• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.786-790
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• 2001

In this paper, we propose an optimum design method for optical pick-up actuators. Using this method, we can design an optimal pick-up actuator having the required tracking/focusing performances. Also, the designed actuator has the small mass, force constant for small size of magnetic circuit and large resistance for reduction of heat generation. Simulation results show that this method can be potentially implemented in all the pick-up actuators.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.193-198
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• 2012

An LED converter used to operate an LED with high efficiency and long lifespan, activates an LED by keeping voltage and current constant. In spite of voltage drop by LED's overheating and over-voltage by damage of a power line and by circuit problem, most existing LED converters supply unchanged constant voltage and current to the LED. Eventually, LED is out of order because of over-voltage or over-current. To avoid the breakdown of an LED by over-voltage and over-current, we propose a new scheme which deactivate the PWM circuit in the event of over-current generating. The PWM circuit operates below the pre-determined level of current. While the over-voltage is generated in PWM circuit, the feedback circuit makes the PWM circuit stopped and therefore prevents LED from being damaged by over-voltage and over-current.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.101-106
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• 2022

In this paper, WBG semiconductor such as SiC and GaN were applied as power switches for LCL circuit that can be applied to satellite power systems and the test results of the LCL circuit are reported. P-channel MOSFET and N-channel MOSFET, which were generally used in the conventional LCL circuit, were applied together to expand the utility of the test results. The design and stability evaluation were performed using a Micro Cap circuit simulation program. For the test circuit, a module using each switch was manufactured, and a total of 5 modules were manufactured and the steady state and transient state characteristics were compared. From the experimental results, the LCL circuit for power supply of the satellite power system constructed in this paper satisfied the constant current and constant voltage conditions under various operating conditions. The P-channel MOSFET showed the lowest efficiency characteristics, and the three N-channel switches of Si, SiC and GaN showed relatively high efficiency characteristics of up to 99.05% or more. In conclusion, it was verified that the on-resistor of the switch had a direct effect on the efficiency and loss characteristics.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.41-48
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• 2004

In this paper, a PFC(Power Factor Correction) electronic ballast with constant voltage-fed is proposed. The proposed PFC electronic ballast is combined of a high-efficiency boost converter and a conventional half bridge inverter. It is proved that the ripple of input-current and the input-current's harmonic of the proposed PFC electronic ballast are reduced using the voltage divider and soft-switching technique. It is demonstrated that simulation results for fluorescent lamp correspond with theoretical analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.76-84
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• 2001

Generally fuel injection system using solenoid have some problems between control signal and mechanical movement like as time lag. Main purpose of the present study is to help the design optimization of GDSI for real engine application. We have adopted two different solenoid driving circuit, namely saturation and pick-hold type and have investigated experimentally the current, needle force, needle opening duration and injection quantity. The pick-hold type driving circuit surpassed a saturation type in the response time and pression control of injection quantity. Accordingly, Using characterization data of operating factors such as time constant, driving force and so on, can be evaluated and adjusted to obtain an optimum injector performance.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.343-348
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• 2003

In this paper, a PFC(Power Factor Correction) electronic ballast with constant voltage-fed is proposed. The proposed PFC electronic ballast is combined of a High-efficiency boost converter and a conventional half bridge inverter. It is proved that the ripple of input-current and the input-current's harmonic of the proposed PFC electronic ballast are reduced using the voltage divider and soft-switching technique. It is demonstrated that simulation results for 40[W] fluorescent lamp correspond with theoretical analysis

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.4
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• pp.23-28
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• 1974

One of the consistent nuisances in accurate design of circuits containing coils with core is how to take into account the frequency dependence of Q of actual coils. The conventional equivalent circuit consisting of an inductance and a series (constant) resistance and possibly a parallel (constant) capacitance is of little use in this situation since the core loss itself is strongly dependent on the frequency. In order to circumvent this difficulty, in this paper, a mathematical expression for Q of a given core as a function of inductance and frequency is first assumed and parameters in this expression are optimiged so as to best fit the data provided by the core manufacturer or obtained experimentally. This expression is then utilized in accurate calculation of the frequency response of a given circuit required in the optimal design of circuits containing coils. In other words the proposed approach is an effective combination of an approximate expression of coil's Q and circuit optimisation technique, which seems to have solved, to a great extent, the stated difficulty associated with actual coils. As for the optimization technique, ths Fletcher-Powell procedure was employed and one example was given to illustrate the proposed approach.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.453-457
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• 1996

DC/DC converter is widely used in computer, electronic communication and industrial apparatus where the regulated dc supply is needed. FB-ZVS converter is suitable for high-power, high-frequency and constant frequency control. Because the voltage stress of the diode rectifier is high due to the ring effect, the clamp circuit is essential to reduce the voltage stress. The nondissipative active clamp circuit eliminates ring effect. Analysis of FB-ZVS converter and the validity of the active clamp circuit are studied through the simulation, and the experimental results show the superior characterics of the proposed system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.42-50
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• 2003

This paper presents an embedded RC oscillator which has temperature compensation circuits. The conventional RC oscillator has frequency deviation about 15%, which is caused by variation of resistors and the reference voltage of schmitt trigger from the temperature condition. In this paper, the proposed circuit use a CMOS bandgap reference having balanced current temperature coefficients as a triggering voltage of schmitt trigger. The constant current sources consist of current mirror circuit with the positive and negative temperature coefficient. The proposed circuit shows less 3% frequency deviation for variation of temperature, supply voltage and process parameters.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2014-2015
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• 2007

This paper deals with design and analysis of thrust magnetic bearing. Using the solutions obtained from equivalent magnetic circuit, we predict the electromagnetic characteristics such as thrust, time constant and power loss according to design parameters. And then, using non-linear finite element analysis, a detailed design is performed considering saturation in order to meet requirements.