• Journal of Power Electronics
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• v.18 no.3
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• pp.672-680
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• 2018

A bidirectional exponential-gain switched-capacitor (SC) DC-DC converter is developed in this paper. When compared with existing exponential SC converters, the number of switches is significantly reduced and its structure is simplified. The voltage transfer features, voltage ripple across capacitors, efficiency and output impedance of the proposed converter are analyzed in detail. Optimization of the output impedance is also discussed and the best type of capacitance distribution is determined. A common function of the voltage gain to the output impedance is found among the proposed converter and other popular SC voltage multipliers. Experimental evaluation is carried out with a 6-24V bidirectional prototype converter.

• Journal of Power Electronics
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• v.11 no.6
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• pp.779-786
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• 2011

This paper presents a soft switching converter to achieve the functions of zero voltage switching (ZVS) turn-on for the power switches and dc voltage step-up. Two circuit modules are connected in parallel in order to achieve load current sharing and to reduce the size of the transformer core. An active snubber is connected between two transformers in order to absorb the energy stored in the leakage and magnetizing inductances and to limit the voltage stresses across the switches. During the commutation stage of the two complementary switches, the output capacitance of the two switches and the leakage inductance of the transformers are resonant. Thus, the power switches can be turned on under ZVS. No output filter inductor is used in the proposed converter and the voltage stresses of the output diodes is clamped to the output voltage. The circuit configuration, the operation principles and the design considerations are presented. Finally, laboratory experiments with a 340W prototype, verifying the effectiveness of the proposed converter, are described.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.464-471
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• 2012

Self-excited induction generators (SEIG) are gaining importance as compared to conventional generators due to their capability toconvert wind energy into electrical energy for a wide range of variation in operating speed. The performance of such a generator depends upon the load, rotor speed and excitation capacitance. Therefore, depending upon the operating conditions, the output voltage and frequency of this machine goes on changing and this imposes a restriction on its usage. In order to maintain constant voltage and frequency, it need controllers, which make the circuit complicated and also increases the overall cost of power generation. This paper presents a simple controller to regulate the output voltage and frequency of SEIG for variation in its operating conditions due to any change in load, rotor speed and excitation capacitance (R, N, C) and their combination. The controller presented is simple in design, user friendly and is also less expensive, as the elements used in the controller are only resistors, inductors and capacitors. A block of SEIG for steady state operation is also modeled and presented in this paper. SEIG, Controller and other components are modeled and simulated using Matlab/Simulink.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.54-59
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• 1985

From the foregoing papers, it has been clarified that the push-pull current-fed DC-DC converter is excellent in stability as compared with the other conventional DC-DC con-verters. The relation between the stability of the converter and the capacitance of smoothing condenser is analyzed, considering the ESR of smoothing condenser and the 1 st order phase lag of the feedback circuit. From the results, it is known that when the capacitance of smoothing condenser is reduced, the stability of the converter is also excellent as compared with the conventional buck type converter, whereas there are limitations for practical use, since the ripple of output voltage increases by increasing of output current.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.443-450
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• 2014

This paper presents a 20-Gb/s optical receiver circuit fabricated with standard 65-nm CMOS technology. Our receiver circuits are designed with consideration for parasitic inductance and capacitance due to bonding wires connecting the photodetector and the circuit realized separately. Such parasitic inductance and capacitance usually disturb the high-speed performance but, with careful circuit design, we achieve optimized wide and flat response. The receiver circuit is composed of a transimpedance amplifier (TIA) with a DC-balancing buffer, a post amplifier (PA), and an output buffer. The TIA is designed in the shunt-feedback configuration with inductive peaking. The PA is composed of a 6-stage differential amplifier having interleaved active feedback. The receiver circuit is mounted on a FR4 PCB and wire-bonded to an equivalent circuit that emulates a photodetector. The measured transimpedance gain and 3-dB bandwidth of our optical receiver circuit is 84 $dB{\Omega}$ and 12 GHz, respectively. 20-Gb/s $2^{31}-1$ electrical pseudo-random bit sequence data are successfully received with the bit-error rate less than $10^{-12}$. The receiver circuit has chip area of $0.5mm{\times}0.44mm$ and it consumes excluding the output buffer 84 mW with 1.2-V supply voltage.

