A High 5292-PPI Pixel Circuit for Micro Displays With 10-Bit Gray Levels Realized via the Technique of Analog Sub-Frame Integral

Abstract

A pixel circuit driven in small range of data voltage (Vdata) is proposed for high pixel-per-inch (PPI) micro displays, using the new driving technique of analog sub-frame integral (A-SFI) to realize the required current integrals of gray levels. This circuit runs with two analog Vdata's configurated by 7-bit digital-to-analog converters (DACs), outputting 10-bit integral currents by receiving a digital voltage of Vsel at each sub-frame that is one of eight (3-bit) equally divided from an illuminating period. With the 1-LSB of 5mV assumed, the estimated Vdata range of 0.64V, which is apparently lower than at least 5V of a conventional circuit made by high voltage FETs (HVFETs), assists the proposed circuit in mainly constructing by the low voltage FETs (LVFETs) that are driven by about 1V; therefore, its pixel layout could be shrank for high PPI. Implementing this circuit in a 1.03-inch, high 5292PPI micro OLED panel made via that 55nm CMOS process for the validations, the simulated results over the displaying range show the iDNL's of within +1.15iLSB and −1.01iLSB, the iINL's of within +1.53iLSB and −1.05iLSB, and the iAD's of within +1.94% and −1.18%, observed the favorable linearities or deviations to the generated integral currents along 10-bit grayscales. The experimental results show the lDNL's of within +3.12lLSB and −1.75lLSB, and the lINL's of within +3.35lLSB and −2.29lLSB, validated the viability of this technique for high PPI displays.

An analog PWM pixel circuit with shaping function for low grayscale display of Micro-LEDs

“…The digital PWM driving method is to divide one frame into some subframes, which can achieve accurate grayscale control since the PWM signal is generated by the peripheral circuit of the panel [12,13]. For the analog PWM driving method, the PWM control signal is generated by the comparison between the data voltage signal coupled with the sweep signal and the threshold voltage of PWM TFTs [14][15][16][17][18][19][20][21][22][23][24]. However, the PWM signal exists a long rising/falling time since the sweep signal voltage slowly cross the PWM TFT subthreshold region, resulting in image distortion especially in the low grayscale display.…”

Proposing an Accurate and Fast Optical Batch Inspection Method of Mini-/Micro-LEDs

“…Compared with organic light-emitting diodes (OLEDs) and liquid-crystal displays (LCDs), the Mini-/Micro-LEDs possess outstanding merits of high brightness, wide color gamut, good color saturation, flexibility, fast response, and long lifespan [4]- [6]. These unparalleled superiorities facilitate a wide range of applications of Mini-/Micro-LEDs, such as televisions (TVs), wearable devices, visible light communications (VLCs), augmented reality (AR), virtual reality (VR), and biomedical applications [7]- [10]. Despite the big progress in the Mini-/Micro-LED technology, there still exist some limitations hindering their quick applications, including mass transfer, monolithic integration, full-color implementation, detection and repairing [11]- [13].…”