• Journal of Power Electronics
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• 제15권6호
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• pp.1480-1488
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• 2015

In this paper, a revolutionary buck converter is proposed with soft-switching technology, which is realized by a coupled inductor. Both zero-voltage switching (ZVS) of main switch and zero-current switching (ZCS) of freewheeling diode are achieved at turn on and turn off without using any auxiliary circuits by the resonance between the parasitic capacitor and the coupled inductor. Furthermore, the peak voltages of the main switch and the peak current of the freewheeling diode are significantly reduced by the coupled inductor. As a result, the proposed converter has the advantages of simple circuit, convenient control, low consumption and so on. The detailed operation principles and steady-state analysis of the proposed ZVS-ZCS buck converter are presented, and detailed power loss analysis and some simulation results are also included. Finally, experimental results based on a 200-W prototype are provided to verify the theory and design of the proposed converter.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권4호
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• pp.465-471
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• 2014

This paper proposes a new switching algorithm for an active clamp snubber to improve the efficiency of a module integrated converter system. This system uses an active clamp method for the snubber circuit for the efficiency and reliability of the system. However, the active clamp snubber circuit has the disadvantage that system efficiency is decreased by switch operating time because of heat loss in resonance between the snubber capacitor and leakage inductance. To address this, this paper proposes a new switching algorithm. The proposed algorithm is a technique to reduce power consumption by reducing the resonance of the snubber switch operation time. Also, the snubber switch is operated at zero voltage switching by turning on the snubber switch before main switch turn-off. Simulation and experimental results are presented to show the validity of the proposed new active clamp control algorithm.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.687-699
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• 2014

Based on the energy method considering the second order effects, the natural frequencies of externally prestressed simply supported beam and the compression softening effect of external prestress force were analyzed. It is concluded that the compression softening effect depends on the loss of external tendon eccentricity. As the number of deviators increases from zero to a large number, the compression softening effect of external prestress force decreases from the effect of axial compression to almost zero, which is consistent with the conclusion mathematically rigorously proven. The frequencies calculated by the energy method conform well to the frequencies by FEM which can simulate the frictionless slide between the external tendon and deviator, the accuracy of the energy method is validated. The calculation results show that the compression softening effect of external prestress force is negligible for the beam with 2 or more deviators due to slight loss of external tendon eccentricity. As the eccentricity and area of tendon increase, the first natural frequency of the simply supported beams noticeably increases, however the effect of the external tendon on other frequencies is negligible.

• Journal of Power Electronics
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• 제16권3호
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• pp.894-904
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• 2016

This study examines the zero-voltage switching (ZVS) operation of an active-clamped forward converter (ACFC) with a current-doubler rectifier (CDR). The ZVS condition can be obtained with a much smaller leakage inductance compared to that of a conventional ACFC. Due to the significantly reduced leakage inductance, the design is optimized and the circulating loss is reduced. The operation of the ACFC with a CDR is analyzed, and a detailed ZVS analysis is conducted on the basis of a steady-state analysis. From the results, a design consideration for ZVS improvement is presented. Loss analyses of the converters shows that enhanced soft-switching contributes to an efficiency improvement under light-load condition. Experimental results from a 100-W (5-V/20-A) prototype verify that the ACFC with a CDR can attain ZVS across an extended load range of loads and achieve a higher efficiency than conventional ACFCs.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.361-366
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• 2003

For regenerative pump performance test we made 5 times enlarged and 3 different kinds blade types impeller with similarity. Due to geometrical characteristic of regenerative pump, there are two kinds of groups which effect on performance of it. One is geometric shape of impeller blade and the other is clearance and inlet/outlet head loss. To study performance of regenerative pump with impeller shape changes, we tested it with reducing clearance. And we reconcile performance data in the case of zero clearance and zero inlet/outlet head loss. Finally we could verify the influence of each group.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.38-40
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• 2002

In the case of conventional high frequency inverter, with damage of switch by surge voltage when switch gets into compulsion extinction by load accident and so on because reactor is connected by series to switch, or there was problem of conduction loss by reactor's resistivity component, Also, it has controversial point of that can not ignore conduction loss of switch in complete work kind action of soft switching. In this paper, as high frequency induction heating power supply, we propose half bridge type multi resonance soft switching high frequency inverter topology that can realize high amplitude operation of load current with controlling switch current by multiplex resonance, mitigating surge voltage when switch gets into compulsion extinction and to be complete operation of zero current switching by opposit parallel connected reactor to inverter switch. and do circuit analysis for choice of most suitable circuit parameter of circuit

• Journal of Power Electronics
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• 제10권4호
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• pp.335-341
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• 2010

In this paper, an interleaved soft switching boost converter for a Photovoltaic Power Conditioning System (PV-PCS) with high efficiency is proposed. In order to raise the efficiency of the proposed converter, a 2-phase interleaved boost converter integrated with soft switching cells is used. All of the switching devices in the proposed converter achieve zero current switching (ZCS) or zero voltage switching (ZVS). Thus, the proposed circuit has a high efficiency characteristic due to low switching losses. To analyze the power losses of the proposed converter, two experimental sets have been built. One consists of normal devices (MOSFETs, Fast Recovery (FR) diodes) and the other consists of advanced power devices (CoolMOSs, SiC-Schottky Barrier Diodes (SBDs)). To verify the validity of the proposed topology, theoretical analysis and experimental results are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1002-1004
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• 2001

In conventional zero-current-switching(ZCS) PWM converters, the switching loss, stress and noise can't be minimized because they adopt auxiliary switches operated in hard-switching. In this paper, new ZCS-PWM converters of which auxiliary switches always operate with soft-switching are proposed. Therefore, the proposed ZCS-PWM converters are most suitable for systems requiring high-power density. The characteristics of these converters are verified by experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.386-389
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• 2002

This paper proposes the boost input type active clamp forward ZVS(zero voltage switching) DC-DC converter which can provide high efficiency and improved EMI characteristics. Moreover, it has active clamp circuit for reducing the voltage stress and zero voltage switching technique for minimizing switching loss. The detailed operation principles and the simulation results are presented.

• Journal of Korean Neurosurgical Society
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• 제56권2호
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• pp.103-107
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• 2014

Objective : This study analyzed clinical and radiological outcomes of a zero-profile anchored spacer (Zero-P) and conventional cage-plate (CCP) for single level anterior cervical discectomy and fusion (ACDF) to compare the incidence and difference of postoperative dysphagia with both devices. Methods : We retrospectively reviewed our experiences of single level ACDF with the CCP and Zero-P. From January 2011 to December 2013, 48 patients who had single level herniated intervertebral disc were operated on using ACDF, with CCP in 27 patients and Zero-P in 21 patients. Patients who received more than double-level ACDF or combined circumferential fusion were excluded. Age, operation time, estimated blood loss (EBL), pre-operative modified Japanese Orthopaedic Association (mJOA) scores, post-operative mJOA scores, achieved mJOA scores and recovery rate of mJOA scores were assessed. Prevertebral soft tissue thickness and postoperative dysphagia were analyzed on the day of surgery, and 2 weeks and 6 months postoperatively. Results : The Zero-P group showed same or favorable clinical and radiological outcomes compared with the CCP group. Postoperative dysphagia was significantly low in the Zero-P group. Conclusions : Application of Zero-P may achieve favorable outcomes and reduce postoperative dysphagia in single level ACDF.