scholarly journals LLC and CLLC Resonant Converters Based DC Transformers (DCXs): Characteristics, Issues, and Solutions

2021 ◽  
Vol 6 (4) ◽  
pp. 332-348
Author(s):  
Yuqi Wei ◽  
Keyword(s):  
Resonant Frequency ◽  
High Frequency ◽  
High Efficiency ◽  
Industrial Applications ◽  
Resonant Converters ◽  
Frequency Tracking ◽  
Main Work ◽  
Small Footprint ◽  
Low Efficiency ◽  
Voltage Conversion

Conventional line frequency transformers have the disadvantages of large volume and low efficiency. The medium or high frequency transformers based on power converters can achieve high power conversion with small footprint have drawn popularity in numerous industrial applications. Unregulated resonant converters, LLC and CLLC resonant converters, with fixed voltage conversion ratio operating at resonant frequency, which are also known as DC transformers (DCXs), are attractive owning to their high efficiency characteristic. Nevertheless, there are issues associated with DCXs in real applications. Regulation capability and automatic resonant frequency tracking capability are the two most important issues for DCXs. The main work of this paper is to characterize the resonant converters based DCXs, and overview the issues and solutions associated with DCXs. Guidelines can be provided for researchers and engineers when designing the resonant converters based DCXs.

scholarly journals A Comparative Analysis of Half-Bridge LLC Resonant Converters Using Si and SiC MOSFETs

2021 ◽  
Vol 12 (1) ◽  
pp. 43
Author(s):  
Hasaan Farooq ◽  
Hassan Abdullah Khalid ◽  
Waleed Ali ◽  
Ismail Shahid
Keyword(s):  
Silicon Carbide ◽  
Renewable Energy ◽  
High Frequency ◽  
High Efficiency ◽  
Low Voltage ◽  
Low Cost ◽  
Renewable Energy Sources ◽  
Input Voltage ◽  
Resonant Converters ◽  
Wide Range

With the expansion of renewable energy sources worldwide, the need for developing more economical and more efficient converters that can operate on a high frequency with minimal switching and conduction losses has been increased. In power electronic converters, achieving high efficiency is one of the most challenging targets to achieve. The utilization of wideband switches can achieve this goal but add additional cost to the system. LLC resonant converters are widely used in different applications of renewable energy systems, i.e., PV, wind, hydro and geothermal, etc. This type of converter has more benefits than the other converters such as high electrical isolation, high power density, low EMI, and high efficiency. In this paper, a comparison between silicon carbide (SiC) MOSFET and silicon (Si) MOSFET switches was made, by considering a 3KW half-bridge LLC converter with a wide range of input voltage. The switching losses and conduction losses were analyzed through mathematical calculations, and their authenticity was validated with the help of software simulations in PSIM. The results show that silicon carbide (SiC) MOSFETs can work more efficiently, as compared with silicon (Si) MOSFETs in high-frequency power applications. However, in low-voltage and low-power applications, Si MOSFETs are still preferable due to their low-cost advantage.

High-Frequency High-Efficiency $CLL$ Resonant Converters With Synchronous Rectifiers

2011 ◽  
Vol 58 (8) ◽  
pp. 3461-3470 ◽  
Author(s):  
Daocheng Huang ◽  
Dianbo Fu ◽  
Fred C. Lee ◽  
Pengju Kong
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
Resonant Converters

scholarly journals High efficiency class-D RF amplifiers and mobile NMR systems

2021 ◽  
Author(s):  
◽  
John Z. Zhen
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
Industrial Applications ◽  
Pulse Generation ◽  
Integrated System ◽  
Mobile System ◽  
Rf Amplifiers ◽  
Fully Integrated ◽  
Class D ◽  
Mobile Nmr

