Abstract
Light-emitting diodes (LEDs) are the major backlighting source used
in liquid crystal displays and dimming the LEDs is a common approach to increase
the contrast ratio or save power. Pulse-width modulation (PWM) is more popular
than analog methods of dimming, because it produces a less pronounced shift
in chromaticity. However, in PWM dimming mode, overcurrent can shorten the
lifespan of the LEDs. This paper proposes a technique to overcome the drawbacks
inherent in conventional approaches to the suppression of overcurrent in LED
devices. The design was implemented using the TSMC 0.25-<i>ยต</i>m 60-V bipolar-CMOS-DMOS
process, resulting in a chip area of 2.2 mm<sup>2</sup>. A comparison with two commercial
chips demonstrates the effectiveness of the proposed design in the suppression
of LED overcurrent and the subsequent extension of the lifespan.
© 2013 IEEE
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