Doron Shmilovitz

Ultrasonic transcutaneous energy transfer for powering implanted devices

This paper investigates ultrasonic transcutaneous energy transfer (UTET) as a method for energizing implanted devices at power level up to a few 100 mW. We propose a continuous wave 673 kHz single frequency operation to power devices implanted up to 40 mm deep subcutaneously. The proposed UTET demonstrated an overall peak power transfer efficiency of 27% at 70 mW output power (rectified DC power at the load). The transducers consisted of PZT plane discs of 15 mm diameter and 1.3mm thick acoustic matching layer made of graphite. The power rectifier on the implant side attained 88.5% power transfer efficiency. The proposed approach is analyzed in detail, with design considerations provided to address issues such as recommended operating frequency range, acoustic link matching, receivers rectifying electronics, and tissue bio-safety concerns. Global optimization and design considerations for maximum power transfer are presented and verified by means of finite element simulations and experimental results.

On the definition of total harmonic distortion and its effect on measurement interpretation

The existence of two different definitions for total harmonic distortion (one in comparison to the fundamental and one in comparison to the signals root mean square) might cause ambiguity and misinterpretation of measured data. The difference between those definitions is stressed out in this letter. It is suggested that total harmonic distortion measurements in the context of power systems should always adopt the first definition and never the second.

A Modified MPPT Scheme for Accelerated Convergence

Fast tracking of photovoltaic maximum power point (MPP) is accomplished by a linear control loop that emulates a nearly matched load line. Thus, the response time of conventional MPP trackers is significantly accelerated.

Maximum Power Point Tracking Employing Sliding Mode Control

A fast and unconditionally stable maximum power point tracking scheme with high tracking efficiency is proposed for photovoltaic generators. The fast dynamics and all range stability are attained by a sliding mode control and the high tracking efficiency by a maximum power point algorithm with fine step. In response to a sudden change in radiation, our experiments show a typical convergence time of 15 ms. This is the fastest convergence time reported to date. In addition we demonstrate stable convergence all across the photovoltaic curve, from short-circuit to open-circuit. The theory is validated experimentally.

A returned energy architecture for improved photovoltaic systems efficiency

A major loss mechanism in photovoltaic (PV) power systems is known as mismatch loss, which may result in up to 30% power reduction, depending on a PV systems installation configuration and atmospheric conditions. To overcome excess losses due to mismatch losses, a new photovoltaic architecture is proposed which applies an internal power feedback (RECCs — returned energy current converters) to restore the symmetry among the PV modules i-v curves. This results in recovery of most of the internally trapped energy. The RECC units are realized by means of power electronics.

Ultrasonic transcutaneous energy transfer using a continuous wave 650 kHz Gaussian shaded transmitter.

This paper proposes ultrasonic transcutaneous energy transfer (UTET) based on a kerfless transmitter with Gaussian radial distribution of its radiating surface velocity. UTET presents an attractive alternative to electromagnetic TET, where a low power transfer density of less than 94 mW/cm(2) is sufficient. The UTET is operated with a continuous wave at 650 kHz and is intended to power devices implanted up to 50mm deep. The transmitter was fabricated using a 15 mm diameter disc shape PZT (Lead Zirconate Titanate) element (C-2 grade, Fujiceramics Corporation Tokyo Japan), in which one surface electrode was partitioned into six equal area electrodes ( approximately 23 mm(2) each) in the shape of six concentric elements. The UTET was experimented using pig muscle tissue, and showed a peak power transfer efficiency of 39.1% at a power level of 100 mW. An efficient (91.8%) power driver for the excitation of the transmitter array, and an efficient rectifier (89%) for the implanted transducer are suggested. To obtain the pressure field shape, the Rayleigh integral has been solved numerically and the results were compared to finite element simulation results. Pressure and power transfer measurements within a test tank further confirm the effectiveness of the proposed UTET.

Distributed Maximum Power Point Tracking in Photovoltaic Systems – Emerging Architectures and Control Methods

The interest in distributed maximum power point tracking increases along with increasing deployment of photovoltaic generators and the constant pressure to reduce the cost of photovoltaic generated energy. Distributed maximum point tracking facilitates a significant boost of captured photovoltaic power. In this paper we compare different distributed maximum power point architectures, and categorize them into two main groups; those which process the entire generated power and partial power processing based architectures. The first ones are found to be easier to control while the second ones exhibit higher efficiency. Some delicate control issues are emphasized; a distinction is made between maximum power point tracking and negative feedback control. For systems consisting of multiple power processors, we derive the required number of maximum point tracking units and their adequate location within a global architecture. Only the right number of units guarantees extraction of the entire potential power as well as system stability. In contrary, we demonstrate how instability occurs due to a redundant control structure.

A Power Management Strategy for Minimization of Energy Storage Reservoirs in Wireless Systems With Energy Harvesting

Wireless transmission systems fed by ambient harvested energy power sources can operate continuously, without needing battery replacement. Such systems are ideal for applications with limited or difficult accessibility. Ambient energy sources exhibit a stochastic nature, so an energy storage device must store the harvested energy. In this work, a control method that minimizes the use of storage is developed. The strategy is to match data transmission rate as close as possible to the availability of harvested power, so the energy storage capacity can be reduced. An audio recording sensor is designed and simulated using SPICE to validate the proposed controller. For this system, the size of storage device is reduced by a factor of 24.

The Mathematical Foundation of Distributed Interleaved Systems

The distribution and interleaving (D&I) of signals is a common method for ripple attenuation in various engineering applications in such areas as control, communication, and power electronics. Similarities to this technique may also been found in nonengineering fields such as biology and medicine. This paper presents a mathematical exploration of distributed interleaved systems along with a simple frequency-domain model of interleaving. We are hoping that the insights provided by this mathematical framework and the newly proposed model for interleaved systems will lead to enhanced techniques for evaluating D&I processes, and facilitate the design of better systems. In particular, we hope this work results in new approaches to low-pass filtering that will exhibit fast dynamics and very efficient ripple attenuation (in theory, this can produce complete ripple removal in some cases)

Self-Sampled All-MOS ASK Demodulator for Lower ISM Band Applications

An all-MOS ASK demodulator with a wide bandwidth for lower industrial, scientific and medical (ISM) band applications is presented. The chip area is reduced without using any passive element. It is very compact to be integrated in a system-on-chip for wireless biomedical applications, particularly in biomedical implants. Because of low area cost and low power consumption, the proposed design is also easy to integrate in other mobile medical devices. The self-sampled loop with a MOS equivalent capacitor compensation mechanism enlarges the bandwidth, which is more than enough to be adopted in any application using lower ISM bands.