OLED Pixel Circuit Separate Current Sensing and Power Lines
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Solution Overview
Problem
Existing active matrix OLED displays face challenges in accurately compensating pixel currents due to shared current lines for both sensing and power supply, leading to unsatisfactory compensation accuracy and increased noise interference.
Innovation Solution
The implementation of separate current sensing and power lines allows a selected pixel to draw current from the sensing line for compensation, while non-selected pixels draw from the power line, enhancing compensation accuracy, and the addition of a compensation capacitor addresses IR drop influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared current line is used for both sensing and power supply, then device complexity is reduced, but measurement precision deteriorates due to noise interference and IR drop
Solution Approach 1:
The patent divides the current line into two separate lines: a sensing line dedicated to current measurement and a power line dedicated to power supply. This segmentation eliminates the interference between sensing and power functions, resolving the contradiction between device simplicity and measurement precision by organizing complexity into specialized components.
Solution Approach 2:
The patent introduces switching transistors as intermediaries to control current flow paths. These switches enable the pixel to selectively connect to either the sensing line or power line based on operational mode, facilitating clean separation of functions while maintaining system controllability.
2Ease of manufacture
If a shared current line is used for both sensing and power supply, then manufacturing process is simplified, but object-generated harmful factors increase due to IR drop and noise
Solution Approach 1:
By segmenting the current path into separate sensing and power lines, the patent eliminates IR drop in the sensing line entirely, as no large current flows through it during measurement. This removes the harmful IR drop effect while maintaining manufacturing feasibility through standardized circuit design.
Solution Approach 2:
The patent converts the potential harm of shared line interference into benefit by using the power line exclusively for high-current power supply and the sensing line exclusively for low-current measurement. This specialization eliminates noise coupling and IR drop effects that would plague a shared design.
3Ease of operation
If current is drawn from the shared line during sensing, then device operation is simplified, but reliability deteriorates due to current interference affecting multiple pixels
Solution Approach 1:
The patent segments the current drawing operation into two distinct modes: sensing mode where current is drawn from the sensing line, and power mode where current is drawn from the power line. This segmentation ensures that sensing operations do not interfere with power supply to other pixels, eliminating current interference while maintaining operational simplicity through mode-based control.
Solution Approach 2:
The patent employs periodic switching between sensing and power modes through clocked switching transistors. During sensing periods, the pixel connects to the sensing line; during power periods, it connects to the power line. This periodic action ensures clean separation of functions and prevents current interference, enhancing reliability while maintaining ease of operation through rhythmic control.
Data Source
AI summary
An exemplary active matrix organic light emitting diode (OLED) display includes a data line, a current sensing line, a power line and a plurality of pixels all electrically coupled to the data line, the current sensing line and the power line. During a data current is writing to a selected one of the pixels, the selected pixel draws a current from the current sensing line, and the data line supplies a particular data voltage to the selected pixel according to the drawn current from the current sensing line until the drawn current matched with the data current; the other non-selected pixels draw currents from the power line for light-emission. Moreover, a pixel circuit and a data current writing method adapted for the above-mentioned active matrix OLED display also are provided.