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Duy T. Nguyen,Eun S. Lee,Sonapreetha. M.R,Chun T. Rim 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
A compact and high efficient LED driver compatible with various electronic ballasts commercially used in markets is newly proposed, which modulates the LED power by controlling a switching duty cycle of a main switch in synchronous voltage doubler rectifier. Thus, the fluorescent lamp can be replaced with the LED lamp without any change of fluorescent lamp fixture. The zero voltage switching (ZVS) is achieved for different switching frequency of electronic ballast, which leads to high efficiency. Furthermore, neither an inductor, a transformer, nor an electrolyte capacitor is used, which makes this LED driver compact size and long lifetime. A prototype of 16 W LED driver was implemented and experimentally verified for 32 W or 36 W electronic ballasts, where high efficiencies of 93.2%, 91.8%, and 92.3% for instant start, rapid start and programmed start ballasts, respectively, were achieved for a wide range of source voltage 180 V < Vs < 260 V, adequately meeting high power factor (PF), low total harmonic distortion (THD).
Eun S. Lee,Bo H. Choi,Duy T. Nguyen,Chun T. Rim 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The analysis of the proposed TRIAC dimming LED driver, which adopts a variable switched capacitor, is proposed in this paper. Because the proposed LED driver adopts a TRIAC switch as the main switch, it is proven to be power-efficient and reliable over long life. Similar to the previous TRIAC dimmers of lamps, turn-on timing of a TRIAC can be controlled by a volume resistor in the proposed LED driver, which modulates the effective capacitance of the variable switched capacitor. Thus, LED power regulation for source voltage change and LED dimming control can be achieved, meeting the standard of power factor (PF) and total harmonic distortion (THD). Because the proposed LED driver has long life and high power efficiency characteristics, it is adequate for industrial lighting applications such as street, factory, parking garage, and emergency stair. The detail analysis of the proposed LED driver is presented in this paper. A prototype of 80 W was fabricated and verified by experiments, which show the efficiency, PF, and THD at Vs = 220 V are 93.8%, 0.95, and 22.5%, respectively, and the LED power variation is well mitigated below 3.75% for 190 V < Vs < 250 V.
Innovative 5-m-Off-Distance Inductive Power Transfer Systems With Optimally Shaped Dipole Coils
Changbyung Park,Sungwoo Lee,Gyu-Hyeong Cho,Rim, Chun T. Institute of Electrical and Electronics Engineers 2015 IEEE transactions on power electronics Vol. No.
<P>5-m-off-distance inductive power transfer systems that have optimally shaped cores in the primary and secondary coils are proposed. Instead of conventional-loop-type coils for magnetic resonance scheme, magnetic dipole type coils with cores are used for drastic reduction in deployment space and quite long wireless power transfer. An optimized stepped core structure is also proposed, where a strong magnetic field section is so thick that magnetic field density may be even. Thus, the proposed optimized stepped core has only 41% core loss compared with an unoptimized even core but delivers 2.1 times more wireless power for a given amount of core. Experimentally obtained maximum output powers and primary-coil-to-load-power efficiencies for 3, 4, and 5 m at 20 kHz were 1403, 471, 209 W, and 29%, 16%, 8%, respectively.</P>
Gyrator-Based Analysis of Resonant Circuits in Inductive Power Transfer Systems
Sohn, Yeong H.,Choi, Bo H.,Gyu-Hyeong Cho,Rim, Chun T. Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>In this paper, first, it is found that not only the magnetically coupled inductors but also all inductive power transfer systems (IPTSs) inherently have the nature of a gyrator. Widely known characteristics of IPTSs such as impedance inversion and source-type conversion are proved to be the nature of the gyrator. A graphical approach that utilizes the gyrator is proposed for the modeling of IPTSs in general. The proposed graphical technique enables manipulations on the circuit diagram instead of on the circuit equations, which are difficult to handle when the system order is higher than 4. Hence, the equivalent model can be obtained