OLED Pixel Circuit Removing Storage Capacitor for Power and Speed
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Solution Overview
Problem
Conventional organic light emitting displays face challenges in accurately displaying gray levels due to power consumption and reduced driving speed, as they rely on storage capacitors for voltage storage and charge/discharge operations.
Innovation Solution
The proposed solution involves a pixel structure with four transistors and an organic light emitting diode, where the transistors are coupled to specific power sources and control lines, allowing for efficient power management and high-speed driving by controlling emission and non-emission states in sub-frames, reducing the need for additional storage capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a storage capacitor is used for each pixel to store voltage for gray level display, then gray levels can be displayed, but power consumption increases due to charge/discharge operations
Solution Approach 1:
The invention extracts and removes the storage capacitor from the pixel structure. Instead of using a dedicated storage capacitor for voltage storage, the patent employs a transistor gate capacitance to hold the voltage signal, thereby eliminating the charge/discharge operations that cause power consumption while maintaining gray level display capability
Solution Approach 2:
The transistor gate in the invention serves multiple functions: it acts as both the control element for the transistor and as the voltage storage mechanism (replacing the dedicated storage capacitor). This multi-functionality reduces the number of components and eliminates the need for separate charge/discharge operations
2Productivity
If a storage capacitor is used for each pixel, then voltage can be stored for gray level display, but driving speed is reduced due to charge/discharge time
Solution Approach 1:
By removing the storage capacitor from the pixel structure, the invention eliminates the time required for charging and discharging the capacitor. The transistor gate capacitance provides instantaneous voltage holding capability, thereby increasing driving speed while maintaining gray level accuracy
Solution Approach 2:
The transistor gate is pre-configured to hold the voltage signal during the display period. The gate capacitance is inherently present and ready to store the voltage immediately when the transistor is turned on, eliminating the need for separate charge/discharge timing operations
3Device complexity
If a storage capacitor is used for each pixel, then voltage storage is enabled, but device complexity increases
Solution Approach 1:
The invention removes the storage capacitor component from the pixel structure, reducing the number of components and simplifying the overall device complexity. The transistor gate serves the dual purpose of control and voltage storage, eliminating the need for additional capacitive elements
Solution Approach 2:
The transistor gate is designed to perform multiple functions: controlling the transistor operation and storing the voltage signal for gray level display. This multi-functionality reduces the total component count and simplifies the pixel structure while maintaining display accuracy
4Measurement precision
If uniform voltage is stored in the storage capacitor for multiple gray levels, then gray levels can be displayed, but brightness difference between adjacent gray levels cannot be correctly displayed
Solution Approach 1:
The invention applies different voltage levels to different transistor gates corresponding to different gray levels. Each pixel's transistor gate receives a specific voltage level tailored to the desired gray level, enabling precise control of brightness differences between adjacent gray levels through localized voltage control
Solution Approach 2:
The invention changes the voltage parameter of the transistor gate to control different gray levels. By varying the gate voltage levels, the invention achieves precise control over the OLED brightness, enabling accurate display of brightness differences between adjacent gray levels
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces power consumption and enhances driving speed while enabling accurate display of gray levels by controlling light emission in sub-frames, improving the overall performance of organic light emitting displays.
Implementation Method 1
organic light emitting displays display an image using organic light emitting diodes (OLEDs) that generate light by recombination of electrons and holes
Data Source
AI summary
A pixel of an organic light emitting display in which the pixel includes: a first transistor including a first electrode coupled to a first power source, a second electrode, and a gate electrode coupled to a first node; a second transistor including a first electrode coupled to a third power source, a second electrode coupled to the first node, and a gate electrode coupled to a reset control line; a third transistor including a first electrode coupled to the first node, a second electrode coupled to a fourth power source, and a gate electrode; a fourth transistor including a first electrode coupled to the gate electrode of the third transistor, a second electrode coupled to a scan line, and a gate electrode coupled to a data line; and an organic light emitting diode (OLED) including an anode electrode coupled to the second electrode of the first transistor, and a cathode electrode coupled to a second power source.