• Title/Summary/Keyword: Energy Recovery Circuit

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A Study on the Development of High-intensity focused Ultrasound Device for the Beauty Treatment Health Care (미용 치료 헬스케어를 위한 고강도 집속 초음파 장치 개발 연구)

  • Lee, Woo-Cheol;Ko, Yun-Seok
    • The Journal of the Korea institute of electronic communication sciences
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    • v.11 no.12
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    • pp.1259-1264
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    • 2016
  • Ultrasonic therapy has received great attention in the field of cosmetics related to the treatment of skin thickening because of its fast recovery and safety. In this study, an output circuit of a high intensity focused ultrasound system was developed for the treatment of beauty. To verify the applicability of the high intensity focused ultrasound system to the cosmetic treatment field, we measured and analyzed the 3D ultrasound intensity energy using a hydrophone. And high-intensity focused ultrasound devices were found to be useful for cosmetic treatment.

Analysis on Current Limiting Characteristics of a Fault-lock Type SFCL Applied into a Simulated Power System (모의전력계통에 적용된 자속구속형 초전도 전류제한기의 전류제한 특성 분석)

  • Han, Tae-Hee;Lim, Sung-Hun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.2
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    • pp.141-146
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    • 2011
  • When the current of the superconducting element exceeds its critical current by the fault occurrence, the quench of the high-$T_C$ superconducting fault current limiter (HTSC) comprising the flux-lock type superconducting fault current limiter (SFCL) occurs. Simultaneously, the magnetic flux in the iron core induces the voltage in each coil, which contributes to limit the fault current. In this paper, the fault current limiting characteristics of the flux-lock type SFCL as well as the load voltage sag suppressing characteristics according to the flux-lock type SFCL's winding direction were investigated. To confirm the fault current limiting and the voltage sag suppressing characteristics of the this SFCL, the short-circuit tests for the simulated power system with the flux-lock type SFCL were carried out. The flux-lock type SFCL designed with the additive polarity winding was shown to perform more effective fault current limiting and load voltage sag suppressing operations through the fast quench occurrence right after the fault occurs and the fast recovery operation after the fault removes than the flux-lock type SFCL designed with the subtractive polarity winding.

Design of High-efficiency Power Amplifier System for High-directional Speaker (고지향성 스피커를 위한 새로운 전력 증폭기 설계)

  • Kim, Jin-Young;Kim, In-Dong;Moon, Wonkyu
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.8
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    • pp.1215-1221
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    • 2017
  • Parametric array transducers are used for highly directional speaker in an air environments. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier system. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier. Furthermore, the proposed power amplifier system gets high efficiency because it contains the DC-DC converter-type power supply which can perform energy recovery and envelope tracking function. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.

Performance Evaluation of 2-Dimensional Light Source using Mercury-free Flat Fluorescent Lamps for LCD Backlight Applications

  • Park, Joung-Hu;Cho, Bo-Hyung;Lee, Ju-Kwang;Whang, Ki-Woong
    • Journal of Power Electronics
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    • v.9 no.2
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    • pp.164-172
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    • 2009
  • Recently, 2-dimensional flat light sources have been attracting much attention for its use in LCD backlight applications because of its high luminous efficiency and uniformity. A long-gap discharge, mercury-tree flat fluorescent lamp has been developed, which shows a high brightness ($>5000\;cd/m^2$) and high luminous efficacy (60 lm/W). Additionally, it has a wide operating margin and stable driving condition with the aid of an auxiliary electrode. For driving the lamp, a narrow pulse power to maintain the glow discharge state is required. Since there has been no research for this kind of lamp driving, this paper proposes a newly developed short-pulse, high-voltage lamp-driving scheme. The proposed lamp system uses a ballast with a coupled-inductor in order to raise the short pulse voltage up to the lamp ignition level and to obtain energy-recovery action during the glow discharge mode. The operation principles are presented and also the system performances such as the lighting efficiency, spatial and angular uniformities are evaluated by hardware experiments. The results show that the proposed lighting system is a good candidate for the next-generation of LCD backlight systems.

Implementation of an Interleaved AC/DC Converter with a High Power Factor

  • Lin, Bor-Ren;Lin, Li-An
    • Journal of Power Electronics
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    • v.12 no.3
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    • pp.377-386
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    • 2012
  • An interleaved bridgeless buck-boost AC/DC converter is presented in this paper to achieve the characteristics of low conduction loss, a high power factor and low harmonic and ripple currents. There are only two power semiconductors in the line current path instead of the three power semiconductors in a conventional boost AC/DC converter. A buck-boost converter operated in the boundary conduction mode (BCM) is adopted to control the active switches to achieve the following characteristics: no diode reverse recovery problem, zero current switching (ZCS) turn-off of the rectifier diodes, ZCS turn-on of the power switches, and a low DC bus voltage to reduce the voltage stress of the MOSFETs in the second DC/DC converter. Interleaved pulse-width modulation (PWM) is used to control the switches such that the input and output ripple currents are reduced such that the output capacitance can be reduced. The voltage doubler topology is adopted to double the output voltage in order to extend the useable energy of the capacitor when the line voltage is off. The circuit configuration, principle operation, system analysis, and a design example are discussed and presented in detail. Finally, experiments on a 500W prototype are provided to demonstrate the performance of the proposed converter.

