Gate Driver On Array Circuit Stability via Bootstrap Voltage Control
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Solution Overview
Problem
The gate driver on array (GOA) circuits, particularly those using metal oxide semiconductor thin film transistors, frequently experience malfunction due to negative threshold voltages, leading to instability and performance issues.
Innovation Solution
A GOA circuit design comprising multiple stages of GOA units connected in cascade, each with a pull-up controlling module, pull-up module, transmission module, bootstrap module, and pull-down holding module, utilizing high-frequency and low-frequency clock signals to manage voltage levels and prevent malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal oxide semiconductor thin film transistors are used to fabricate GOA circuits, then the complexity and scale of the circuit are reduced and productivity is improved, but the threshold voltages become negative values frequently leading to circuit malfunction
Solution Approach 1:
The patent applies preliminary action by pre-charging the bootstrap capacitor during specific time periods before the transistor switches on. This ensures that when the transistor turns on, the capacitor already has the necessary charge to maintain proper voltage levels, preventing negative threshold voltage conditions. The capacitor is charged in advance through controlled switching of transistors during the off-period, ensuring readiness for the next switching cycle.
Solution Approach 2:
The patent implements periodic action through the cyclic charging and discharging of the bootstrap capacitor. The capacitor is charged during the off-period of the transistor and discharged during the on-period, creating a periodic charge transfer mechanism. This periodic operation ensures that voltage levels are continuously maintained within appropriate ranges, preventing cumulative voltage drift that would cause negative threshold voltages.
2Device complexity
If metal oxide semiconductor thin film transistors are used to fabricate GOA circuits, then the number of power supply is reduced, but the threshold voltages become negative values frequently leading to circuit malfunction
Solution Approach 1:
The patent applies self-service by using the circuit's own internal nodes to charge the bootstrap capacitor. Specifically, the voltage at the drain node of the transistor is used to charge the capacitor when the transistor is off, and this stored charge is then used to maintain the gate-source voltage when the transistor is on. This self-charging mechanism eliminates the need for external power supply circuits while ensuring proper voltage levels are maintained.
Solution Approach 2:
The patent changes the voltage parameters dynamically by utilizing different voltage levels at different time periods. The bootstrap capacitor stores voltage information from one switching cycle and applies it in the next cycle, effectively changing the voltage parameter timing and magnitude to prevent negative threshold voltages. The gate-source voltage is modulated through the capacitor's charge/discharge cycles rather than using a fixed power supply.
3Device complexity
If conventional GOA circuit design is used, then the structure is simpler, but the circuit malfunctions due to negative threshold voltages
Solution Approach 1:
The patent introduces the bootstrap capacitor as an intermediary element between the power supply and the transistor gate. This capacitor acts as a voltage buffer that mediates the voltage transfer, ensuring that the gate receives appropriate voltage levels even when the transistor is switching. The intermediary capacitor isolates the transistor from direct voltage fluctuations and prevents negative threshold voltage conditions.
Solution Approach 2:
The patent applies preliminary action by pre-charging the bootstrap capacitor during specific time periods before the transistor switches on. This ensures that when the transistor turns on, the capacitor already has the necessary charge to maintain proper voltage levels, preventing negative threshold voltage conditions. The capacitor is charged in advance through controlled switching of transistors during the off-period, ensuring readiness for the next switching cycle.
Data Source
AI summary
A GOA circuit uses the high voltage level of a high-frequency clock signal for pulling up the voltage level of a second node during the period of outputting a scan signal, to make the voltage level of the second node be larger than the voltage level of a stage transmitting signal of the (n−4)th stage of GOA unit, thereby to keep the pull-up controlling module in off state during the period of outputting the scan signal, for promoting the stability of the GOA circuit and preventing the GOA circuit from malfunction.