LCD Driving Circuit Parasitic Capacitance Compensation
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Solution Overview
Problem
The existing liquid crystal display (LCD) driving circuits face issues with parasitic capacitance causing feed-through effects, which degrade display quality and increase power consumption due to the need for additional circuits to modulate common voltage.
Innovation Solution
A driving control circuit with a first voltage switch unit and a selection unit, coupled to scan lines and pixel units, transmits specific output voltages based on control signals to mitigate parasitic capacitance effects, reducing power consumption and circuit costs by maintaining a constant common voltage level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC common voltage is used to modulate the storage capacitor common voltage terminal, then the feed-through effect is mitigated and display quality is improved, but the device complexity increases due to additional driving circuits
Solution Approach 1:
The patent applies dynamics by transitioning from a static DC common voltage to a dynamic AC modulated common voltage. The common voltage terminal of the storage capacitor is connected to an AC voltage source that can be switched on or off based on scan signal timing. This dynamic modulation allows the system to mitigate the feed-through effect during data writing by applying AC voltage, while maintaining simplicity during other periods when AC voltage is not applied.
Solution Approach 2:
The patent implements periodic action by using scan signals to periodically control the switching of the AC voltage to the common voltage terminal. The AC voltage is applied periodically during the data writing period when the scan signal is high, and disconnected when the scan signal is low. This periodic application of AC voltage effectively mitigates the feed-through effect during critical periods without requiring continuous complex circuit operation.
2Reliability
If additional circuits are added to modulate common voltage, then parasitic capacitance effects are reduced, but manufacturing cost increases
Solution Approach 1:
The patent applies universality by making the AC voltage source serve multiple functions: it acts as both the modulation signal for the storage capacitor common voltage terminal and as a replacement for complex dedicated driving circuits. The same AC voltage generation mechanism that modulates the common voltage also serves the purpose of compensating for parasitic capacitance effects, thereby reducing the need for separate specialized circuits and lowering manufacturing costs.
Solution Approach 2:
The patent utilizes parameter changes by varying the voltage level at the common voltage terminal between DC and AC modulated states. By changing the voltage parameter dynamically based on scan signal timing, the system achieves effective parasitic capacitance compensation without requiring additional complex circuit components. The parameter change approach allows a simple voltage switching mechanism to replace what would otherwise require elaborate driving circuits.
3Use of energy by moving object
If voltage swing of data signal is decreased to reduce power consumption, then energy efficiency improves, but the ability to compensate for feed-through effect is reduced
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of an AC voltage source that mediates between the data signal and the storage capacitor common voltage terminal. This AC voltage acts as a mediator that compensates for the voltage changes caused by parasitic capacitance during data writing, allowing the data signal to have reduced voltage swing for lower power consumption while still maintaining accurate voltage levels at the storage capacitor through the intermediary AC modulation.
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
This solution effectively reduces the impact of parasitic capacitance on display quality, decreases power consumption, and lowers manufacturing costs by using a simplified driving circuit design that maintains a constant common voltage, achieving both AC and DC driving effects.
Implementation Method 1
there is a parasitic capacitance 14 between the gate G and the drain D of the TFT 11. Consequently, when the control signal received at the gate G transitions from a positive level to a negative level or vice versa, the voltage difference will be coupled to the storage capacitor 13 and thus, alters the voltage across the storage capacitor 13.
Data Source
AI summary
A liquid crystal display device and a driving control circuit thereof are provided. The driving control circuit includes a voltage switch unit and a selection unit. The selection unit selects the voltages in accordance with the control signal, while the voltage switch unit outputs the selected voltage to the common terminal of pixels according to the corresponding scan signal. The driving control circuit, controlled by the control signal and the scan signal, can reduce the modulation frequency and the voltage amplitude, so the power consumption of the liquid crystal display device can be reduced.