Pixel Circuit Aperture Ratio and Program Time via Merged Capacitor
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Solution Overview
Problem
Current active matrix drive display devices with organic EL elements face challenges in achieving short program time and high aperture ratio due to the need for a large threshold holding capacitor, which increases power consumption and reduces luminance and reliability.
Innovation Solution
The use of the display element itself as a capacitor to hold the threshold voltage, eliminating the need for a separate threshold holding capacitor, thereby increasing the data current and aperture ratio without adding extra components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate threshold holding capacitor is added to the pixel circuit, then the threshold voltage can be held, but the aperture ratio decreases and program time increases
Solution Approach 1:
The patent combines the threshold holding capacitor and data holding capacitor into a single capacitor within the pixel circuit. This merged capacitor structure eliminates the need for separate capacitors, thereby increasing the aperture ratio while maintaining both threshold voltage holding and data holding functions simultaneously.
Solution Approach 2:
The single capacitor in the pixel circuit is designed to serve multiple functions: it acts as both the threshold holding capacitor and the data holding capacitor. This multi-functional design reduces the total component count and increases the aperture ratio without compromising the reliability of voltage holding.
2Reliability
If a separate threshold holding capacitor is added to the pixel circuit, then the threshold voltage can be held, but the program time increases
Solution Approach 1:
By merging the threshold holding capacitor and data holding capacitor into a single capacitor, the patent reduces the total capacitance value required in the pixel circuit. This reduction in total capacitance directly decreases the charging time, thereby shortening the program time while maintaining reliable threshold voltage holding.
3Reliability
If the capacitor area is increased to hold threshold voltage, then the threshold can be held, but the data current decreases
Solution Approach 1:
The patent merges the threshold holding capacitor and data holding capacitor into a single capacitor with optimized capacitance value. This merged structure reduces the total capacitance area required compared to having separate capacitors, thereby increasing the aperture ratio and allowing larger data current to flow through the pixel without compromising threshold voltage holding capability.
Data Source
AI summary
To solve the lack of program time, which is a problem of a display device including an EL element, and to provide a display device including a pixel circuit with a high aperture ratio and a driving method thereof. In a circuit including a driving transistor, a capacitor, a display element which can be used as a capacitor, a first power supply line and a second power supply line, potentials of the first power supply line and the second power supply line are set to be almost the same, thereby a threshold voltage of the driving transistor is held in the display element, and after that, a charge is divided into the display element and the capacitor.