• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.302-305
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• 2021

Selection of the optimal inductance for power factor improvement of a buck AC/DC light-emitting diode (LED) driver with wide input voltage range is described in this study. The power factor change based on the slope compensation is obtained for various normalized output current (NOC) values using discrete-time domain analysis. The possibility of implementing constant slope compensation is described using power factor curves for various NOC values. NOC = 0.5 is chosen for the value of inductance with consideration for the simple implementation and reduction of inductor size. Experimental results of the inductance corresponding to NOC = 0.5 are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.35-42
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• 2010

This paper presents the Two-stage LED Driving system using LLC resonant converter for LED lighting application. Due to the existence of the nonisolation DC/DC converter to control the LED current and the light intensity, the conventional three-stage LED Driving system has the problem of low power conversion efficiency. To solve this problem, a novel scheme without any nonisolation DC/DC converter is proposed, in which, the isolated DC/DC converter, e.g., LLC resonant converter in the paper, can perform the LED current control and stage, e.g., PFC stage and LLC stage, the efficiency can be significantly improved. Moreover, the cost and the volume of the whole LED driving system can be reduced compared to those of the conventional ones. The operational principle and the characteristics of the proposed scheme are presented. The proposed scheme is verified experimentally with a 45W output prototype LED driver.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.502-506
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• 2012

본 논문은 LED 조명 환경에서 Zigbee를 이용해서 Dimming 제어 모듈을 구성 하였다. 현재 사용되고 있는 LED 제어 모듈는 일반적으로 단일 출력을 사용하여 LED 조명의 일정한 밝기를 고정 출력이 되도록 사용되어지고 있다. 본 논문에서 구성된 무선 통신 모듈은 Zigbee를 이용하여 실내 환경에서 측정된 조도값을 무선으로 전송하도록 조도 센서 모듈을 구성 하였으며, 무선으로 전송된 조도값에 대한 출력을 제어하도록 구성하였다. MCU는 LED Driver IC를 이용하여 PWM 신호에 따라서 LED Driver IC에서 출력 전압을 변화하도록 하여 6단계의 밝기로 LED조명을 Dimming하도록 구성하였으며, 무선조도 센서는 10~15m의 거리에서 안정적으로 동작된다.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.103-107
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• 2012

Due to improvement of the semiconductor technology, the LED replaces the conventional lighting source and LED drivers have been studied and developed. The LED is driven by the constant current control method according to its characteristics. For the constant current control method, the linear regulator and the switching regulator is used. The switching regulator is usually used to LED drivers because it has specific characteristics as the wide input dynamic range and the high efficiency. In this paper, we have described the principle and the implement of the switching regulator, using the drive IC and the low cost DSP chip. Also, both methods have been implemented and its electrical characteristics had almost same experimental results in the steady state and the transient state.

• Journal of Digital Convergence
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• v.14 no.1
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• pp.181-187
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• 2016

Typical Retro-reflectors installed on road have problems such as limiting a driver's visibility at night when it is foggy or rainy. On the other hand, LED illuminated studs, called cat's eye system, extends a driver's visibility under these conditions. In this paper, we present a design of the LED cat's eye system using solar energy that can sustain vehicles with about 30-ton weight and is compliant with the IP68 code for water proof as IEC standard 60529. In addition, we propose a scheme of designing a LED driving circuit consuming low power to take into accounts cold weather or rainy season with limited sunlight. This LED cat's eye studs is currently installed and used on expressway and bike route nationally as well as overseas.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.114-119
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• 2017

In this paper we present the search on HC-06 Bluetooth based driver module for emergency LED Multi-Directional Indicator. Nowadays, a growing trends in which electronic displays such as LED, LCD or plasma monitors are being installed in public places like bars, stores, entertainment areas, restaurants, lobbies, etc. In this paper, the study is curried out on efficiency of HC-06 Bluetooth module based controller driver that relates generally to the field of emergency signage management systems for displaying various indicator contents remotely on electronic displays in public and privates venues. It allows user smart devices interaction remotely with digital signage by providing content for displaying on at least one display in a venue. Depending on the emergency case, HC-06 Bluetooth based driver module proves the high efficiency as well as good performance of processing and communicating remotely the indicator based message that is displayed from a venue management control system by using smart devices. The system combines smart device that linked to HC-06 Bluetooth module with ATmega168/328 embedded micro controller which result by switching the displayer containing the digital signage indicator based message.

• Journal of Power Electronics
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• v.18 no.2
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• pp.640-650
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• 2018

A TRIAC dimmable LED driver with a wide tuning range and a two-stage uniform dimming scheme is proposed in this paper. To solve the restricted dimming range problem caused by the limited conduction ratio of TRIAC dimmers, a conduction ratio compensation technique is introduced, which can increase the output current up to the rated output current when the TRIAC dimmer turns to the maximum conduction ratio. For further optimization, a two-stage uniform dimming diagram with a rapid dimming curve and a slow dimming curve is designed to make the LED driver regulated visually uniform in the whole adjustable range of the TRIAC dimmer. The proposed control chip is fabricated in a TSMC $0.35{\mu}m$ 5V/650V CMOS/LDMOS process, and verified on a 21V/500mA circuit prototype. The test results show that, in the 90V/60Hz~132V/60Hz ac input range, the voltage linear regulation is 2.6%, the power factor is 99.5% and the efficiency is 83%. Moreover, in the dimming mode, the dimming rate is less than 1% when the maximum dimming current is 516mA and the minimum dimming current is only about 5mA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.14-14
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• 2010

A high voltage current sensing circuit for LED driver IC is designed and verfied by Cadence SPECTRE simulations. The current mirror pair, power and sensing MOSFETs with size ratio of K, is used in our on-chip current sensing circuit. Very low drain voltages of the current mirror pair should be matched to give accurate current sensing, so a folded-cascode opamp with a PMOS input pair is used in our design. A high voltage high side LDMOST switch is used between the current sensing circuit and power MOSFET to protect the current sensing circuit from the high output voltage. Simulation results using 0.35um BCD process show that current sensing is accurate with properly frequency compensated opamp.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.292-300
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• 2009

This paper presents an LED BLU driving circuit with a local-dimming structure. The efficiency of the proposed LED driver has been improved by parallel driving 8 serial-connected LED arrays. It employed the soft-switching boost converter topology to reduce the switching power loss of the hard switching boost converter. Soft- and hard-switching converters have the same structure except that the free-wheeling diode in the hard-switching converter is replaced with the n-channel MOSFET in the soft-switching one. The proposed boost converter was compared with the hard switching converter. The soft-switching converter reveals superior ripple and efficiency. A smaller inductance can be used for the soft-switching converter contrasting to the hard-switching one. We also studied on an over-voltage protection circuit of the output of the driver at the no load condition. The protection circuit was applied to the proposed driver, and its operation was confirmed by experiment. Using a local-dimming technique, power consumption of LCD BLUs can be reduced as low as possible according to the brightness of its image.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.235-240
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• 2010

In order to substitute incandescent lamps, a power supply device for 7W class LED lamps which are environmentally friendly and energy saving is designed LED lamps consist of a multitude of chip LED connected in parallel and series. 11ms it is necessary to supply LED lamps with DC voltage and current. However, when LED lamps are in use, they are connected directly to AC 220V. This is why we need to have AC/DC, DC/DC power converters including a control system of voltage and current. For this, a transformerless and simple LED lamp driver is designed 조ich can control the current and output voltage for LED string of LED lamp.