Overdriving Voltage Buffer for Faster LCD Source Driver Slew Rate
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Solution Overview
Problem
Conventional voltage buffers in LCD source drivers face challenges in quickly regulating output voltage due to large load capacitance, leading to a lower slew rate, which degrades LCD display quality as LCD dimensions increase.
Innovation Solution
A voltage buffer with an operational amplifier and an overdriving unit that compares input and output voltages to generate an overdriving voltage, enhancing the slew rate by varying the voltage difference between input and output, thereby improving the driving capability and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional voltage buffer with operational amplifier is used to drive LCD panel, then the circuit structure is simple, but the slew rate is low due to large load capacitance
Solution Approach 1:
The overdriving unit performs preliminary action by generating an overdriving voltage that exceeds the target voltage difference before the operational amplifier completes its regulation. This advance action compensates for the slow response caused by large load capacitance, enabling the output voltage to reach the target level faster and thereby improving the slew rate without significantly complicating the circuit structure.
2Adaptability or versatility
If the load capacitance increases with larger LCD dimensions, then the driving capability must be enhanced, but the conventional voltage buffer fails to quickly regulate output voltage
Solution Approach 1:
The invention changes the voltage parameter by generating an overdriving voltage that is higher than the normal input voltage. This parameter change creates a larger voltage difference across the operational amplifier, which accelerates the charging current through the load capacitance and reduces the voltage regulation time, thereby enabling the system to adapt to larger LCD dimensions without sacrificing response speed.
3Speed
If the overdriving voltage is greater than the input voltage to enhance slew rate, then the voltage regulation speed improves, but the circuit complexity increases
Solution Approach 1:
The overdriving unit acts as an intermediary component between the input voltage source and the operational amplifier. It generates the overdriving voltage by adding a compensation voltage to the input voltage, then feeds this enhanced voltage to the operational amplifier. This intermediary approach achieves faster voltage regulation speed while keeping the added circuit complexity minimal and modular.
Data Source
AI summary
A voltage buffer and the source driver thereof are disclosed. The above-mentioned voltage buffer includes an operational amplifier and an overdriving unit, wherein the operational amplifier outputs an output voltage. The overdriving unit is coupled between an input voltage and the operational amplifier for comparing the input voltage with the output voltage and outputting an overdriving voltage to the positive input terminal of the operational amplifier. Herein if the input voltage is greater than the output voltage, the overdriving voltage is greater than the input voltage; if the input voltage is less than the output voltage, the overdriving voltage is less than the input voltage; if the input voltage is equal to the output voltage, the overdriving voltage is equal to the input voltage.