OLED Driving Circuit Current Sensing for Fast Threshold Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional external compensation methods for organic light emitting displays face challenges in accurately and efficiently sensing variations in electrical characteristics of driving TFTs due to large parasitic capacitance and time-consuming voltage sensing, especially in low-grayscale conditions.
Innovation Solution
The implementation of a current sensing method using a current integrator and sampler within the data driver IC, which generates multiple sensing pulses to integrate and digitize source-drain current, allowing for faster and more accurate determination of threshold voltage and mobility variations, reducing reliance on parasitic capacitance and enabling multi-time current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If voltage sensing method is used to sense electrical characteristics of driving TFT, then sensing can be performed using existing parasitic capacitance, but sensing time becomes excessively long and accuracy deteriorates especially in low-grayscale conditions
Solution Approach 1:
The patent replaces the voltage sensing method with a current sensing method. Instead of measuring voltage across parasitic capacitance, the invention directly senses the source-drain current of the driving TFT through a sensing line connected to the source electrode. This substitution of measurement principle dramatically reduces sensing time while improving accuracy, especially in low-grayscale conditions where voltage sensing fails.
Solution Approach 2:
The invention changes the sensing parameter from voltage to current. By measuring the source-drain current directly rather than converting current to voltage through parasitic capacitance, the system achieves faster and more accurate sensing. The current sensing approach allows for real-time measurement without the time-consuming charging/discharging cycles required by voltage-based methods.
2Device complexity
If voltage sensing through parasitic capacitance is used, then no additional sensing circuitry is needed, but measurement precision deteriorates due to large parasitic capacitance and slow charging time
Solution Approach 1:
The patent substitutes voltage measurement with direct current measurement. The sensing line is configured to carry the source-drain current directly to the data driving circuit, eliminating the need to charge/discharge parasitic capacitance. This current-based approach provides superior measurement precision because it directly reflects the actual electrical characteristics of the driving TFT without the distorting effects of parasitic capacitance.
3Device complexity
If conventional voltage sensing is used, then sensing can be performed with simple circuit configuration, but productivity decreases due to inability to perform multiple sensing operations within line sensing time
Solution Approach 1:
The invention replaces slow voltage sensing with fast current sensing. The current sensing method enables multiple sensing operations to be performed within a single line sensing time period, significantly improving productivity. The data driving circuit can sequentially sense multiple pixels' current values without the time penalty associated with charging parasitic capacitance, allowing for more frequent compensation operations.
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 significantly reduces sensing time and enhances accuracy by directly measuring current, allowing for quicker and more precise compensation of electrical characteristics, even in low-grayscale conditions, and enables multiple sensing operations within a single line sensing time.
Implementation Method 1
a current integrator and sampler, which integrates and samples a sensed current
Implementation Method 2
When a driving voltage is applied to the anode and the cathode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the emission layer EML to form excitons. As a result, the emission layer EML generates visible light.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An organic light emitting display is provided which offers shorter sensing time and higher sensing accuracy when sensing variations in electrical characteristics of a driving element. The organic light emitting display comprises a display panel with a plurality of pixels, a gate driving circuit and a data driving circuit. the gate driving circuit generates a sensing gate pulse corresponding to one line sensing ON time in a sensing operation and sequentially supplies the same to gate lines (15) in a line sequential manner. The data driving circuit comprises a plurality of current integrators (CI) that perform an integration of the source-drain current of the driving TFT (DT) of each pixel input through the sensing lines and an ADC that sequentially digitizes the output of the current integrators (CI) to output digital sensed values. A timing controller controls the operations of the gate driving circuit and the data driving circuit such that integrations of first and second source-drain currents are performed in respective sensing and sampling periods within one line sensing ON time, the first and second source-drain currents being caused by sensing data voltages of a first level and a second level.