LC Driving Circuit Voltage Overflow Protection
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Solution Overview
Problem
Liquid crystal display devices are vulnerable to damage from external voltage overflows, leading to abnormal driving and image distortion due to the lack of a protective mechanism against high input voltages.
Innovation Solution
A driving device comprising a control voltage signal generator, a clock signal generator with a duty ratio that changes according to the control voltage, and a DC-DC converter that outputs a driving voltage, which includes a protective circuit using diodes and resistors to regulate and prevent overflow voltages from damaging the internal circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the liquid crystal driving voltage generator directly receives power from an external source without protection, then the device structure is simple, but the internal circuits are vulnerable to damage from voltage overflow
Solution Approach 1:
A protective circuit is introduced as an intermediary component between the external power source and the liquid crystal driving voltage generator. This protective circuit includes voltage detection circuitry that monitors the external voltage and activates protection mechanisms when abnormal voltage levels are detected, thereby preventing direct damage to the internal DC-DC converter and other sensitive circuits while maintaining overall system functionality.
Solution Approach 2:
The protective circuit performs preliminary detection and protection actions before voltage overflow can damage the internal circuits. By continuously monitoring the external voltage and preparing protection mechanisms in advance, the system can quickly respond to abnormal voltage conditions and prevent damage before it occurs, ensuring the reliability of the driving device.
2Reliability
If the liquid crystal driving voltage generator is damaged by voltage overflow, then the circuit damage occurs, but the switching voltage and liquid crystal driving voltage become non-constant causing image distortion
Solution Approach 1:
The protective circuit implements a feedback mechanism that continuously monitors the external voltage and the internal voltage levels. When abnormal voltage conditions are detected, the feedback system activates protection mechanisms to regulate the voltage output, ensuring that the switching voltage PWM_SW and liquid crystal driving voltage AVDD remain constant. This prevents the voltage instability that would otherwise cause gray voltage level shifts and image distortion.
3Object-affected harmful factors
If no leakage path is available for external voltage, then the voltage generator is protected, but the input voltage is directly applied causing damage
Solution Approach 1:
The protective circuit extracts and isolates the harmful high voltage from the internal circuits through voltage detection and regulation mechanisms. By separating the voltage monitoring function from the power conversion function, the system can identify abnormal voltage conditions and activate protection pathways that prevent the harmful voltage from reaching sensitive components like the DC-DC converter.
Solution Approach 2:
The protective circuit provides beforehand cushioning by preparing protection mechanisms in advance and activating them before voltage overflow can cause damage. The voltage detection circuitry continuously monitors external voltage levels and activates protection modes when abnormal conditions are detected, cushioning the internal circuits from the full impact of voltage overflow and preventing catastrophic failure.
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 overcurrent and voltage overflow damage to the liquid crystal display's internal circuits, ensuring stable and constant voltage levels for gray voltages, thereby preventing circuit damage and maintaining image quality.
Implementation Method 1
a DC-DC converter outputting a driving voltage for converting an input voltage in response to the clock signal
Implementation Method 2
A driving device comprising a control voltage signal generator, a clock signal generator with a duty ratio that changes according to the control voltage, and a DC-DC converter that outputs a driving voltage, which includes a protective circuit using diodes and resistors to regulate and prevent overflow voltages from damaging the internal circuits
Data Source
AI summary
A driving circuit for a liquid crystal display and the liquid crystal display are disclosed. The liquid crystal display includes a display panel for displaying an image and a driving voltage generating circuit connected to the display panel, wherein the driving circuit includes a DC-DC converter for converting an input voltage level of a power input terminal to drive the display panel and outputting it as a driving voltage, a power line for connecting the power input terminal and the DC-DC converter, a first diode connected to a first node of the power line, a driving voltage terminal connected to an output terminal of the DC-DC converter, and a second diode connected to the first diode and the driving voltage terminal, wherein the power line includes a second node connected to a ground electrode between the first diode and the second diode.