OLED Data Driving Circuit Brightness Control via Pixel Feedback
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Solution Overview
Problem
Organic light emitting diode (OLED) displays struggle to emit light with desired brightness due to variations in threshold voltage of transistors across pixels and lack of real-time current measurement and control.
Innovation Solution
A data driving circuit comprising a current digital-analog converter, a current control unit, and a selection unit that alternately connects the data line to either the converter or the control unit to adjust the current flowing through pixels, ensuring the pixel current matches the gradation current for desired brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transistors are provided in each pixel for supplying current corresponding to data signal, then the organic light emitting diode display can emit light, but the display cannot achieve desired brightness due to variations in threshold voltage of transistors across pixels
Solution Approach 1:
The patent implements a feedback mechanism where the data driver receives pixel current information from each pixel and adjusts the gradation current accordingly. The data driver compares the received pixel current with the target gradation current and modifies subsequent current supply to compensate for threshold voltage variations, thereby achieving uniform brightness across all pixels despite manufacturing variations in transistor characteristics
Solution Approach 2:
The patent enables pixels to self-measure their own current consumption and report it back to the data driver. Each pixel includes current measurement circuitry that allows it to autonomously determine its actual current intake and communicate this information through the data line, enabling the system to self-correct brightness uniformity issues without external intervention
2Illumination intensity
If there is no method of measuring and controlling real current flowing in each pixel, then the circuit structure remains simple, but the display cannot achieve desired brightness control
Solution Approach 1:
The patent makes the data line serve multiple functions: it not only transmits data signals from the data driver to pixels for light emission control, but also carries pixel current measurement information back from pixels to the data driver. This dual-function usage of the existing data line structure allows current measurement and feedback control to be implemented without adding separate dedicated measurement and control wiring, thus limiting the increase in device complexity
Solution Approach 2:
The patent uses the data line as an intermediary medium to transfer pixel current information from pixels to the data driver. By utilizing the existing data communication pathway for dual purposes (data transmission and current feedback), the system achieves current measurement capability without requiring separate measurement circuits or additional control infrastructure
3Illumination intensity
If the data driver supplies gradation current to pixels without adjusting for pixel current variations, then the driving circuit operation is simple, but the displayed image lacks uniform brightness
Solution Approach 1:
The patent implements periodic measurement and adjustment cycles where the data driver alternates between supplying gradation current for light emission and receiving pixel current feedback information. During specific time periods, the data driver receives current information from pixels and adjusts subsequent current supply accordingly. This periodic feedback-adjustment cycle achieves uniform brightness while maintaining relatively simple operational procedures through time-division multiplexing
Data Source
AI summary
A data driving circuit for displaying an image with a desired brightness comprises: a current digital-analog converter for generating a gradation current corresponding to external data, and for receiving a first current corresponding to the gradation current from a pixel via a data line; a current control unit for receiving a pixel current from the pixel via the data line, and for selectively increasing and decreasing a level of the first current in accordance with the received pixel current; and a selection unit for selectively connecting the data line to either the current digital-analog converter or the current control unit. An organic light emitting diode and a method of driving same are similarly configured. With these configurations, an image is displayed with desired brightness.