OLED Pixel Circuit Auxiliary Transistor Crosstalk Reduction
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Solution Overview
Problem
Display devices experience crosstalk due to delayed transistor turn-on times caused by channel capacitance, leading to insufficient data voltage input and luminance differences between pixels.
Innovation Solution
Incorporating an auxiliary transistor with a gate electrode directly connected to the data line and a compensation transistor to offset channel capacitance, ensuring timely data voltage input and reducing crosstalk by applying a compensated data voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the channel capacitance of the switching transistor is increased, then the transistor can handle higher data voltages, but the turn-on time is delayed causing insufficient data voltage input
Solution Approach 1:
The patent divides the switching function into two separate transistors: a first switching transistor that turns on early to charge the channel capacitance, and a second switching transistor that turns on later to transmit the data voltage. This segmentation allows each transistor to be optimized for its specific function, resolving the contradiction between handling high voltages and turning on quickly.
Solution Approach 2:
The first switching transistor performs a preliminary action by turning on before the second switching transistor to pre-charge the channel capacitance of the second transistor. This preliminary charging action ensures that when the second transistor turns on, it can immediately transmit the data voltage without delay, solving the turn-on time issue.
2Strength
If the channel capacitance is increased to handle higher voltages, then voltage handling capability improves, but crosstalk occurs due to delayed response
Solution Approach 1:
By segmenting the switching operation into two transistors with different turn-on timings, the patent eliminates the crosstalk problem. The first transistor handles the capacitive loading without causing crosstalk, while the second transistor transmits the data voltage cleanly after the capacitance is already charged.
Solution Approach 2:
The first switching transistor acts as an intermediary that charges the channel capacitance before the second transistor transmits the data voltage. This intermediary action prevents the direct conflict between high voltage handling and fast response that would otherwise cause crosstalk.
3Device complexity
If a single transistor is used for switching, then device complexity is reduced, but luminance uniformity deteriorates due to crosstalk
Solution Approach 1:
The patent segments the switching function into two transistors to achieve luminance uniformity across pixels. Although this increases device complexity slightly, it eliminates crosstalk and ensures that each pixel receives the correct data voltage, resulting in uniform luminance display.
Data Source
AI summary
A display device includes: an organic light emitting diode (OLED); a pixel circuit configured to control an amount of a current flowing from a first power voltage to the OLED; and a gate line and a data line that are connected to the pixel circuit, the pixel circuit including: an auxiliary transistor including a gate electrode electrically connected to the data line and a first electrode and a second electrodes connected to the gate line, the first electrode and the second electrode of the auxiliary transistor being electrically connected to each other.