almost by inspection conveniently, giving fruitful physical insights that are limitedly achieved with the equation manipulations. Steady-state analyses at any frequency are possible, and equivalent series resistances can also be included in the proposed model. Five selected electrical characteristics, i.e., source-to-load gain, load-independent output voltage/current characteristics, power factor at the source, sign of the source phase angle, and allowances of open/short loads are evaluated for three widely used IPTS topologies. Also, this technique is extended to the mistuned case for verifying the general use of the approach. An experimental prototype of the voltage-source-type inductor-capacitor-inductor secondary-parallel (V-LCL-P) topology was built to demonstrate the proposed approach for both perfectly tuned and mistuned situations at 85 W and 100 kHz.</P>
Changbyung Park,Sungwoo Lee,Gyu-Hyeong Cho,Su-Yong Choi,Rim, Chun T. IEEE 2014 IEEE transactions on industry applications Vol.50 No.1
<P>The inductive power transfer system for mobile robots, which has the single wire layer of easily fabricated power floor structure and the evenly displaced multiple pickup structure for receiving uniform power, is proposed. Due to its simple structure, a wide-area power floor of 3.52 m<SUP>2</SUP> (1.6 m ×2.2 m) could be fabricated as a prototype. Three pickups with evenly displaced angle and space are adopted, considering the limited bottom area of the free-moving mobile robot. The size and position of each pickup are appropriately selected for the given subwinding size of the power floor and magnetic pole arrangement. Experiments for the prototype show that the proposed multiple pickup structure lowers the spatial output power variation and that enough output power of 10 W can be obtained for the mobile robots.</P>
Changbyung Park,Sungwoo Lee,Seog Yong Jeong,Gyu-Hyeong Cho,Rim, Chun T. Institute of Electrical and Electronics Engineers 2015 IEEE transactions on power electronics Vol. No.
<P>A narrow-width power-invariant inductive power transfer system (IPTS) along the driving direction is newly proposed in this paper. The conventional I-type power supply rail for on-line electric vehicles (OLEVs) has a very narrow power supply rail with 10-cm width and exposes pedestrians to a very low electromagnetic field due to its alternatively arranged magnetic poles along the driving direction of electric vehicles; however, it has a major drawback: Sinusoidal variation of the induced pick-up voltage depending on pick-up positions on the power supply rail along driving direction. To overcome this disadvantage, a dq-power supply rail fed by two high-frequency ac currents of the d-phase and q-phase is introduced in this paper. The d -phase and q-phase magnetic poles are alternatively arranged in a line; hence, the induced voltage of a pickup becomes spatially uniform. The power invariant characteristic of the proposed IPTS for OLEV has been verified by analysis, simulations, and experiments. A practical winding method is suggested as well.</P>
Choi, Su Y.,Huh, Jin,Lee, Woo Y.,Rim, Chun T. IEEE 2014 IEEE transactions on power electronics Vol.29 No.12
<P>Asymmetric coil sets for wireless stationary electric vehicle (EV) chargers, which has significantly larger lateral tolerance than previous ones, is proposed. The pick-up coil set is much smaller than the power supply coil set, thereby allowing large lateral and longitudinal displacements as well as robustness to air-gap displacement. Electromagnetic field (EMF) is reasonably reduced by arranging magnetic poles along the EV's moving direction so that alternating magnetic flux through adjacent poles cancels each other. A dominant field analysis useful for complex vector magnetic flux simulation is newly proposed, which is applicable to any resonating coils of an inductive power transfer system (IPTS). Furthermore, a hysteresis loss model is suggested, which appropriately reflects the partial core saturation on a system analysis. A prototype IPTS including the proposed coil sets were designed and successfully verified by experiments. In the quick charging mode, maximum output power of 15 kW, large lateral displacement of 40 cm, longitudinal displacement of 20 cm, air gap of 15 cm were achieved, and low EMF of 6.1 μT at 20 kHz was achieved in the normal charging mode of 5 kW.</P>