OLED Pixel Link Transistor Circuit for Voltage Drop Compensation
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Solution Overview
Problem
Active matrix OLED displays face challenges in maintaining uniform screen luminance and reducing power consumption due to increased voltage differences across pixels, leading to higher power consumption and potential luminance uniformity issues caused by wire length voltage drops.
Innovation Solution
The implementation of a display device with specific pixel configurations, including compensation capacitors and transistors, and a driving method that alternates pixel types to reduce voltage drops and optimize power source voltage distribution, using oxide thin film transistors to manage current flow efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the voltage difference between power source voltage terminals is increased to maintain luminance in simultaneous light emitting method, then luminance is maintained, but voltage drop caused by wire is increased and power consumption is increased
Solution Approach 1:
The pixel circuit is divided into multiple transistor components (switching transistor, driving transistor, compensation transistor, link transistor) and capacitor components (compensation capacitor, coupling capacitor) that work together to independently control voltage distribution. This segmentation allows precise control of current flow and voltage differences, enabling luminance maintenance with optimized power consumption by avoiding excessive voltage differences across the entire pixel circuit.
Solution Approach 2:
The coupling capacitor is introduced as an intermediary element that couples the data line to the power source voltage terminal. This intermediary component enables voltage transfer and stabilization without requiring increased power source voltage, thereby maintaining luminance while reducing the voltage difference and power consumption across the pixel circuit.
2Reliability
If the voltage difference between power source voltage terminals is increased to compensate for wire voltage drop, then power source voltage margin is improved, but voltage drop across the display is increased and luminance uniformity decreases
Solution Approach 1:
The link transistor is configured to transmit power source voltage to specific nodes locally within the pixel circuit where needed. This local voltage transmission ensures that each pixel receives adequate voltage without requiring increased overall power source voltage, thereby maintaining luminance uniformity across the display while providing sufficient voltage margin for reliable operation.
Solution Approach 2:
The circuit design uses complementary transistor configurations (n-type and p-type transistors) that replicate and balance voltage distribution patterns across different pixel locations. This copying approach ensures consistent voltage margins and luminance characteristics across the entire display panel, compensating for wire voltage drops without sacrificing uniformity.
Data Source
AI summary
A display device including a display unit having a plurality of pixels is disclosed. In one aspect, at least one first pixel among the pixels includes: a first compensation capacitor including one electrode connected to a data line and the other electrode connected to a first node; a first switching transistor including a gate electrode configured to have a scan signal, one electrode connected to the first node, and the other electrode connected to a second node; a first driving transistor including a gate electrode connected to the second node, one electrode connected to a first power source voltage, and the other electrode connected to a first organic light emitting diode (OLED); and a first link transistor including a gate electrode configured to have a link control signal, one electrode connected to the data line, and the other electrode connected to the first power source voltage. Pixels of the type with four transistors may be alternated with pixels of the type having three transistors (no link transistor) according to a desired aspect ratio.