Pixel Circuit Leakage Current Management in OLED Displays
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Solution Overview
Problem
Conventional pixel circuits using low temperature polysilicon thin film transistors suffer from larger leakage currents, leading to uneven brightness when displaying low gray scales due to the anode reset transistor shunting the organic light emitting diode.
Innovation Solution
The introduction of a pixel circuit design that includes a leakage preventing transistor with a metal oxide active layer, connected between the compensating transistor and the driving transistor, and an anode reset transistor with a metal oxide active layer, which collects and redirects leakage current to improve brightness uniformity during low gray scale display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low temperature polysilicon thin film transistors are used in the pixel circuit, then the device can be manufactured with existing processes, but larger leakage currents occur leading to brightness unevenness at low gray scales
Solution Approach 1:
An anode reset transistor is introduced as an intermediary component between the driving transistor and the organic light emitting diode anode. This reset transistor actively manages the leakage current path, preventing the harmful shunting effect that causes brightness unevenness while maintaining compatibility with existing low temperature polysilicon manufacturing processes
Solution Approach 2:
The leakage current path is extracted and separated from the main driving current path by introducing the anode reset transistor. This allows the leakage current to be independently controlled and redirected, preventing it from causing brightness unevenness while the main driving function remains intact
2Ease of operation
If the anode reset transistor is turned off to reset the anode, then the anode can be discharged, but leakage current shunts through the turned off transistor causing brightness unevenness
Solution Approach 1:
The leakage current that would normally cause harm (brightness unevenness) is converted into a beneficial effect by redirecting it through the anode reset transistor back to the driving transistor. The previously harmful shunting current becomes a controlled path that actually improves brightness uniformity by preventing charge accumulation at the anode
Data Source
AI summary
A pixel circuit, a method of driving the same, and a display device are provided. An input end of an anode reset transistor is connected to an output end of a driving transistor, and an output end of the anode reset transistor is connected to an anode of an organic light emitting diode to collect a leakage current from the anode of the organic light emitting diode through the anode reset transistor to the output end of the driving transistor in an light emitting state. Part of the collected current at the output end of the driving transistor enters the anode of the organic light emitting diode.