The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Huangjen Chiu - One of the best experts on this subject based on the ideXlab platform.
-
design and implementation of rgb led drivers for lcd Backlight modules
IEEE Transactions on Industrial Electronics, 2009Co-Authors: Kaijun Pai, Huangjen ChiuAbstract:In this paper, a Backlight module driver driving high-power red, green, and blue light-emitting diodes (RGB LEDs) for a 19-in liquid crystal display is proposed. The DC-DC series resonant converters (SRCs) with zero-voltage switching and constant-output-current control are implemented to drive the RGB LED arrays. Phase-shifted pulsewidth modulation dimming control is adopted to effectively narrow the load variations and improve the output voltage regulations of the SRCs. A DSP-based hysteresis control algorithm is performed to track the white-color point and the specified Backlight luminance. Analysis and design considerations of the proposed drivers are presented in detail. Experimental results agree well with the theoretical predictions and confirm the validity of the proposed approach.
-
design of an rgb led Backlight circuit for liquid crystal display panels
IEEE Transactions on Industrial Electronics, 2009Co-Authors: Huangjen Chiu, Tingpeng Lee, Shannchyi Mou, Hsiuming HuangAbstract:This paper presents a red, green, and blue (RGB) light-emitting diode (LED) Backlight circuit for liquid crystal display (LCD) panels. Some studies have been conducted to devise dimming methods that regulate the RGB LED currents. In this paper, design considerations for the RGB LED Backlight are presented. A laboratory prototype for 20-in panels is implemented and tested. The color gamut of an LCD panel with the designed RGB LED Backlight is measured and discussed. The experimental results of the laboratory prototype are also shown to verify feasibility of the findings.
-
led Backlight driving system for large scale lcd panels
IEEE Transactions on Industrial Electronics, 2007Co-Authors: Huangjen Chiu, Shihjen ChengAbstract:This paper presents an LED Backlight driving system for large-scale liquid crystal display panels. High efficiency, high power factor, circuit simplicity, and low cost can be achieved by using a single-stage charge-pump asymmetrical half-bridge converter. To regulate the LED current and brightness for the LED Backlight system, some current sharing methods are presented and compared. The requirements for the current sharing and luminance balance among paralleled LED arrays can be satisfied while current ripple is eliminated significantly. Because of the addition of bypass diodes, an alternative current path can be offered when a single LED fails. The LED array will not be extinguished. Reliability of the LED Backlight system can thus be improved effectively. A laboratory prototype has been built and tested. The simulation and experimental results are shown to verify the feasibility of the proposed method.
-
eliminating the temperature effect of piezoelectric transformer in Backlight electronic ballast by applying the digital phase locked loop technique
IEEE Transactions on Industrial Electronics, 2007Co-Authors: Ying Lu, Huangjen Chiu, Chunglun OuAbstract:A new controller for eliminating the temperature effect of a piezoelectric transformer (PT) in a Backlight electronic ballast is proposed in this paper. First, a class-D Backlight inverter is employed to simplify the circuit configuration and to raise system efficiency. Next, to reduce the dimensions of the Backlight module for satisfying the thin-shaped design trend and to overcome the drawbacks of a conventional transformer, a PT is incorporated instead. Then, a digital phase-locked-loop (DPLL) controller is embedded into the Backlight system as a feedback control mechanism to track the optimal operating frequency of the PT, so that the PT's temperature effect is removed; hence, system efficiency and stability is improved. The design considerations are detailed, and the experimental results confirm the validity of the proposed control strategy
Hau Chen Yen - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of balancing driver for multiple cold cathode fluorescent lamps
IEEE Transactions on Industrial Electronics, 2010Co-Authors: Hau Chen YenAbstract:This paper proposes a novel topology to drive the cold cathode fluorescent lamps (CCFLs) for liquid crystal displays (LCDs) in a direct-type Backlight module. The topology is capable of driving an even number of lamps with identical current without additional balancing circuits, thereby significantly reducing the display's size, weight, and cost. Aiming at alleviating the influence of parasitic capacitance and thus balancing the lamp currents and light output, the proposed topology comprises series CCFLs and the secondary sides of transformers, takes the leakage inductances of the transformer and the parasitic capacitances of the metal back-plank as a resonance tank, and provides both ends of lamps the voltages of equal magnitude and opposite phase. A prototype of the multi-CCFLs driver is designed and built for a Backlight module with 14 lamps in a 32-in LCD. Experimental results demonstrate the effectiveness and feasibility of the current balance topology.
-
analysis of balancing driver for multiple cold cathode fluorescent lamps
International Conference on Industrial Technology, 2009Co-Authors: Hau Chen YenAbstract:This paper proposes a novel scheme to drive the cold cathode fluorescent lamps (CCFLs) for liquid crystal display (LCD) in direct-type Backlight module. The topology is capable of driving an arbitrarily even numbers of lamps with same lamp current without add to balancing circuit, while achieving significant size, weight, and cost reduction. This proposed scheme is composed of series CCFLs and the secondary side of transformers, with the aim to alleviate the influence of parasitic capacitance induced in between the interface of lamps and the aluminum back-plank and thus to balance the lamp currents and light output. A prototype of the multi-CCFLs driver is designed and built for a Backlight module with 14 lamps in a 32-inch LCD. Experimental results demonstrate the effectiveness and feasibility of the current's balance scheme.
