There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.

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Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

In this paper, we discuss the impact of digital control in high-frequency switched-mode power supplies (SMPS), including point-of-load and isolated DC-DC converters, microprocessor power supplies, power-factor-correction rectifiers, electronic ballasts, etc., where switching frequencies are typically in the hundreds of kHz to MHz range, and where high efficiency, static and dynamic regulation, low size and weight, as well as low controller complexity and cost are very important. To meet these application requirements, a digital SMPS controller may include fast, small analog-to-digital converters, hardware-accelerated programmable compensators, programmable digital modulators with very fine time resolution, and a standard microcontroller core to perform programming, monitoring and other system interface tasks. Based on recent advances in circuit and control techniques, together with rapid advances in digital VLSI technology, we conclude that high-performance digital controller solutions are both feasible and practical, leading to much enhanced system integration and performance gains. Examples of experimentally demonstrated results are presented, together with pointers to areas of current and future research and development.

Impact of digital control in power electronics

Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for a continuation of this trend. For identifying and quantifying such technological barriers this paper investigates the volume of the cooling system and of the main passive components for the basic forms of power electronics energy conversion in dependency of the switching frequency and determines switching frequencies minimizing the total volume. The analysis is for 5 kW rated output power, high performance air cooling, advanced power semiconductors, and single systems in all cases. A power density limit of 28 kW/dm3@300 kHz is calculated for an isolated DC-DC converter considering only transformer, output inductor and heat sink volume. For single-phase AC-DC conversion a general limit of 35 kW/dm3 results from the DC link capacitor required for buffering the power fluctuating with twice the mains frequency. For a three-phase unity power factor PWM rectifier the limit is 45 kW/dm3@810 kHz just taking into account EMI filter and cooling system. For the sparse matrix converter the limiting components are the input EMI filter and the common mode output inductor; the power density limit is 71 kW/dm3@50 kHz when not considering the cooling system. The calculated power density limits highlight the major importance of broadening the scope of research in power electronics from traditional areas like converter topologies, and modulation and control concepts to cooling systems, high frequency electromagnetics, interconnection technology, multi-functional integration, packaging and multi-domain modeling and simulation to ensure further advancement of the field along the power density trajectory.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/IEEJ_PowerDensity_Paper_FinalRevised_03.pdf

PWM Converter Power Density Barriers

Data from the ITRS2003 roadmap for 2010 predicts voltages for microprocessors in hand-held electronics will decrease to 0.8V with current and power increasing to 4A and 3W, respectively. Consequently, low power converters will move to multimegahertz frequencies with a resulting reduction in capacitor and inductor values by factors of 5 and 20, respectively. Values required at 10 MHz, for a low power buck converter, are estimated at 130 nH and 0.6 uF, compatible with the integration of magnetics onto silicon and the concept of power supply-on-chip (PSOC). A review of magnetics-on-silicon shows that inductance values of 20 to 40nH/mm/sup 2/ can be achieved for winding resistances less than 1/spl Omega/. A 1-/spl mu/H inductance can be achieved at 5 MHz with dc resistance of 1/spl Omega/ and a Q of four. Thin film magnetic materials, compatible with semiconductor processing, offer power loss density that is lower than ferrite by a factor of 5 at 10 MHz. Other data reported includes, lowest dc resistance values of 120 m/spl Omega/ for an inductance of 120 nH; highest Q of 15 for an inductance of 350 nH and a current of 1 A for a 1- /spl mu/H inductor. Future technology challenges include reducing losses using high resistivity, laminated magnetic materials, and increasing current carrying capability using high aspect-ratio, electroplated copper conductors. Compatible technologies are available in the power switch, control, and packaging space. Integrated capacitor technology is still a long-term challenge with maximum reported values of 400 nF/cm/sup 2/.

https://www.researchgate.net/profile/K_Rinne/publication/3280720_Magnetics_on_silicon_an_enabling_technology_for_power_supply_on_chip/links/0c960525d73b366c6f000000.pdf

Magnetics on silicon: an enabling technology for power supply on chip

This paper presents an extensive survey of techniques and technologies used to implement planar magnetic structures in modern DC to DC converters. The survey emphasises the practical applications of these devices. The trends are analyzed in the context of the marketplace and some predictions of future direction are attempted.

A review of planar magnetic techniques and technologies

This paper describes the implementation of a novel and highly versatile digital pulse width modulator (DPWM) -probably the most critical component in any digitally controlled switching power converter. Its new architecture, composed of a delay-locked loop (DLL) and programmable DPWM module, allows the generation of high resolution, high switching frequency (f/sub m/) PWM signals. The DPWM IC was designed using a standard 0.35-/spl mu/m CMOS process and supports switching frequencies beyond 15 MHz.

A programmable digital pulse width modulator providing versatile pulse patterns and supporting switching frequencies beyond 15 MHz

This paper presents a self-compensating adaptive digital regulator applied to dc to dc converters. Implementing linear prediction, it adapts online, and may be operated continuously, characterizing disturbances in the loop, allowing optimal disturbance rejection. A dual purpose controller-predictor provides robust performance in low complexity hardware.

http://ieeexplore.ieee.org/iel5/10769/33947/01620617.pdf

A self-compensating adaptive digital regulator for switching converters based on linear prediction

This paper demonstrates a DC-DC converter application in which a multi-bit digital sigma-delta modulator pre-processes the duty-cycle value before application to the DPWM, increasing the effective resolution of the DPWM dramatically. In this method, the DPWM duty-cycle command is pre-processed by a multi-bit digital sigma-delta modulator, so that the DPWM quantization noise is shaped in frequency. As a result, the total quantization noise at the output of the DC-DC converter is reduced, and the effective resolution of the DPWM in the control loop is increased dramatically. A prototype converter was seen to perform with an effective DPWM resolution of at least 11 bits, with an actual DPWM resolution of less than 6 bits

Karl Rinne

Papers

Magnetics on silicon: an enabling technology for power supply on chip

A review of planar magnetic techniques and technologies

A programmable digital pulse width modulator providing versatile pulse patterns and supporting switching frequencies beyond 15 MHz

A self-compensating adaptive digital regulator for switching converters based on linear prediction

High Resolution DPWM in a DC-DC Converter Application Using Digital Sigma-Delta Techniques