• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.8
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• pp.392-401
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• 2001

This paper presents the single-stage high power factor AC to DC converter operated in active-clamp mode. The proposed converter is added active-clamping circuit to boost-flyback single-stage power factor corrected power supply. The active-clamping circuit limits voltage spikes, recycles the energy trapped in the leakage inductance, and provides a mechanism for achieving soft switching of the electronic switches to reduce the switching loss. The auxiliary switch of active-clamping circuit uses the same control and driver circuit as the main switch to reduce the additional cost and size. To verify the performance of the proposed converter, a 100W converter has been designed. The proposed converter gives good power factor correction, low line current harmonic distortions, and tight output voltage regulation, as used unity power factor.

• Progress in Superconductivity
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• v.7 no.1
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• pp.36-40
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• 2005

The problem of fluctuation-induced digital errors in a rapid single flux quantum (RSFQ) circuit has been a very important issue. In this work, we calculated the bit error rate of an RSFQ switch used in superconductive arithmetic logic unit (ALU). RSFQ switch should have a very low error rate in the optimal bias. Theoretical estimates of the RSFQ error rate are on the order of $10^{-50}$ per bit operation. In this experiment, we prepared two identical circuits placed in parallel. Each circuit was composed of 10 Josephson transmission lines (JTLs) connected in series with an RSFQ switch placed in the middle of the 10 JTLs. We used a splitter to feed the same input signal to both circuits. The outputs of the two circuits were compared with an RSFQ exclusive OR (XOR) to measure the bit error rate of the RSFQ switch. By using a computerized bit-error-rate test setup, we measured the bit error rate of $2.18{\times}10^{-12}$ when the bias to the RSFQ switch was 0.398 mA that was quite off from the optimum bias of 0.6 mA.

• Journal of Power Electronics
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• v.7 no.1
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• pp.44-54
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• 2007

Ac-dc power conversion can either be done with two separate converter stages or with a single converter stage. Two-stage ac-dc converters, however, can be costly and complex, while the performance of single-stage converters is compromised due to a reduced number of components. Several researchers have therefore proposed adding some sort of auxiliary circuit consisting of a second switch and some passive elements to single-stage converters to improve their performance. Although these modified single-stage converters may have two converters, they are not two-stage converters as they do not have two separate and independently controlled converters that are always operating to convert power from one form to another. In this paper, the operation of ac-dc single-stage converters is first reviewed and their strengths and weaknesses are noted. The operation of several modified single-stage converters, including one proposed by the authors, is then discussed, and the paper concludes by presenting experimental results that confirm the feasibility of the proposed converter.

• Journal of Power Electronics
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• v.12 no.1
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• pp.75-82
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• 2012

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converter-driven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.320-327
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• 2016

We propose a multi-channel current-balancing single switch light-emitting diode (LED) driver for a 3D TV. Conventional LED drivers require non-isolated DC/DC converters as many as the number of LED channels, whereas the proposed LED driver needs only one power switch and several balancing capacitors instead of expensive non-isolated DC/DC converters. Therefore, the proposed driver features a simple structure with low cost and high efficiency. In particular, because its power switch can be turned off under the zero-current switching condition, the proposed driver has desirable advantages, such as improved electromagnetic interference characteristics and high efficiency. Moreover, it only uses a small number of DC blocking capacitors with no additional active devices for the current balancing of multi-channel LEDs. Therefore, the proposed driver exhibits high reliability and cost effectiveness. To confirm the validity of the proposed driver, we perform a theoretical analysis and present design considerations and experimental results obtained from a prototype that is applicable to a 46" LED TV.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.992-999
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• 2008

This paper describes the design of SPST PIN diode switch which has a 2 kW high power handling capability within $50{\mu}s$ switching speed in $20{\sim}100$ MHz VHF-band. Design factors were investigated and it was confirmed by simulation that the characteristics of insertion loss, VSWR, and isolation met design goal. Also, the capability to handle 2 kW high power with maximum fast switching speed less than $20{\mu}s$ was confirmed and insertion loss less than 0.2 dB, VSWR less than 1.17:1, and isolation higher than 40 dB were obtained by experiments.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.953-956
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• 2005

Low voltage actuation and high isolation characteristics are key features to be solved in electrostatic RF switch design. Since these parameters in the conventional parallel plate MEMS switch design are in trade-off relation, both requirements cannot be met simultaneously. In vertical comb design, however, the actuation voltage is independent to the vertical separation distance between the contact electrodes. Then, we can design the large separation distance between contact electrodes to get high isolation. We have designed an RF MEMS switch which has -40dB isolation at 5 GHz and 6 V operation voltages. The characteristics of the fabricated switch are being evaluate.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.448-452
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• 1997

Theoretical average current and rms current equations are solved using the analytical method in the 3phase voltage-fed inverter. Experimental switch current equations are established by simulation and compared with theoretical equations. As a result of analysis, average and rms currents of switch devices are represented by a function as power factor and modulation index. Especially, equations of this paper are represented as a function of a single factor(K) equal to the product of the power factor and modulation index. Method that can find current levels of switch devices for inverter design and conduction loss of inverter in a simple and accurate manner is presented. Influences of modulation method on switch current are also studied.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.519-524
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• 2002

This paper presents a soft-switching technique of single-stage power conversion Matrix Converter of AC-AC converters. Conventional hard-switching method is limited to operate at low switching frequency due to increased switching loss. In this paper, by additional auxiliary switch circuits, it is shown that the main switch of the matrix converter operate as a zero-voltage switches, and the auxiliary switch operate as a zero current switch. Finally, the soft-switching technique with auxiliary switches is compared with conventional hard-switching technique, and Is analyzed by simulation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.4
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• pp.1-11
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• 1997

In this paper, modeling of the communication channel occupancy characteristics at the base station in the wide area radio trunking syste has been performed. Using the results, mathematical analysis for the switching capacity at the network switch has also been done. Specificatlly, we propose a G/M/m queueing model for the single service area modeling, and analyze changes in call blockingprobabilities accoridng to changes in the burstness characteristics of group paging calls. As a result, we have observe dthat the channel occupancy variations become larger as the burstness characteristics become more apparent, to make the call blocking probability higher. Next, based on the single service area analysis, we have anayzed mathematically the average switching capacity required to serve mobile subscribers for a wide area radio trunking sytem, where multiple switching port assignments are required when the people in the same group are distributed over several base stations. Accordingly, we have observed that the average and the variance of switching channel occupancy are closely related to the mobility characteristics of subscribers, and that we need a netowrk switch having bigger capacity as subscribers show wider distribution. Especially, with the call dropping probability within 0.2%, a switch having about 5 to 6 times bigger can be required, compared with the one when the mobility of subscribers is mostly restricte dto a single service area.