• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.953-958
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• 2007

In this paper, multilayer actuator structured-ultrasonic nozzle and resonant inverter driving circuit were manufactured, respectively. Its electrical properties were investigated. Multilayer actuator structured ultrasonic nozzle was fabricated using PMN-PNN-PZT ceramics showing excellent piezoelectric characteristics. In order to drive ultrasonic nozzle, resonant PWM inverter was used. The purpose of this study is to find the optimal driving condition of ultrasonic nozzle. Accordingly, electrical and temperature characteristic of multilayer ultrasonic driving system were investigated by experiments as a function of the series resonance inductance. The driving current of ultrasonic nozzle showed the maximum current of 27 mA. Also, the surface temperature of ceramic vibrator showed $44^{\circ}C$ at driving time for 20 min. The ultrasonic nozzle was stably operated in the case of driving for more than 20 min.

• Journal of Information Display
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• 제11권4호
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• pp.173-181
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• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.

• Journal of Power Electronics
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• 제12권6호
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• pp.869-877
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• 2012

This paper presents a current-balancing circuit for security lights that uses parallel-connected LEDs. The parallel connection of LEDs causes current differences between the LED strings because of characteristic deviations. These differences can reduce the lifespan of a particular point of LEDs by thermal spotting. They can also cause non-uniform luminance of the lighting device. Among the different methods for solving these problems, the method using current-balancing transformers makes it easy to compensate for current differences and it has a simple circuitry. However, while the balancing transformer has been applied to AC light sources, LEDs operate on a DC source, so the driving circuitry and the design method have to be changed and their performances must be verified. Thus in this paper, a design method of the balancing transformer network and the driving circuitry for LEDs is proposed. The proposed design method could have a smaller size than the conventional design method. The proposed circuitry is applied to three types of 100-watt LED security lights, which use different LEDs. Experimental results are presented to verify the performance of the designed driving circuits.

• 한국표면공학회지
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• 제50권5호
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• pp.398-404
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• 2017

In order to study the AC driving mechanism for OLED lighting, the fluorescent OLEDs were fabricated and the electroluminescent characteristics of the OLEDs by AC forward bias were analyzed. In the case of the driving method of OLED by AC forward bias under the same voltage and the same current density, degradation of luminescent characteristics for elapsed time progressed faster than in the case of the driving method by DC bias. These phenomena were caused by the peak voltage of AC forward bias which is ${\sqrt{2}}$ times higher than the DC voltage. In addition, the degradation of the OLED was accelerated because the AC forward bias had come close to the upper limit of the allowable voltage range even though the peak voltage didn't exceed the allowable range of the OLED. However, the fabricated fluorescent OLED showed little degradation of OLED characteristics due to AC forward bias from 0 V to 6.04 V. Therefore, OLED lighting by AC driving will become commercialized if sufficient luminance is realized at a voltage at which the characteristics of the OLED are not degradation by the AC driving method.

• 한국분무공학회지
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• 제24권3호
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• pp.114-121
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• 2019

The effect of injector driving current pattern on fuel injection rate of solenoid diesel common rail injector was studied by computer simulation. The time resolved fuel injection rate and injected quantity per stroke of a common rail injector driven with the five current patterns were computer simulated. The fuel injection rate and injected quantity per stroke according to the rail pressure and fuel injection period were also computer simulated. When the common rail injector was driven with the five driving current patterns of peak & hold, there was no difference in the fuel injection rate in the peak section regardless of all the current patterns of the five cases. On the other hand, the magnitude of the hold current value influenced the injection rate and injected quantity per stroke. That is, in the current pattern of three cases where the hold current value is equal to or more than a constant value of the peak current value, the fuel injection rates for the given common rail rail pressure and injection period are same one another. On the other hand, the current pattern of the two cases, in which the hold current value is smaller than a certain value, there is a large fluctuation in the fuel injection rate.

