WO2021257680A1 - Isolated gate driver power supply device and related applications - Google Patents

Abstract

An isolated gate driver power supply device disclosed herein comprises an enclosure element configured to contain an electronic encapsulant material. The device further includes a first planar coil element situated in the electronic encapsulant material, a second planar coil element situated in the electronic encapsulant material, and a repeater coil element situated in the electronic encapsulant material. The repeater coil element is positioned in between the first planar coil element and the second planar coil element and is separated from the second planar coil element by a gap distance based on minimizing a coupling capacitance between the first planar coil element and the second planar coil element.

Description

ISOLATED GATE DRIVER POWER SUPPLY DEVICE AND RELATED APPLICATIONS PRIORITY CLAIM This application claims the priority benefit of U.S. Provisional Patent Application Serial No.63/039,761, filed June 16, 2020, the disclosure of which is incorporated herein by reference in its entirety. GOVERNMENT INTEREST The present invention was made with United States government support under grant number DE-EE0008450 awarded by the U.S. Department of Energy and under grant number 1746939 awarded by the National Science Foundation. The United States government has certain rights in the invention. TECHNICAL FIELD The subject matter described herein relates to power supply devices and transformers utilized in wireless power transfer based systems. More specifically, the subject matter relates to an isolated gate driver power supply device and related applications. BACKGROUND With the advancement of wide-bandgap semiconductors devices, medium voltage (1-35kV) power converters are being increasingly deployed in traction and transportation electrification applications. When dealing with such voltage levels, the power switching devices, often times Silicon Carbide (SiC) MOSFETs, require driving stages that are galvanically isolated. More specifically, the gate driver must be powered from a galvanically isolated power source. The figures of merit that dictate this isolation capability are breakdown voltage, which is determined by partial discharge inception voltage, and common mode current immunity, which is determined by coupling capacitance. There are numerous commercially available isolated gate driver power supply (IGDPS) solutions for applications less than 10kV. However, almost no commercially available devices exist that can reliably provide above 10kV isolation. Furthermore, most commercially available IGDPS note isolation capacitance in the range of 4pF to 10pF, which may be inadequate considering the fast turn-on and off times of the new generation of wide-bandgap semiconductors devices. A high partial discharge voltage is of particular importance to the voltage isolation capability. Partial discharge is an electrical discharge phenomenon that occurs in the insulation between two conducting electrodes. This discharge occurs in areas of the insulation where the electric field strength exceeds the breakdown strength of the insulation material present in that area. Oftentimes, voids that are present in insulation material, due to their lower breakdown voltages, are the first areas which experience partial discharge. To obtain a reliable performance metric for high voltage isolation, a partial discharge test is performed.  Numerous studies have attempted to characterize the partial discharge inception phenomenon, with some attempting to come up with approaches to predict the inception voltage onset. For example, FEA based partial discharge analysis has been presented to predict partial discharge inception performance of the isolated transformer. In other studies, the critical electric field of a particular air filed void size is first calculated and then subsequently used to predict the inception voltage in which the critical electric field would be present. These values are then compared to experimentally obtained inception voltage values in order to demonstrate a tight correlation. Further, common mode current can also be detrimental to the operation of IGDPS. The form of conducted electromagnetic interference (EMI) is typically caused by dispersed coupled capacitance found throughout the power supply, with the most significant oftentimes being the parasitic capacitance of the isolation transformer. There are numerous methods used to measure this parasitic coupling capacitance. These include impedance analyzers and common mode current measurements during a switching event such as a double pulse test. To achieve high levels of galvanic isolation and common mode current immunity, some approaches have used either transformer or wireless power transfer (WPT) based approaches. Transformer based approaches typically use ferrite cores to provide tight coupling. WPT based approaches utilize loosely coupled transmitter and receiver coils which behave as an air core transformer that provides a high degree of isolation through physical distance. For example, at least one approach uses a WPT based system within a resonant DC-DC topology to obtain a reported 55kV RMS isolation voltage. However, this isolation voltage figure is based on the air gap of the WPT system and the dielectric breakdown of air, rather than actual inception voltage measurements. It is well known that environmental conditions and debris can significantly affect the inception voltage in systems that are not potted. Likewise, other approaches present a WPT based series-CL resonant converter for a gate driver power supply for 10kV SiC devices. The system features a 100W power output with 4pF of isolation capacitance and a reported isolation voltage of 24kV. Most of the aforementioned approaches/studies lack a comprehensive analysis of their claimed isolation performance. Notably, voltage isolation values are typically reported based on the dielectric breakdown of air or encapsulated material, and not on a partial discharge analysis. It should be noted that the area of partial discharge analysis pertaining to IGDPS design has not been investigated thoroughly. Furthermore, isolation capacitance is not verified through common mode current measurements by way of a double pulse test in many of the studies. Therefore, it is difficult to compare the performance figures of the aforementioned studies to commercially available designs. SUMMARY An isolated gate driver power supply device disclosed herein comprises an enclosure element configured to contain an electronic encapsulant material. The isolated gate driver power supply device further includes a first planar coil element situated in the electronic encapsulant material and a second planar coil element situated in the electronic encapsulant material. The first planar coil element and the second planar coil element are adjacent with each other and are separated by a gap distance related to a dimension of the coil elements contained in each of the first planar coil element and the second planar coil element. In one example embodiment of the isolated gate driver power supply device, the enclosure element is configured to enclose the first planar coil element and the second planar coil element submerged in the encapsulant material. In one example embodiment of the isolated gate driver power supply device, the electronic encapsulant material comprises a dielectric material, a silicone material, a silicone resin material, an epoxy material, or a gel. In one example embodiment of the isolated gate driver power supply device, the gap distance causes the first planar coil element