David J. Perreault

Opportunities and Challenges in Very High Frequency Power Conversion

THIS paper explores opportunities and challenges in power conversion in the VHF frequency range of 30-300 MHz. The scaling of magnetic component size with frequency is investigated, and it is shown that substantial miniaturization is possible with increased frequencies even considering material and heat transfer limitations. Likewise, dramatic frequency increases are possible with existing and emerging semiconductor devices, but necessitate circuit designs that either compensate for or utilize device parasitics. We outline the characteristics of topologies and control methods that can meet the requirements of VHF power conversion, and present supporting examples from power converters operating at frequencies of up to 110 MHz.

Analysis and synthesis of randomized modulation schemes for power converters

After establishing that the proper objects of study for randomized modulation of converters are the power spectra of signals, we classify such modulation schemes and present associated spectral formulas, several of which are new. We also discuss numerical (Monte Carlo) verification issues for power spectral formulas. A general spectral formula for stationary randomized modulation schemes is presented, and specialized to several modulation schemes of practical interest for DC/DC converters. Analytical results are then given for block-stationary randomized modulation schemes that are suitable for inverter operation. In the process, we present results for several modulation schemes that have been reported in the literature without analytical explanations. Experimental verifications of some of our analytical results are presented. We formulate narrow-band and wide-band synthesis problems in randomized modulation, and solve them numerically. Our results suggest that randomized modulation is very effective in satisfying narrow-band power constraints, but has limited effectiveness in meeting wide-band constraints. >

Distributed interleaving of paralleled power converters

This paper introduces a distributed approach to interleaving paralleled power converter cells. Unlike conventional methods, the distributed approach requires no centralized control, automatically accommodates varying numbers of converter cells, and is highly tolerant of subsystem failures. A general methodology for achieving distributed interleaving is proposed, along with a specific implementation approach. The design and experimental verification of a 50 kHz prototype system is presented, and quantitative performance comparisons are made between synchronized clocking, independent clocking, and interleaved clocking of the converter cells. The experimental results corroborate the analytical predictions and demonstrate the tremendous benefits of the distributed interleaving approach.

Automotive power generation and control

This paper describes some new developments in the application of power electronics to automotive power generation and control. A new load-matching technique is introduced that uses a simple switched-mode rectifier to achieve dramatic increases in peak and average power output from a conventional Lundell alternator, along with substantial improvements in efficiency. Experimental results demonstrate these capability improvements. Additional performance and functionality improvements of particular value for high-voltage (e.g., 42 V) alternators are also demonstrated. Tight load-dump transient suppression can be achieved using this new architecture. It is also shown that the alternator system can be used to implement jump charging (the charging of the high-voltage system battery from a low-voltage source). Dual-output extensions of the technique (e.g., 42/14 V) are also introduced. The new technology preserves the simplicity and low cost of conventional alternator designs, and can be implemented within the existing manufacturing infrastructure.

Submodule Integrated Distributed Maximum Power Point Tracking for Solar Photovoltaic Applications

This paper explores the benefits of distributed power electronics in solar photovoltaic applications through the use of submodule integrated maximum power point trackers (MPPT). We propose a system architecture that provides a substantial increase in captured energy during partial shading conditions, while at the same time enabling significant overall cost reductions. This is achieved through direct integration of miniature MPPT power converters into existing junction boxes. We describe the design and implementation of a high-efficiency (>;98%) synchronous buck MPPT converter, along with digital control techniques that ensure both local and global maximum power extraction. Through detailed experimental measurements under real-world conditions, we verify the increase in energy capture and quantify the benefits of the architecture.

Resistance Compression Networks for Radio-Frequency Power Conversion

A limitation of many high-frequency resonant inverter topologies is their high sensitivity to loading conditions. This paper introduces a new class of matching networks that greatly reduces the load sensitivity of resonant inverters and radio frequency (RF) power amplifiers. These networks, which we term resistance compression networks, serve to substantially decrease the variation in effective resistance seen by a tuned RF inverter as loading conditions change. We explore the operation, performance characteristics, and design of these networks, and present experimental results demonstrating their performance. Their combination with rectifiers to form RF-to-dc converters having narrow-range resistive input characteristics is also treated. The application of resistance compression in resonant power conversion is demonstrated in a dc-dc power converter operating at 100MHz

A High-Frequency Resonant Inverter Topology With Low-Voltage Stress

This paper presents a new switched-mode resonant inverter, which we term the inverter, that is well suited to operation at very high frequencies and to rapid on/off control. Features of this inverter topology include low semiconductor voltage stress, small passive energy storage requirements, fast dynamic response, and good design flexibility. The structure and operation of the proposed topology are described, and a design procedure is introduced. Experimental results demonstrating the new topology are also presented. A prototype inverter is described that switches at 30 MHz and provides over 500 W of radio frequency power at a drain efficiency above 92%. It is expected that the inverter will find use as a building block in high-performance dc-dc converters among other applications.

New Architectures for Radio-Frequency DC–DC Power Conversion

This document proposes two new architectures for switched-mode dc–dc power conversion. The proposed architectures enable dramatic increases in switching frequency to be realized while preserving features critical in practice, including regulation of the output across a wide load range and high light-load efficiency. This is achieved in part by how the energy conversion and regulation functions are partitioned. The structure and control approach of the new architectures are described, along with representative implementation methods. The design and experimental evaluation of prototype systems with cells operating at 100MHz are also described. It is anticipated that the proposed approaches and ones like them will allow substantial improvements in the size of switching power converters and, in some cases, will permit their integrated fabrication.

Design Considerations for Very High Frequency dc-dc Converters

This document describes several aspects relating to the design of dc-dc converters operating at frequencies in the VHF range (30–300 MHz). Design considerations are treated in the context of a dc-dc converter operating at a switching frequency of 100 MHz. Gate drive, rectifier and control designs are explored in detail, and experimental measurements of the complete converter are presented that verify the design approach. The gate drive, a self-oscillating multi-resonant circuit, dramatically reduces the gating power while ensuring fast on-off transitions of the semiconductor switch. The rectifier is a resonant topology that absorbs diode parasitic capacitance and is designed to appear resistive at the switching frequency. The small sizes of the energy storage elements (inductors and capacitors) in this circuit permit rapid start-up and shut-down and a correspondingly high control bandwidth. These characteristics are exploited in a high bandwidth hysteretic control scheme that modulates the converter on and off at frequencies as high as 200 kHz.

The future of electronics in automobiles

The present 14 V automotive electrical system will soon become 42 V. New electrical features and electrification of present mechanically driven functions will provide commercial opportunities for a new high volume application of power electronics. Cost and the thermal environment present difficult challenges to device designers. SiC is shown as a promising material for this environment. A new high efficiency power supply design using the existing automotive alternator is presented.