Pixel Driving Circuit Compensation for TFT Threshold Voltage and Leakage Current
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Solution Overview
Problem
Display unevenness and flicker in display devices due to inconsistencies in threshold voltages and leakage currents in Thin Film Transistor (TFT) manufacturing processes.
Innovation Solution
A pixel driving circuit with a first compensation sub-circuit to adjust the anode voltage based on reference and data signals, and a second compensation sub-circuit to manage leakage currents, utilizing a specific configuration of transistors and capacitors to eliminate the influence of threshold voltages and leakage currents on the operating current of the pixel unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If TFT manufacturing process is used, then display devices can be produced with mature technology, but threshold voltage inconsistencies occur at various positions resulting in display unevenness
Solution Approach 1:
The patent applies preliminary action by introducing a compensation circuit that pre-adjusts the threshold voltage of TFTs before they are used in the final display circuit. The compensation circuit measures and compensates for threshold voltage variations in advance, ensuring consistent display performance across all pixel positions without requiring perfect manufacturing precision.
Solution Approach 2:
The patent implements feedback by using a compensation circuit that continuously monitors and adjusts for threshold voltage variations in TFTs. The circuit measures the actual threshold voltage of each TFT and applies compensatory signals to maintain uniform display characteristics, creating a closed-loop system that corrects manufacturing variations in real-time.
2Reliability
If TFT is used in display device, then the device can operate, but leakage currents occur in the TFT causing flicker in the display
Solution Approach 1:
The patent converts the harmful leakage current into a beneficial compensation signal. The compensation circuit intentionally generates a compensatory current that mirrors and counteracts the leakage current, transforming the harmful effect into a useful correction mechanism that eliminates flicker while maintaining device operation.
Solution Approach 2:
The patent introduces a compensation circuit as an intermediary element between the TFT and the display output. This intermediary circuit measures and compensates for leakage currents, acting as a buffer that isolates the harmful effects of TFT leakage from the final display signal, thereby eliminating flicker while preserving reliable device operation.
3Manufacturing precision
If compensation circuits are added to correct threshold voltage and leakage current, then display unevenness and flicker are reduced, but the circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the compensation function into distinct modular circuits: a threshold voltage compensation circuit and a leakage current compensation circuit. Each module handles a specific compensation task independently, making the overall complex system manageable through functional segmentation and allowing for targeted optimization of each subsystem.
Data Source
AI summary
A pixel driving circuit and a display device are provided. The pixel driving circuit is configured to drive a pixel unit to operate, and the pixel driving circuit includes a first compensation sub-circuit and a second compensation sub-circuit. The first compensation sub-circuit is configured to compensate a voltage of an anode of the pixel unit according to a reference signal and a data signal, and the second compensation sub-circuit is configured to compensate a leakage current generated by at least one transistor in the first compensation sub-circuit according to a leakage current generated by the second compensation sub-circuit.