• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.104-109
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• 2014

To operate organic light emitting device (OLED) with alternating current (AC) power source without AC/DC(direct current) converter, we fabricated the fluorescent OLED and measured the emission characteristics with AC and DC. The OLED operated by AC showed higher maximum current efficiency of 8.2 cd/A and maximum power efficiency of 8.3 lm/W. But current efficiency and power efficiency of AC driven OLED showed worse than DC driven OLED at high voltage above 10 V. This result can be explained by the peak voltage of AC was $\sqrt{2}$ times than DC, In case of low driving voltage the emission characteristics were improved by the peak voltage of AC, but in case of high driving voltage the emission efficiencies were decreased by the roll off phenomena. Finally, serial OLED arrays using twelve OLEDs driven by AC 110 V showed average voltage of 9.17 V, voltage uniformity of 99.0%, average luminance of $1,175cd/m^2$, luminance uniformity of 94.4%.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.125-134
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• 2016

We propose an efficient high voltage level shifter for a high side Buck converter driving a light-emitting diode (LED) lamp. The proposed circuit is comprised of a low voltage pulse width modulation (PWM) signal driver, a coupling capacitor, a resistor, and a diode. The proposed method uses a property of a PWM signal. The property is that the signal repeatedly transits between a low and high level at a certain frequency. A low voltage PWM signal is boosted to a high voltage PWM signal through a coupling capacitor using the property of the PWM signal, and the boosted high voltage PWM signal drives a p-channel metal oxide semiconductor (PMOS) transistor on the high side Buck converter. Experimental results show that the proposed level shifter boosts a low voltage (0 to 20 V) PWM signal at 125 kHz to a high voltage (370 to 380 V) PWM signal with a duty ratio of up to 0.9941.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.2
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• pp.211-216
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• 2018

This paper presents a numerical optimization technique and switching phase control technique aiming at improvement of efficiency of the low voltage BLDC motor. The optimization technique is performed using the generalized sensitivity technique, response surface method(RSM) and sampling minimization technique. In order to minimize current consumption of the BLDC motor, the switching method of the driving device is optimized using RSM with finite element analysis. The ratings of BLDC motor are 50 W, 24 V, 1200 rpm. As optimizing results, the input current is reduced from 2.78 to 2.51 [A] when the switching phase is shifted by -2.65 [DEG_ELC] at the rated driving speed of 1200 [rpm]. It is confirmed that the proposed method reduces the consuming current of the low voltage BLDC motor through switching phase control method using the numerical optimization method.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.9-10
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• 2000

The wide viewing angle and fast response time characteristics of negative dielectric anisotropy nematic liquid crystal (NLC) using a novel vertical-alignment (VA) - 1/4 ${\pi}$ cell mode on a homeotropic alignment layer were investigated. Good voltage-transmittance curves and low driving voltage using the novel VA - 1/4 ${\pi}$ cell mode without a negative compensation film were obtained. The iso-viewing angle characteristics of NLC using the novel VA - 1/4 ${\pi}$ cell mode without a negative compensation film can be achieved. The fast response time of 24.4 ms in NLC was successfully measured. The iso-viewing angle, fast response time, and low driving voltage characteristics using the novel VA - 1/4 ${\pi}$ cell mode can be achieved.

• Journal of the Semiconductor & Display Technology
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• v.2 no.3
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• pp.25-30
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• 2003

In this study, the controller using TMS320LF2407 low voltage DSP for motor control is designed and realized. It has 40 MIPS calculating ability and its driving voltage is 3.3 V for low power. The peripheral elements, however usually use 5 V and they need voltage transfer interface. In this study, voltage transformation and reducing noise are studied and space vector PWM is adopted as a motor control scheme. According to these methods, the efforts for software programming and calculation processes are reduced. In addition, the hardware is also simplified by substituting the current control part with software programming. Through this study, the DSP based servo controller increases its ability for high performance multi-function on semiconductor transportation equipments..