<p>This thesis details the development of a hand held mobile NMR system. The new system addressed the drawbacks on most of the existing NMR systems of being physically large and heavy with poor power inefficiency. In order to achieve the goal of producing a compact and power efficient NMR system, several high efficiency Class D RF amplifiers were developed which showed efficiencies of over 80%. The single cycle controlled PWM amplifier working at 2 MHz was a novel design and no other PWM Class D amplifiers has been reported to operate at high frequency with output power greater than 100 W. Development of the 20 MHz amplifier with 100 W constant amplitude output showed that the Class D amplifiers are suitable for NMR applications even at high frequency and further development of this amplifier to work at 17 MHz with amplitude modulation was successful. It paved the way for the development of a full mobile system with the newly available 17 MHz Mini-MOUSE sensor. The fully integrated mobile system was developed using SoC FPGA technologies. The use of a 400 Msps DDS device for RF pulse generation results in a broadband system. A duplexer was developed to enable sensor tuning and matching with the receiver amplifiers on the duplexer output stage provided 72 dB gain. The web based control program running on an iPad has shown great portability and it allows the system to be operated outdoors, even in remote areas. Experiments on industrial applications has shown successful T2eff measurements on polymer composites and rubber samples and showed the potential for such a system to be used in industrial applications. The fully integrated system prototype fits in a case measuring 140x120x100 mm (LxWxH) and weighs 800 grams and fulfil all the requirements for a mobile NMR system.</p>

scholarly journals The design of auto-tuning capacitive power transfer for rotary applications using phased-locked-loop

2019 ◽  
Vol 10 (1) ◽  
pp. 307
Author(s):  
N. Nabila ◽  
Shakir Saat ◽  
Y. Yusop ◽  
M.S. M Isa ◽  
A.A. Basari
Keyword(s):  
High Frequency ◽  
Power Efficiency ◽  
High Efficiency ◽  
Plate Thickness ◽  
Industrial Applications ◽  
Power Transfer ◽  
Wireless Power ◽  
Surrounding Environment ◽  
Self Tuning ◽  
Tuning Circuit

<span>Wireless power transfer (WPT), through the transmission of contactless energy, is not only being used for charging batteries in smartphones, but it is also being increasingly used in the field of industrial applications. The capacitive based approach is utilized in this paper because of its ability to transmit power in a metal surrounding environment where the inductive-based approach failed to perform. This work focuses on the coupling study of a rotary CPT application where the power supply is stationary while the load rotates and therefore allows the load to rotate 360<sup>o</sup> free rotation. The Class E MOSFET power inverter is used here due to its ability to achieve high efficiency compared to other class of converters at high frequency. The prototype of the CPT for rotary application has also been successfully developed with disk plate thickness of 1mm-2mm. Overall, the developed CPT system for rotary application is able to deliver 5.5Watt with 83.33% efficiency. To enhance the power efficiency and ZVS conditions, a self-tuning circuit using phased-locked-loop has been proposed in this paper. The efficiency of the developed system with self-tuning circuit is increased to 97.%.</span>

scholarly journals The adaptive market hypothesis and high frequency trading

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260724
Author(s):  
Ke Meng ◽  
Shouhao Li
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
High Frequency Trading ◽  
Order Book ◽  
Lower Efficiency ◽  
Processing Information ◽  
Low Efficiency ◽  
Exchange Traded Fund ◽  
The Relationship ◽  
Over Time

This paper uses NASDAQ order book data for the S&P 500 exchange traded fund (SPY) to examine the relationship between one-minute, informational market efficiency and high frequency trading (HFT). We find that the level of efficiency varies widely over time and appears to cluster. Periods of high efficiency are followed by periods of low efficiency and vice versa. Further, we find that HFT activity is higher during periods of low efficiency. This supports the argument that HFTs seek profits and risk reduction by actively processing information, through limit order additions and cancellations, during periods of lower efficiency and revert to more passive market-making and rebate-generation during periods of higher efficiency. These findings support the argument that the adaptive market hypothesis (AMH) is an appropriate description of how prices evolve to incorporate information.

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