and the second planar coil element to exhibit a low coupling capacitance. In one example embodiment of the isolated gate driver power supply device, the gap distance causes the first planar coil element and the second planar coil element to exhibit a high degree of voltage isolation. In one example embodiment of the isolated gate driver power supply device, each of the coil elements comprises a copper solenoid wire element. In one example embodiment of the isolated gate driver power supply device, each of the coil elements is formed in a square solenoid shape. In one example embodiment of the isolated gate driver power supply device, the first planar coil element is configured to function as a primary side of a transformer that is configured to provide power to a high voltage power converter device. In one example embodiment of the isolated gate driver power supply device, the second planar coil element is configured to operate as a transmitter element on a secondary side of a transformer that is configured to provide power to a high voltage power converter device. For example, the power supply device functions by way of the primary side acting as a transmitter of power and the secondary side as a receiver of power. An isolated gate driver power supply device disclosed herein comprises an enclosure element configured to contain an electronic encapsulant material. The isolated gate driver power supply device further includes a first planar coil element situated in the electronic encapsulant material, a second planar coil element situated in the electronic encapsulant material, and a repeater coil element situated in the electronic encapsulant material. The repeater coil element is positioned in between the first planar coil element and the second planar coil element and is separated from the second planar coil element by a gap distance based on minimizing a coupling capacitance between the first planar coil element and the second planar coil element. In one example embodiment of the isolated gate driver power supply device, the first planar coil element is associated with a Class EF inverter circuit component and the second planar coil element is associated with a Class E rectifier component. In one example embodiment of the isolated gate driver power supply device, the enclosure element is configured to enclose the first planar coil element, repeater coil element, and the second planar coil element submerged in the encapsulant material. In one example embodiment of the isolated gate driver power supply device, the electronic encapsulant material comprises a dielectric material, a silicone material, a silicone resin material, an epoxy material, or an elastomer material. In one example embodiment of the isolated gate driver power supply device, the gap distance causes the first planar coil element and the second planar coil element to exhibit a low coupling capacitance. In one example embodiment of the isolated gate driver power supply device, the gap distance causes the first planar coil element and the second planar coil element to exhibit a high degree of voltage isolation. In one example embodiment of the isolated gate driver power supply device, each of the coil elements comprises a copper solenoid wire element. In one example embodiment of the isolated gate driver power supply device, each of the coil elements is formed in a square solenoid shape or a circular solenoid shape. In one example embodiment of the isolated gate driver power supply device, the first planar coil element is configured to function as a primary side of a transformer that is configured to provide power to a high voltage power converter device. In one example embodiment of the isolated gate driver power supply device, the second planar coil element is configured to operate as a receiver element on a secondary side of a transformer that is configured to provide power to a high voltage power converter device. In one example embodiment of the isolated gate driver power supply device, a repeater coil is positioned based on a determination of peak transfer efficiency. BRIEF DESCRIPTION OF THE DRAWINGS The subject matter described herein will now be explained with reference to the accompanying drawings of which: Figure 1 depicts a diagram illustrating an exemplary isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 2 depicts a diagram illustrating an exemplary planar coil element according to an embodiment of the subject matter described herein; Figure 3 depicts a diagram illustrating an exemplary circuit of an isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 4 depicts an exemplary implementation of an isolated gate driver power supply with a medium voltage converter topology according to an embodiment of the subject matter described herein; Figure 5 depicts a block diagram of an exemplary layout of an isolated gate driver power supply according to an embodiment of the subject matter described herein; Figure 6 depicts a diagram illustrating an exemplary encapsulated isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 7 depicts a circuit diagram of an exemplary isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 8 depicts a circuit diagram of an exemplary Class EF inverter section of an isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 9 depicts a circuit diagram of an exemplary Class E rectifier section of an isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 10 depicts a circuit diagram of an exemplary isolated gate driver power supply device used for repeater coil location analysis according to an embodiment of the subject matter described herein; Figure 11 depicts a graph illustrating the power and efficiency at nominal resonant frequency values of an isolated gate driver power supply device according to an embodiment of the subject matter described herein; Figure 12 depicts a plurality of graphs illustrating the progression of power transfer performance over varying repeater coil placement distances within an isolated gate driver power supply device according to an embodiment of the subject matter described herein; and Figure 13 depicts a block diagram of an exemplary design procedure for an isolated gate driver power supply device according to an embodiment of the subject matter described herein. DETAILED DESCRIPTION The disclosed subject matter pertains to an isolated gate driver power supply that exhibits very high levels of galvanic isolation and low coupling capacitance. Both of these characteristics are achieved through the utilization of a loosely coupled coreless transformer device. Notably, the coreless transformer device operates as a wireless power transfer system with a converter and control electronics, along with the transformer coils, being embedded within electronic encapsulant material. This configuration allows for the system specifications for isolation voltage and coupling capacitance to remain stable in a wide range of environmental conditions. At present, currently available isolated power supplies are aimed at medium voltage converter typologies that utilize at most 6 kilovolt (kV) insulated-gate bipolar transistor (IGBT) devices. Moreover, there are higher powered devices, such as 10 kV and 15 kV silicon carbide (SiC) metal–oxide– semiconductor field-effect transistors (MOSFETs) being developed that will be in widespread use within five years. These higher power devices can be used in applications such as, electric vehicle traction drives, railroad power supplies, light rail vehicles, industrial drives, high voltage direct current (HVDC) applications, medium voltage power converters, flexible alternating current (AC) transmission systems, and the like. In