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.295-297
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• 2005

This paper presents a novel current driving method for the synchronous rectifier (SR) in a Flyback topology. The proposed current driven synchronous rectifier features low Power loss, good performance and the gate voltage of FET in the synchronous rectifier is easily controlled by zener voltage. The proposed SR driving method is implemented in a 200W Flyback converter with 400Vdc input and achieved excellent performance at full load.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.286-293
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• 2004

This paper presents the result of a study on the starter control for a turbo generator. Because a starter in gear box type turbo-generator system is composed of gearbox and brush DC motor, it should be replaced with High Speed Generator(HSG)) in HSG type Turbo-generator. There-ore, it is necessary to design a new starting algorithm and starter. In gearbox type system, brush DC motor is rotated to the designed speed using low voltage-high current battery power. After brush DC motor speed is increased to several times by gearbox, gas turbine engine can be rotated to designed starting speed. If we implement a starter with High Speed Generator(HSG), it is necessary to drive high-speed generator to high-speed motor. High-speed generator with permanent magnet on rotor has a low leakage inductance fur driving high-speed rotation, and it is necessary high DC link voltage for inverter when High-speed generator is driven to high speed. This paper presents result of development of the boost converter for converting high voltage DC from low battery voltage and design of the inverter for controlling a high frequency current to be injected to motor winding. Also, we show performance of the designed starter by driving the turbo generator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.432-436
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• 2017

IZO transistors with $Al_2O_3$ as gate dielectrics have been investigated. To improve permittivity in an ambient dielectric layer, we grew $Al_2O_3$ by atomic layer deposition directly onto the substrates. Then, we prepared IZO semiconductor solutions with 0.1 M indium nitrate hydrate [$In(NO_3)_3{\cdot}xH_2O$] and 0.1 M zinc acetate dehydrate [$Zn(CH_3COO)_2{\cdot}2H_2O$] as precursor solutions; the IZO solution made with a molar ratio of 7:3 was then prepared. It has been found that these oxide transistors exhibit low operating voltage, good turn-on voltage, and an average field-effect mobility of $0.90cm^2/Vs$ in ambient conditions. Studies of low-voltage driving of IZO transistors with atomic layer-deposited high-k $Al_2O_3$ as gate dielectric provide data of relevance for the potential use of these materials and this technology in transparent display devices and displays.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.3
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• pp.111-115
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• 2012

Generally, brushless DC motor(BLDCM) driving system uses hall sensors or encoders as the mechanical position or speed sensor. It is necessary to achieve the informations of rotor position for driving trapezoidal type brushless DC motor without any position sensor. In this paper, the commutation signals are obtained without the motor neutral voltage, multistage analog filters, A/D converters, or the complex digital phase shift circuits which are indispensable in the conventional sensorless control algorithms. In the proposed method, in stead of detecting the zero crossing point of the nonexcited motor back electromagnetic force for the average motor terminal to neutral voltage, the commutation signal are extracted directly from the specific average line to line voltage with low-pass filter, adder and comparators circuit. In contrast to conventional methods, the neutral voltage is not need; therefore, the commutation signals are insensitive to the common mode noise. Moreover, the complex phase shift circuit can be eliminated. The effectiveness of the proposed method is verified through simulation results.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.153-156
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• 2004

A newly developed flexible active-matrix (AM-) electrophoretic display (EPD) is reported. The AM-EPD features: (1) low-temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology, (2) fully integrated scan- and data-drivers, (3) flexibility and light-weight realized by transferring the whole circuits onto a plastic substrate using $SUFTLA^{TM}$ (Surface Free Technology by Laser Annealing/Ablation) process. A large storage capacitor is formed in each pixel so that driving electric field can be kept sufficiently strong during a writing period Two-phase driving scheme, a reset-phase which erases a previous image and a writing-phase for writing a new image, was chosen to cope with EPD's high driving voltage. The flexible AM-EPD has been successfully operated with a driving voltage of 8.5 V.