Young Hwan Kim - One of the best experts on this subject based on the ideXlab platform.
-
image quality aware Backlight dimming with color and detail enhancement techniques
IEEE\ OSA Journal of Display Technology, 2013Co-Authors: Sung In Cho, Sukju Kang, Young Hwan KimAbstract:In this paper, we propose an advanced Backlight dimming technique that preserves the quality of color and details in images even when the Backlight luminance of liquid crystal display (LCD) devices is lowered. The proposed Backlight dimming technique consists of the following two steps: Backlight luminance level selection and pixel compensation. In the first step, to reduce power consumption, the proposed approach selects an optimal level of Backlight luminance for a given image based on image quality evaluation that considers the peak signal-to-noise ratio (PSNR) and color distortion level. In the second step, it adaptively adjusts the RGB ratio depending on image details, thereby enhancing image color and details, which are degraded by the lowered Backlight luminance level calculated in the first step. The simulation results showed that the proposed method successfully selected the optimal Backlight luminance level and prevented severe color distortion, while the benchmark method induced severe color distortion in some images. In addition, for the same Backlight luminance level, pixel compensation in the proposed method reduced color difference for color distortion evaluation and the loss rate of edge strength, which showed detail loss by up to 3.58% and 40.55%, compared to benchmark methods, respectively.
-
dynamic Backlight dimming using multiple histograms for low power liquid crystal displays
International Conference on Consumer Electronics, 2011Co-Authors: Sukju Kang, Young Hwan KimAbstract:This paper presents a dynamic Backlight dimming algorithm that uses multiple histograms. The proposed method greatly reduces gray-level error for some pixels whose gray levels are beyond the compensation limit, thereby enhancing the image quality.
Takashi Takeda - One of the best experts on this subject based on the ideXlab platform.
-
wide color gamut Backlight for liquid crystal displays using three band phosphor converted white light emitting diodes
Applied Physics Express, 2009Co-Authors: Rongjun Xie, Naoto Hirosaki, Takashi TakedaAbstract:This work reports a wide color gamut Backlight for liquid crystal display (LCD) utilizing a three-band white light-emitting diodes (LED). The LED Backlight was fabricated by combining a blue LED chip with β-sialon:Eu (green) and CaAlSiN3:Eu (red) phosphors. This 2-phosphor-converted white LED shows a discrete spectrum with distinct separation of red, green, and blue primary colors due to a narrow and asymmetric emission band of the green phosphor. By applying typical color filters of LCDs and color-matching functions, a wide color gamut of 91.9% of the National Television Standard Committee standard is attained, compared to 71.6% for the conventional two-band white LED.
Chienchih Chen - One of the best experts on this subject based on the ideXlab platform.
-
multistring led Backlight driving system for lcd panels with color sequential display and area control
IEEE Transactions on Industrial Electronics, 2008Co-Authors: Changyu Wu, T F Wu, Jiunren Tsai, Yaowming Chen, Chienchih ChenAbstract:In this paper, a multistring light-emitting diode (LED) Backlight driving system for liquid crystal display (LCD) panels with color sequential display (CSD) and area control is proposed. In large-scale LCD panels, multistring LED Backlights are required to provide sufficient back lighting. The most popular structure to achieve multistring current regulation is a current mirror. However, it cannot be applied to high-power LED (>100 mA) driving, and the number of LEDs in each string is highly limited. In the driving system, a multioutput flyback converter associated with a novel control IC is proposed to tightly regulate LED driving currents and to readily achieve CSD and area control. The proposed driving system for a 32-in LCD panel has been built, from which experimental measurements have verified that the proposed driving system has the following features: low power consumption, high power conversion efficiency, stable driving currents, and high reliability.
-
sequential color led Backlight driving system for lcd panels
IEEE Transactions on Power Electronics, 2007Co-Authors: Chienchih Chen, Yaowming ChenAbstract:In this paper, a sequential color light emitting diode (LED) Backlight driving system for liquid crystal display (LCD) panels is proposed. Due to improvement on luminous efficacy, long life and wide color gamut, LED has gradually substituted for cold cathode fluorescent lamp as Backlight. The proposed driving system adopts sequential color scanning scheme to improve light utilization efficiency by removing color filter. To meet display performance requirement that chromaticity variation Deltauv needs to be limited below 0.002, this paper also proposes a family of output current ripple free topologies to control the average driving current precisely, which in turn can reduce chromaticity variation. In addition, an LED bypass circuit is proposed to prevent LED arrays from open-circuit, and a driving voltage resetter is introduced to eliminate current spikes, improving Backlight reliability and availability significantly. A forward-type output current ripple free converter has been built to sequentially drive color LED arrays, from which experimental measurements have verified the discussed performance and feasibility of the proposed system
