Dual Driver Pixel Circuit for AMOLED Brightness Stability
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Solution Overview
Problem
In active-matrix organic light emitting diode (AMOLED) display devices, the long-term operation of driver thin film transistors (TFTs) leads to threshold voltage drift, affecting the stability of OLED brightness due to defect states like trap stages within the TFTs.
Innovation Solution
A pixel driving circuit with a dual driver unit structure, comprising two sub-driver units and switching units, alternately drives the light emitting unit, reducing the time each driver unit operates and minimizing threshold voltage drift through capacitive voltage compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single driver TFT is used to drive the light emitting unit, then the device structure is simple, but the threshold voltage drift occurs during long-term operation leading to unstable brightness
Solution Approach 1:
The driver unit is segmented into a first driver TFT and a second driver TFT, which alternately drive the light emitting unit. This segmentation distributes the operating time and reduces the cumulative threshold voltage drift in each individual driver TFT, thereby improving brightness stability while maintaining reasonable structural complexity.
2Device complexity
If the driver TFT operates continuously, then the device structure is simple, but the threshold voltage drift increases due to long-term operation
Solution Approach 1:
The driving mechanism uses periodic action by alternately switching between the first driver TFT and the second driver TFT. Each driver TFT operates for a limited duration before being switched off and allowed to recover, preventing continuous operation and reducing threshold voltage drift accumulation.
Solution Approach 2:
Before a driver TFT is switched on to drive the light emitting unit, the other driver TFT is switched off and its gate electrode is connected to a reference potential through a capacitor in advance. This preliminary action prepares the switching transition and ensures proper voltage compensation before the active driver begins operation.
3Device complexity
If threshold voltage drift is not compensated, then the circuit operation is simple, but the output current of driver TFT changes abnormally affecting OLED luminous intensity
Solution Approach 1:
The circuit implements feedback through capacitors connected between the gate electrodes of the driver TFTs and reference potential nodes. When one driver TFT is switched off, its gate voltage is fed back to a reference potential through the capacitor, compensating for threshold voltage drift and stabilizing the output current for the next driving cycle.
Solution Approach 2:
The voltage compensation mechanism changes the gate voltage parameter of the inactive driver TFT by connecting it to a reference potential through a capacitor. This parameter change compensates for threshold voltage drift and ensures stable output current characteristics when the driver TFT is重新 activated.
Data Source
AI summary
The present disclosure relates to a pixel driving circuit and a driving method for the same and a display panel. The pixel driving circuit includes a driver unit, a circuit switching unit, and a storage capacitor unit. The driver unit includes a first sub-driver unit and a second sub-driver unit. The circuit switching unit has a first switching unit and a second switching unit. Two terminals of the first switching unit are electrically connected to a first terminal of the light emitting unit and the first sub-driver unit, respectively, two terminals of the second switching unit are electrically connected to the light emitting unit and the second sub-driver unit, respectively, and the circuit switching unit is configured to switch conductive states of the first switching unit and the second switching unit.