• Transactions on Electrical and Electronic Materials
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• v.9 no.3
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• pp.128-133
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• 2008

In this paper, in order to analyze property of frequency response in microphone using optical sensor, acousto-optic sensor system has been implemented. The capacitance microphone and fiber-optic transmission path type fiber-optic microphone (FOM) have weaknesses in directivity, size, weight, and price. However suggested optical microphone can be constituted by cheap devices, so it has many benefits like small size, light weight, high directivity, etc. Head part of optical microphone which is suggested in this paper is movable back and forth by sound pressure with the attached reflection plate. Operating point has also been determined by measuring the response characteristics. The choosing the point, which has maximum linearity and sensitivity has changing the distance between optical head and vibrating plate. We measured the output of the O/E transformed signal of the optical microphone while frequency of sound signal is changed using sound measurement /analysis program, "Smaart Live" and "USBPre", which are based on PC, and compared the result from an existing capacitance microphone. The measured optical microphone showed almost similar output characteristics as those of the compared condenser microphone, and its bandwidth performance was about 4 kHz at up to 3 dB.

• Journal of Power Electronics
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• v.16 no.3
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• pp.849-860
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• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• Journal of IKEEE
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• v.18 no.1
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• pp.31-36
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• 2014

In this paper, self-resonant characteristics of transformers were analyzed in accordance with changes of characteristics regarding to the stray capacitance, the volume of winding and the winding ratio were organized by formulas. Generally, the stray capacitance is considered as an unnecessary factor in processing transformers design as well as one of the inherent characteristics. In particular, these characteristics can be appeared clearly in the high frequency driving and Electrical resonance occurs in transformer, according to coupling with a magnetic factor at a particular frequency. In the case of high-voltage output applications, such as medical equipments, It is required to output high-voltage gain. Therefor, If Self-Resonant Characteristic is applied to High-Voltage transformer design, Not only the transformer and circuit but also related the system size can be reduced. So we propose it as one of additional high voltage transformer design methods.

• Journal of Power Electronics
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• v.13 no.1
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• pp.20-30
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• 2013

This paper presents a soft switching DC/DC converter for high voltage application. The interleaved pulse-width modulation (PWM) scheme is used to reduce the ripple current at the output capacitor and the size of output inductors. Two converter cells are connected in series at the high voltage side to reduce the voltage stresses of the active switches. Thus, the voltage stress of each switch is clamped at one half of the input voltage. On the other hand, the output sides of two converter cells are connected in parallel to achieve the load current sharing and reduce the current stress of output inductors. In each converter cell, a half-bridge converter with the asymmetrical PWM scheme is adopted to control power switches and to regulate the output voltage at a desired voltage level. Based on the resonant behavior by the output capacitance of power switches and the transformer leakage inductance, active switches can be turned on at zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The current doubler rectifier is used at the secondary side to partially cancel ripple current. Therefore, the root-mean-square (rms) current at output capacitor is reduced. The proposed converter can be applied for high input voltage applications such as a three-phase 380V utility system. Finally, experiments based on a laboratory prototype with 960W (24V/40A) rated power are provided to demonstrate the performance of proposed converter.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1931-1933
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• 1999

In this paper, the current and voltage properties on the gate oxide film due to the variation of thickness are studied. The specimen is used for n-ch power MOSFET. It is shows the leakage current and current density characteristics due to the applied electric field when the oxide thickness is each $600[\AA],\;800[\AA]$ and $1000[\AA]$, respectively. We known that the leakage current is a little higher when the voltage as reverse bias contrast with forward bias in poly gate is applied. In order to experiment for AC properties is measured for capacitance characteristics. It is confirmed that the value of input capacitance have been a lot of influenced on $SiO_2$ thickness contrast with the value of output capacitance.