• 대한전자공학회논문지SP
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• 제47권1호
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• pp.62-72
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• 2010

PM OLED는 차세대 디스플레이의 하나로 많은 애플리케이션에 사용되고 있다. PM OLED를 애플리케이션에 적용하는데 있어 가장 큰 문제는 전력 소모와 제품 수명을 꼽을 수 있다. PM OLED 시장의 확대를 위해 이를 개선하기 위한 노력이 패널과 회로 측면에서 이루어지고 있다. 전력소모와 제품 수명은 상호 연관 관계가 있어, 회로 상에서 전력 소모를 줄이면 인가 전류가 감소하여 제품 수명이 향상된다. 그러므로 전력 소모를 회로적으로 보완하는 방법을 적용하여 구동 방식을 개선함으로 전력 소모 감소와 제품 수명 향상이 가능하다. 종래 Row-to-Row 방식을 개선하여 여러 Row를 동시에 구동하는 기술을 적용하면 전력 소모를 감소 시키고 수명을 연장할 수 있다. 본 논문은 여러 Row를 동시에 구동하는 방식을 적용함에 있어 Row 별 Column 데이터에 대해 확률적 개념을 도입하여 유사성이 높은 Row를 하나의 Group으로 분리하고 Group별로 차별적으로 Row 구동 방식을 적용하여 전력을 감소하여 패널 수명을 향상하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.36-37
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• 2013

This paper presents high voltage operation sensing boost converter with high side current. Proposed topology has three functions which are high voltage driving, high side current sensing and low voltage boost controller. High voltage gate driving block provides LED dimming function and switch function such as a load switch of LED driver. To protect abnormal fault and burn out of LED bar, it is applied high side current sensing method with high voltage driver. This proposed configuration of boost converter shows the effectiveness capability to LED driver through measurement results.

• 전력전자학회논문지
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• 제20권3호
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• pp.223-231
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• 2015

LEDs have been widely used in lighting displays, automobiles, and airplanes owing to their excellent light output characteristics and long lifespan. Though LEDs are manufactured under the same process, variations in impurity concentrations cause electrical deviation among LEDs. The resulting electrical deviation can not only reduce the life time of the LED but also cause non-uniform luminance of LEDs connected in parallel. LED driving circuit is required to solve these problems. In this paper, we propose a LED driving system using Y-type current balancing transformer to maximize the efficiency of the system by removing output stage Schottky diodes. Experimental results are presented to verify the performance of proposed LED driving system that is applied to 80 W LED modules.

• 한국산업정보학회논문지
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• 제6권2호
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• pp.74-79
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• 2001

로봇과 자동화기기에 범용으로 사용되는 Stewing Motor의 Driving을 위하여 unipolar 방식과 bipolar 방식의 Controller Circuit를 design 하였으며 특히 design시 Digital logic을 이용하여 Controller를 설계 제작하여 실험을 통해 그 응용성을 실험하였다. 또한 Motor의 효율 향상을 위하여 Motor의 Winding에 흐르는 전류를 제어하기 위하여 constant Current Limit Methode와 Constant Voltage Limit Methode를 분석하고 실재 회로 제작 시 응용하여 Motor의 효율을 향상시켰다.

• 방송공학회논문지
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• 제21권5호
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• pp.760-769
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• 2016

본 논문에서는 LED의 색 영역을 확장하기 위해서 Hybrid LED 구동회로와 제어 기법을 제안하였다. 제안된 Hybrid LED 구동회로는 고 전류에서는 스위칭 레귤레이션 동작을 하고 저 전류에서는 리니어 레귤레이션 동작을 함으로써 LED에 일정한 정 전류를 공급하였다. 또한 고 전류와 저 전류의 크기를 각각 CC 제어기법과 PWM 제어기법으로 제어하였다. 제안된 구동회로와 제어 기법으로 RGB LED 각각의 전류를 가변하였고, 전류가 최대 전류대비 2%까지 선형적으로 제어됨 실험을 통해 확인하였다. 게다가 출력된 광색을 CIE1931 색도좌표로 측정하였다. 그 결과 기존의 표현할 수 없었던 색이 균일하게 출력됨을 확인하였으며, 제안된 구동회로와 제어 기법이 저 전류제어가 가능함으로 색 영역 확장이 가능함을 증명하였다.