Pixel Driving Circuit Voltage Stabilization for LCDs
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Solution Overview
Problem
High-frequency operating conditions in liquid crystal displays (LCDs) lead to reduced dielectric coefficients, capacitance, and voltage differences across LC capacitors, affecting grayscale display and causing power consumption issues and aperture ratio loss, especially in applications with high operating frequencies or dielectric coefficients.
Innovation Solution
A pixel driving circuit comprising a first capacitor, a data input unit, a liquid crystal capacitor, a driving unit, and a control unit, where the driving unit controls the voltage of the liquid crystal capacitor based on a data signal, and a control unit generates a scanning signal to reset the voltage, allowing continuous charging of the liquid crystal capacitor even during high-frequency operations, reducing the impact of sub-threshold currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional storage capacitors are implemented to stabilize voltage difference, then voltage stability is improved, but aperture ratio is reduced due to large area requirements
Solution Approach 1:
The patent combines the storage capacitor function with the liquid crystal capacitor by using the same capacitor structure for both purposes. The liquid crystal capacitor serves dual functions: storing charge for voltage stability and driving the liquid crystal display, eliminating the need for separate storage capacitors and preserving aperture ratio.
Solution Approach 2:
The liquid crystal capacitor is designed to perform multiple functions simultaneously: it acts as both the display element capacitor and the storage capacitor for maintaining voltage stability during high-frequency operations, thereby reducing the need for additional dedicated storage components.
2Productivity
If operating frequency is increased to achieve higher refresh rate, then productivity is improved, but voltage difference across LC capacitor decreases due to reduced dielectric coefficient
Solution Approach 1:
The patent applies a compensation voltage in advance to counteract the expected voltage drop caused by high-frequency operations. By pre-charging the liquid crystal capacitor or applying compensation signals before the voltage drop occurs, the system maintains stable voltage difference even at high refresh rates.
Solution Approach 2:
The patent implements a feedback mechanism that monitors the voltage difference across the liquid crystal capacitor and dynamically adjusts compensation signals to maintain stable operation. The compensation voltage is adjusted based on the actual voltage drop observed, ensuring consistent performance across varying frequencies.
3Ease of operation
If data input unit is kept enabled for continuous data signal input, then ease of operation is improved, but sub-threshold currents cause over-charge voltages and excessive power consumption
Solution Approach 1:
The patent employs periodic enabling and disabling of the data input unit transistor rather than keeping it continuously enabled. Data signals are input during specific time windows when the transistor is activated, and the transistor is turned off during other periods to prevent sub-threshold currents, thereby reducing power consumption while maintaining operational effectiveness.
Data Source
AI summary
A pixel driving circuit includes a first capacitor, a data input unit, a liquid crystal capacitor, a control unit and a driving unit. The first capacitor has a first terminal and a second terminal, wherein the first terminal is configured for receiving a first reference voltage. The data input unit is configured for inputting a data signal to the second terminal of the first capacitor according to a first scanning signal. The liquid crystal capacitor has a first terminal and a second terminal. The first terminal receives a first operating signal. The control unit is configured to control a voltage of the second terminal of the liquid crystal capacitor according to a second scanning signal. The driving unit is configured to control the voltage of the second terminal of the liquid crystal capacitor in response to the data input unit is disabled by the first scanning signal.