding.

13. A gradient driver system according to claim 12, wherein the primary winding and the secondary winding are arranged concentrically with respect to each other.

14. The gradient driver system of claim 13, wherein the resonant converter comprises a plurality of capacitors, and the plurality of capacitors comprises a first capacitor and a second capacitor coupled in series to the primary resistance and the secondary resistance, respectively.

15. A gradient driver system according to claim 14, wherein the resonant converter is configured to compensate for a leakage inductance of the air-core transformer.

16. The gradient driver system of claim 15, wherein the resonant converter is configured to enable the isolated gate driver power supply circuit to generate a load-independent output voltage.

17. The gradient driver system of claim 11, wherein the gate driver circuit is configured to be disposed within and used within a scan room with the MRI system.

18. The gradient driver system of claim 11, wherein the isolated gate driver power supply circuit comprises: a power supply configured to provide power to the isolated gate driver power supply circuit; and a rectifier providing a power output from the isolated gate driver power supply.

19. A method of manufacturing an isolated gate driver power supply circuit for a gate driver circuit, comprising:

coupling a coreless transformer to a resonant converter, wherein the coreless transformer includes a primary winding and a secondary winding, the primary winding and the secondary winding being linked by an interconnect line;

coupling a power source to the coreless transformer; and

a rectifier is coupled to the resonant converter.

20. The method of claim 19, wherein the resonant converter comprises a first capacitor and a second capacitor, and wherein coupling the coreless transformer to the resonant converter comprises coupling the first capacitor and the second capacitor in series to the primary winding and the secondary winding, respectively.