Pixel Circuit Driving Method for OLED Display Luminance Uniformity
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Solution Overview
Problem
In organic electroluminescence (EL) display apparatuses, the variation in threshold voltage of driving transistors across pixels leads to inconsistent light emission luminance, causing screen burn and gradation issues due to time-dependent variations and differences in gate-source voltage during high and low gradation displays.
Innovation Solution
A driving method for pixel circuits that includes initializing the gate-source voltage of the driving transistor during the no-light emitting period, applying a driving voltage to correct the threshold value, and using a holding capacitor to maintain a consistent gate-source voltage during light emission, thereby reducing the difference in current degradation across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the gate-source voltage of the driving transistor is allowed to vary during operation, then the circuit operation is simpler, but the light emission luminance becomes inconsistent across pixels causing screen burn
Solution Approach 1:
The patent applies preliminary action by initializing the gate-source voltage of the driving transistor to a predetermined potential during the no-light emitting period before the light emission phase begins. This pre-initialization ensures that all pixels start with a consistent gate-source voltage, preventing screen burn and luminance inconsistency while maintaining relatively simple circuit operation.
Solution Approach 2:
The patent implements periodic action by repeatedly initializing the gate-source voltage during each no-light emitting period in a cyclic manner. This periodic initialization maintains consistent light emission luminance across pixels over time without requiring continuous complex control, balancing reliability with operational simplicity.
2Reliability
If the gate-source voltage is fixed during no-light emitting period, then screen burn is reduced, but additional control steps are required
Solution Approach 1:
The patent merges the initialization of gate-source voltage with the existing no-light emitting period timing structure. By utilizing the already-present timing framework for light emission control, the patent implements voltage fixation without requiring separate dedicated control circuits or steps, thus achieving screen burn prevention with minimal increase in device complexity.
Solution Approach 2:
The driving transistor's gate-source voltage is automatically initialized to the predetermined potential during the no-light emitting period through the circuit's own operation timing. This self-service mechanism reduces the need for external complex control signals while maintaining reliable screen burn prevention.
3Manufacturing precision
If threshold value correction is applied, then luminance consistency is improved, but the driving cycle becomes longer
Solution Approach 1:
The threshold value correction is performed as a preliminary action during the no-light emitting period, preparing the driving transistor's threshold voltage before the light emission phase. This timing strategy achieves luminance consistency without extending the actual light emission duration, minimizing the perceived loss of time.
Solution Approach 2:
The threshold value correction is applied periodically during each no-light emitting period, allowing the system to maintain luminance consistency over time without requiring continuous correction that would extend the overall driving cycle. The periodic application efficiently balances precision with time consumption.
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 method ensures consistent light emission luminance across pixels by fixing the gate-source voltage during the no-light emitting period and correcting threshold values, reducing screen burn and current degradation differences, thus improving display uniformity.
Implementation Method 1
a holding capacitor connected between the gate and the source of the driving transistor for holding the input signal value
Data Source
AI summary
Disclosed here is a driving method for a pixel circuit which includes a light emitting element, a driving transistor for applying current in response to a signal value applied between a gate and a source thereof to the light emitting element when a driving voltage is applied between a drain and the source thereof, and a holding capacitor connected between the gate and the source of the driving transistor for holding the input signal value, the driving method comprising steps carried out within a light emitting period of one cycle which includes a no-light emitting period and the light emitting period, the steps including a first step to a sixth step.