• Journal of Information Display
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• 제13권2호
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• pp.73-82
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• 2012

In this paper, a light-emitting diode (LED) backlight driver integrated circuit (IC) for medium-sized liquid crystal displays (LCDs) is proposed. In the proposed IC, a linear current regulator with matched internal resistors and an adaptive phase-shifted pulse-width modulation (PWM) dimming controller are also proposed to improve LED current uniformity and reliability. The double feedback loop control boost converter is used to achieve high power efficiency, fast transient characteristic, and high dimming frequency and resolution. The proposed IC was fabricated using the 0.35 ${\mu}m$ bipolar-CMOS-DMOS (BCD) process. The LED current uniformity and LED fault immunity of the proposed IC were verified through experiments. The measured power efficiency was 90%; the measured LED current uniformity, 97%; and the measured rising and falling times of the LED current, 86 and 7 ns, respectively. Due to the fast rising and falling characteristics, the proposed IC operates up to 39 kHz PWM dimming frequency, with an 8-bit dimming resolution. It was verified that the phase difference between the PWM dimming signals is changed adaptively when LED fault occurs. The experiment results showed that the proposed IC meets the requirements for the LED backlight driver IC for medium-sized LCDs.

• Journal of Power Electronics
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• 제17권5호
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• pp.1137-1149
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• 2017

In order to reduce the cost, improve the efficiency and simplify the complicated control of existing isolated LED drivers, an improved boundary conduction mode (BCM) Buck ac-dc light emitting diode (LED) driver with extended output voltage and low total harmonic distortion is proposed. With a coupled inductor winding and a stacked output, its output voltage can be elevated to a much higher value when compared to that of the conventional Buck ac-dc converter, without sacrificing the input harmonics and power factor. Therefore, the proposed Buck LED driver can meet the IEC61000-3-2 (Class C) limitation and has a low THD. The operating principle of the topology and the design methodology of the ac-dc LED driver are presented. A 150 W ac-dc prototype was built in the laboratory and it shows that the input current harmonics meet the lighting standard. In addition, the THD is less than 16% at a typical ac input. The peak efficiency is higher than 96.5% at a full load and a normal input.

• Journal of Power Electronics
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• 제17권2호
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• pp.315-322
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• 2017

LED is a promising new generation of green lighting with the advantages of high efficiency, good optical performance, long lifetime and environmental friendliness. A pulsating current can be used to drive LEDs. However, current with a high peak-to-average ratio is unfavorable for LEDs. A novel control scheme for the ac-dc critical conduction mode (CRM) flyback LED driver is proposed in this paper. By using the input voltage, output voltage and average output current to control the turn-on time of the switch, the peak-to-average ratio of the output current can be reduced. The operation principle is analyzed and an implementation circuit is put forward. Experimental results show the effectiveness of the proposed scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1613_1614
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• 2009

In this paper, thermal movement of high power LED on the MCPCB is analyzed with structural function and CFdesign V10 program. thermal resistance is decreased as 10.1 [$^{\circ}C$/W] in MCPCB from 12.2 [$^{\circ}C$/W] in LED package. Junction temperature which is calculated with thermal computational analysis program shows 85.113 [$^{\circ}C$] and almost same to measured data.

• 한국콘텐츠학회논문지
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• 제10권5호
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• pp.62-69
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• 2010

LCD 패널은 자체적으로 발광할 수 없어 외부 광원인 BLU가 필요하다. BLU는 LCD 모듈에 포함되어 사용되고 LCD 패널의 불량을 검사하는 테스터에서도 사용된다. 최근에는 BLU가 CCFL에서 LED로 빠르게 변화되고 증가해왔다. CCFL은 초고압 전원이 필요하고, 열도 많이 발생하며, 일정한 휘도를 유지하기가 어렵다. LED는 전력소모량이 적고, 일정한 휘도를 유지한다. 그러나 현재 테스터에서 사용되는 BLU는 CCFL을 사용하고 있다. 본 연구에서는 LCD 패널의 불량을 검사할 수 있는 검사용 LED BLU를 개발한다. 또한 12~24인치의 LCD 패널을 모두 검사할 수 있도록 LED BLU를 24인치 크기로 제작하고 LCD패널의 크기에 따라 LED BLU가 동작하도록 개발한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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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.

