LCD Source Driver Power-Down Control for Noise-Free Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal displays (LCDs) experience abnormal images such as line defects or band mura due to power supply fluctuations during power on/off, causing channel malfunctions and noise in the source driver.
Innovation Solution
A source driver with a power down detector that asserts a reset signal when the power supply is turning on/off, setting data to a predetermined value and keeping latch units and multiplexers active to maintain a stable driving voltage, preventing abnormal image display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply is turned off to save energy, then power consumption is reduced, but the channels may malfunction due to insufficient power causing abnormal images
Solution Approach 1:
The power down detector proactively detects power supply transitions before they cause channel malfunction. By detecting the power on/off state in advance and asserting a reset signal, the system prepares the latch units and multiplexer to maintain stable output, preventing abnormal images during power transitions
Solution Approach 2:
The power down detector continuously monitors the power supply voltage and provides feedback about power status. This feedback mechanism enables the system to adjust its operation dynamically - keeping latch units and multiplexer active during power transitions to maintain stable driving voltage output
2Use of energy by moving object
If the latch units are turned off during power on/off to reduce power consumption, then energy use is reduced, but noise and abnormal images occur on the display
Solution Approach 1:
The invention converts the harmful effect of power supply fluctuations into a controllable condition. By detecting power transitions and maintaining latch unit and multiplexer operation during these transitions, the system ensures stable output that prevents noise and abnormal images, while still allowing power savings during normal operation
3Use of energy by moving object
If the multiplexer is turned off during power on/off to save power, then energy consumption is reduced, but the driving voltage becomes unstable causing line defects and band mura
Solution Approach 1:
The power down detector proactively identifies power supply transitions and triggers a reset signal that keeps the multiplexer active during these critical transitions. This preliminary action ensures the multiplexer maintains stable driving voltage output before, during, and after power changes, preventing line defects and band mura
Data Source
AI summary
The present invention discloses a source driver and a method for restraining noise output by a source driver during power on/off of a power supply. The source driver includes a data bus, a plurality of channels, a multiplexer and a plurality of output pads. The channels are connected to the output pads via the multiplexer. Each channel has a latch unit. Data is transmitted on the data bus and stored in the latch units. The source driver is powered by a first supply voltage from the power supply. The method comprises determining whether the first supply voltage is insufficient, and if yes, performing the following steps. First, set the data transmitted on the data bus to be a predetermined value. Then, keep the latch units turned on, thereby the data is sent out from the latch units. Then, keep the multiplexer turned on for outputting a driving voltage based on the data via the output pads.