Self-luminous Display Device with Dummy Vth Correction
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Solution Overview
Problem
Self-luminous display devices using organic electroluminescence elements suffer from a 'flashing phenomenon' due to variations in transistor characteristics, particularly threshold voltage and mobility, leading to instantaneous changes in screen brightness during transitions between different displays.
Innovation Solution
The implementation of a driving method that includes preliminary threshold voltage correction (dummy Vth correction) and mobility correction, performed after initializing the voltage held by the holding capacitor, ensures a constant reverse bias setting period, thereby stabilizing light emission intensity across the screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If threshold voltage and mobility corrections are performed with the light-emitting diode reverse-biased to prevent image quality degradation, then brightness uniformity is improved, but the screen undergoes instantaneous brightness changes (flashing phenomenon) during transitions between displays
Solution Approach 1:
The patent applies preliminary action by performing a dummy threshold voltage correction before the actual threshold voltage and mobility corrections. This preliminary correction initializes the voltage held by the holding capacitor and sets a constant reverse bias period, preventing the flashing phenomenon that occurs during transitions between displays while maintaining brightness uniformity during the subsequent corrections
2Reliability
If the light-emitting diode is reverse-biased during threshold voltage and mobility corrections, then transistor characteristic variations are compensated, but light emission intensity becomes unstable during screen transitions
Solution Approach 1:
The dummy threshold voltage correction serves as a preliminary action that stabilizes the holding capacitor voltage before the actual corrections. This preliminary step ensures that when the light-emitting diode is reverse-biased during threshold voltage and mobility corrections, the light emission intensity remains stable even during screen transitions, as the capacitor is already initialized to appropriate voltage levels
Solution Approach 2:
The patent implements periodic action by establishing a constant reverse bias setting period through the dummy correction. This regular, predetermined reverse bias duration ensures consistent compensation of transistor characteristic variations while maintaining stable light emission intensity, as the periodic timing prevents erratic behavior during screen transitions
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 effectively prevents or suppresses the flashing phenomenon by maintaining consistent light emission intensity between pixels for the same data voltage input, ensuring improved brightness uniformity and reducing the impact of transistor characteristic variations.
Implementation Method 1
a light-emitting diode adapted to emit light when applied with a bias voltage
Implementation Method 2
a holding capacitor coupled to a control node of the drive transistor
Data Source
AI summary
Disclosed herein is a self-luminous display device including: pixel circuits; and a drive circuit, wherein each of the pixel circuits includes a light-emitting diode, a drive transistor connected to a drive current path of the light-emitting diode, and a holding capacitor coupled to a control node of the drive transistor, during a period in which at least actual threshold voltage and mobility corrections are performed on the drive transistor before the light-emitting diode can emit light, the drive circuit performs a preliminary threshold voltage correction of the drive transistor, i.e., a dummy Vth correction, with the light-emitting diode in a non-light emitting state, the drive circuit next performs a correction preparation for a constant period by reverse-biasing the light-emitting diode and initializing the voltage held by the holding capacitor, and the drive circuit performs the actual threshold voltage correction and mobility correction after the correction preparation.