Gate Driving Circuit Reverse Bias for TFT Threshold Offset
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Solution Overview
Problem
The existing gate driving circuits in liquid crystal display panels face operational issues due to threshold voltage offset in thin-film transistors, leading to failure in normal operation and affecting the reliability of the gate driving circuit and display panel.
Innovation Solution
A gate driving circuit with an additional third pull-down unit that applies a reverse bias voltage to transistors during the vertical blanking interval, offsetting the positive threshold voltage and improving the operation reliability by pulling the driving voltage down to a second reference voltage lower than the first reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin-film transistors are used in the gate driving circuit, then the circuit can be manufactured on the array substrate (GOA circuit), but the threshold voltage of the transistors offsets with increased operation time, causing malfunction
Solution Approach 1:
The invention applies a reverse bias voltage to the gate and source electrodes before the transistor is needed for normal operation. This preliminary action compensates for the threshold voltage offset that will occur during operation, ensuring the transistor can still be properly activated when required. The compensation is performed in advance during a blanking interval, preventing the offset from causing malfunction.
Solution Approach 2:
The invention changes the voltage parameter by applying a reverse bias voltage (negative voltage) to the gate electrode relative to the source electrode. This voltage parameter change compensates for the threshold voltage offset by creating an opposing electrical effect that counteracts the positive threshold voltage drift, thereby restoring the transistor's switching characteristics.
2Reliability
If reverse bias voltage is applied to compensate threshold voltage offset, then transistor operation reliability is improved, but additional circuit components and control signals are required
Solution Approach 1:
The third pull-down unit is designed to serve multiple functions: it compensates for threshold voltage offset by applying reverse bias voltage, and it can be integrated with existing circuit structures. The same circuit elements are used for both normal signal processing and threshold compensation, reducing the need for entirely separate compensation circuits.
Solution Approach 2:
The gate driving circuit performs its own threshold voltage compensation using internally generated control signals and existing circuit components. The third pull-down unit utilizes the circuit's own voltage references and control logic to generate the necessary reverse bias voltage, eliminating the need for external compensation circuits or additional power supplies.
3Reliability
If third pull-down unit is added to apply reverse bias voltage, then threshold voltage offset is eliminated, but the circuit structure becomes more complex
Solution Approach 1:
The gate driving unit is segmented into distinct functional modules: actuating unit, energy storage unit, pull-up unit, first pull-down unit, second pull-down unit, and third pull-down unit. Each module has a specific function, and the third pull-down unit is added as a separate functional segment dedicated to threshold voltage compensation, making the overall structure more manageable and modular.
Data Source
AI summary
The present invention relates to a gate driving circuit, and a array substrate and a display using the same. The gate driving circuit comprises multiple-stage gate driving units, and each gate driving unit includes: an actuating unit configured to transmit an actuation signal; an energy storage unit configured to execute a charging process under the action of the actuation signal to output a driving voltage; a pull-up unit, a first pull-down unit, a second pull-down unit and a third pull-down unit operating under the action of the driving voltage, wherein a third pull-down unit pulls the driving voltage down to a second reference voltage to apply a reverse bias voltage to the gate-source and/or the gate-drain of transistors in the gate driving circuit, such that the threshold voltage of respective transistors under positive offset can offset reversely, thus effectively eliminating adverse effects of a threshold voltage offset phenomenon of the transistors on the gate driving circuit and improving the operation reliability of the gate driving circuit as well as the array substrate and the display panel thereof.