GOA Bootstrap Circuit for Gate Driving Pulse Width
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Solution Overview
Problem
High-resolution and high-frequency display panels face insufficient charging ability due to heavy capacitive loads on scan lines, leading to distortions and a high risk of wrong charging, as the falling time of gate pulse signals is large and the time interval between scan and data lines is lengthened.
Innovation Solution
A GOA device with cascaded GOA units, each comprising a pull-up control unit, a bootstrap unit, a pull-up unit, and a pull-down unit, which sequentially control the control node to reach high voltage levels, outputting a gate driving signal with increased pulse width to address the charging ability issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the time interval from scan line transition to data line transition is lengthened to reduce wrong charging risk, then the charging time is shortened, but the charging ability becomes insufficient
Solution Approach 1:
The patent introduces a bootstrap capacitor that is pre-charged during the display period to a voltage higher than the high voltage level. This preliminary charging action ensures that when the gate electrode needs charging, the bootstrap capacitor can immediately provide the necessary charge without waiting for the extended time interval, thus maintaining fast charging capability while preventing wrong charging through proper voltage level control
Solution Approach 2:
The patent changes the voltage parameter by using a bootstrap capacitor charged to a voltage higher than the normal high voltage level (VGH). This parameter change allows the capacitor to provide sufficient charging current to the gate electrode within the original time frame, eliminating the need to extend the time interval while still preventing wrong charging through appropriate voltage level management
2Productivity
If the falling time of gate pulse signal is reduced to improve charging speed, then the charging ability increases, but the risk of wrong charging increases
Solution Approach 1:
The bootstrap capacitor is pre-charged during the display period to a voltage higher than VGH, preparing the charge in advance. This preliminary action allows the gate electrode to be charged quickly when needed without extending the falling time, while the controlled discharge through the switching element ensures proper timing and prevents wrong charging
Solution Approach 2:
The bootstrap capacitor acts as an intermediary energy storage element between the power supply and the gate electrode. It stores energy at a higher voltage level and releases it quickly when needed, enabling fast charging while the switching element controls the discharge timing to prevent wrong charging, thus resolving the contradiction between charging speed and reliability
Data Source
AI summary
A GOA device and a gate driving circuit are provided. A pull-up control unit and a bootstrap unit sequentially control a control node of an Nth stage GOA unit to be pulled up to a first high voltage level and a second high voltage level. A pull-up unit outputs a gate driving signal according to a change of a voltage level of the control node and a stage transfer signal of the Nth stage GOA unit. As such, a pulse width of the gate driving signal is increased, and the problem that the charging ability is not sufficient can be solved.