order for these higher voltage devices to be operated in a practical manner, there is a need for highly isolated gate driver power supplies. In particular, the disclosed subject matter provides a highly isolated gate driver power supply that is two to three times more effective in voltage isolation and four times more effective in coupling capacitance reduction when compared to currently available power supply devices. In particular, the disclosed subject matter provides a solution to any application that utilizes electrical power to be delivered to a part of a system that requires a high degree of voltage isolation from adjacent power delivery pathways. For example, if sensitive computing circuitry for controlling a high power converter while contemporaneously being fed from the same electrical power source that is powering the power converter, the distributed power will need to be routed to the computing circuitry via the disclosed isolated power supply in order to protect the sensitive electronics from any high-voltage pulsations, surges, and noise that can damage microprocessors and related circuit elements. In some embodiments, the isolated gate driver power supply is characterized by a coreless transformer design that contributes to the device’s high level of voltage isolation and low coupling capacitance. Figure 1 depicts a diagram illustrating an exemplary isolated gate driver power supply device according to an embodiment of the subject matter described herein. Specifically, Figure 1 depicts an isolated gate driver power supply device 100 comprising an enclosure element 102 that is configured to contain a first planar coil element 104 and a second planar coil element 106. Notably, first planar coil element 104 and second planar coil element 106 are situated (e.g., positioned and/or suspended) in an electronic encapsulant material 108 that is contained within enclosure element 102. In some embodiments, enclosure element 102 includes an acrylonitrile butadiene styrene (ABS) plastic material, a composite material, a metallic material, or any other material conducive for power supply applications. As shown in Figure 1, encapsulant material 108 is used to situate and/or suspend first planar coil element 104 and second planar coil element 106 in such a manner that the planar coils are separated by a gap 112 (e.g., an “air gap” in which only encapsulant material separates the two planar coils). For example, first planar coil element 104 and second planar coil element 106 can be loosely coupled (e.g., coupling factor k that is less than or equal to 0.05) in electronic encapsulant material 108 such that the planar coil elements are separated by a gap 112 of approximately 20 millimeters (mm). In particular, the distance of gap 112 allows for power supply device 100 to exhibit a high level of voltage isolation. Electronic encapsulant material 108 also enables the maintaining of the voltage isolation level experienced by power supply device 100 in various environmental and/or atmospheric conditions. For example, encapsulating the coil elements permits isolated gate driver power supply device 100 to operate in a consistent manner regardless of the heat, cold, humidity, dust, or any other unfavorable environment in which the power supply device is located. In some embodiments, electronic encapsulant material 108 comprises a dielectric material, a silicone material (e.g., Loctite 5620), a silicone resin composition, an epoxy material, or any like elastomer material. In some embodiments, each of the first planar coil element 104 and the second planar coil element 106 can be constructed using a plurality of layers. For example, an exemplary planar coil element is depicted in Figure 2, which illustrates a planar coil element 202 that is presented in an isometric view 200 and a side view 201. Planar coil element 202 may include a control electronics printed circuit board (PCB) layer 204, a ferrite layer 206, and a coil PCB layer 208. Control electronics PCB layer 204 is the layer of the planar coil element 202 that is configured to contain the circuit elements that facilitate the control and operating functionalities (e.g., receiving, transmitting, management, converter function, regulator function, etc.) of planar coil element 202. These circuit elements may include microchips, microcontrollers, digital circuits, and other sensitive electronic components that operate under a low voltage. Notably, the circuit elements in the control electronics PCB layer 204 need to be isolated from the high voltage switching elements coupled to the power supply device. Likewise, planar coil element 202 includes a ferrite layer 206. In some embodiments, ferrite layer 206 is a piece of flexible ferrite material that is positioned in between control electronics PCB layer 204 and coil PCB layer 208 (e.g., “sandwiched” between layers 204 and 208). Notably, ferrite layer 206 provides a measure of insulation and separation between control electronics PCB layer 204 and coil PCB layer 208. Coil PCB layer 208 may include a plurality of coil layers configured as a square solenoid. For example, coil PCB layer 208 can include a metallic coil element (e.g., metal wire) that is formed in a square shape (or any other suitable shape, such as a square, circle, and/or solenoid) that is looped to include a plurality of turns (e.g., 4 turns), each of which is embedded in a single PCB layer. The metallic coil element may comprise any suitable metallic element, such as copper wire. As indicated above, the metallic coil element/component can be shaped as a square, circular, and/or solenoid shape (or any other suitable shape) such that the surface area of the coil element is reduced and/or minimized. By reducing the surface area (or cross-sectional area) of the coil element, the capacitance of the coil element is similarly reduced and/or minimized. As such, the quality factor of the coil element is improved, thereby providing a high transfer efficiency. Notably, a smaller cross-sectional surface area exhibited by a planar coil element lowers the coupling capacitance value of the associated power supply device. Advantages to reducing the coupling capacitance value is discussed in detail below. In some embodiments, the dimensions of the square sides of the coil element is directly related to the distance of the aforementioned gap 112. For example, if gap 112 measures 20 mm, each side of the square shaped coil element is also designed to be approximately 20 mm. Although the above description indicates that the gap between the two planar coil elements and the side of a square shape coil element are approximately equal (e.g., 20 mm), differing or other dimensions or gap distances can be used without departing from the scope of the disclosed subject matter. Returning to Figure 2, each of the layers 204-208 can be stacked together in order to assemble a planar coil element 202 (e.g., an electronics assembly element). For example, the three planar coil elements can be adhered to each other using an adhesive or soldering to form the planar coil element. Once assembled, the entire planar coil element 202 can be positioned in the electronic encapsulant material contained in an enclosure element of the power supply device as depicted in Figure 1. Returning to Figure 1, each of planar coil elements 104 and 106 includes a pair of power terminals. For example, the first planar coil element 104 (e.g., a primary side electronics assembly element) includes a pair of power terminals 114 and the second planar coil element 106 (e.g., a secondary side electronics element) includes a pair of power terminals 116. Each of the power terminals has at