Adaptive Voltage Source for Shift Register Threshold Drift
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Solution Overview
Problem
Existing GOA circuits for high-performance TV panels face reliability issues due to threshold voltage shift of TFTs under constant gate biasing, leading to rapid degradation and shortened circuit life, as the constant biasing method results in excessive gate over-drive voltage, accelerating threshold voltage shift and reducing the circuit's operational lifespan.
Innovation Solution
An adaptive voltage source and shift register unit are introduced, featuring a sensing module that monitors threshold voltage shifts and adjusts the supply voltage accordingly, using a reference resistor forming module cascaded between the voltage source and low-level holding module to maintain optimal voltage levels and slow down threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If constant gate biasing method is used for low level holding TFTs, then the circuit structure is simple and easy to manufacture, but the threshold voltage shift of TFT is large and the circuit life is shortened
Solution Approach 1:
The patent applies dynamics principle by transitioning from constant gate biasing to adaptive dynamic biasing. The gate voltage is dynamically adjusted based on the threshold voltage shift of TFTs over time and operating conditions. The bias voltage switches between different levels (e.g., first bias voltage and second bias voltage) to optimize performance during different operational phases, thereby reducing threshold voltage shift while maintaining circuit functionality.
Solution Approach 2:
The patent implements parameter changes by modifying the gate bias voltage parameter. Instead of using a fixed constant voltage, the system changes the bias voltage parameter adaptively based on threshold voltage shift detection. This includes adjusting voltage magnitude and timing parameters to compensate for TFT degradation, thereby extending circuit life without complicating the manufacturing process.
2Reliability
If high gate over-drive voltage is applied to low level holding TFTs, then the conducting ability is improved, but the threshold voltage shift accelerates and the circuit lifetime is reduced
Solution Approach 1:
The patent applies periodic action by implementing time-dependent voltage switching. The gate bias voltage is periodically adjusted between different levels based on the operational phase. During active conduction periods, higher over-drive voltage is applied to maintain conducting ability, while during holding periods, lower voltage is used to minimize threshold voltage shift accumulation, thereby extending circuit lifetime.
Solution Approach 2:
The system dynamically adjusts the gate over-drive voltage based on real-time threshold voltage shift detection. The bias voltage parameter is changed adaptively to maintain optimal conducting ability while minimizing degradation. This dynamic adjustment ensures high conducting ability when needed while reducing stress on TFTs during non-critical periods.
3Stability of the object's composition
If constant high voltage is applied to low level holding devices, then the low level holding is maintained, but the threshold voltage increases over time and the circuit starts to malfunction
Solution Approach 1:
The patent implements feedback mechanism by monitoring the threshold voltage shift of TFTs and using this information to adjust the gate bias voltage. The system detects changes in TFT characteristics and feeds this information back to the voltage control circuit, which then adjusts the bias voltage accordingly to maintain stable low level holding while preventing threshold voltage from increasing to malfunction levels.
Solution Approach 2:
The system changes the gate bias voltage parameter adaptively based on detected threshold voltage shifts. When threshold voltage increases are detected, the bias voltage is adjusted to compensate and maintain stable low level holding. This parameter adjustment prevents the circuit from malfunctioning while maintaining the stability of low level holding function.
Data Source
AI summary
An adaptive voltage source, comprising a signal output end, and a reference resistance forming circuit and a sensing module connected in series between a voltage source and a low power level; the sensing module comprises a sensing end coupled to a transistor to be sensed to sense the threshold voltage drift of the transistor to be sensed in a device circuit; the equivalent resistance of the sensing module increases with the increase of the sensed threshold voltage drift; and the signal output end is coupled to a first node coupled to the reference resistance forming circuit and the sensing module, and is used to output adaptive voltage. The output adaptive voltage is adjusted via the threshold voltage drift sensed by the sensing module. Based on the circuit, also disclosed are a shift register and unit thereof, and display.