OLED Display Compensation Circuit for External Light Interference
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices face image quality deterioration due to deteriorated driving transistors and threshold voltage deviations, which can lead to improper compensation of data voltage when external light is present, causing distortion in the current received from pixels.
Innovation Solution
Incorporating a photo-sensor and a compensation circuit that measures current flowing through pixels to generate a compensation value, and a signal controller that applies this value to the image signal only when no external light is detected, preventing external light from interfering with the compensation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external compensation is performed using current from pixels, then threshold voltage deviation and transistor deterioration are compensated, but external light causes distortion in received current leading to incorrect compensation
Solution Approach 1:
The patent applies preliminary action by performing compensation measurement in advance under controlled conditions (no external light) before actual display operation. The controller stores compensation values obtained during manufacturing or initialization when external light is absent, then uses these pre-stored values during normal operation when external light may be present. This separates the compensation measurement phase from the display phase, ensuring accurate baseline compensation without light interference.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a dedicated compensation period or mode that acts as a mediator between the pixel current measurement and the compensation calculation. During this intermediary phase, the display operation is suspended or controlled, and compensation is performed using stored reference values rather than real-time pixel currents that would be distorted by external light. This intermediary process isolates the compensation measurement from harmful light effects.
2Reliability
If compensation is performed continuously to maintain image quality, then transistor deterioration is addressed, but external light causes ongoing distortion in current measurements
Solution Approach 1:
The patent applies periodic action by performing compensation measurements at specific intervals or periods rather than continuously. Compensation is executed during designated compensation frames or periods when the display is in a controlled state without external light interference. Between these periodic compensation events, the display operates normally using the last valid compensation values. This periodic approach balances the need for ongoing compensation with the constraint of avoiding light-induced measurement errors.
Solution Approach 2:
The patent uses preliminary action by pre-calculating and storing compensation values during manufacturing or initialization phases when external light is controlled. These pre-computed compensation values are then applied during normal display operation without requiring continuous re-measurement. This eliminates the need for ongoing current measurements that would be distorted by external light, while still maintaining compensation benefits throughout the display's operation.
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 method effectively prevents data voltage miscompensation by external light, maintaining image quality by ensuring accurate compensation only when external light is not incident on the driving transistor, thus addressing the issue of threshold voltage deviations and transistor deterioration.
Implementation Method 1
a photo-sensor configured to measure external light to generate a light sensing signal
Implementation Method 2
The plurality of photodiodes may be configured to convert light energy to electrical energy
Data Source
AI summary
An organic light emitting diode display device includes: a display area including a plurality of pixels; a compensation circuit configured to receive a current flowing through the plurality of pixels through a plurality of receiving lines connected to the plurality of pixels, and to generate a compensation value to compensate for deterioration of a driving transistor in each of the plurality of pixels based on the received current; a photo-sensor configured to measure external light to generate a light sensing signal; and a signal controller configured to cause the compensation circuit to generate the compensation value when no external light is incident on the photo-sensor such that the light sensing signal is received at a first voltage level and to perform external compensation to generate an image data signal by applying the compensation value to an image signal received from an external device.