least a portion of the terminal that is not submerged in the encapsulant material (i.e., a portion of the power terminals is exposed and accessible). Thus, once assembled completely, first and second planar coil elements 104-106 and electronic encapsulant material 108 are completely enclosed by enclosure element 102, thereby leaving only a portion (e.g., the tips) of power terminals 114 and power terminals 116 exposed. In some embodiments, first planar coil element 104 is configured to function as a transmitter component of the power supply device while power terminals 114 serve as input power terminals. Notably, the coil element of the first planar coil element 104 may be adapted to function as the primary coil of a transformer. Likewise, second planar coil element 106 is configured to function as a receiver component of the power supply device while power terminals 116 serve as output power terminals. Further, the coil element of the second planar coil element 106 may be adapted to function as the secondary coil of the coreless transformer design. Figure 3 depicts a diagram illustrating an exemplary isolated gate driver power supply device 300 according to an embodiment of the subject matter described herein. In some embodiments, a first planar coil element 301 is driven by a converter (e.g., Class E, Class D, or Class DE converter) and gate driver component 304 on the primary side (e.g., circuitry to the left of primary coil 306) of the transformer associated with the power supply device 300. Likewise, a second planar coil element 302 is driven by a rectified receiver on the secondary side (e.g., circuitry to the left of primary coil 306) of the transformer associated with the power supply device 300. Although Figure 3 depicts one exemplary power supply device circuit design, other circuit designs that achieve a high level of voltage isolation and low coupling capacitance in the manner described herein can be utilized without departing from the scope of the disclosed subject matter. In some embodiments, the disclosed isolated gate driver power supply device can function as a power supply that is configured to provide auxiliary power to circuitry of high power converters that utilize high-voltage switching devices (e.g., an electric vehicle fast charger). In order for high-voltage switching devices to be practically implemented, voltage protection isolation between the highly sensitive, low voltage parts of the power converter (e.g., the compute elements, microcontrollers, control circuitry, digital circuits, microchips, etc.) and the high powered components of the power converter (e.g., switching devices experiencing 10,000 volts - 15,000 volts) is necessary. As such, the disclosed isolated gate driver power supply device serves as an exemplary power supply that permits both sides of a power converter to be powered by one power supply. Thus, the disclosed power supply device serves as an interface that isolates the low-voltage digital portions of the power converter from the higher power portions of the power converter. Specifically, the power supply device is configured and designed to achieve a high degree of isolation voltage while also reducing the isolation capacitance. In some embodiments, the disclosed power supply device has been found to attain an RMS isolation voltage of 22 kV and an peak isolation voltage of approximately of 31 kV. Likewise, the power supply device has been tested to achieve an isolation capacitance of approximately 1 picofarad (pF) or less. As such, the disclosed power supply device exhibits a four-fold improvement in isolation capacitance and triples the level of voltage isolation. As indicated above, these metrics are achieved by the unique design and positioning of the planar coil elements. Utilizing a wireless power transfer approach, the planar coil elements are situated with sufficient gap distance while operating at a high frequency. Similarly mentioned above, the planar coil elements are constructed with coil elements (e.g., copper wire) that are formed in a square solenoid shape (e.g., 4 turns) that effectively reduces the cross- sectional/surface area of the coil elements functioning as capacitor “plates”. In some embodiments, the side dimension of the square coil element corresponds approximately to the gap distance by which the planar coil elements are adjacent to each other (e.g., situated in parallel to each other) within the enclosure element. For example, the gap distance separating two facing planar coil elements can be 20 mm while the side dimension (e.g., the length of one side of the solenoid square shape) of the coil element may be similarly measured at 20 mm. Utilization of these dimensions and the associated reduction of the planar coil element surface areas significantly reduces the isolation capacitance, thereby improving the quality factor of the coil element (and achieving a high transfer efficiency). Encapsulating these planar coil elements in the enclosure element with electronic encapsulate material permits the power supply device to maintain consistent performance parameters in all environmental and atmospheric conditions while operating at a high frequency. Power switching devices used in medium voltage power converters require driving stages that provide for a high level of galvanic isolation to ensure noise immunity and high voltage arc protection. The disclosed subject matter presents an isolated gate driver power supply that is based on a wireless power transfer system utilizing a repeater coil element (i.e., a “repeater coil”). The repeater coil increases power transmit distance, which allows for improved galvanic isolation performance. The power supply hardware is encapsulated in its entirety in order ensure performance in a wide range of environmental conditions. Analysis is also presented on the placement of the repeater coil to minimize sensitivity to de-tuning and primary-to-secondary coupling capacitance while maximizing the partial discharge inception voltage. In some embodiments, the configuration of the disclosed isolated gate driver power supply achieves 26.3kV partial discharge inception voltage, less than 2pF isolation capacitance, and is able to transfer up to 10W of power. The disclosed isolated gate driver power supply can be used in a number of applications. For example, Figure 4 depicts an exemplary implementation and placement of an isolated gate driver power supply 402 with a medium voltage converter topology 400 according to an embodiment of the subject matter described herein. In Figure 4, gate driver 404 is powered from a galvanically isolated power source. Further, an exemplary design for an IGDPS based on an industrial scientific medical (ISM) band 6.78MHz WPT system is described herein and illustrated in Figure 5. Notably, Figure 5 depicts an exemplary layout of an isolated gate driver power supply 500. Further, isolated gate driver power supply 500 is completely encapsulated (i.e., encapsulant material 512) to guarantee isolation performance in a wide variety of environmental conditions. Further, isolated gate driver power supply 500 comprises a Class EF inverter 504, a WPT link 506 (e.g., a 6.78MHz repeater coil), a Class E rectifier 508, and a step-down regulator 510. As indicated above, each of these elements are encapsulated in encapsulant material 512. Further, isolated gate driver power supply 500 may be configured to receive power from a single DC power source 502 via inverter 504. Detailed design of the isolated power supply topology, repeater coil placement, partial discharge performance and common-mode current immunity is presented below. In particular, one exemplary design of