Liquid Crystal Drive Device Contrast Adjustment Circuit
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Solution Overview
Problem
Existing liquid crystal drive devices face challenges in adjusting image contrast without increasing the size of the circuit, as they require voltage boosting circuits and additional adjustment circuits to manage low power source voltages, leading to increased size, cost, and complexity.
Innovation Solution
A liquid crystal drive device with a contrast adjustment unit that generates contrast adjustment periods and outputs a contrast control signal to synchronize with scanning and display signals, allowing for contrast adjustment by equalizing potentials on common and segment wirings, thereby eliminating the need for voltage boosting and reducing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a voltage boosting circuit is added to adjust drive voltage for contrast control, then image contrast adjustment capability is improved, but circuit size and power consumption increase
Solution Approach 1:
The patent changes the timing parameter of voltage application rather than the voltage magnitude. By adjusting the contrast adjustment period duration, the liquid crystal molecules are allowed to relax for different lengths of time, achieving contrast control without voltage boosting. This transforms a voltage-based control problem into a time-based control problem, eliminating the need for complex voltage adjustment circuits.
Solution Approach 2:
The patent employs periodic contrast adjustment periods inserted between frame periods. These periodic relaxation periods allow liquid crystal molecules to return to their initial state, and by varying the period duration, contrast is controlled. This periodic action replaces the need for continuous voltage adjustment, simplifying the circuit design while maintaining contrast control capability.
2Adaptability or versatility
If a contrast adjustment period is added to control image shading, then contrast adjustment is improved, but frame period becomes variable requiring additional adjustment circuits
Solution Approach 1:
The patent merges the contrast adjustment function with the existing frame period structure. The contrast adjustment periods are systematically inserted between consecutive frame periods, combining two functions (display refresh and contrast control) into a unified timing structure. This eliminates the need for separate adjustment circuits to synchronize frame periods, as the contrast control is inherently synchronized with the display refresh cycle.
3Illumination intensity
If voltage is increased to improve image contrast, then contrast increases, but power consumption increases
Solution Approach 1:
The patent replaces the electrical field-based contrast control (voltage adjustment) with a time-based control mechanism. Instead of using stronger electrical fields to increase contrast, the system uses temporal control of the electrical field application, allowing liquid crystal molecules more or less time to align with the field. This substitution of electrical intensity control with temporal control reduces power consumption while achieving the same contrast effect.
Data Source
AI summary
A liquid crystal drive device includes a common driver configured to sequentially output a scanning signal having a plurality of voltage levels to a plurality of common wirings in a time division manner, a segment driver configured to output a display signal having a plurality of voltage levels to a plurality of segment wirings, and a contrast adjustment unit configured to generate contrast adjustment periods that are inserted into all duty periods, and output, to the common driver and the segment driver, a contrast control signal to control the timing of when the contrast adjustment periods are inserted into the duty periods in synchronization with the timing of the scanning signal and the display signal. The scanning signal and the display signal are output at an identical potential when a contrast adjustment period is indicated by the output of the contrast control signal.