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.

/pdf/opportunities-and-challenges-in-very-high-frequency-power-2j4vslax8q.pdf

Opportunities and Challenges in Very High Frequency Power Conversion

https://research.chalmers.se/publication/503205/file/503205_Fulltext.pdf

A review of fractional-order techniques applied to lithium-ion batteries, lead-acid batteries, and supercapacitors

Batteries have been widely applied in many high-power applications, such as electric vehicles (EVs) and hybrid electric vehicles, where a suitable battery management system (BMS) is vital in ensuring safe and reliable operation of batteries. This paper aims to give a brief review on several key technologies of BMS, including battery modelling, state estimation and battery charging. First, popular battery types used in EVs are surveyed, followed by the introduction of key technologies used in BMS. Various battery models, including the electric model, thermal model and coupled electro-thermal model are reviewed. Then, battery state estimations for the state of charge, state of health and internal temperature are comprehensively surveyed. Finally, several key and traditional battery charging approaches with associated optimization methods are discussed.

/pdf/a-brief-review-on-key-technologies-in-the-battery-management-epnx1tchkf.pdf

A brief review on key technologies in the battery management system of electric vehicles

Embodiments of the subject invention pertain to a method and apparatus for contactless power transfer. A specific embodiment relates to an impedance transformation network, a new class of load network for application to a contactless power system. Embodiments of the impedance transformation network enable a contactless power system to operate without encountering the common problems of: 1) over-voltage and/or under-voltage conditions; 2) over-power and/or under-power conditions; 3) power oscillations; and 4) high heat dissipation.

Method and apparatus for contactless power transfer

A novel six-band dual circular polarization (CP) rectenna for ambient radio frequency (RF) energy harvesting is presented. Due to the nonlinearity and complex input impedance of the rectifying circuit, the design of a multiband and/or broadband rectenna is always challenging and its performance can be easily affected by variation in the input power level and load. Therefore, an improved impedance matching technique is introduced, which is aimed to improve the performance of the rectifier with a varying condition. A broadband dual CP receiving antenna is proposed, which has a very wide bandwidth (from 550 to 2.5 GHz) and a compact size. An annular ring structure and a novel feeding technique are employed in order to reduce the size and improve the antenna performance. As a result, the proposed rectenna is the first design that covers six frequency bands, including part of the digital TV and most cellular mobile and WLAN bands in the U.K., while the optimal load range for a constant conversion efficiency is from 10 to 75 $\text{k}\Omega $ . The measured results show that the maximum harvested dc power of the rectenna in typical outdoor and indoor environments are 26 and 8 $\mu \text{W}$ , respectively; it can therefore be applied to a range of low-power wireless applications.

A Novel Six-Band Dual CP Rectenna Using Improved Impedance Matching Technique for Ambient RF Energy Harvesting

This paper introduces a module-integrated distributed battery energy storage and management system without the need for additional battery equalizers and centralized converter interface. This is achieved by integrating power electronics onto battery cells as an integrated module. Compared with the conventional centralized battery system, the modular design brings several advantages such as reduced power rating and voltage stress of power electronics, no extra equalizers or centralized converters, active thermal distribution control ability, enhanced safety and reliability, etc. The battery system can now be built by simply attaching integrated modules together. The integrated module is implemented by a synchronous bidirectional dc/dc converter with digital control techniques. The design considerations and control strategy of the system are discussed. A prototype is built that the power electronics are integrated onto the battery cell. Experimental results of a three-module system verified that the module-integrated distributed system provides satisfied functional performance without extra equalizers, centralized charger, or bidirectional dc/dc converter.

A Module-Integrated Distributed Battery Energy Storage and Management System

This paper investigates the loss characteristics of RF magnetic materials for power conversion applications in the 10 to 100 MHz range. A measurement method is proposed that provides a direct measurement of an inductor quality factor QL as a function of inductor current at RF frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of several commercial RF magnetic-core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The use of the method and data is demonstrated in the design of a magnetic-core inductor, which is applied in a 30-MHz inverter. The results of this paper are thus useful for the design of magnetic components for very high frequency applications.

/pdf/evaluation-of-magnetic-materials-for-very-high-frequency-2ym3uc9i7a.pdf

Evaluation of Magnetic Materials for Very High Frequency Power Applications

This paper presents a resonant single-ended-primary-inductor-converter (SEPIC) converter and control method suitable for high frequency (HF) and very high frequency (VHF) dc-dc power conversion. The proposed design provides high efficiency over a wide input and output voltage range, up-and-down voltage conversion, small size, and excellent transient performance. In addition, a resonant gate drive scheme is presented that provides rapid startup and low-loss at HF and VHF frequencies. The converter regulates the output using an ON-OFF control scheme modulating at a fixed frequency (170 kHz). This control method enables fast transient response and efficient light-load operation while providing controlled spectral characteristics of the input and output waveforms. A hysteretic override technique is also introduced which enables the converter to reject load disturbances with a bandwidth much greater than the modulation frequency, limiting output voltage disturbances to within a fixed value. An experimental prototype has been built and evaluated. The prototype converter, built with two commercial vertical MOSFETs, operates at a fixed switching frequency of 20 MHz, with an input voltage range of 3.6-7.2 V, an output voltage range of 3-9 V, and an output power rating of up to 3 W. The converter achieves higher than 80% efficiency across the entire input voltage range at nominal output voltage and maintains good efficiency across the whole operating range.

/pdf/high-frequency-resonant-sepic-converter-with-wide-input-and-5275if9mjz.pdf

High-Frequency Resonant SEPIC Converter With Wide Input and Output Voltage Ranges

This document presents a new switched-mode resonant inverter, which we term the Phi2 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 Phi2 inverter is described that switches at 30 MHz and provides over 500 W of rf power at a drain efficiency above 92%. It is expected that the Phi2 inverter will find use as a building block in high performance dc-dc converters among other applications [1], [2].

/pdf/a-high-frequency-resonant-inverter-topology-with-low-voltage-3c7ng4472b.pdf

A High-Frequency Resonant Inverter Topology with Low Voltage Stress

This document presents a resonant SEPIC converter and control method suitable for high frequency (HF) and very high frequency (VHF) dc-dc power conversion. The proposed design features high efficiency over a wide input and output voltage range, up-and-down voltage conversion, small size, and excellent transient performance. In addition, a resonant gate drive scheme is presented which provides rapid startup and low-loss at HF and VHF frequencies. The converter regulates the output using an on-off control scheme modulating at a fixed frequency. This control method enables fast transient response and efficient light load operation while providing controlled spectral characteristics of the input and output waveforms. An experimental prototype has been built and evaluated. The prototype converter, built with two commercial vertical MOSFETs, operates at a fixed switching frequency of 20 MHz, with an input voltage range of 3.6 V to 7.2 V, an output voltage range of 3 V to 9 V and an output power rating of up to 3 W. The converter achieves higher than 80% efficiency across the entire input voltage range at nominal output voltage, and maintains good efficiency across the whole operating range.

Yehui Han

Papers

A Module-Integrated Distributed Battery Energy Storage and Management System

Evaluation of Magnetic Materials for Very High Frequency Power Applications

High-Frequency Resonant SEPIC Converter With Wide Input and Output Voltage Ranges

A High-Frequency Resonant Inverter Topology with Low Voltage Stress

High frequency resonant SEPIC converter with wide input and output voltage ranges