A Pixel Circuit With Leakage Current Compensation Using PWM-Based Data Cycling for AMLED Displays

Abstract

This brief presents a leakage current compensation scheme by using a data cycling function to a pixel driver circuitry of the active-matrix light emitting diode (AMLED) displays. The proposed function cycles the stored dimming data to repeat pulse width modulation (PWM) multiple times at a given frame time. It compensates for a decay of the LED driving current due to leakage by repeatedly charging the target dimming data across a storage capacitor in the current driver. The proposed circuit has been fabricated using a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{\mu }\text{m}$ </tex-math></inline-formula> CMOS process. The test chip includes a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,\,\mathbf {\times }\,\,16$ </tex-math></inline-formula> pixel circuit array with a control system. The functional operation has been verified at a prototype using an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\,\,\mathbf {\times }\,\,16$ </tex-math></inline-formula> LED array system.