LCD Driving Circuit With Dynamic Slew-Rate Control
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Solution Overview
Problem
Existing driving methods for liquid crystal molecules, such as fixed and variable common voltage methods, result in significant power consumption due to the need for large voltage ranges and long stabilization times, which restrict application range and increase energy usage.
Innovation Solution
A driving apparatus and method that dynamically adjusts the stabilization time of the output voltage by using a digital to analog converter and signal amplifier, which dynamically changes the driving capability based on digital data bits, allowing for optimal balance between transition time and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output voltage of the operational amplifier varies over a large voltage range to drive liquid crystal molecules from positive polarity to negative polarity, then the liquid crystal molecules can be driven in both directions, but the stabilization time increases and power consumption increases
Solution Approach 1:
The patent applies dynamics by making the common voltage variable rather than fixed. The common voltage is dynamically adjusted based on the polarity of the input signal, allowing the operational amplifier to operate with smaller voltage swings. This dynamic adjustment resolves the contradiction by adapting the voltage range to the actual driving needs, reducing power consumption while maintaining full driving capability.
Solution Approach 2:
The patent changes the parameter of common voltage from a fixed value to a variable value that depends on signal polarity. By changing this parameter dynamically, the system achieves efficient voltage utilization, where the operational amplifier only needs to provide voltage differences relative to the dynamically adjusted common voltage, thereby reducing overall power consumption while maintaining adaptability.
2Adaptability or versatility
If the output voltage of the operational amplifier varies over a large voltage range, then the liquid crystal molecules can be driven effectively, but the transition time increases
Solution Approach 1:
The dynamic adjustment of common voltage based on polarity allows the system to achieve faster transitions. When the polarity changes, the common voltage shifts accordingly, so the operational amplifier only needs to bridge the voltage gap to the new polarity level rather than swinging through the entire voltage range, significantly reducing stabilization time.
Solution Approach 2:
The system performs preliminary action by pre-adjusting the common voltage to the appropriate level based on the incoming signal polarity. This preparation reduces the actual voltage transition time required when the signal changes, as the operational amplifier starts from a more favorable voltage state rather than from a fixed common voltage.
3Device complexity
If a fixed common voltage is used to drive liquid crystal molecules, then the circuit is simple, but the voltage range required is large leading to high power consumption
Solution Approach 1:
The patent introduces dynamic control of the common voltage through polarity detection and switching circuits. While this adds some complexity, the added components are relatively simple (comparators, switches, voltage sources) and enable significant power savings by reducing the voltage swing requirements of the operational amplifier, achieving an optimal balance between complexity and energy efficiency.
Data Source
AI summary
A driving apparatus and a driving method thereof are provided. The driving apparatus includes a digital to analog converter and a signal amplifier. The digital to analog converter is used for receiving a digital data and converting the digital data to an analog signal. The signal amplifier is coupled to the digital to analog converter. The signal amplifier is used for receiving the analog signal to generate a driving signal. The signal amplifier also dynamically changes the driving ability of the driving signal according to at least one bit of the digital data.