Pixel Circuit Bias Control for Low-Frequency Luminance Stability
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Solution Overview
Problem
As organic light-emitting display apparatuses increase in resolution and decrease in pixel size, the capacity of storage capacitors decreases, leading to fluctuations in gate voltage due to leakage currents, affecting display element luminance, and low frame rate driving increases power consumption.
Innovation Solution
A pixel design that operates at different scanning rates in two modes, incorporating transistors and capacitors to stabilize gate voltage and reduce luminance differences, using specific scan signal timings and voltage levels to maintain consistent luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of organic light-emitting display apparatuses is increased and pixel size is decreased, then display quality is improved, but the capacity of storage capacitors decreases leading to gate voltage fluctuations and luminance instability
Solution Approach 1:
The pixel circuit dynamically adjusts its operating characteristics by introducing a control transistor that modulates the storage capacitor's effectiveness. The circuit transitions between different operational states based on driving conditions, optimizing performance for both high resolution and luminance stability.
Solution Approach 2:
The invention changes the electrical parameters of the pixel circuit by introducing a control transistor that adjusts the storage capacitor's charge-discharge characteristics. This modifies the gate voltage stability parameter to compensate for the reduced capacitor capacity in smaller pixels.
2Use of energy by moving object
If low frame rate driving is applied to reduce power consumption, then energy efficiency is improved, but luminance uniformity deteriorates due to increased voltage fluctuations from leakage currents
Solution Approach 1:
The control transistor provides feedback control by monitoring the storage capacitor's charge state and adjusting its operation accordingly. This feedback mechanism compensates for leakage currents and maintains gate voltage stability even at low frame rates where power consumption is reduced.
Solution Approach 2:
The invention employs periodic charging and discharging cycles of the storage capacitor through the control transistor. This periodic action refreshes the gate voltage at optimal intervals, preventing accumulation of voltage fluctuations that would otherwise occur during low frame rate operation.
Data Source
AI summary
A pixel in which a luminance difference may be reduced during low-frequency driving, and a display apparatus including the same, there is provided a pixel that operates at a first scanning rate in a first mode and operates at a second scanning rate in a second mode, wherein the pixel includes a display element having an anode and a cathode, a first transistor that controls the magnitude of a driving current flowing to the display element according to a gate-source voltage, and a second transistor that is in an off state in the first mode and transmits a bias voltage to the first transistor in response to a first scan signal in the second mode.