the system is characterized by a plurality of factors including high isolation capability, efficiency, simple control, and high power density. For example, the topology can be selected to operate in the 6.78 MHz ISM band, which allows for smaller passive components. Since power transfer efficiency is proportional to coupling factor and coil quality factor, high frequency operation also permits longer power transfer distances while maintaining a reasonable efficiency. This longer distance allows for better isolation capability. Another important design attribute includes simplified control. To achieve this, only secondary side control may be utilized for regulation using an off-the-shelf step down converter. As such, this eliminates the need for communication between the primary and secondary sides, which aids in achieving high isolation. As indicated above, the system topology of an isolated gate driver power supply device 500 may be based on a class EF primary stage (i.e., inverter 504), repeater coil (i.e., WPM link 506), and class E rectifier (EF-R-E) (i.e., rectifier 508), as shown in Figure 5. Figure 6 depicts a diagram illustrating an exemplary encapsulated isolated gate driver power supply device according to an embodiment of the subject matter described herein. Notably, Figure 6 depicts an embodiment of an isolated gate driver power supply device 600 comprising an enclosure element 602 that is configured to contain a first planar coil element 606, a repeater coil element 607, and a second planar coil element 609. In some embodiments, first planar coil element 606 is a transmitter coil element and second planar coil element 609 is a receiver coil element. Further, first planar coil element 606 is coupled to transmitter electronics 604, which in turn is equipped with input lead connectors 614. Likewise, second planar coil element 609 is coupled to receiver electronics 610, which in turn is equipped with output lead connectors 616. As shown in Figure 6, each of first planar coil element 606, repeater coil element 607, and second planar coil element 609 is situated and/or suspended in an electronic encapsulant material 608 that is contained within enclosure element 602. In some embodiments, enclosure element 602 includes an acrylonitrile butadiene styrene (ABS) plastic material, a composite material, a metallic material, or any other material conducive for power supply applications. As shown in Figure 6, encapsulant material 608 is used to suspend first planar coil element 606, repeater coil element 607, and second planar coil element 609 in such a manner that the repeater coil is positioned in between first planar coil element 606 and second planar coil element 609. In particular, repeater coil element 607, and second planar coil element 609 are separated by a gap 612 (e.g., an “air gap” in which encapsulant material separates these two coils). Gap 612 is also described as ^^, and can be initially adjusted (i.e., prior to encapsulation) in the manner described below. In particular, gap 612 is adjusted in order to tune isolated gate driver power supply device 600 such that peak transfer efficiency and/or peak power transfer between first planar coil element 606 and second planar coil element 609 is achieved. As such, the distance between first planar coil element 606 and second planar coil element 609 can be strategically selected to allow for power supply device 600 to exhibit a high level of voltage isolation. Electronic encapsulant material 608 also enables the maintaining of the voltage isolation level experienced by power supply device 600 in various environmental and/or atmospheric conditions. For example, encapsulating the coil elements permits isolated gate driver power supply device 600 to operate in a consistent manner regardless of the heat, cold, humidity, dust, or any other unfavorable environment in which the power supply device is located. In some embodiments, electronic encapsulant material 608 comprises a dielectric material, a silicone material (e.g., Loctite 5620), a silicone resin composition, an epoxy material, or any like elastomer material. As described herein, each of first planar coil element 606, repeater coil element 607, and second planar coil element 609 may include a plurality of coil layers configured as a square solenoid. For example, each coil element can include a metallic coil element (e.g., metal wire) that is formed in a square shape (or any other suitable shape, such as a square, circle, and/or solenoid) that is looped to include a plurality of turns (e.g., 4 turns), each of which is embedded in a single PCB layer. The metallic coil element may comprise any suitable metallic element, such as copper wire. As indicated above, the metallic coil element can be shaped as a square, circular, and/or solenoid shape (or any other suitable shape) such that the surface area of the coil element is reduced and/or minimized. By reducing the surface area (or cross-sectional area) of the coil element, the capacitance of the coil element is similarly reduced and/or minimized. As such, the quality factor of the coil element is improved, thereby providing a high transfer efficiency. Notably, a smaller cross-sectional surface area exhibited by a planar coil element lowers the coupling capacitance value of the associated power supply device. Figure 7 depicts a circuit diagram of an exemplary isolated gate driver power supply device according to an embodiment of the subject matter described herein. Notably, isolated gate driver power supply device 700 depicted in Figure 7 is an example circuit diagram of isolated gate driver power supply device 600 depicted in Figure 6. As shown in Figure 7, isolated gate driver power supply device 700 includes a primary stage 702 (e.g., an inverter), a repeater coil element 704, and a secondary stage 706 (e.g., a rectifier). These elements are described in greater detail below. Overview of Class EF approach The class EF inverter 800, shown in Figure 8, implements an LC series branch shunted across the switching device. The LC filter is typically tuned to a certain harmonic of the switching frequency. In some cases, the LC filter is tuned to the second harmonic, in which case the inverter 800 is known as a Class EF₂ (or EF₄, EF₆, etc.). If inverter 800 is tuned to an odd harmonic, inverter 800 is known as a class EF/3 (or EF/5, EF/7, etc.). In all cases, the additional LC filter reduces the high V_ds experienced during operation. This allows for operation at higher DC bus voltages and reduces the influence of C_oss on the circuit. The LC filter also eliminates switching voltage and current harmonics, which improves the high frequency converter’s EMI performance. Recently, a specialized version of the Class EF inverter 800 has been shown to allow for load independent operation. That is, the inverter is able to maintain the ZVS condition throughout a wide load range of operation. In this configuration, the aforementioned LC filter is tuned to a particular fractional harmonic of the inverter’s fundamental switching frequency. The advantage here is that no primary side control is needed. The converter can run with reasonable efficiency with open loop operation. A regulator (e.g., step down regulator 510 in Figure 5) can be added to the output of the second stage to maintain a constant voltage output. Due to the aforementioned advantages, the load independent Class EF inverter was chosen as the topology for the IGDPS. Component selection for the load independent class EF topology is an iterative process. There are several design values that should be identified before component selection. These are detailed in the equations below.

