OLED Driving Circuit with Dual Scan Signals for Threshold Voltage Drift
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Solution Overview
Problem
Conventional OLED driving circuits face issues with voltage stress leading to threshold voltage drift, affecting brightness and display consistency across pixel units over time.
Innovation Solution
A driving circuit comprising a first and second scan driving circuit, a selector, and multiple thin film transistors, which alternately provide scan driving signals to pixel units in different durations to ensure consistent display quality by controlling the switching states of thin film transistors based on triggering signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional OLED driving circuit with 2T1C structure is used, then the circuit can realize stable display initially, but the driving thin film transistor is subjected to severe voltage stress causing threshold voltage drift and inconsistent display over time
Solution Approach 1:
The scan driving circuit is divided into two separate circuits: a first scan driving circuit for normal display operation and a second scan driving circuit for compensation. This segmentation allows each circuit to be optimized for its specific function, reducing the voltage stress on the driving transistor during normal operation while maintaining display consistency through periodic compensation.
Solution Approach 2:
The compensation operation is performed in advance during non-display periods (e.g., during horizontal blanking intervals). The second scan driving circuit applies compensation signals to correct threshold voltage drift before it significantly impacts display quality, preventing inconsistent display rather than correcting it after the fact.
2Duration of action of stationary object
If the driving thin film transistor operates continuously for long working time, then the OLED can maintain display function, but the threshold voltage of the driving transistor drifts affecting brightness and display consistency
Solution Approach 1:
The circuit alternates between normal display mode and compensation mode periodically. During normal display operation, the first scan driving circuit drives the OLED. At predetermined intervals (e.g., every frame or every few frames), the circuit switches to compensation mode where the second scan driving circuit applies compensation signals to restore the driving transistor's threshold voltage, ensuring long-term stability.
Solution Approach 2:
The compensation mechanism discards the accumulated threshold voltage drift that occurs during continuous operation and recovers the driving transistor's original characteristics through periodic compensation signals. This allows the circuit to maintain performance over extended working periods despite continuous operation.
3Reliability
If a selector with multiple thin film transistors is used to switch between different scan driving circuits, then display consistency can be maintained, but the device complexity increases
Solution Approach 1:
The selector circuit and its thin film transistors serve multiple functions: they act as switches to select between the first and second scan driving circuits, functions as signal routing elements, and participate in the compensation mechanism itself. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The selector circuit merges the switching function with the signal distribution function. The same thin film transistors that switch between the two scan driving circuits also route the compensation signals to the appropriate pixel units. This combining of functions reduces overall circuit complexity compared to having separate switching and signal distribution paths.
Data Source
AI summary
Disclosed are a driving circuit and a display device, comprising a first scan driving circuit, a second scan driving circuit, a selector and at least one pixel unit; wherein the first scan driving circuit and the second scan driving circuit are respectively coupled to the selector and the selector is coupled to the at least one pixel unit; the selector outputs a first scanning signal of the first scan driving circuit to the at least one pixel unit in a first duration to make the at least one pixel unit in a display state; the selector outputs a second scanning signal of the second scan driving circuit to the at least one pixel unit in a second duration to make the at least one pixel unit in a compensation state; wherein the first duration and the second duration are different.