OLED Driving Transistor Threshold Voltage Compensation Circuit
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Solution Overview
Problem
Active matrix OLED displays face challenges in maintaining high image quality due to variations in threshold voltage and power source voltage, leading to luminance inconsistencies across pixels, especially under high resolution and high frequency driving conditions.
Innovation Solution
A driving circuit and method that includes threshold voltage compensation lines and a scan driver generating threshold voltage compensation signals with at least two pulses to diode-connect the driving transistor, ensuring sufficient compensation time for each pixel, thereby stabilizing the gate electrode voltage and maintaining consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high frequency driving is applied to achieve fast response speed, then the response time is improved, but the threshold voltage compensation time becomes insufficient leading to luminance variation
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before the data signal is written to the driving transistor. The compensation signal is applied in advance to the driving transistor's gate electrode, allowing the threshold voltage to be adjusted prior to the main driving operation. This ensures that even under high frequency driving conditions, the threshold voltage is fully compensated before the OLED is activated, preventing luminance variation while maintaining fast response speed.
2Manufacturing precision
If high resolution driving is implemented to improve image quality, then the display resolution is improved, but the compensation time for each pixel becomes insufficient
Solution Approach 1:
The patent implements periodic action by using a compensation signal that consists of multiple periodic pulses applied sequentially to each pixel's driving transistor. Instead of a single long compensation pulse, the system uses multiple shorter pulses repeated at a fixed period. This periodic structure allows the compensation to be distributed over time, ensuring complete compensation even when driving at high resolution where time is constrained, while maintaining the required image quality.
3Reliability
If threshold voltage compensation is performed with sufficient time, then the luminance consistency is improved, but the driving frequency must be reduced
Solution Approach 1:
The patent resolves this contradiction by performing threshold voltage compensation as a preliminary action before the main driving operation. The compensation signal is applied to the driving transistor's gate electrode in advance, allowing the threshold voltage to be adjusted prior to data signal writing. This temporal separation enables sufficient compensation time without reducing the overall driving frequency, as compensation occurs in a dedicated pre-phase that does not interfere with the main display refresh cycle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures complete threshold voltage compensation, resulting in high image quality by stabilizing the driving transistor's operation and reducing current variations caused by threshold voltage fluctuations, thus enhancing the overall display performance.
Implementation Method 1
The driving transistor is further for diode-connecting according to one of the threshold voltage compensation signals during a threshold voltage compensation period to compensate for a threshold voltage of the driving transistor
Implementation Method 2
the OLED display, which uses OLEDs to generate light by a recombination of electrons and holes for the display of images
Data Source
AI summary
A pixel, a display device including the pixel, and a driving method are disclosed. Each of a plurality of pixels included in the display device includes: an organic light emitting diode (OLED); a driving transistor for transmitting a driving current to the OLED according to a data signal; a first transistor for transmitting the data signal to the driving transistor according to a scan signal; and a first capacitor including a first terminal coupled to the first transistor and a second terminal coupled to a gate electrode of the driving transistor. In addition, the driving transistor is for diode-connecting in response to a threshold voltage compensation signal during a threshold voltage compensation period to compensate for a threshold voltage of the driving transistor. The threshold voltage compensation signal includes at least two pulses.