The variable q₁ refers to the ratio of the resonant frequency of the shunt filter L₂C₂ to the switching frequency of the converter. The variable k is the ratio of the MOSFET shunt capacitor C₁ to the shunt filter capacitor C₂. It should be noted that the MOSFET’s output capacitance C_oss is included here in the value of C₁.

The variable p is the loading factor and represents the ratio of the load current I_m to the DC bus voltage.

Finally, X is the residual reactance used to calculate C_p. Solutions for the ZVS load independent Class EF performance of the converter for a range of operating conditions have been previously been reported. An operating point for a duty cycle of 30% was selected to provide the required output power of 5-10W. The component values are listed in Table I below.

Class E rectifier design and approach The class E rectifier utilized on the secondary side allows for low d_v/d_t operation, which results in ZVS. The basic topology of this rectifier type is shown in Figure 9. In this example and as shown in Figure 9, rectifier 900 is fed by a current source, which may be a series LC combination. The shunting capacitor C_E across the diode shapes the voltage waveform across the diode to allow for its switching at low d_v/d_t. This behavior results in reduced losses and noise. The design equations to derive values for C_E for a particular load R_L at any given duty cycle D are given below. First, the phase angle Φ for the desired duty cycle D is calculated by way of:

Next, the ωC_ER_Lis defined:

Next, the ratio of input capacitance C_i to shunt capacitance C_E is defined:

Finally, the ratio of input resistance R_i to load resistance R_L is:

The chosen values for the Class E Rectifier (e.g., rectifier 900) used in this study is shown in Table II.

The minimum values for the L_EC_out output filter are defined as:

In the formulas presented above, V_o is the output voltage across the load R_L, f is the frequency, and I_r is the ripple current. It should be noted that the input impedance of the of the class E rectifier, seen by the current source, is represented by a series combination of R_i and C_i. Therefore, the value of C in the LC receiver branch, which constitutes the current source, is recalculated to account for this increased input capacitance so that the branch remains tuned. In some embodiments, one exemplary circuit, including the repeater coil and excluding the receiver side power regulator, is shown in Figure 7. More specifically, Figure 7 depicts a circuit diagram of an exemplary isolated gate driver power supply device 700 according to an embodiment of the subject matter described herein. As depicted, isolated gate driver power supply device 700 includes a primary stage 702 (e.g., an inverter), a repeater coil element 704, and a secondary stage 706 (e.g., a rectifier). Notably, primary stage 702 is also depicted as inverter 800 in Figure 8 and secondary stage 706 is also depicted as rectifier 900 in Figure 9. Analysis of Repeater Coil Placement In some embodiments, the IGDPS design may include a repeater coil, which is used to improve power transfer performance for the large air gap (e.g., an “isolation gap” between the encapsulated transmitter coil and the receiver coil). However, the use of a repeater coil increases the number of total resonant components within the system. Notably, an increase in resonant components increases the system’s overall sensitivity to mistuning. To ensure the reliability of the IGDPS isolation performance, the hardware components of the power supply device can be encapsulated in electronic encapsulate, such as a Loctite epoxy. One challenge with this disclosed approach is to ensure that the system’s resonant components do not become mistuned when encapsulated. Some studies have investigated the power and efficiency optimization for a three coil system through compensation. Notably, the disclosed subject matter focuses on the location placement of the repeater coil for improved immunity to mistuning. A circuit diagram which includes the repeater coil 1002 can be seen in Figure 10. In particular, Figure 10 depicts a circuit diagram of an exemplary isolated gate driver power supply device 1000 used for repeater coil location analysis according to an embodiment of the subject matter described herein. The Class EF inverter primary side 1004 is represented by current source I₁. The location of the repeater coil placement effects the coil’s coupling to the transmitter and receiver coil, which influences the power transfer and efficiency capability of the repeater coil, as shown in Figure 11. In particular, Figure 11 depicts a graph 1100 illustrating the power and efficiency at nominal resonant frequency values ω₂ and ω₃ of an isolated gate driver power supply device according to an embodiment of the subject matter described herein. In this example, the transmitter coil and receiver coil are placed 18 millimeters (mm) apart. The repeater coil is placed in discrete 2 mm intervals between the transmitter coil and receiver coil to analyze performance. Peak transfer efficiency and power can be observed as ΔX (i.e., distance between repeater coil and receiver coil) approaches 14 mm. At this position, the repeater coil is 2 mm away from the transmitter coil. From this embodiment, the power transfer and efficiency improves as the repeater coil is positioned closer to the transmitter coil. The impedance equations corresponding to Figure 10 for the primary, repeater and receiver coils, Z₁, Z₂ and Z₃ respectively, are shown below:

The impedance seen by the primary side is defined by Z_in:

By keeping the transmitter current I₁ constant, and using the induced voltages on each coil, the current in the repeater coil and receiver coil is defined by I₂ and I₃ respectively:

In Figure 11, ω₂ and ω₃ represent the resonant frequencies of the repeater coil and receiver coil respectively, which are tuned to their nominal values. In other words, the coils’ inductance L₂ and L₃ are fully compensated by the series capacitors C₂ and C₃. In order to characterize the boards mistuning immunity, ω₂ and ω₃ are swept to +/-50 percent of their nominal values. The intention is to investigate the range of mistuning from the nominal that the LC branch in the repeater and receiver can tolerate at each repeater position. Tolerance can be defined by the application, but for this study it is the ability to transfer at least 5W of power and operate at 40 to 50 percent efficiency. In Figure 12, the progression of power transfer performance is shown in plots 1201-1206. The distance ΔX, representing the distance of the repeater coil from the reciever coil, is varied from 4mm to 14mm. The dark area in each of plots 1201-1206 is where the inverter class EF operating condition is met and there is at least 5W of transferred power. It can be seen that at 12mm, the largest area of the plot is included in this zone. At this distance, it can also be seen that the area around the nominal value of ω₂ and ω₂ is within the 5w Zone up to approximately 10 percent in each direction, with more mistuning allowed in ω₂. Further, the center boxes in each of plots 1201- 1206 represents the area where only +/-25 percent variation occurs. Similarly, the efficiency progression is also analyzed. Notably, behavior similar to the power progression plots can be observed. As ΔX increases, the area of peak efficiency forms around the nominal values of ω₂ and ω₃, with more flexibility given to ω₂. Therefore in practical terms, the placement of the repeater coil should be in close proximity to the transmitter coil. For example, in some embodiments, placement should be at 12mm from the receiver coil. This distance allows for some mistuning and still allows for the transfer of the target power and efficiency. Design Procedure Figure 13 depicts a block diagram of an exemplary design procedure and results for an isolated gate driver power supply device according to an embodiment of the subject matter described herein. In some embodiments, a design procedure 1300 for the IGDPS includes the following blocks 1301-1304. In block 1301, a desired isolation voltage is defined. Based on the dielectric breakdown of the encapsulated material, this will determine the total air gap (i.e., isolation gap) length between the main transmitting coils and receiving coils. In block 1302, a desired output power for the IGDPS is identified. This will determine the design parameters for the class EF inverter primary stage. In block 1303, the repeater coil placement to meet desired power output and maximum ω₂ and ω₃ flexibility is identified. This will provide for a degree of mistuning immunity once the system is encapsulated. In block 1304, a class E rectifier is designed on the receiver for desired output power and load. Encapsulation In some embodiments, the IGDPS inverter board, coils, and receiver boards can be encapsulated with encapsulant material (e.g., Loctite 5620 material) to preserve and enhance isolation performance. In order to minimize the formation of voids, the curing of the encapsulate may take place in a pressurized chamber at 40 PSI. In some embodiments, the disclosed isolated gate driver power supply device can be utilized in various applications. For example, potential application areas include electric vehicle traction motor applications, railroad power supply applications, light rail vehicles, industrial drives, high voltage direct current (HVDC) applications, flexible alternating current (AC) transmission systems (FACTS) applications, medium voltage converter applications, and the like. While the methods, compositions, and systems have been described herein in reference to specific aspects, features, and illustrative embodiments, it will be appreciated that the utility of the subject matter is not thus limited, but rather extends to and encompasses numerous other variations, modifications and alternative embodiments, as will suggest themselves to those of ordinary skill in the field of the present subject matter, based on the disclosure herein. Various combinations and sub-combinations of the structures and features described herein are contemplated and will be apparent to a skilled person having knowledge of this disclosure. Any of the various features and elements as disclosed herein can be combined with one or more other disclosed features and elements unless indicated to the contrary herein. Correspondingly, the subject matter as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its scope and including equivalents of the claims. The disclosure of each of the following references is incorporated herein by reference in its entirety to the extent not inconsistent herewith and to the extent that it supplements, explains, provides a background for, or teaches methods, techniques, and/or systems employed herein. REFERENCES [1] H. Abu-Rub, J. Holtz, J. Rodriguez, and G. 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Gohil et al., “Dual-output isolated gate driver power supply for medium voltage converters using high frequency wireless power transfer,” in 2020 IEEE Applied Power Electronics Conference and Exposition (APEC). IEEE, 2020, pp.1821–1828. [21] C. Cheng, C. Wang, Z. Zhou, W. Li, Z. Deng, and C. C. Mi, “Repeater coil-based wireless power transfer system powering multiple gate drivers of series-connected igbts,” IET Power Electronics, vol.13, no.9, pp. 1722–1728, 2020. [22] K. Hata, T. Imura, and Y. Hori, “Simplified measuring method of kq product for wireless power transfer via magnetic resonance coupling based on input impedance measurement,” in IECON 2017-43rd Annual Conference of the IEEE Industrial Electronics Society. IEEE, 2017, pp.6974–6979. [23] S. Aldhaher, P. D. Mitcheson, J. M. Arteaga, G. Kkelis, and D. C. Yates, “Light-weight wireless power transfer for mid-air charging of drones,” in 201711th European Conference on Antennas and Propagation (EUCAP), 2017, pp.336–340. [24] S. Aldhaher, P. D. Mitcheson, J. M. Arteaga, G. Kkelis, and D. C. Yates, “Light-weight wireless power transfer for mid-air charging of drones,” in 201711th European Conference on Antennas and Propagation (EUCAP). IEEE, 2017, pp.336–340. [25] J. M. Arteaga, S. Aldhaher, G. Kkelis, C. Kwan, D. C. Yates, and P. D. Mitcheson, “Dynamic capabilities of multi-mhz inductive power transfer systems demonstrated with batteryless drones,” IEEE Transactions on Power Electronics, vol.34, no.6, pp.5093–5104, 2018. [26] M. K. Kazimierczuk, “Analysis of class e zero-voltage-switching rectifier,” IEEE Transactions on Circuits and Systems, vol.37, no.6, pp.747–755, 1990. [27] M. K. Kazimierczuk and D. Czarkowski, Resonant power converters. John Wiley & Sons, 2012. [28] Q. Wang and Y. Wang, “Power efficiency optimisation of a threecoil wireless power transfer using compensatory reactance,” IET Power Electronics, vol.11, no.13, pp.2102–2108, 2018 It will be understood that various details of the presently disclosed subject matter can be changed without departing from the scope of the presently disclosed subject matter. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.

