• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.967_968
• /
• 2009

For lighting application, high-power LED nowadays is driven at 350mA and a sensing resistor is used to provide feedback for LED-current regulation. This method adds an IR drop at the output branch, and limits power efficiency as LED current is large and keeps increasing. In this paper, a power efficient LED-current sensing circuit is proposed. The circuit does not use any sensing resistor but extracts LED-current information from the output capacitor of the driver. Controlling the brightness of LEDs requires a driver that provides a constant, regulated current. In one case, the converter may need to step down the input voltage, and, in another, it may need to boost up the output voltage. These situations often arise in applications with wide-ranging ""dirty"" input power sources, such as automotive systems. And, the driver topology must be able to generate a large enough output voltage to forward bias the LEDs. So, to provide this requirements, 13W prototype Buck-Boost Converter is used.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.05a
• /
• pp.382-384
• /
• 2013

LED is much brighter than the traditional incandescent, and low power consumption. Development and commercialization of LED fluorescent lamp is made in order to improve efficient fluorescent lamps with this existing and environmental problems. Because, unlike fluorescent lamps, it is not possible to directly use AC power to the unidirectional element having a polarity, LED requires a power supply. The power supply function is lowered as compared with the fluorescent lamp common in terms of maintenance costs because of the high price large. In this study, we constructed a circuit that can be controlled with a constant current in order to eliminate a phenomenon that brightness of the light which rectifies the AC power supply easy to place in the power supply due to the current change due to the voltage fluctuation is changed, in maintenance, I would like to propose how to develop a device which can be easily replaced less expensive composed of interchangeable modules of Plug in / out method to distinguish the LED module this.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.2
• /
• pp.111-118
• /
• 2010

Recently, LCD TV using LED backlight has a great attention due to its low power consumption, slim construction, mercury free, wide color gamut and fast response. For the uniform brightness of the LCD panel, multi channel LEDs and DC/DC converter for each LED are required in conventional system. Therefore energy conversion efficiency is poor, the system size bulky and the cost of production high. To overcome these above mentioned drawbacks, a new current-balancing multi-channel LED driver is proposed in this paper. It can not only drive multi-channel LEDs with one DC/DC converter but also provide all LEDs with constant balanced current. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for 46" LCD TV.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.11
• /
• pp.4483-4488
• /
• 2010

In comparison with some other light sources, LED has merits such as long lifetime, pollution free, and high energy efficiency. Lately, due to development of LED with high brightness and capacity, LED, which has been applied in display system only, has applied in the field of lighting system. Driving current of power LED has to be controlled below the designed value. In this paper, half-bridge LLC series resonant converter, which has the current limiting function, has been described. Half-bridge LLC series resonant converter allows in relatively wide input voltage and output load range when compared to the other resonant converter. Also, it is possible to reduce a magnetic component, because leakage inductance of transformer is used as a resonant inductance. It has been validated by designing and testing 200[W] half-bridge LLC converter of DC24[V] output voltage for LED lamp driver, which includes a current limiting function and power factor correction(PFC) function.

• Journal of Industrial Technology
• /
• v.27 no.B
• /
• pp.125-128
• /
• 2007

This paper presents Spectral-Domain optical measurement system using self-fabricated CCD sensor driver. The light source is a high brightness white LED and the detector is a 2048 array typed CCD image sensor. I have fabricated the CCD sensor driver to generate four pulse signals, which are the CCD-driving pulses. Using this Spectral Domain optical measurement system, the distance value between the reference mirror and the sample mirror can be obtained successfully.

