OLED Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The uniformity of display brightness in OLED panels is affected by the variability and drifting of threshold voltage in driving transistors, leading to non-uniform driving currents and brightness across the panel, exacerbated by voltage drops along the driving voltage line.
Innovation Solution
An OLED pixel driving circuit comprising an electroluminescent element, a switching unit, a storage unit, a compensation unit, a driving transistor, a reset unit, and a partition unit, where the compensation unit prestores and compensates for the threshold voltage, and the reset unit resets the gate electrode, ensuring uniformity and stability of the driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional 2T1C pixel unit driving circuit is used, then the device complexity is low, but the display brightness uniformity deteriorates due to threshold voltage variability and drifting
Solution Approach 1:
The compensation unit prestores the threshold voltage value in the storage unit before the driving transistor operates. By performing the threshold voltage compensation in advance, the circuit ensures that the data signal is adjusted according to the actual threshold voltage, thereby maintaining display brightness uniformity without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The pixel unit driving circuit is segmented into distinct functional modules: a switching unit for signal control, a storage unit for threshold voltage preservation, a compensation unit for threshold voltage compensation, and a driving transistor for current control. This segmentation allows each module to perform its specific function independently, improving overall circuit performance and brightness uniformity.
2Power
If the driving voltage Vdd is transmitted across the OLED display panel, then the driving function is achieved, but voltage drops (IR Drop) occur causing display brightness non-uniformity
Solution Approach 1:
The compensation unit provides localized threshold voltage compensation to each pixel unit independently. By measuring and storing the specific threshold voltage of each driving transistor in its local storage unit, the circuit compensates for variations caused by IR Drop and other factors on a per-pixel basis, ensuring uniform display brightness across the entire panel.
3Duration of action of stationary object
If the threshold voltage Vth of the driving transistor drifts over time, then the driving function continues, but the driving current becomes non-uniform influencing display effect
Solution Approach 1:
The compensation unit continuously monitors the threshold voltage of the driving transistor and feeds back the threshold voltage value to the storage unit for updates. This feedback mechanism ensures that any drift in threshold voltage over time is detected and compensated, maintaining driving current uniformity and display quality throughout the transistor's operational lifetime.
Solution Approach 2:
The compensation unit performs threshold voltage measurement and compensation in advance before the driving transistor undergoes significant drift. By establishing the baseline threshold voltage early in the transistor's operation, the circuit can maintain accurate compensation throughout its operational duration.
Data Source
AI summary
The present disclosure provides a display device, an OLED pixel driving circuit and a driving method therefore. The OLED pixel driving circuit includes: an electroluminescent element, a switching unit, a storage unit, a compensation unit, a driving transistor, a reset unit and a partition unit; wherein, the switching unit is connected with a data signal and is connected with the storage unit; the compensation unit is connected with the storage unit; the storage unit is connected with a gate electrode of the driving transistor; a source electrode of the driving transistor is connected with a driving voltage, a drain electrode thereof is connected with the compensation unit; the partition unit is connected with the drain electrode and is connected with the electroluminescent element; the reset unit is connected with a reset signal and is connected with the gate electrode.