Analysis and Suppression of Overcurrent in Boost LED Drivers

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- μm 60-V bipolar-CMOS-DMOS process, resulting in a chip area of 2.2 mm
²
. 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.