• Journal of Power Electronics
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• 제12권6호
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• pp.886-894
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• 2012

This paper presents a secondary-side, dual-mode feedback LLC resonant controller IC with dynamic PWM dimming for LED backlight units. In order to reduce the cost, master and slave outputs can be generated simultaneously with a single LLC resonant core based on dual-mode feedback topologies. Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) schemes are used for the master stage and slave stage, respectively. In order to guarantee the correct dual feedback operation, Phased-Locked Loop (PLL)-based automatic duty control circuit is proposed in this paper. The chip is fabricated using $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology, and the die size is $2.5mm{\times}2.5mm$. The frequency of the gate driver (GDA/GDB) in the clock generator ranges from 50 to 425 kHz. The current consumption of the LLC resonant controller IC is 40 mA for a 100 kHz operation frequency using a 15 V supply. The duty ratio of the slave stage can be controlled from 40% to 60% independent of the frequency of the master stage.

• 전자공학회논문지SC
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• 제42권3호
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• pp.63-70
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• 2005

유도방전을 이용한 무전극 램프는 전극을 필요로 하지 않기 때문에 긴 수명을 갖으며 안정기 출력의 변화에 대해서도 매우 강한 특성을 갖는다. 본 논문에서는 무전극 램프 조광제어를 위한 두 가지 새로운 알고리즘을 제안하였고 이를 적용한 공진형 인버터에 대하여 기술하였다. 제안된 두 가지 조광제어 알고리즘은 주로 LCD 백라이트의 조광제어에 적용되는 버스트 디밍 기법을 기초로 한다. 제안된 두 가지 방식중 하나는 개선된 버스트 디밍 기법으로 간단한 디지털 논리회로를 이용한 제어회로를 통해 $5\%$ 단위의 시비율로 조도조절이 가능한 방식이며, 나머지 하나는 버스트 PWM 평균 시비율 제어 기법으로 다소 복잡한 제어회로를 통해 $1\%$ 단위의 시비율로 조도조절이 가능한 방식이다. 본 논문에서는 100W급 무전극 램프를 대상으로 실시한 실험결과를 통해 제안된 조광제어 알고리즘의 유효성을 입증하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2847-2850
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• 2003

A input voltage conversion dimming control formula and a PMW dimming control formula which have been used for dimming control of CCFL driving inverter in TFT-LCD backlight, are the existing facilities so far, however, in this thesis the circuit is designed by applying The rover inverter that are able to measure output brightness according to changing of duty ratio at PWM and voltage. consequently, it's able to be confirmed that we can have dimming control more detailed than before.

• 전력전자학회논문지
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• 제19권4호
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• pp.320-326
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• 2014

In this paper, the new smart dimming algorithm which is mixed with PWM and PAM control method is proposed for reducing the power consumption of LED TV Backlight. The proposed technique is using the curve characteristics of LED forward voltage and current which is proportionally changing LED forward voltage as changing LED forward current. Therefore, each PWM and PAM control method has different LED forward voltage and current in the same brightness condition. The PWM control method adjusts the brightness of LED TV Backlight by only varying the duty ratio of PWM and constantly sustaining the amplitude of LED forward current and voltage. So, the level of LED forward current and voltage in the PWM control method is relatively high and constant regardless of duty ratio of PWM. On the other hand, the PAM control method adjusts the brightness of LED TV Backlight by directly varying the level of LED forward current. So, the level of LED forward current and voltage in the PAM control method is lowered according to the brightness level. For the above-mentioned reason, the PAM control method has the advantage of reducing the total power consumption of LED TV Backlight at the brightness condition of below 100%, compared with PWM control method. By implementing this characteristic to LED driver circuit with control algorithm in MCU, the power consumption of LED TV Backlight can expect to be reduced. The effectiveness of the proposed method, new smart dimming algorithm, CPWAM(=Conditional Pulse Width Amplitude Modulation), has been verified by experimental results.

