Design and testing of LED driving circuits for next generation display

Abstract

This project is an investigation into micro-LEDs as next-generation display technology. There is an emerging market for micro-LED displays. These displays offer numerous advantages over competitors such as LCD and OLED technology such as high brightness and contrast and a slimmer design potential with no need for a backlight. Micro-LED displays have an increasing range of potential applications including wearables and AR products. This project will contribute to the development of micro-LED display technology. This project will focus on the driving and testing of micro-LED displays. Unfortunately, the micro-LED display prototype being developed by SMART-LEES was not ready during this project. Consequently, all circuits were designed with micro-LEDs in mind and were physically implemented using LEDs for the purpose of testing. It was decided that the most efficient way to form the display would be to use an array in which the common cathodes and common anodes in the same rows and columns of the display would be tied together. With regards to the driving of these circuits, two methods were considered. The first method used the 74HC595 driver and the second used the MAX7219 driver which allowed for a larger array to be driven. Finally, a preassembled RGB matrix display was used to develop an understanding of the driving of RGB micro-LED displays. This report contributes several driving circuit designs, experimental implementation and testing of these designs and code written for the control of these displays using Arduino software. The driving circuits worked successfully to control the individual LEDs on each of the displays. It was decided that shift registers were an efficient way of controlling LED arrays and that binary code manipulation was the most economical way of controlling the brightness of the LEDs. Furthermore, the importance of an RC circuit to reduce noise and protect the LEDs was also highlighted. It can be concluded that this project has been a successful investigation into micro-LED driving circuits; however, further investigation, when the micro-LED display is available, into testing and development of the driving circuits using micro-LEDs will be necessary.