Liquid Crystal Display Drive Circuit Voltage Drop Correction
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Solution Overview
Problem
Conventional liquid crystal display devices for portable devices face challenges in enhancing definition due to increased wiring resistance, voltage drop, and signal waveform dulling, particularly with common alternate driving methods that require narrower wiring widths and longer wiring lengths, leading to insufficient charge supply and high load on the drive circuit.
Innovation Solution
A liquid crystal display device with a drive circuit that includes a gray scale voltage generating circuit with a variable resistor circuit, gamma correction circuit, and equalizer circuit to adjust the resistance value based on the position of the scanning signal line, ensuring optimal data signal correction and voltage amplitude adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the definition of the liquid crystal display device is enhanced, then the display quality is improved, but the wiring resistance increases and voltage drops
Solution Approach 1:
The patent applies local quality by varying the resistance values of specific resistors (R1-R4) in the voltage division circuit based on the position of the scanning signal line. Different resistance configurations are used for different vertical positions (e.g., first vertical edge vs. second vertical edge) to compensate for position-dependent voltage drops caused by wiring resistance, thereby maintaining voltage stability across the entire display while achieving high definition.
2Use of energy by moving object
If common alternate driving is employed to reduce power consumption, then the driving voltage is lowered, but the common voltage becomes unstable due to narrow wiring width and long wiring length
Solution Approach 1:
The patent implements feedback by using the unstable common voltage (Vcom) itself as an input to the voltage division circuit. The circuit continuously monitors Vcom and adjusts the output voltages (Vgh, Vgl, V0-V63) based on the actual Vcom level, thereby compensating for Vcom fluctuations and maintaining stable display voltages even under common alternate driving conditions with narrow and long wiring.
3Productivity
If the wiring width is narrowed to maintain high aperture ratio, then the display efficiency is improved, but the wiring resistance increases further
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the resistance values in the voltage division circuit based on the scanning signal line position and common voltage level. This allows the circuit to compensate for the increased wiring resistance caused by narrow wiring, maintaining signal integrity and voltage stability without sacrificing aperture ratio.
Data Source
AI summary
Provided is a drive circuit low in power consumption and high in display quality for a liquid crystal display device that is used in a small-sized portable device. The liquid crystal display device includes liquid crystal display elements and a liquid crystal driving circuit. The liquid crystal driving circuit is mounted to one of the four sides of a liquid crystal display panel, and is capable of outputting two-system counter electrode voltages. A variable resistor circuit having a resistance value which is variably adjusted by a register is used to correct and output a gray scale voltage according to a position of a relevant scanning signal line. Equalization is also performed by short-circuiting two counter electrode signal lines.