71.4: High Efficiency and/or Low Cost LED Backlight System for Color Sequential Technique in Color Filter‐Less LCD System

Abstract

This paper proposes a design methodology for implementing a high efficiency and/or a low cost RGB backlight module in color sequential notebook computers' display. A RGB LED driver composed of an asynchronous 1.5MHz DC/DC boost converter with dual loop control is fabricated by TSMC 0.25 μm BCD 40V to generate 17V or 21V output voltage to turn on more than 6 series‐red, 6 series‐green, or series‐blue LEDs at the same time for the notebooks' backlight. Besides, charge‐recycling technique is used to restore extra energy at the output node when switching to different forwarding light emitting diodes (LEDs) and release the energy next time. The total power consumption of a 15.4′ LCD panel of a notebook computer can be reduced from 5W to about 2–3W.

A fast transient LED driver with adaptive frequency control according to load variation for large‐sized LCD backlights

“…The current regulators are generally used to provide the accurate LED current for the high luminance uniformity of the display. [10][11][12][13][14] Among the several types of current regulators used for LED drivers, a current regulator with the PWM driving technique 28,29 is employed in this work for adjusting the brightness of each channel, while maintaining the high uniformity of display. Figure 7 shows the schematic of the current regulator in the LED current controller.…”

“…Several LED drivers have been studied to improve the power efficiency using the lowest channel selection technique, [5][6][7][8][9][10][11][12][13][14] which adjusts the output voltage considering the minimum voltage margin of the current regulator. However, this technique can lead to a critical problem in LED drivers, namely, that the current of multichannel LED strings may not be accurately regulated when the output voltage fluctuates due to the load variation.…”