OLED Pixel Circuit Impulse Driving Control for Luminance Precision
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in achieving satisfactory display quality due to limitations in controlling the emission of organic light emitting diodes, particularly in efficiently managing the turn-on and turn-off periods of transistors within a frame, which affects the luminance and gray scale levels.
Innovation Solution
The proposed solution involves a pixel structure with multiple transistors and a specific control signal timing scheme, where the second transistor turns on multiple times and the third transistor turns on once during a frame period, with overlapping turn-off periods, and a storage capacitor to manage the emission control signals, allowing for impulse driving and adjustment of the turn-on to turn-off ratio based on data signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second transistor turns on multiple times and the third transistor turns on once during a frame period, then emission control precision is improved, but device complexity increases
Solution Approach 1:
The emission control function is segmented into two separate transistors: the second transistor handles multiple turn-on events for gray scale control, while the third transistor handles a single turn-on for emission enablement. This segmentation allows each transistor to specialize in a specific control aspect, improving overall emission control precision while distributing the complexity across dedicated components.
Solution Approach 2:
The control scheme employs dynamic turn-on/turn-off timing for the second transistor during the frame period, allowing it to switch multiple times based on gray scale requirements. The third transistor provides a static single turn-on to enable the emission period. This dynamic control approach enables precise luminance adjustment without requiring continuous complex signaling.
2Object-generated harmful factors
If turn-off periods of transistors overlap, then crosstalk is reduced, but control signal complexity increases
Solution Approach 1:
The control signals are designed so that turn-off periods of the second and third transistors overlap in a predetermined manner. This preliminary arrangement of timing ensures that when one transistor is turning off, the other is already in the off state or turning off, preventing simultaneous conduction and eliminating crosstalk between the emission control paths.
3Manufacturing precision
If impulse driving is implemented with adjusted turn-on to turn-off ratio, then display quality is improved, but energy consumption increases
Solution Approach 1:
The pixel employs impulse driving where the second transistor is turned on and off multiple times during the frame period in a periodic manner. By adjusting the ratio of turn-on duration to turn-off duration, precise gray scale levels are achieved. The periodic switching allows the organic light emitting diode to accumulate charge during turn-on periods and stabilize during turn-off periods, improving display quality through controlled luminance pulses.
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 approach enhances the display quality by enabling precise control of emission periods, reducing crosstalk and luminance deviation, and allowing for improved gray scale representation and energy efficiency.
Implementation Method 1
An organic light emitting display device displays an image using an organic light emitting diode that generates light by recombination of electrons and holes
Implementation Method 2
a storage capacitor connected between the first power source and the first node
Data Source
AI summary
A pixel includes an organic light emitting diode, a first transistor, a second transistor, and a third transistor. The first transistor includes a first electrode, a second electrode, and a gate electrode and may control a current applied to the organic light emitting diode from a first power source, wherein the gate electrode is electrically connected to a first node. The second transistor is electrically connected between the organic light emitting diode and the second electrode of the first transistor and may turn on in response to a first emission control signal. The third transistor is electrically connected between the first power source and the first electrode of the first transistor and may turn on in response to a second emission control signal. The second transistor may turn on two or more times during one frame. The third transistor may turn on exactly once in the one frame.