OLED Pixel Back Gate Voltage for Leakage Current Compensation
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices using low-frequency driving technology face image quality deterioration due to distortion of stored data signals caused by leakage currents from transistors, leading to reduced display quality.
Innovation Solution
The OLED display device incorporates a pixel structure with a back gate electrode connected to the first transistor, which receives a delayed back gate voltage, and an adjustable swing width of the back gate voltage to compensate for voltage variations, thereby reducing leakage current effects and improving image quality during low-frequency driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-frequency driving technology is used to reduce power consumption, then power consumption is reduced, but image quality deteriorates due to leakage current distortion
Solution Approach 1:
The patent applies preliminary anti-action by introducing a back gate voltage before the data signal to preemptively counteract the leakage current effects. The back gate voltage is applied in advance during the emission period to prevent the gate node voltage from being distorted by leakage currents that would otherwise accumulate during low-frequency driving, thus maintaining image quality while enabling power reduction.
Solution Approach 2:
The patent changes the electrical parameters of the transistor by applying a back gate voltage to the back gate electrode. This parameter change modifies the transistor's threshold voltage and channel characteristics dynamically, allowing the device to compensate for leakage currents and maintain proper signal levels during low-frequency operation, thereby preserving image quality.
2Use of energy by moving object
If low-frequency driving is implemented, then power consumption decreases, but stored data signals become distorted by leakage currents
Solution Approach 1:
The back gate voltage is applied in advance during the emission period to preemptively counteract the leakage current effects on the stored data signal. This preliminary action prevents the signal distortion before it occurs, maintaining data integrity during low-frequency driving.
Solution Approach 2:
The patent implements a feedback mechanism where the back gate voltage is controlled based on the driving frequency and timing. The back gate driver receives control signals and adjusts the back gate voltage accordingly to compensate for leakage current effects, ensuring the stored data signal remains intact despite low-frequency operation.
3Reliability
If back gate voltage is applied to compensate for leakage current, then image quality improves, but device complexity increases
Solution Approach 1:
The patent segments the gate control into two independent parts: the main gate electrode receiving the data signal and the back gate electrode receiving the back gate voltage. This segmentation allows independent control of the two gates, enabling leakage current compensation without interfering with the primary data signal transmission, thus improving image quality while maintaining manageable complexity.
Solution Approach 2:
The back gate electrode structure serves multiple functions: it compensates for leakage current effects, maintains threshold voltage stability, and enables low-frequency driving operation. By making this single structural element multi-functional, the patent achieves image quality improvement without proportionally increasing overall device complexity.
Data Source
AI summary
A pixel includes a first capacitor including a first electrode connected to a wire of a first power supply voltage, and a second electrode connected to a gate node, a first transistor including a gate electrode connected to the gate node, and a back gate electrode connected to a back gate line, a second transistor which transmits a data signal to a source of the first transistor in response to a first gate signal, a third transistor which diode-connects the first transistor in response to the first gate signal, a fourth transistor which transmits an initialization voltage to the gate node in response to a second gate signal. The first transistor receives a back gate voltage, which is obtained by delaying the first gate signal by a ½ frame, through the back gate electrode in a low-frequency driving mode.