Implementation of an LED tile controller for high-quality image display

The development of large-size light-emitting diode (LED) screen area is emerging as an important application to keep step with progress in image technology. Recent large LED screens are required to display high-quality images. However, rapid changes and high pulses of the LED current cause wide hot spots and EMI problems in highly dense LED arrays, making implementation in up-scale, energy-efficient, low-pitch LED screens aiming is difficult and expensive.This paper presents a novel LED control method and its architecture, based on pulse width modulation (PWM) dimming, to overcome the aforementioned problems. We proposed a system to stochastically choose the timing of PWM pulses, using affordable hardware cost, and to handle LED arrays for which size is unrestricted. The experimental results, obtained using a commercial LED tile, show that the proposed PWM method is very efficient in diminishing the magnitude as well as the average variation in the LED current. In addition, considering the scalability and feasibility of the hardware structure, the practical value of our proposed LED tile controller seems to be very promising and competitive.

► Probabilistic PWM dimming can mitigate the thermal and EMI problems in LED screens. ► PPWM can reduce the average peak value and the variation of the LED current. ► PPWM satisfies not only the circuit feasibility but also the image quality.