Pixel Circuit Layout for Stable Luminance at Low Refresh Speeds
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Solution Overview
Problem
Display devices experience poor image quality due to increased node voltage in gate drivers caused by current leakage and noise during skip periods when driven at low speeds for extended periods, reducing the driving force and affecting power consumption.
Innovation Solution
A pixel design that reduces the number of switching transistors connected to the driving transistor by removing a switching transistor and using a simplified control circuit with fewer emission signals, including a driving transistor, transistors for reference and data voltage transmission, and capacitors for voltage storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the display panel is driven at low speed for a long time, then power consumption is reduced, but node voltage increases due to current leakage and noise causing poor image quality
Solution Approach 1:
The patent applies preliminary action by initializing the gate electrode voltage to a reference voltage before the emission period through the first transistor during an initializing period. This pre-initialization prevents voltage drift caused by current leakage during skip periods, ensuring stable image quality even when driven at low speeds for extended periods.
Solution Approach 2:
The patent implements feedback by using a sensing period where the gate electrode voltage is sensed and compensated. The first transistor transmits a reference voltage to the gate electrode based on sensed conditions, correcting voltage deviations caused by current leakage and noise, thereby maintaining reliable image quality during low-speed operation.
2Adaptability or versatility
If multiple switching transistors are connected to the driving transistor, then control flexibility is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes unnecessary switching transistors from the conventional circuit configuration. By eliminating redundant transistors while retaining the essential first transistor for reference voltage transmission and the fourth transistor for emission control, the design achieves simplified device complexity while maintaining adequate control flexibility through streamlined transistor connections.
Solution Approach 2:
The patent applies multi-functionality by designing the first transistor to serve multiple purposes: transmitting reference voltage to the gate electrode, initializing the gate voltage during the initializing period, and participating in voltage compensation during the sensing period. This consolidation of functions reduces the total transistor count while preserving control flexibility.
Data Source
AI summary
A pixel comprises a driving transistor having a gate electrode at a first node, a first electrode connected to a high potential driving voltage, a second electrode connected to the light emitting element, and the driving transistor controlling the amount of driving current supplied to the light emitting element; a first transistor configured to transmit a reference voltage to the gate electrode of the driving transistor in response to a first gate signal; a second transistor configured to transmit a data voltage to the gate electrode of the driving transistor in response to a second gate signal; a third transistor electrically connecting the gate electrode of the driving transistor to the second electrode of the driving transistor in response to the first gate signal; and a fourth transistor electrically connecting the driving transistor with the light emitting element in response to an emission signal.