Gate Driving Circuit Negative Voltage Control for LCD TFT Turn-Off
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Solution Overview
Problem
Conventional liquid crystal display (LCD) technologies face challenges in ensuring proper turn-off capability of thin film transistors (TFTs), leading to potential malfunctions due to inadequate voltage control.
Innovation Solution
A gate driving circuit is designed with a shift register circuit and a level transition circuit that generates clock signals, selection signals, and negative voltage reference signals, where the negative voltage reference signals have a larger value than the clock or selection signals, ensuring better TFT turn-off capability by differentiating and maximizing negative voltage inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional level transition circuit is used to generate clock signals and selection signals for shift register circuit, then the circuit structure is simple, but the TFTs cannot be turned off normally due to insufficient negative voltage
Solution Approach 1:
The level transition circuit is divided into multiple independent modules: first level transition module for generating first clock signal, second level transition module for generating second clock signal, third level transition module for generating selection signal, and fourth level transition module for generating negative voltage reference signal. Each module operates independently to provide precise voltage control for different circuit components, ensuring reliable TFT turn-off while maintaining modular simplicity.
Solution Approach 2:
The circuit generates multiple voltage levels with different negative voltage values: first clock signal with first negative voltage value, second clock signal with second negative voltage value, selection signal with third negative voltage value, and negative voltage reference signal with fourth negative voltage value. By changing voltage parameters across different signals, the patent ensures that the negative voltage reference signal provides sufficient voltage to turn off TFTs reliably without requiring complex additional circuitry.
2Reliability
If single negative voltage input is used in level transition circuit, then the circuit is simple, but it cannot provide differentiated voltage levels needed for proper TFT control
Solution Approach 1:
The level transition circuit includes four separate input ports: first input port for first negative voltage input signal, second input port for second negative voltage input signal, third input port for third negative voltage input signal, and fourth input port for fourth negative voltage input signal. Each input port receives a different negative voltage signal, allowing the circuit to generate differentiated voltage levels for precise TFT control while keeping each input stage simple and independent.
3Reliability
If negative voltage reference signal has same voltage level as clock signals, then the circuit design is uniform, but TFTs cannot be turned off properly
Solution Approach 1:
The patent establishes a hierarchical voltage level structure where the negative voltage reference signal has a fourth negative voltage value that is greater than the first, second, and third negative voltage values of the clock and selection signals. This parameter differentiation ensures that the negative voltage reference signal provides sufficient voltage level to turn off TFTs reliably, while the uniform circuit design maintains simplicity through consistent module architecture.
Data Source
AI summary
A LCD and the gate driving circuit thereof are disclosed. The gate driving circuit includes a shift register circuit and a shift register circuit and a level transition circuit connected with the shift register circuit. The level transition circuit generates clock signals, selection signals, and negative voltage reference signals for the shift register circuit. The clock signals, the selection signals, and the negative voltage reference signals are configured for driving the shift register circuit. A negative voltage value of the negative voltage reference signals (VSS) is larger than the negative voltage value of one of the clock signals or the selection signals. In this way, the TFTs of the shift register circuit own better turn-off capability so as to avoid malfunction.