OLED Pixel Circuit Bias Reset for DTFT Lag Compensation
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Solution Overview
Problem
The lag phenomenon in OLED displays due to fluctuating characteristics of driving thin-film transistors (DTFTs) caused by previous cycle light emitting conditions leads to issues like short-term ghost shadows, slow response, and flicker, primarily attributed to inter-layer defects in low-temperature polycrystalline silicon film transistors.
Innovation Solution
A pixel circuit design incorporating a driving sub-circuit, data writing sub-circuit, first and second reset sub-circuits, bias sub-circuit, and compensation sub-circuit, with specific voltage settings to ensure a unified initial state and compensate for threshold voltage fluctuations, thereby alleviating the lag phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuits are used in OLED displays, then the basic light emitting function is achieved, but lag phenomenon occurs due to fluctuating characteristics of driving transistors caused by previous cycle light emitting conditions
Solution Approach 1:
The pixel circuit applies preliminary actions by resetting the gate electrode voltage and source electrode voltage to predetermined values before the light emitting cycle begins. This preliminary reset operation ensures that the driving transistor starts each cycle in a known stable state, preventing lag phenomena caused by residual effects from previous cycles.
Solution Approach 2:
The invention changes the voltage parameters of the driving transistor by dynamically adjusting the gate electrode voltage and source electrode voltage based on the light emitting control signals. This parameter control ensures that the voltage difference between gate and source remains within optimal ranges, stabilizing the transistor characteristics throughout the operation cycle.
2Ease of manufacture
If the driving transistor characteristics fluctuate due to inter-layer defects, then manufacturing constraints are accepted, but display quality deteriorates with ghost shadows and flicker
Solution Approach 1:
The invention converts the harmful effect of inter-layer defects and transistor characteristic fluctuations into a manageable parameter by implementing voltage reset mechanisms. Instead of attempting to eliminate the defects, the circuit uses predetermined voltage levels to counteract their effects, transforming the manufacturing limitation into a controlled operational parameter.
Solution Approach 2:
The pixel circuit implements feedback control by monitoring the light emitting control signals and adjusting the gate and source electrode voltages accordingly. The reset operation is triggered based on the timing and state of the light emitting cycle, creating a feedback loop that maintains display quality despite underlying transistor imperfections.
3Stability of the object's composition
If standard reset operations are applied, then basic circuit stability is maintained, but response speed remains slow due to insufficient voltage control
Solution Approach 1:
The reset operation is performed as a preliminary action before the light emitting phase begins, ensuring that the circuit is fully prepared and stabilized before needing to respond. This timing optimization allows the circuit to switch states more rapidly without compromising stability during the actual light emitting operation.
Data Source
AI summary
A pixel circuit, a display substrate, and a display apparatus are provided. The pixel circuit includes a driving sub circuit, a data writing sub circuit, a first light-emitting control sub circuit, a first reset sub circuit, and a bias sub circuit; the first reset sub circuit is connected to a first node and configured to write a first reset voltage to the first node in response to a first reset control signal; and the bias sub circuit is connected to a second node and configured to write a reference voltage to the second node in response to a bias control signal, thereby turning on the driving sub circuit.