Pixel Driving Circuit for TFT Threshold and IR-Drop Compensation
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Solution Overview
Problem
The active matrix LED display technology faces issues with threshold voltage shift in driving TFTs over time and current variations due to IR-drop and LED unevenness, leading to Mura issues and reduced stability.
Innovation Solution
A pixel driving circuit comprising a first TFT, a third TFT, a fourth TFT, a first capacitor, and a light emitting diode, where the threshold voltage of the first TFT is detected through the fourth TFT, and the data voltage is written into the first node using the third TFT, with the first capacitor and light emitting diode connected in parallel to stabilize voltage and compensate for IR-drop and LED unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If active matrix driving mechanism is used to avoid huge instant current, then power consumption is reduced, but threshold voltage shift and current variations occur over time leading to Mura issues
Solution Approach 1:
The patent performs threshold voltage detection and compensation in advance before normal display operation. The detection TFT measures the threshold voltage of the driving TFT during an initialization phase, and compensation values are pre-calculated and stored. This preliminary action ensures that even though threshold voltage shifts occur over time, the display maintains uniformity because the compensation has already been applied in advance.
Solution Approach 2:
The patent implements a feedback mechanism where the threshold voltage of the driving TFT is continuously monitored through the detection TFT, and the measured values are used to adjust and compensate for current variations. The system feeds back the threshold voltage information and uses it to correct the data signals, ensuring that display uniformity is maintained despite threshold voltage drift over time.
2Duration of action of stationary object
If driving TFT works for long period, then display duration is extended, but threshold voltage shifts reducing LED current
Solution Approach 1:
The patent performs threshold voltage detection and compensation in advance before normal display operation. The detection TFT measures the threshold voltage of the driving TFT during an initialization phase, and compensation values are pre-calculated and stored. This preliminary action ensures that even though threshold voltage shifts occur over time, the display maintains uniformity because the compensation has already been applied in advance.
Solution Approach 2:
The patent dynamically adjusts the data signal parameters based on the detected threshold voltage of the driving TFT. By changing the voltage or current parameters of the data signal in response to measured threshold voltage shifts, the system compensates for the drift and maintains stable LED current over extended display durations.
3Illumination intensity
If signal line current increases, then LED brightness is improved, but IR-drop in signal line causes current variations
Solution Approach 1:
The patent implements a feedback mechanism where the threshold voltage of the driving TFT is continuously monitored through the detection TFT, and the measured values are used to adjust and compensate for current variations. The system feeds back the threshold voltage information and uses it to correct the data signals, ensuring that display uniformity is maintained despite threshold voltage drift over time.
Solution Approach 2:
The patent dynamically adjusts the data signal parameters based on the detected threshold voltage of the driving TFT. By changing the voltage or current parameters of the data signal in response to measured threshold voltage shifts, the system compensates for the drift and maintains stable LED current over extended display durations.
Data Source
AI summary
A pixel driving circuit, a pixel driving method and a display device are proposed. In a threshold detecting phase, a threshold voltage of a first TFT is detected. In a data write-in phase, data voltage is written into the first node to alleviate the coupling effect of the voltage variation of the first node on the third node such that the voltage of the third node could be stabilized. In a light emitting phase, the first capacitor and the light emitting diode work together to compensate for the threshold voltage, IR drop in the signal and the unevenness of the LEDs.