AMOLED Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The AMOLED pixel driving circuit faces instability due to threshold voltage drift in the drive thin film transistor, leading to unstable luminescence, and existing compensation methods shorten the charge time of the data signal.
Innovation Solution
An AMOLED pixel driving circuit with a specific configuration of thin film transistors and capacitors, where the restore signal controls the source voltage of the mirror thin film transistor to equalize the gate-source voltages with the drive thin film transistor, allowing for extended charge time and normal panel driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data signal is recovered to the ground to pull down the source voltage of the mirror thin film transistor, then the gate-source voltages of the mirror and drive thin film transistors are equalized, but the charge time of the data signal is shortened
Solution Approach 1:
The patent applies preliminary action by pre-charging the first node D to a high voltage level before the data signal charging phase. This preliminary voltage setup allows the mirror thin film transistor to achieve proper gate-source voltage equalization without requiring the data signal to be recovered to ground, thereby extending the data signal charge time while maintaining threshold voltage compensation accuracy
Solution Approach 2:
Instead of recovering the data signal to ground to achieve voltage equalization (conventional approach), the patent inverts the approach by controlling the mirror thin film transistor's source voltage through a dedicated restore switch. This inverted method equalizes the gate-source voltages of the mirror and drive transistors without shortening the data signal charge time
2Reliability
If the threshold voltage drift of the drive thin film transistor is compensated using the mirror thin film transistor, then the luminescence stability is improved, but the circuit complexity increases
Solution Approach 1:
The patent uses the copying principle by creating a mirror thin film transistor that replicates the electrical characteristics and stress conditions of the drive thin film transistor. This mirror transistor serves as a copy that experiences identical threshold voltage drift, enabling accurate compensation by comparing and equalizing their gate-source voltages without requiring complex compensation circuits
Solution Approach 2:
The mirror thin film transistor serves multiple functions: it acts as both a compensation element for threshold voltage drift and a reference element for voltage equalization. By integrating these functions into a single transistor component, the circuit achieves luminescence stability improvement without proportionally increasing circuit complexity
Data Source
AI summary
The present invention provides an AMOLED pixel driving circuit and a pixel driving method. The AMOLED pixel driving circuit comprises: a first, a second, a third, a fourth, a fifth, a sixth thin film transistors (M1, M2, M3, M4, M5, M6), a first, a second capacitors (C1, C2) and an organic light emitting diode (D1); wherein the third thin film transistor (M3) is a mirror thin film transistor, and the fourth thin film transistor (M4) is a drive thin film transistor, and the second thin film transistor (M2) is located between the third and the fourth thin film transistors (M3, M4). By controlling activation and deactivation of the second thin film transistor (M2) according to time sequence with the restore signal (Restore), the source voltage of the third thin film transistor (M3) is controlled to be pulled down to the earth voltage level (GND) in the restore stage to ensure that ensure that the gate-source voltages of the third, the fourth thin film transistors (M3, M4) are equal. Meanwhile, the data signal can be efficiently simplified to increase the charge time of the data signal.