Juan Rivas Davila

27.12 MHz isolated high voltage gain multi-level resonant DC-DC converter

This paper demonstrates a high efficiency, high power density, and fast transient response dc-dc converter design capable of providing a high-voltage isolated output from a low-voltage input. Specifically, we demonstrate two 100 W, 2000 Vdc proof of concept prototype dc-dc converters operating at a switching frequency of 27.12 MHz with input voltages of 40 V and 100 V respectively. Capacitive isolation provides an efficient means of allowing for multiple rectified outputs to be combined serially without exceeding semi-conductor device limits. Further, it can provide a more efficient means of impedance matching at frequencies of 10s of MHz than traditional methods such as passive matching networks or transformers by the reduction of or elimination of those stages altogether.

13.56 MHz high voltage multi-level resonant DC-DC converter

This paper demonstrates a dc-dc converter that combines resonant rectifiers in a way to achieve impedance matching and significant voltage gains without the need for a high quality factor (Q) impedance matching network. Multiple stages are stacked in a way that allows for higher output voltages without suffering efficiency penalties common to traditional serial type high-voltage converter topologies such as the Crockroft-Walton Multiplier. Application of this design results in an isolated resonant dc-dc converter design that promises high efficiency, fast transient response, and high power density while providing a high-voltage isolated output from a lower-voltage input. Specifically, we demonstrate a 2000 W, 2000 Vdc output proof of concept prototype dc-dc converter operating at a switching frequency of 13.56 MHz from an input voltage of 275 Vdc. Capacitive isolation provides an efficient means of allowing for multiple rectified outputs to be combined serially without exceeding semiconductor device limits. Further, it allows for implementation of a more efficient method of impedance matching at frequencies of 10s of MHz than traditional methods such as passive matching networks or transformers by the reduction of or elimination of those stages altogether.

Low mass RF power inverter for cubesat plasma thruster using 3D printed inductors

This paper presents the design of a low mass RF power inverter at moderate to high power levels (e.g. tens of watts and above) for weight critical applications such as cubesat plasma thrusters. Our approach for mass reduction includes resonant switching operation at tens of MHz, and the 3D printing of light-weight scaffolds that form air core inductors after plating with a thin layer of copper. Specifically, we present a 14.2 MHz 50 W resonant DC-RF power inverter implemented with 3D printed and plated air core toroidal inductors. As a demonstration of design flexibility of the 3D printing process, these toroidal inductors are designed and implemented with optimal cross sections [1] to improve quality factors. The weight of the proposed inverter is reduced by 50% when compared to a 40 W state-of-the-art counterpart in which all the inductors were implemented within the printed circuit board (PCB). The inverter achieves 90% electrical efficiency when operated on a 50 Ω resistive load at an input voltage of 50 V. Then the inverter was implemented with a low pass matching network to drive a helicon double layer (HDL) plasma intended for a cubesat thruster application. The combined inverter and matching network outputs 40 W and achieves 86% DC input to plasma efficiency at an input voltage of 40 V.

Low-Mass RF Power Inverter for CubeSat Applications Using 3-D Printed Inductors

This paper presents the design of a low-mass RF power inverter at moderate to high power levels (e.g., tens of watts and above) for weight critical applications such as CubeSat plasma thrusters. Our approach for mass reduction includes resonant switching operation at tens of MHz, and the 3-D printing of lightweight scaffolds that form air core inductors after plating with a thin layer of copper. Specifically, we present a 14.2-MHz 50-W resonant dc-RF power inverter implemented with 3-D printed and copper plated air core toroidal inductors. As a demonstration of design flexibility of the 3-D printing process, these toroidal inductors are designed and implemented with optimal cross sections [1] to improve quality factors. The weight of the proposed inverter is reduced by 50% when compared to a 40-W state-of-the-art counterpart in which all the inductors were implemented within the printed circuit board. The inverter achieves 91% electrical efficiency when operated on a 50-

Resonant bi-polar DC pulse power supply for electroporation applications

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Inductance cancellation in RF resonant power converters

resistive load at an input voltage of 50 V. To prove its capability of driving plasma loads, the inverter was first tested with a matching network running an inductively coupled plasma (ICP) in a low-pressure argon ampoule outside vacuum environment. The inverter drew 50 W to run the ICP at an input voltage of 20 V. Then as an example application, the inverter was tested with another specifically tuned matching network to drive a helicon double layer (HDL) plasma intended for CubeSat thruster applications. The HDL plasma was formed in a vacuum chamber and was fed with argon. The combined inverter and matching network outputs 40 W and achieves 86% dc input to plasma efficiency at an input voltage of 40 V.

