Scan Driving Circuit Signal Timing for Display Noise Reduction
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Solution Overview
Problem
Conventional flat display apparatuses experience current leakage due to signal coupling and current leakage effects, leading to erroneous displays with high-level ripple voltages during the blanking time, causing the gate and source voltages of driving transistors to be close, resulting in incorrect pixel voltage control.
Innovation Solution
A display apparatus with a scan driving circuit that includes stages of driving units with a shift control device, a driving device, and a release device, where the rising transition time of the second trigger signal overlaps the falling transition time of the first trigger signal, or the release device is controlled by a release signal to eliminate high-level noise during the blanking time, ensuring the voltage difference between the gate and source of the driving transistor remains below the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the clock signal CK2 transitions from lower level to higher level during blanking time, then the driving force is sufficient, but high-level ripple voltage is generated causing current leakage and erroneous display
Solution Approach 1:
The patent applies preliminary anti-action by using the clock signal CK1 to generate a counteracting signal before the harmful ripple occurs. The clock signal CK1 transitions are timed to create rippling effects that oppose and cancel the high-level ripple voltage generated by clock signal CK2 transitions during the blanking time period, thereby preventing the harmful effect before it can cause current leakage or display errors
Solution Approach 2:
The patent converts the harmful high-level ripple voltage into a beneficial effect by utilizing the signal coupling effect and current leakage path that were originally problematic. The clock signal CK1 is designed to create a controlled rippling effect through the same coupling mechanism, transforming the harmful ripple into a useful counteracting signal that eliminates the net ripple voltage during blanking time
2Ease of operation
If the gate and source voltages of driving transistor are close during blanking time, then the transistor is properly controlled, but current leakage occurs causing bright or dark lines
Solution Approach 1:
The patent prevents current leakage by applying preliminary anti-action through the clock signal CK1 transitions. These transitions create counteracting rippling effects that occur before the harmful current leakage can develop, thereby maintaining proper voltage control while preventing the conditions that lead to bright or dark line defects in the display
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively eliminates high-level noise during the blanking time, preventing current leakage and erroneous displays by maintaining the voltage difference below the threshold voltage, thus ensuring accurate pixel voltage control and preventing bright or dark lines.
Implementation Method 1
when the clock CK2 has a level transition (i.e. from a lower level to a higher lever or reversely), a rising or falling ripple (can be regarded as a noise) will be generated on the gate of the TFT due to the signal coupling effect
Implementation Method 2
when the clock signal CK2 is changed from a lower level to a higher level, a current leakage path will formed in the last driving component (e.g. TFT), resulting in a larger ripple
Data Source
AI summary
A scan driving circuit of a display apparatus is electrically connected to the display panel through a plurality of scan lines and includes a plurality of stages of driving unit. The driving unit comprises a shift control device outputting a control signal according to a starting signal and a driving device. The driving device outputs an output signal to the corresponding scan line according to the control signal, a first trigger signal and a second trigger signal. The output signal is used as the starting signal of the next stage of driving unit, and the rising transition time of the second trigger signal and the falling transition time of the first trigger signal have an overlap.