A Secondary Resonance Soft Switching Half Bridge DC-DC Converter with an Inductive Output Filter

  • Chen, Zhang-yong;Chen, Yong
    • Journal of Power Electronics
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    • v.17 no.6
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    • pp.1391-1401
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    • 2017
  • In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

Start and Stop Characteristics of Single-Rod Electro-Hydrostatic Actuator (전동기 일체형 편로드 유압액추에이터의 기동 및 정지특성해석)

  • Jung, Gyu-Hong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.11
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    • pp.1483-1490
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    • 2011
  • Electro-hydrostatic actuators(EHAs), which are usually composed of a direct motor-driven hydraulic pump and a cylinder, have been widely adopted as aircraft actuation systems because of their benefits in terms of improved efficiency, weight savings and the fact that they use a standalone power source. Since the recent trend in construction vehicles has been focus on energy savings in their hydraulic systems, EHAs are expected to be potential substitutes for conventional power transmission, since they are capable of energy recovery as well as highly efficient pump control. In this paper, the start and stop characteristics of EHAs were investigated through cracking pressure analysis of the pilot-operated check valve(PCV), which enables the cylinder to standstill against an external load with no holding effort from the hydraulic pump. A mathematical model that includes the load dynamics and the EHA's internal hydraulic circuit was derived for simulation with the MATLAB Simulink package. This model verified the PCV's opening and closing sequence, which in turn affects the EHA's start and stop characteristics.

A Study on Performance Characteristics of Multi-level PDP Driver Circuit in Accordance of Signal Timing Variation (Multi-Level을 사용한 PDP 구동회로에서 Timing 변화에 따른 특성 변화에 관한 연구)

  • Kim Jung-Soo;Roh Chung-Wook;Hong Sung-Soo;Sakong Sug-Chin
    • The Transactions of the Korean Institute of Power Electronics
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    • v.10 no.6
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    • pp.560-568
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    • 2005
  • The proposed Multi-level PDP sustain Driver is composed of the semiconductor devices with low voltage rating compared to those used in the prior circuit proposed by L. Wether, and it has two resonant periods during the charging (rising period) and discharging (falling period) the PDP in the sustaining voltage waveforms. In accordance with the change of timing phase$(T_{r1},\;T_{i1},\;T_{r2})$, the performance characteristics of a commercial PDP module has been carried out and compared the characteristic with the 42V6, made of LG Electronics co., Experimental results show that the performance characteristics of PDP module are greatly influenced by the variation of $T_{i1}\;and\;T_{r2}$. The variation of $T_{r1}$ do not influence much on the performances of PDP. With the conditions that $T_{r1}=60ns,\;T_{i1}=120ns,\;and\;T_{r2}=350ns$, we could get the performances listed as the luminance is increased $14.6\%$, the power consumptions is decreased $5.9\%$, the panel efficiency is increased $24.2\%$, module efficiency is increased $21.2\%$, compared to those shown in the commercial PDP module (42V6). Therefore, the proposed multi-level PDP sustain driver expected to be suitable to actual PDP module application.

A Study of the Research Trends and the Material flow on the Unrecycled Materials in Korea - The Current Situation of Recycling Technology for Waste Resources in Korea(2) - (국내(國內) 미이용자원(未利用資源)을 위한 회수(回收) 연구동향(硏究動向) 및 물질(物質)흐름 - 국내자원(國內資源)의 유효이용(有效利用)을 위한 처리(處理) 및 회수기술(回收技術) 동향조사(動向調査)(2) -)

  • Oh, Jae-Hyun;Kim, Mi-Sung;Shin, Hee-Duck;Min, Ji-Won
    • Resources Recycling
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    • v.16 no.2 s.76
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    • pp.63-76
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    • 2007
  • Typical examples as unrecycled materials in Korea were Zinc from the electric arc furnace dust (EAF Dust), and Moiybdenium and Vanadium from the desulfurizing spent catalyst of petrochemical industries. In the otherwise, though recovery of valuable metals from the waste electronic scrap such as printed circuit boards (PCBs) and platinum group metals (PGM) from the waste automobile catalyst have been interesting issues, it is difficult to collect the exact informations or statistics on their material flow system. In this article, The current domestic research trends for unrecycled or less recycled materials have been reviewed, and material flow and recycling technologies on the desulfurizing spent catalyst were surveyed.