DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Mathematica--A System for Doing Mathematics by Computer.

This paper presents a state-of-the-art review on a hot topic in the literature, i.e., vibration based energy harvesting techniques, including theory, modelling methods and the realizations of the piezoelectric, electromagnetic and electrostatic approaches. To minimize the requirement of external power source and maintenance for electric devices such as wireless sensor networks, the energy harvesting technique based on vibrations has been a dynamic field of studying interest over past years. One important limitation of existing energy harvesting techniques is that the power output performance is seriously subject to the resonant frequencies of ambient vibrations, which are often random and broadband. To solve this problem, researchers have concentrated on developing efficient energy harvesters by adopting new materials and optimising the harvesting devices. Particularly, among these approaches, different types of energy harvesters have been designed with consideration of nonlinear characteristics so that the frequency bandwidth for effective energy harvesting of energy harvesters can be broadened. This paper reviews three main and important vibration-to-electricity conversion mechanisms, their design theory or methods and potential applications in the literature. As one of important factors to estimate the power output performance, the energy conversion efficiency of different conversion mechanisms is also summarised. Finally, the challenging issues based on the existing methods and future requirement of energy harvesting are discussed.

A comprehensive review on vibration energy harvesting: Modelling and realization

A review of thermoelectric cooling: Materials, modeling and applications

Energy harvesting is an emerging technology with applications to handheld, portable and implantable electronics. Harvesting ambient heat energy using thermoelectric generators (TEG's) [1] is a convenient means to supply power to body-worn electronics and industrial sensors. Using TEG's for body-wearable applications limits the output voltage to 50mV for temperature differences of 1–2K usually found between the body and ambience. Several existing systems [2, 3] use a battery or an initial high voltage energy input to kick-start operation of the system from this low voltage. Further, changing external conditions cause the voltage and power generated by the TEG to vary, necessitating efficient control circuits that can adapt and extract the maximum possible power out of these systems. In this paper, a battery-less thermoelectric energy harvesting interface circuit which uses a mechanically assisted startup circuit to operate from 35mV input is presented. An efficient control circuit that performs maximal end-to-end transfer of the extracted energy to a storage capacitor and regulates the output voltage at 1.8V is demonstrated.

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A Battery-Less Thermoelectric Energy Harvesting Interface Circuit With 35 mV Startup Voltage

The objective of this paper is to develop a SPICE- compatible equivalent circuit of a thermoelectric module. A methodology is developed for extracting the parameters of the proposed model from manufacturers' data of thermoelectric coolers (TECs) and thermoelectric generators (TEGs). The model could be helpful in analyzing the drive requirements of TECs and loading effects of TEGs. The present model is compatible with PSPICE or other electric circuit simulators. An important feature of the model is its ability to generate small-signal transfer functions that can be used to design feedback networks for temperature control applications

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Modeling and Analysis of Thermoelectric Modules

The controller in a pulse-width-modulation (PWM) power converter has to stabilize the system and guarantee an almost constant output voltage in spite of the perturbations in the input voltage and output load over as large a bandwidth as possible. Boost and flyback power converters have a right-half-plane zero (RHPZ) in their transfer function from the duty cycle to the output voltage, which makes it difficult to achieve the aforementioned goals. Here, the authors propose to design a controller using H/sup /spl infin// control theory, via the solution of two algebraic Riccati equations. The almost optimal H/sup /spl infin// controller is of the same order as the converter and has a relatively low DC gain. The closed-loop characteristics of a typical low-power boost power converter with four different control schemes were compared by computer simulation. The H/sup /spl infin// control was found to be superior in a wide frequency range, while being outperformed by the others at extremely low frequencies. Good agreement was found between simulation results and experimental measurements.

H/sup /spl infin// control applied to boost power converters

The objective of this work was to develop a SPICE compatible equivalent circuit of a thermoelectric module (TEM). A methodology is developed for extracting the parameters of the proposed model from manufacturers' data of thermoelectric coolers (TEC) and thermoelectric generators (TEG). The model could be helpful for analyzing the drive requirements of TECs and loading effects of TECs. The present model is compatible with PSPICE or other electric circuit simulators. An important feature of the model is its ability to generate small signal transfer functions that can be used to design feedback networks for temperature control applications.

/pdf/modeling-and-analysis-of-thermoelectric-modules-10fua5zc9m.pdf

Modeling and analysis of thermoelectric modules

A system and method for supplying power to a load (RL) and for controlling the power Factor presented to the power line. Output voltage (Vo) is controlled by a digital, outer, control loop (Digital), and inner, analog, control loop (Analog) causes the input current (Iina) to be substantially proportional to the input voltage (Vin) at any particular point in the power line cycle. Thus, the system presents a load (RL) to the power line that appears to be purely resistive. The use of an analog multiplier is not required, nor is sampling of input voltage. Limiting of inrush current provides for brown-out protection and soft-start.

Method and control circuitry for improved-performance switch-mode converters

The universal attributes of piezoelectric transformers (PT) were derived by an approximate analysis that yielded closed form equations relating the normalized load resistance to the voltage gain, output power per unit and efficiency. Based on the results of the study, a calculation procedure is developed for specifying a PT for any given application and is demonstrated by considering the design of a fluorescent lamp driver. It is suggested that the closed form formulae, developed in this study, could be invaluable when studying, specifying and designing practical PTs applications.

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Shmuel Ben-Yaakov

Papers

Modeling and Analysis of Thermoelectric Modules

H/sup /spl infin// control applied to boost power converters

Modeling and analysis of thermoelectric modules

Method and control circuitry for improved-performance switch-mode converters

Generic operational characteristics of piezoelectric transformers