Liquid Crystal Display Driving Circuit Mode Transition Control
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Solution Overview
Problem
Liquid crystal display devices experience abnormal voltage and current changes when operating modes are switched, leading to reduced lifespan of backlight unit components and perceived flicker due to increased brightness.
Innovation Solution
A driving method for liquid crystal display devices that halts image display operations and sequentially changes sub-circuit operations when mode changes occur, minimizing load changes and shared voltage levels between the driving circuit and backlight unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operating mode is changed and sub-circuits stop operation simultaneously, then the response time to mode change is reduced, but the voltage and current changes become abrupt causing backlight unit damage and display flicker
Solution Approach 1:
The patent applies preliminary action by stopping sub-circuits in a predetermined sequence before the mode change is fully completed. The control unit generates control signals that halt sub-circuits one by one according to a pre-established sequence, preventing simultaneous discharge of capacitors and avoiding abrupt voltage changes to the backlight unit.
Solution Approach 2:
The patent segments the simultaneous shutdown process into multiple sequential steps. Instead of stopping all sub-circuits at once, the control unit divides the shutdown process into individual sub-circuit stoppages occurring at different time points, thereby distributing the discharge current over time and preventing harmful current surges.
2Power
If multiple capacitors in DC-DC converter discharge simultaneously during mode change, then the energy is released quickly, but the discharged charges flow to backlight unit causing abnormal voltage levels
Solution Approach 1:
The control unit performs preliminary action by predicting which sub-circuits will stop and in what sequence. It generates control signals in advance that stagger the stopping times of sub-circuits containing capacitors, ensuring that capacitor discharge occurs progressively rather than simultaneously, thus preventing voltage spikes to the backlight unit.
Solution Approach 2:
The control unit acts as an intermediary between the sub-circuits and the backlight unit. It mediates the energy discharge process by controlling the timing of sub-circuit shutdowns, thereby regulating the flow of discharged charges and preventing harmful voltage levels from reaching the backlight unit.
3Device complexity
If the driving circuit and backlight unit share common voltage, then the circuit design is simplified, but load changes in driving circuit cause abnormal voltage changes in backlight unit
Solution Approach 1:
The control unit implements feedback control by monitoring the operating mode changes and automatically adjusting the shutdown sequence of sub-circuits. When a mode change is detected, the control unit activates a predetermined sequence that staggers sub-circuit stoppages, thereby compensating for the shared voltage arrangement and maintaining voltage stability for the backlight unit.
Solution Approach 2:
The patent introduces dynamic control into the previously static voltage sharing arrangement. The control unit dynamically adjusts the operation timing of sub-circuits based on mode change conditions, creating a time-varying shutdown sequence that maintains voltage stability despite the simplified shared voltage design.
Data Source
AI summary
A liquid crystal display device includes a liquid crystal panel, a driving circuit and a backlight unit supplying light to the liquid crystal panel. The liquid crystal display device further includes a power management unit. The driving circuit includes a plurality of sub-circuits. The power management unit may provide a common voltage to the driving circuit and the backlight unit. A driving method of the liquid crystal display device includes halting an image display operation of a liquid crystal panel in response to a change of an operation mode. The driving method further includes sequentially changing operations of the plurality of sub-circuits.