Browsing by Author "Chiu, Chia-Lin"

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A High Accuracy Current-Balanced Control Technique for LED Backlight
(2008)
Chiu, Chia-Lin
;
Chen, Ke-Horng
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper proposes a new circuit to regulate current in parallel LED (Light Emitting Diodes) strings. The new technique not only enhances the current matching in each string but also reduces device numbers and external resistance requirements. In this new circuit, the LED current has a low correlation to its forward voltage (V-f). The LEDs should have constant driving current as LCD backlight for two reasons. Firstly, keeping the maximum current and maintain the reliability. Secondly, obtaining expected luminous intensity for each LED. Furthermore, this circuit matches the current of eight LED strings and keeps high accuracy by using only two operational amplifiers. In other words, it reduces the power consumption and die size. There are two benefits for having just one resistance outside. Firstly, it can reduce pin numbers of the driving circuit. Secondly, it is easy for user to determine the maximum current of LED strings instead of predefined by the driving IC. The current accuracy of LED strings with a total forward voltage variation (Delta V) around 1.1V is less than 0.1%.
RGB LED Backlight of Color Sequential Display with Precise Current-Balance Control Technique
(2009)
Chiu, Chia-Lin
;
Lee, Yu-Huei
;
Hsieh, Chun-Yu
;
Ho, Ming-Tsung
;
Chen, Ke-Horng
This paper proposes a high efficiency and precise current balance circuit in parallel RGB Light Emitting Diodes (LED) channels for color filter-less panel display. The new technique not only enhances the current matching in each channel but also reduces the requirement of device numbers and external resistors. The error percentage of all channel LED currents can kept within 0.1% when the channel voltage has a voltage variation ((Delta) V(CH)) around 1.IV. Furthermore, the proposed load dependent minimum drain voltage can effectively reduce the voltage drop across the precise current balance circuit. As a result, the efficiency of the LED driver can be improved.