OLED Storage Capacitor Threshold Voltage Compensation
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Solution Overview
Problem
Existing organic light emitting diode (OLED) displays face image quality deterioration due to threshold voltage deviations in driving transistors, which are not adequately compensated by data driving ICs with limited output ranges, leading to increased power consumption and costs when wider output ranges are required.
Innovation Solution
A display device and driving method that utilize a reference voltage driver to apply first and second reference voltages during data writing and light emission periods, respectively, with a storage capacitor to manage threshold voltage deviations, allowing for a controlled output range of the data driving IC without the need for a wide output range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data driving IC outputs data voltage with compensation value reflected to compensate threshold voltage deviation, then threshold voltage deviation compensation is improved, but the output range of data driving IC is exceeded
Solution Approach 1:
The patent segments the compensation function into two parts: the data driving IC outputs data voltage without full compensation (staying within its output range), and the storage capacitor provides additional compensation by maintaining a compensation voltage equal to the threshold voltage deviation. This division allows compensation without exceeding the data driving IC's output capabilities.
Solution Approach 2:
The storage capacitor acts as an intermediary element that stores and provides compensation voltage to counteract threshold voltage deviation. By introducing this intermediate component, the system achieves compensation functionality without requiring the data driving IC to output voltages beyond its specified range.
2Reliability
If a data driving IC with sufficiently wide output range is used to accommodate compensation voltage, then threshold voltage deviation compensation is improved, but power consumption and cost increase
Solution Approach 1:
The compensation function is segmented between the data driving IC (which outputs only within its normal range) and the storage capacitor (which provides the additional compensation voltage). This segmentation allows the use of a standard, lower-power data driving IC while still achieving full compensation through the combined system.
Solution Approach 2:
The storage capacitor serves itself by automatically maintaining a compensation voltage equal to the threshold voltage deviation without requiring additional power from the data driving IC. The capacitor charges to the compensation voltage during the writing period and maintains it during the light emission period, providing self-sufficient compensation.
3Reliability
If the storage capacitor maintains compensation voltage during light emission period, then threshold voltage deviation compensation is improved, but the circuit complexity increases
Solution Approach 1:
The storage capacitor is given multiple functions: it stores data voltage during the writing period and simultaneously provides compensation voltage during the light emission period. By making the storage capacitor multi-functional, the patent avoids adding separate compensation circuitry, thus limiting the increase in circuit complexity.
Solution Approach 2:
The patent merges the data storage function and the threshold voltage compensation function into a single storage capacitor. This combination eliminates the need for separate compensation capacitors or circuits, reducing overall circuit complexity while achieving compensation.
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 enables effective compensation of threshold voltage deviations without increasing power consumption or costs, allowing for improved image quality and reduced power usage by using a data driving IC with a smaller output range.
Implementation Method 1
a storage capacitor including one electrode connected to the first node and the other electrode to which any one of the first reference voltage and the second reference voltage is applied
Data Source
AI summary
A first reference voltage is applied to a plurality of pixels during a data writing period when data is written and a second reference voltage is applied to the plurality of pixels during a light emitting period when the plurality of pixels emit light, in which each of the plurality of pixels includes a switching transistor to transfer a data voltage applied to a data line to a first node; a driving transistor controlling a driving current flowing into an OLED according to the voltage of the first node and a first power supply voltage; and a storage capacitor including a first electrode connected to the first node and a second electrode receiving one of the first reference voltage and the second reference voltage. A difference between the first reference voltage and the second reference voltage is determined according to a threshold voltage deviation characteristic of the display unit.