Source Driver Power-Down Detection for Stable LCD Output
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Solution Overview
Problem
Conventional source drivers in LCDs experience malfunction and produce abnormal images such as line defects or band mura when the power supply is turned off, due to insufficient power, leading to suboptimal display performance.
Innovation Solution
A power down detector is integrated into the source driver, comprising voltage dividers, comparators, and an OR gate to detect insufficient supply voltages and generate a reset signal, which controls switches to disconnect channels from output pads, preventing abnormal data transmission and ensuring a stable display during power on/off transitions.
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 buffers malfunction and produce abnormal images on the display
Solution Approach 1:
The power down detector proactively detects power supply status changes before they cause buffer malfunction. By monitoring the power supply voltage and generating a reset signal in advance, the system prepares the output pads by turning on switches to connect them to predetermined voltages, preventing abnormal images from appearing when power is reduced or turned off
2Power
If the power supply voltage decreases during power off, then energy consumption is reduced, but the buffers cannot maintain proper operation and generate abnormal images
Solution Approach 1:
The power down detector acts as an intermediary between the power supply and the buffer output stage. It monitors power supply voltage changes and mediates the transition by controlling switches that connect output pads to predetermined voltages, ensuring stable operation even when the main power supply voltage decreases during power off
3Device complexity
If no power down detection mechanism is used, then the device structure remains simple, but abnormal images such as line defects or band mura appear on the display during power transitions
Solution Approach 1:
The power down detector enables the source driver to self-monitor and self-protect against power-induced malfunctions. The detector automatically detects power supply status, generates reset signals, and controls switches to maintain proper output pad voltage levels, allowing the system to protect itself without external intervention during power transitions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents abnormal images from appearing on the display by detecting power supply insufficiency and generating a reset signal to maintain a stable output, ensuring a clear image, either black or white, during power transitions, thus enhancing display reliability.
Implementation Method 1
a first voltage divider for generating a first divided voltage based on the first supply voltage
Implementation Method 2
a first comparator for comparing the first divided voltage with a threshold voltage to determine whether the first supply voltage is insufficient
Data Source
AI summary
The present invention discloses a source driver powered by a power supply comprising at least one channel, at least one output pad coupled to the channel, at least one switch connected between the output pad and a predetermined voltage, and a power down detector for detecting whether a first supply voltage from the power supply is insufficient and generating a reset signal to turn on the switch when the first supply voltage from the power supply is insufficient.