Claims

CLAIMS What is claimed is: 1. An isolated gate driver power supply device, comprising: an enclosure element configured to contain an electronic encapsulant material; and a first planar coil element situated in the electronic encapsulant material; a second planar coil element situated in the electronic encapsulant material; and wherein the first planar coil element and the second planar coil element are positioned adjacent to each other and are separated by a gap distance related to a dimension of coil elements contained in each of the first planar coil element and the second planar coil element.

2. The isolated gate driver power supply device of claim 1 wherein the enclosure element is configured to enclose the first planar coil element and the second planar coil element submerged in the encapsulant material.

3. The isolated gate driver power supply device of claim 1 wherein the electronic encapsulant material comprises a dielectric material, a silicone material, a silicone resin material, an epoxy material, or an elastomer material.

4. The isolated gate driver power supply device of claim 1 wherein the gap distance causes the first planar coil element and the second planar coil element to exhibit a low coupling capacitance.

5. The isolated gate driver power supply device of claim 1 wherein the gap distance causes the first planar coil element and the second planar coil element to exhibit a high degree of voltage isolation.

6. The isolated gate driver power supply device of claim 1 wherein each of the coil elements comprises a copper solenoid wire element.

7. The isolated gate driver power supply device of claim 1 wherein each of the coil elements is formed in a square solenoid shape or in a circular solenoid shape.

8. The isolated gate driver power supply device of claim 1 wherein the first planar coil element is configured to function as a primary side of a transformer that is configured to provide power to a high voltage power converter device.

9. The isolated gate driver power supply device of claim 1 wherein the second planar coil element is configured to operate as a receiver element on a secondary side of a transformer that is configured to provide power to a high voltage power converter device.

10. An isolated gate driver power supply device, comprising: an enclosure element configured to contain an electronic encapsulant material; a first planar coil element situated in the electronic encapsulant material; a second planar coil element situated in the electronic encapsulant material; and a repeater coil element situated in the electronic encapsulant material, wherein the repeater coil element is positioned in between the first planar coil element and the second planar coil element and is separated from the second planar coil element by a gap distance based on minimizing a coupling capacitance between the first planar coil element and the second planar coil element.

11. The isolated gate driver power supply device of claim 10 wherein the first planar coil element is associated with a Class EF inverter circuit component and the second planar coil element is associated with a Class E rectifier component.

12. The isolated gate driver power supply device of claim 10 wherein the enclosure element is configured to enclose the first planar coil element, repeater coil element, and the second planar coil element submerged in the encapsulant material.

13. The isolated gate driver power supply device of claim 10 wherein the electronic encapsulant material comprises a dielectric material, a silicone material, a silicone resin material, an epoxy material, or an elastomer material.

14. The isolated gate driver power supply device of claim 10 wherein the gap distance causes the first planar coil element and the second planar coil element to exhibit a low coupling capacitance.

15. The isolated gate driver power supply device of claim 10 wherein the gap distance causes the first planar coil element and the second planar coil element to exhibit a high degree of voltage isolation.

16. The isolated gate driver power supply device of claim 10 wherein each of the coil elements comprises a copper solenoid wire element.

17. The isolated gate driver power supply device of claim 10 wherein each of the coil elements is formed in a square solenoid shape or a circular solenoid shape.

18. The isolated gate driver power supply device of claim 10 wherein the first planar coil element is configured to function as a primary side of a transformer that is configured to provide power to a high voltage power converter device.

19. The isolated gate driver power supply device of claim 10 wherein the second planar coil element is configured to operate as a receiver element on a secondary side of a transformer that is configured to provide power to a high voltage power converter device.

20. The isolated gate driver power supply device of claim 10 wherein a repeater coil is positioned based on a determination of peak transfer efficiency.