TFT Gate Driving Method for LCD Threshold Voltage Stability
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Solution Overview
Problem
In liquid crystal displays (LCDs), reducing the refreshing rate leads to threshold voltage shifting of transistors, causing abnormal operation, particularly when gate voltages are applied for extended periods, which affects display quality and power consumption.
Innovation Solution
A driving method and device that adjust gate driving signals to cut off specific transistors and generate compensation waveforms between data updating periods, preventing prolonged exposure to gate low voltage and mitigating threshold voltage shifts by using a control module and driving module to manage gate driving signals based on ambient light and temperature sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the refreshing rate of the LCD is reduced to ultra-low frequency to save power consumption, then power consumption is reduced, but the threshold voltage of the TFT gradually decreases causing abnormal operation
Solution Approach 1:
The patent applies periodic action by alternating the polarity of gate voltages applied to TFTs at different pixel locations. During ultra-low frequency refreshing, pixels are divided into groups that receive positive and negative gate voltages in alternating periods. This periodic polarity switching prevents charge accumulation at the semiconductor interface, thereby mitigating threshold voltage shifting while maintaining ultra-low power consumption operation
Solution Approach 2:
The patent changes the parameter of gate voltage polarity to resolve the threshold voltage instability issue. By dynamically switching between positive and negative gate voltage polarities for different pixel groups, the system prevents the gradual decrease of threshold voltage that occurs under continuous ultra-low frequency operation, thus maintaining reliable display performance while saving power
2Duration of action of stationary object
If the gate voltage is applied for a long period of time to maintain display at ultra-low refreshing rate, then display continuity is maintained, but threshold voltage shifting occurs
Solution Approach 1:
The patent implements periodic polarity reversal of gate voltages applied to TFTs. Pixels are organized into multiple groups that receive gate voltages with alternating polarities over time. This periodic action ensures that no single group is exposed to the same polarity for extended periods, preventing threshold voltage drift while maintaining continuous display operation at ultra-low refreshing rates
3Reliability
If threshold voltage shifting is prevented by maintaining normal refreshing rate, then threshold voltage stability is maintained, but power consumption increases
Solution Approach 1:
The patent enables ultra-low frequency refreshing operation by implementing periodic polarity switching of gate voltages. This allows the display to operate at extremely low refreshing rates (e.g., 1 Hz or lower) while preventing threshold voltage shifting through the alternating voltage application, thereby achieving both low power consumption and threshold voltage stability simultaneously
Solution Approach 2:
The patent changes the gate voltage parameter from static to dynamically alternating polarity. By switching between positive and negative voltage polarities for different pixel groups over time, the system prevents threshold voltage accumulation effects that would normally require higher refreshing rates, thus enabling ultra-low power operation with maintained voltage stability
Data Source
AI summary
A driving method for a display device with a plurality of pixels, wherein each pixel includes a plurality of transistors connected in series, includes adjusting a first gate driving signal of a first transistor among the plurality of transistors to make the first transistor cut-off and generating compensation waveform on at least one second gate driving signal of at least one second transistor among the plurality of transistors within a compensation interval of a plurality of intervals between every two contiguous data updating periods among a plurality data updating periods; wherein the plurality of transistors of each pixel are conducted in a specific period within the plurality of data updating periods, to update a data voltage of each pixel.