Organic EL Display Panel Mobility Correction Circuit
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Solution Overview
Problem
In display devices using organic electroluminescence (EL) elements, variations in the mobility correction period due to wiring delays cause uneven luminance across the panel surface, leading to poor shading and luminescence variations.
Innovation Solution
A display panel device with a luminescence element, capacitors, and a driver configuration that includes a controller to manage the mobility correction by separating the control of the start and end of the mobility correction period, using a predetermined bias voltage and reverse bias voltage to ensure uniformity in the mobility correction period across all pixel units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional mobility correction method is used in active-matrix organic EL display devices, then the luminance variations due to transistor characteristic variations can be compensated, but wiring delays cause variations in the mobility correction period leading to uneven luminance and poor shading across the panel surface
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a predetermined voltage level before the mobility correction period begins. This ensures that the capacitor starts from a known state, and the mobility correction can be performed with a fixed time period regardless of wiring delays, thereby achieving uniform luminance across the panel surface without shading variations
2Manufacturing precision
If the mobility correction period is extended to compensate for all pixel variations, then more accurate luminance correction can be achieved, but the display refresh rate decreases and power consumption increases
Solution Approach 1:
The patent changes the parameter of capacitor initial voltage from variable (depending on previous frame) to fixed (predetermined voltage). This parameter change allows the mobility correction to be completed in a fixed time period, maintaining high display refresh rates while achieving accurate luminance correction through the predetermined voltage level that ensures complete correction within the fixed time
3Adaptability or versatility
If the capacitor initial voltage varies before mobility correction, then the correction can adapt to different operating conditions, but the correction period varies due to wiring delays causing luminance non-uniformity
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a predetermined voltage level before the mobility correction period begins. This ensures that the capacitor starts from a known state, and the mobility correction can be performed with a fixed time period regardless of wiring delays, thereby achieving uniform luminance across the panel surface without shading variations
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
The solution reduces variations in the mobility correction period, resulting in more accurate control of the luminescence, preventing unevenness in shading and improving the overall display quality by ensuring consistent luminescence across the panel surface.
Implementation Method 1
image display devices using organic electroluminescence (EL) elements are known. The organic EL display devices using the organic EL elements, which are self-luminous
Implementation Method 2
a first capacitor including a first capacitor electrode and a second capacitor electrode that holds a capacitor voltage
Data Source
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AI summary
A display panel device includes: an organic EL element (13); a capacitor (14); a driving transistor (11) that passes a drain current through the organic EL element (13); a data line (20) that supplies a signal voltage to the capacitor (14); a selecting transistor (12) that switchably interconnects the data line (20) and the capacitor (14); and a controller. The controller is configured to: apply a predetermined bias voltage to a second capacitor electrode to prevent a flow of the drain current; turn ON the selecting transistor (12) to supply the signal voltage to a first capacitor electrode; apply a reverse bias voltage to the second capacitor electrode to flow a discharge current between a source of the driving transistor (11) and the second capacitor electrode; and turn OFF the selecting transistor (12), after a lapse of a predetermined period of time since the discharge current is caused to flow, to stop the supply of the signal voltage to the first capacitor electrode.