LCD Driving Circuit Charge Sharing for Power Reduction
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Solution Overview
Problem
Existing LCD driving circuits consume high power when continuously adjusting voltages to prevent damage to liquid crystal molecules by alternating their polarity, which is necessary for maintaining image stability over time.
Innovation Solution
A driving circuit utilizing charge sharing and pre-charging techniques to reduce power consumption by transferring charge between the display electrode and AC voltage output terminal, allowing the AC voltage to be raised efficiently without significant power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving circuit continuously adjusts the voltage of the common electrode to alternate the polarity of liquid crystal molecules, then the liquid crystal molecules are protected from damage and can maintain their rotational characteristics, but the power consumption of the driving circuit increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging the display electrode to the same voltage level as the AC voltage output terminal before charge sharing occurs. This pre-charging ensures that when the charge sharing switch is activated, the voltage difference between the display electrode and AC voltage output terminal is minimized, thereby reducing the power consumption required for polarity switching of the common electrode while maintaining the reliability of liquid crystal molecule protection
2Stability of the object's composition
If a large coupling capacitor is used to maintain voltage difference across the common electrode, then the voltage stability is improved, but the power consumption increases due to the large capacitor size
Solution Approach 1:
The patent introduces the display electrode as an intermediary element in the charge sharing process. By using the display electrode to share charge with the AC voltage output terminal, the system can adjust the voltage across the coupling capacitor without requiring the capacitor to continuously charge and discharge large currents. This intermediary mechanism maintains voltage stability across the common electrode while significantly reducing the power consumption associated with capacitor operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution significantly reduces power consumption during polarity changes of the common electrode, outperforming traditional methods by minimizing energy required for voltage adjustments, thereby extending device usability and reducing carbon emissions.
Implementation Method 1
The coupling capacitor CAC is designed as much larger than the effective loading formed by the common electrode 34. Hence, even if the voltage of the output terminal A of the AC voltage generating unit 12 changes, the voltage difference across the coupling capacitor CAC roughly keeps unchanged.
Implementation Method 2
A driving circuit utilizing charge sharing and pre-charging techniques to reduce power consumption by transferring charge between the display electrode and AC voltage output terminal
Data Source
AI summary
A driving circuit for an LCD system is provided. The LCD system includes a common electrode, a display electrode, and a capacitor. An AC voltage output terminal of the driving circuit is coupled to the common electrode via the capacitor. The display electrode and a charging/discharging unit in the driving circuit are respectively coupled to the AC voltage output terminal through a switch. According to requirements to change the electrical polarity of the common electrode, a control unit in the driving circuit turns on/off the two switches respectively so as to charge or discharge the AC voltage output terminal.