• 한국정보통신학회논문지
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• 제18권9호
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• pp.2280-2288
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• 2014

기존의 고출력 LED의 디밍(Dimming) 제어 방법에는 펄스폭변조, 주파수변조, 아날로그 제어 방법이 있으며, 아날로그 디밍은 순방향 고출력 LED 전류를 조정하는 방법으로 0%~100%의 전 범위에서 선형 밝기 조절이 가능하나 순방향 전류를 변화시킴으로써 파장의 변화가 존재하고, 펄스폭변조 디밍 제어는 고출력 LED에 흐르는 정격 전류의 듀티를 가변하여 조도를 제어하는 방식으로 저 레벨(0%~10%)에서 선형 밝기 조정이 어렵다. 그리고 주파수변조 디밍 또한 저 레벨의 디밍에서 빛이 깜박거리는 문제를 내포하고 있다. 본 논문은 이러한 디밍 방식의 단점을 보완하고자 저 레벨 디밍 제어 시 아날로그 방식을 적용하고, 10%~100%의 디밍 제어 시에 펄스폭변조 방식을 적용하는 효율적인 디밍 제어 회로의 설계 및 구현을 제안한다. 전 범위에 걸쳐 선형 밝기 조절이 가능하고, 다양한 디밍 레벨에서 일정한 파장의 출력이 가능한 디밍 제어 회로를 구현하였으며, 실험 결과는 제안한 방법의 우수성을 보여주고 있다.

• Journal of information and communication convergence engineering
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• 제11권4호
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• pp.247-252
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• 2013

An intelligent light emitting diode (LED) dimming system is designed and implemented for energy-saving lighting systems. An LED light bulb is powered by an LED driver controlled by a microcontroller using pulse width modulation (PWM) signals. By changing the duty cycle of the PWM signals, the LED driver generates a driving current of up to 1,000 mA. The current consumption by the LED light bulb exhibits a very linear characteristic that indicates that the level of LED dimming can be finely tuned. Multiple sensors-lighting intensity and ultrasonic range sensors-are combined with the LED dimming system to realize an automatically controllable LED lighting system. The light intensity sensor is capable of sensing ambient light. The ultrasonic range sensor can detect objects from 0.15 to 5.6 m at a resolution of 0.0254 m. The collected information by the light intensity and ultrasonic range sensors is processed by the microcontroller that in turn automatically controls the brightness of the LED light bulb. The algorithm of the software for the LED dimming system is also described.

• 한국전기전자재료학회논문지
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• 제19권9호
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• pp.843-848
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• 2006

This paper explains the design and fabrication of an inverter for LCD backlight using a multilayer piezoelectric transformer. That inverter is operated by the burst dimming method whose dimming signal is controlled by the duty ratio of rectangular switching signal to a PWM controller. The brightness of CCFL's are investigated according to the various dimming signals, and when those CCFL's are turned on, the temperature distributions on the piezoelectric transformer and circuit components of the inverter are also investigated by a thermo-camera.

• 전자공학회논문지
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• 제51권7호
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• pp.89-95
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• 2014

주위 밝기 및 환경에 따라서 LED 조명등의 밝기를 조절하기 위한 장치를 PWM 기술과 전력 소자를 이용하여 구현하였다. 주위의 광량 측정을 위하여 CdS 센서를 사용하였으며, PWM 신호 생성을 위하여 MCU를 사용하여 제어 보드를 설계한 다음 광량에 따라 듀티비를 조절하였다. 고전압, 대전류를 필요로 하는 LED 조명등을 디밍하기 위하여 전력 소자를 사용하여 DC 전원장치의 출력을 스위칭하였으며, PowerMOSFET, IGBT, PowerBJT를 각각 사용하여 특성을 서로 비교하였다. 실험결과 선형성 면에서는 IGBT가 양호하였으나, 효율 및 가격 면까지 고려하면 PowerBJT도 우수한 특성을 보였다.

• Journal of the Optical Society of Korea
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• 제16권2호
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• pp.107-114
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• 2012

In this paper, we propose a new modulation scheme called multi-coded variable pulse position modulation (MC-VPPM) for visible light communication systems. Two groups of signals (Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) groups) are multi-coded by orthogonal codes for transmitting data simultaneously. Then, each multi-level value of the multi-coded signal is converted to pulse width and position which results in not only an improved data rate, but also a processing gain in reception. In addition, we introduce average duty ratio and cyclic shift concepts in PWM through which dimming control for light illumination can be supported without any degradation in communication performance. Through simulation, we confirm that the proposed MC-VPPM shows a comparable BER curve and much greater achievable data rate than the conventional VPPM scheme using a visible light optical channel environment.

• 전기학회논문지P
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• 제60권2호
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• pp.72-75
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• 2011

In this paper, the voltage across the LED system supplied by positive voltage of power supply system the power consumption of the LED itself, and uses a lot of transformers and analog devices, such as converter startup problems and constant temperature even when the voltage driving abnormally LED current in the destruction caused by the flow of a lot of problems can occur. In this paper, we obtain the technology of consistent current using PWM(pulse width modulation) mode in order to minimize analog devices and eventually discuss the technology to develop consistent output converter using power drive IC.