OLED Ageing Compensation via Linear Mode Driver Transistor
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Solution Overview
Problem
Existing OLED displays face significant hardware complexity and inefficiency in measuring and compensating for the ageing of organic light-emitting diodes, which affects luminance and requires extensive circuitry for current-voltage characteristic curve measurement.
Innovation Solution
A method involving a single current measuring circuit to determine the current-voltage value pairs of OLEDs in a display matrix, allowing for ageing compensation by comparing present and known values, with the driver transistor operated in linear mode to calculate the ageing state and adjust driving parameters, thereby minimizing circuitry and hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual current-voltage characteristic curve measurement for each OLED pixel is implemented, then ageing compensation precision is improved, but device complexity and hardware outlay increase considerably
Solution Approach 1:
The patent segments the measurement process by separating the OLED pixel from its driver transistor, measuring only the OLED's current-voltage characteristic while using the known driver transistor characteristics to calculate the OLED parameters mathematically, thereby avoiding the need for complex per-pixel measurement circuitry
Solution Approach 2:
The patent introduces the driver transistor as an intermediary element whose known characteristic curve is used to indirectly determine the OLED's ageing state, eliminating the need for direct complex measurement of each OLED pixel's full characteristic curve
2Measurement precision
If extensive measurement circuitry is used to determine current-voltage characteristic curves, then measurement precision is improved, but ease of manufacture deteriorates due to increased hardware requirements
Solution Approach 1:
The patent applies preliminary action by storing the driver transistor's characteristic curve in advance, allowing the OLED measurement to be performed using simple circuitry that leverages this pre-stored information to achieve precise ageing compensation
Solution Approach 2:
The patent uses copying by utilizing the known driver transistor characteristic curve as a reference model to infer OLED ageing parameters, replacing the need for complex direct measurement with a simpler indirect measurement approach
3Reliability
If OLED ageing is compensated using complex per-pixel measurement, then reliability is improved, but productivity deteriorates due to increased measurement and processing time
Solution Approach 1:
The patent applies partial action by measuring only the essential OLED current-voltage characteristic points needed for ageing compensation, rather than performing complete per-pixel characteristic curve measurements, thereby reducing processing time while maintaining compensation reliability
Solution Approach 2:
The patent replaces complex mechanical/electrical measurement systems with mathematical calculations, using the measured OLED characteristics combined with stored driver transistor characteristics to compute ageing parameters, thereby speeding up the process while maintaining accuracy
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
Enables efficient ageing compensation of OLEDs with reduced hardware complexity, allowing for precise determination and storage of ageing states for brightness correction and gamma adaptation, using a single current measuring circuit for the entire display matrix.
Implementation Method 1
OLEDs have a forward current flowing through them during operation in the forward direction and exhibit electroluminescence phenomena in the process
Data Source
AI summary
The invention relates to a method and a circuit arrangement for the ageing compensation of an organic light-emitting diode (OLED) which is fed from a supply voltage and is switched by means of a driver transistor operated in saturation operation, by means of a driving of the light-emitting diode. The method comprises the following steps of: storing at least one desired current-voltage value pair of a desired current-voltage characteristic curve of the light-emitting diode; transferring the driver transistor from saturation operation to linear operation during a measurement cycle; measuring a current value for the current through the light-emitting diode by means of a current measuring circuit in the measurement cycle; determining at least one present current-voltage value pair of a present current-voltage characteristic curve of the light-emitting diode by means of the measured current value; comparing the at least one present current-voltage value pair of the light-emitting diode with the desired current-voltage value pair of the light-emitting diode; and generating driving parameters for driving the light-emitting diode in a manner dependent on the result of the comparison.