• 전력전자학회논문지
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• 제19권1호
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• pp.8-14
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• 2014

This paper presents the intra capacitance modeling according to the winding method and section bobbin for CM choke capable of the EMI attenuation of broad bands from lower frequency bands to higher frequency bands and high frequency type common-mode choke capable of the EMI attenuation of high frequency band used in the EMI Block of LED-TV SMPS. In case of high frequency type CM choke, it can be explained the parasitic capacitance of A type and section bobbin type winding methods among them is much smaller than the other. The first resonant frequency of the proposed CM choke tends to increase as the parasitic capacitance becomes small and its impedance characteristics also show improved performance as the first resonant frequency increases. In the future, the CM chokes of high frequency type show it can be practically used in not only LED/LCD-TV SMPS but also several applications such as LED Lighting, Adapter and so on.

• 한국화재소방학회논문지
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• 제16권2호
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• pp.1-7
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• 2002

유도등은 일정한 조도를 가지고 상용전원에 의하여 항상 점등되어 있어야 함으로 전력소비 및 광원 교체등 경제적 손실과 관리상의 문제가 있게 된다. 본 논문은 이제까지 광원으로 사용하고 있던 형광등이나 백열전구 대신에 소비전력이 적은 고효율 발광다이오드를 사용하여 전력소비의 절감과, 점검시의 문제점을 개선하기 위해 원격제어가 가능한 새로운 유도등회로를 제안하고 실험한 것이다. 그 결과 원격제어 스위치에 의한 유도등 점검을 제어각의 범위에서 쉽게 제어할 수 있었으며 반응시간은 600〔$\mu$s〕로 매우 빠르게 동작하였다. 또한 출력 상승시간(Rise time)과 하강고시간(Fall time)은 최대 200〔ns〕로 예민하게 반응하였다. 광원으로 고효율 발광다이오드를 사용함으로 광원을 교체해야 하는등의 문제를 제거하였으며 전력소비를 감소시킬 수 있음을 확인하였다.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.593-600
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• 2010

In this paper, High brightness LED (light-emitting diodes) driver IC (integrated circuit) using new current sensing circuit is proposed. This LED driver IC can provide a constant current with high current precision over a wide input voltage range. The proposed current-sensing circuit is composed of a cascode current sensor and a current comparator with only one reference voltage. This IC minimizes the voltage stress of the MOSFET (metal oxide semiconductor field effect transistor) from the maximum input voltage and has low power consumption and chip area by using simple-structured comparator and minimum bias current. To confirm the functioning and characteristics of our proposed LED driver IC, we designed a buck converter. The LED current ripple of the designed IC is in ${\pm}5%$ and a tolerance of the average LED current is lower than 2.43%. This shows much improved feature than the previous method. Also, protections for input voltage and operating temperature are designed to improve the reliability of the designed IC. Designed LED driver IC uses 1.0 ${\mu}m$ X-Fab. BiCMOS process parameters and electrical characteristics and functioning are verified by spectre (Cadence) simulation.

• 한국산학기술학회논문지
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• 제11권11호
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• pp.4483-4488
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• 2010

LED는 다른 광원에 비해 동작수명이 길고, 친환경적이며, 에너지 효율이 높은 장점을 가지고 있다. 최근 LED 기술의 발전으로 인해 고휘도, 고용량의 LED가 개발됨에 따라, 표시장치에만 적용되던 LED를 조명장치에도 적용하는 기술이 확산되고 있다. 파워 LED는 동작의 안정성 및 신뢰성을 확보하기 위해 구동전류를 일정한 값 이하로 유지하는 전류제한기능이 필요한데, 본 논문에서는 전류제한기능을 포함한 하프브리지 LLC 직렬공진형 컨버터를 제안한다. 하프브리지 LLC 직렬공진형 컨버터는 다른 공진형 컨버터에 비해 상대적으로 입력전압 및 출력부하 범위가 광범위한 장점이 있으며, 변압기의 누설인덕턴스를 공진인덕터로 이용할 수 있기 때문에 마그네틱 소자를 줄일 수 있는 장점이 있다. 전류제한기능 및 역률개선기능을 포함하고 있는 출력전압 DC24[V], 200[W]급의 LED 조명장치 구동용 하프브리지 LLC 직렬공진형 컨버터의 설계 및 실험을 통해 타당성을 입증하였다.