Voltage Compensating Circuit for LCD Gate Scan Driving
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Solution Overview
Problem
In active matrix liquid crystal displays, temperature variations in the gate scan driving circuit lead to non-uniform grayscale and decreased display quality due to inaccurate temperature sensing, causing overcompensation or undercompensation of the gate scan driving voltage.
Innovation Solution
A voltage compensating circuit and method that includes a thin film transistor circuit, a controlling circuit with a power management chip, and a scan driving chip, which detects voltage variations and adjusts the gate driving signal high level in real time based on temperature changes, using resistors to calculate the necessary voltage adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external temperature sensor is used to monitor substrate temperature and modulate gate scan driving voltage, then temperature compensation function is provided, but the detected substrate temperature is inconsistent with actual TFT temperature, causing overcompensation or undercompensation
Solution Approach 1:
The patent introduces a test transistor as an intermediary element that experiences the same temperature conditions as the GOA circuit. By measuring the threshold voltage of this test transistor, the system obtains an accurate indirect measurement of the actual TFT temperature without requiring direct temperature sensing of the GOA circuit itself.
Solution Approach 2:
The patent replaces the external temperature sensor (thermal field measurement) with an electrical measurement system that uses transistor threshold voltage characteristics. This substitution allows direct electrical detection of temperature effects on the GOA circuit transistors, providing more accurate compensation data.
2Ease of manufacture
If GOA technology is used to manufacture gate scan driving circuit on substrate, then product cost and panel frame are decreased, but TFT temperature varies easily with ambient temperature, causing electron mobility drift and grayscale non-uniformity
Solution Approach 1:
The patent implements a feedback mechanism where the measured threshold voltage of the test transistor is continuously used to adjust and compensate the gate scan driving voltage. This closed-loop feedback ensures that temperature-induced variations in electron mobility are dynamically corrected, maintaining stable display performance despite temperature changes.
Solution Approach 2:
The patent changes the operating parameter (gate scan driving voltage) based on measured temperature effects. By dynamically adjusting the driving voltage according to the test transistor's threshold voltage, the system compensates for temperature-induced parameter drift in the GOA circuit transistors.
Data Source
AI summary
A voltage compensating circuit and a method thereof are disclosed. The circuit includes a first TFT circuit, a controlling circuit and a scan driving chip. An output terminal of the power management chip of the controlling circuit connects to a first terminal of the third resistor, a second terminal of the third resistor connects to a first terminal of the first resistor, the second terminal of the third resistor connects to a feedback terminal of the chip, the feedback terminal of the chip connects to a first terminal of the second resistor, a second terminal of the second resistor connects to a ground, a second terminal of the first resistor connects to an input terminal of the scan driving chip. A source of the first TFT connects to a first input terminal of the chip, a second input terminal of the chip connects to the first gate driving signal.