Johan Strydom

Understanding the Effect of PCB Layout on Circuit Performance in a High-Frequency Gallium-Nitride-Based Point of Load Converter

The introduction of enhancement-mode gallium-nitride-based power devices such as the eGaN FET offers the potential to achieve higher efficiencies and higher switching frequencies than possible with silicon MOSFETs. With the improvements in switching performance and low parasitic packaging provided by eGaN FETs, the printed circuit board (PCB) layout becomes critical to converter performance. This paper will study the effect of PCB layout parasitic inductance on efficiency and peak device voltage stress for an eGaN FET-based point of load (POL) converter operating at a switching frequency of 1 MHz, an input voltage range of 12-28 V, an output voltage of 1.2 V, and an output current up to 20 A. This paper will also compare the parasitic inductances of conventional PCB layouts and propose an improved PCB design, providing a 40% decrease in parasitic inductance over the best conventional PCB design.

Design of planar integrated passive module for zero-voltage-switched asymmetrical half-bridge PWM converter

Integrated L-L-C-T (inductor-inductor-capacitor-transformer) technology has been the subject of intensive research over the last few years. Its application to resonant power electronic converters has been reported by many previous publications. This paper presents the application of a planar L-L-C-T module to the integration of passive module for a zero-voltage-switched asymmetrical half bridge PWM converter for application in distributed power systems. Two output transformers, two current doubler inductors, the ZVS resonant inductor and the transformer DC decoupling capacitor are integrated into a single module. The design procedure is discussed and some special considerations of the L-L-C-T module in nonresonant applications are addressed. A 1 kW 300 V-400 V input, 48 V output asymmetrical half bridge PWM converter (AHBC) employing the L-L-C-T module is constructed. A comparison of the AHBC using the integrated passive module and the same circuit using discrete components is given.

Understanding the effect of PCB layout on circuit performance in a high frequency gallium nitride based point of load converter

The introduction of enhancement mode gallium nitride based power devices such as the eGaN®FET offers the potential to achieve higher efficiencies and higher switching frequencies than possible with Silicon MOSFETs. With the improvements in switching performance and low parasitic packaging provided by eGaN FETs, the PCB layout becomes critical to converter performance. This paper will study the effect of PCB layout parasitic inductance on efficiency and peak device voltage stress for an eGaN FET based point of load (POL) converter operating at a switching frequency of 1 MHz, an input voltage range of 12-28 V, an output voltage of 1.2 V, and an output current up to 20 A. This work will also compare the parasitic inductances of conventional PCB layouts and propose an improved PCB design providing a 40% decrease in parasitic inductance over the best conventional PCB design.

Evaluation of Gallium Nitride Transistors in High Frequency Resonant and Soft-Switching DC–DC Converters

The emergence of gallium nitride (GaN)-based power devices offers the potential to achieve higher efficiencies and higher switching frequencies than possible with mature silicon (Si) power MOSFETs. In this paper, we will evaluate the ability of gallium nitride transistors to improve efficiency and output power density in high frequency resonant and soft-switching applications. To experimentally verify the benefits of replacing Si MOSFETs with enhancement mode GaN transistors (eGaNFETs) in a high frequency resonant converter, 48-12 V unregulated isolated bus converter prototypes operating at a switching frequency of 1.2 MHz and an output power of up to 400 W are compared using Si and GaN power devices.

A comparison of fundamental gate-driver topologies for high frequency applications

The gate-driver in most power electronic converters is seldom given sufficient attention during the design stage even though it is the circuit exposed to much of the same voltage stresses as the switching devices and yet despite this, is a crucial component to a sound functioning system. At higher switching frequencies, and either low power or high voltage applications, the effect of the gate-driver on the overall converter performance becomes even more pronounced. When considering a gate-driver for a power electronic system, the converter topology, operating conditions and requirements, voltage and current ratings, and switching frequency determines the suitability and applicability of a chosen gate-driver to the application. This paper discusses different gate-drivers, represented by three fundamental gate-driver topologies that are evaluated in terms of suitable operating conditions, construction and losses. These gate-drivers, constructed using two different methods, a hybrid and SMD, also forms part of the evaluation. In addition, some of the issues as switching frequencies keep increasing is also addressed.

Some limits of integrated L-C-T modules for resonant converters at 1 MHz

Integrated LCT (inductor-capacitor-transformer) technology has been the subject of intensive research over the last few years. Research into producing optimum design equations has been conducted. To determine some of the physical and technological limitations of the integrated LCT technology, a 1 kW, 1 MHz resonant DC-DC power converter was designed and built. The design was limited only by material, construction and physical restrictions. Through this process, it is hoped that some of the current technological limitations can be quantified. The design and construction process is given, while some of the limits of this technology are derived from experimental results.

Integration of a 1 MHz converter with active and passive stages

Integration of passive components, such as the planar LCT (inductor-capacitor-transformer) technology has been the subject of research over the last few years and has been proven to be viable at high frequencies, but no consideration was given to the rest of the converter. In this paper, the integration of these passive components and active components into a single hybrid converter is presented. From inception, the design process of each of these stages is directed by the nature of the other for the realization of an overall improved converter.

Volumetric limits of planar integrated resonant transformers: a 1 MHz case study

The integrated planar resonant/transformer structures analyzed are constructed from planar ferrites, conductive layers, leakage layers and ceramic dielectric substrates. The minimum dimensions for these electromagnetically integrated structures are determined based on electromagnetic and technological limits respectively. Thus to answer the question as to what is the minimum required volume that can be theoretically achieved, the electromagnetic material limits are analyzed. These material limits are expressed in terms of the permeabilities, permittivities and conductivities, skin effect and breakdown field of the different materials. A design based solely on these electromagnetic limits is developed and compared to the present constructional limitations. This is conducted for an example of a particular integrated resonant/transformer structure, the L-L-C-T, to illustrate the analysis. This analysis indicates that design based on the electromagnetic limits results in volumes two orders of magnitude smaller than the present prototypes, illustrating that the power density is at present only limited by constructional technology. The thermal limit, however, is expected to be the next barrier within one order of magnitude.

Improved loss determination for planar integrated power passive modules

Integration of passive components, such as the planar L-C-T (Inductor-Capacitor-Transformer) technology has been the subject of research over the last few years and has been proven to be viable at high frequencies. Research to determine the volumetric limits of these structures has shown that better loss modeling is required before any volume reduction and optimization is possible. A comprehensive, yet simple loss model for the planar integrated L-L-C-T is presented and verified using experimental case studies. The loss model takes non-sinusoidal core excitation losses, both skin- and proximity-effect conductor losses and dielectric losses into account.

Wide band modeling of integrated power passive structures: the series resonator

This paper presents a higher order frequency plane model for an integrated series resonant power conversion module. The cause for the occurrence of high frequency impedance peaks is identified as the parallel resonance between the winding inductance and its inter-winding capacitance. The inter-winding capacitance can be calculated from a transmission-line-based lumped model using Schwartz-Christoffel transformation. The simulation results using the proposed model correlate the small-signal test results very well. The proposed higher order impedance model will help to evaluate the high frequency behavior of an ISRM or to minimize the high frequency parasitics. It can also be easily implemented in the design-oriented algorithm to facilitate the design and optimization of an ISRM. The application of this model to more complicated structures as well as some practical design issues is also discussed.