• Journal of IKEEE
• /
• v.19 no.2
• /
• pp.168-175
• /
• 2015

In this paper, we propose FPGA design technique for rotating LED display device which is capable of displaying videos with the use of the afterimage effect. The proposed technique is made up of image data correction process based on inverse gamma correction and error diffusion, block interleaving process, and data serial output process. The data correction process based on inverse gamma correction and error diffusion is an image data correction step in which image data received are corrected by inverse gamma correction process to convert the data into linear brightness characteristics, and by error diffusion process to reduce the brightness reduction phenomenon in low-gray-level which is caused by inverse gamma correction. In the block interleaving process, the data of the frames entered transversely are first saved in accordance with entrance order, and then only the longitudinal image data are read. The data serial output process is applied to convert the parallel data in a rotating location into serial data and send them to LED Driver IC, in order to send data which will be displayed on high-speedy rotating LED Bar. To evaluate the accuracy of the proposed FPGA design technique, this paper used XC6SLX45-FG484, a Spartan 6 family of Xilinx, as FPGA, and ISE 14.5 as a design tool. According to the evaluation analysis, it was found that goal values were consistent with simulation values in terms of accurate operation of inverse gamma and error diffusion correction, block interleaving operation, and serialized operation of image data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.713-716
• /
• 2008

This paper presents an automatic back-light brightness control system for mobile displays. One of the most important factors in mobile display is the power consumption due to the limited and movable power source. More than 80% of power of the LCD display is consumed by LED bark-light unit (BLU). The target brightness also becomes higher because of its moving picture and high resolution image, so there are some side effects for not only excessive power consumption but also ergonomic inconvenience in dark environment. To prevent this discomfort and reduce power consumption, this paper proposes automatic brightness control (ABC) technique in mobile displays. Developed system contains TFT-LCD panel with built-in photo sensor, driver IC capable of controlling photo sensor, and BLU. Since the photo sensor array built in panel detects automatically outdoor ambient light intensity, the power of BLU in dark environment is reduced. Developed ABC system showed reduced power consumption of 50% in dark environment. We believe that the proposed system is very useful to control power of mobile TFT-LCD.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.1
• /
• pp.104-110
• /
• 2011

High-brightness LED control is required for stable operation, thus the driver and control system must be designed to deliver a constant current to optimize reliability and ensure consistent luminous flux. In this paper, the sliding mode current controller is designed to adjust the illumination density of power LEDs. The controller design model of power LEDs, including its driving circuit, is proposed to realize the dimming control of power LEDs. A buck converter is introduced to drive the power LEDs and reduce the input voltage to a lower level. The sliding mode software controller is implemented to adjust the dimming of power LEDs. The proposed strategy for driving power LEDs is investigated and comparatively studied by experiments.

• Journal of Power Electronics
• /
• v.11 no.3
• /
• pp.271-278
• /
• 2011

This paper presents a LLC resonant controller IC for secondary side control without external active devices to achieve low profile and low cost LED back light units. A gate driving transformer is adopted to isolate the primary side and the secondary side instead of an opto-coupler. A new integrated dimming circuitry is proposed to improve the dynamic current control characteristic and the current density of a LED for the brightness modulation of a large screen LCD. A dual-slope clock generator is proposed to overcome the frequency error due to the under shoot in conventional approaches. This chip is fabricated using 0.35 ${\mu}m$ BCD technology and the die size is $2{\times}2\;mm^2$. The frequency range of the clock generator is from 50 kHz to 500 kHz and the range of the dead time is from 50 ns to 2.2 ${\mu}s$. The efficiency of the LED driving circuit is 97 % and the current consumption is 40 mA for a 100 kHz operation frequency from a 15 V supply voltage.

• Convergence Security Journal
• /
• v.14 no.7
• /
• pp.29-36
• /
• 2014

In this study, we design and develop a VLC test-bed system which has been recently issued and focused as good convergence technology in the world. We classify the developed system into transmission part including analog LED driver module, digital signal modulation module, and receiver part with light sensing module and signal demodulation module. Then we introduce important characteristics and components. We analyze some factors for each module. To validate the communication of the designed VLC system, we develop a VLC sender-receiver simulator which can control the dimming factor and flicker-free effect. From the developed system, we observed about 12Mbps of data transmission rate with 0.5m~1m of distance, without packet loss. We verified the real-time communication with multimedia streaming which can be considered as very high date rate. The developed system and technology will be useful for some converged data services like indoor positing, home appliances, and indoor parking system.