Pulse‐width modulation with current uniformization for AM‐OLED micro‐displays on Si LSI chips

Abstract

We have developed pulse-width modulation (PWM) with current uniformization for active-matrix organic light-emitting diode (AM-OLED) micro-displays on Si large-scale integration (LSI) chips. This driving method can simultaneously solve luminance unevenness and image sticking due to characteristic deviations and degradations of driving transistors and OLEDs. With the use of circuit simulation, it is verified that the PWM with current uniformization (PWM-CU) can simultaneously achieve precise gray scale and exceedingly improve luminance uniformity. Moreover, an actual panel is designed and fabricated, where the OLEDs are layered on the Si LSI chip. It

14‐3: OLEDoS Microdisplay with OLED Threshold Voltage Detection and Fast‐Progressive Compensation

“…The length of each line-time can be shortened to keep the frame rate unchanged. (5) shows the calculation of the new line-time ( ′ ) in the proposed fastprogressive compensation scheme…”

“…A pixel circuit used in traditional OLEDoS microdisplays adopts a current-driving method by controlling the gate-source voltage difference of a driving transistor to generate a current to drive OLED to emit light [1][2][3][4][5]. This method is unfavorable to generate pA-level current.…”

“…[1][2][3] use capacitors to form a voltage divider to widen the programming voltage by only transferring part of the programming voltage to the gate of the driving transistor of the pixel circuit. [5] generates a higher current, then uses PWM (Pulse Width Modulation) signal to control the average current passing through the OLED. Besides the above voltage programming designs, current programming is another choice for OLEDoS, yet the settling time is too long for high resolution display system [4].…”

64‐4: Student Paper: MiniLED Driving Circuit with Power‐Saving Mechanism for Use in LCD Backlight Module

“…Besides, the Mini-LED in the circuit is driven by the pulseamplitude modulation (PAM) method so the Mini-LED cannot be maintained at the best luminance-efficacy point, increasing the power consumption. The pulse-width modulation (PWM) driving circuit proposed by Kimura et al can solve the abovementioned issues [11]. In the PWM method, the gray level is represented by the time length of the driving current, so the Mini LED can be driven at the operation point with high luminance efficacy.…”

A digital driving method using pulse‐density modulation with a random dither matrix for higher motion image quality

“…Hence, most of the panel supply voltage is applied to the OLED, then the current through the OLED is determined by the supply voltage, and the negative effect of the characteristics of the driving TFT is minimized. As methods of PWM driving, analog PWM (A‐PWM) 17–21 and digital PWM (D‐PWM) 22 have been proposed for AMOLED displays. In A‐PWM, an analog voltage is changed into a pulse width in a pixel circuit.…”