Implementing an impedance compression network to compensate for misalignments in a wireless power transfer system

Electroporation is a technique that uses high pulsed electric fields to create pores in biological cell walls for medical, liquid sterilization and other applications. Many systems use mono-polar pulses for simplicity but electro-migration can limit electrode life. The following paper demonstrates a resonant circuit design for creating high voltage bi-polar dc pulses using a simple control strategy. The circuit topology consists of two Radio Frequency (RF) amplifiers each coupled to a multi-level resonant rectifier employing capacitive isolation and operating at 15 MHz. The RF signals generated by the amplifiers themselves are used to control the pulse duration and output polarity. Any sequence of positive and negative pulse trains can be generated between several μs through dc. This paper presents a proof of concept design providing 800 V positive and negative pulses into a resistive load.

Evaluation of GaN transistor losses at MHz frequencies in soft switching converters

Parasitic inductance cancellation is employed in order to operate a resonant power inverter at 27.12 MHz using a TO-220 through-hole package. A Cauer-type 1 LC network permits the coupling of inductors to achieve cancellation of multiple parasitic inductances and reduces semiconductor device stress in the same way as the Φ2 inverter topology. The elimination of parasitic inductances allows for system cost reduction, increased power handling, and/or relaxation of PCB layout constraints. The inductance cancellation technique is demonstrated through two prototypes (based upon the same silicon MOSFET die) providing 60 W of RF power to a 50 Ω load from a 48 V DC input: one prototype utilizes a small surface-mount package, and another a larger through-hole TO-220 package. (Without inductance cancellation, the lead inductance of the TO-220 is too large and cannot be used in a 27.12 MHz resonant application.) Inductance cancellation was verified through comparing impedances, operating waveforms, and efficiencies between the prototypes with different MOSFET packages.

The “Smart Dim Fuse”: A new approach to load control as a distributed energy resource

This paper presents an impedance compression network (ICN) design in a wireless power transfer (WPT) system to compensate for distance or alignment variations between coils. In midrange WPT applications, magnetic resonant coupling coils are mainly implemented to achieve high efficiency for charging batteries. However, a distance or horizontal alignment variation between coils changes their coupling coefficient, and it decreases the overall performance of WPT systems because the zero voltage switching in a resonant inverter is lost. In order to reduce coil impedance variation, we propose an ICN that compresses variations in coil impedance. The ICN consists of a resistance compression network and a phase compression network to suppress magnitude and phase variations, respectively, in the coil impedance. Only passive components, such as inductors and capacitors, are used to implement an ICN.

Design of very-high-frequency synchronous resonant DC-DC converter for variable load operation

On paper, Gallium nitride (GaN) transistor promises exceptional performance when used in converters operating at high switching frequency; nonetheless, reduction in their performance when used in real circuits have been observed. Previous experiments show that tested GaN transistors can display excessive loss of up to three times their predicted values under certain test conditions. This paper evaluates power losses in GaN transistors when used in class Φ 2 resonant soft-switching inverter topologies at MHz frequencies. Thermometric loss calibration technique is used to calculate the power losses. To gain better insight, experiments are set up to subdivide these losses into two components, one associated with on-state transistors and one associated with off-state transistors. Two GaN devices from two different companies were selected for the study. Further, a control study with a silicon (Si) transistor is also done to confirm the validity of the test method, and to compare the performance of GaN transistors to an existing Si transistor. The following paper presents the loss separation method, and the resulting loss breakdown for the tested devices. The tested operating frequency ranges from 3.39 MHz to 27.12 MHz.