DC Voltage Conversion Circuit Protection for LCD VGH Line
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Solution Overview
Problem
Liquid crystal display (LCD) devices face component damage during Electrical Over Stress (EOS) tests due to the lack of a proper protection mechanism in their DC voltage conversion circuits, leading to potential burnout of the VGH line and other components.
Innovation Solution
A DC voltage conversion circuit incorporating a booster circuit and a protection circuit with detection, feedback, and adjustment mechanisms to adjust equivalent resistances in the feedback circuits, ensuring the VGH line voltage is restored to its original state during EOS tests, preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DC voltage conversion circuit lacks a protection mechanism, then the circuit structure remains simple, but the VGH line and components are prone to burnout during EOS tests
Solution Approach 1:
The protection circuit is activated before EOS testing begins. The detection circuit detects the VGH line voltage in advance, and the adjustment circuits pre-adjust the equivalent resistance of feedback circuits to predetermined values, preparing the system to withstand upcoming over-stress conditions
Solution Approach 2:
The protection circuit uses feedback mechanisms where the detection circuit continuously monitors VGH line voltage and feeds this information back to adjustment circuits. These adjustment circuits dynamically adjust the equivalent resistance of feedback circuits based on detected voltage levels, creating a closed-loop control system that maintains protection during EOS tests
2Reliability
If the equivalent resistance of feedback circuits is dynamically adjusted, then the VGH line voltage can be restored during EOS tests, but the control circuit complexity increases
Solution Approach 1:
The adjustment circuits change the equivalent resistance parameter of feedback circuits based on detected voltage conditions. During EOS tests, when over-voltage is detected, the adjustment circuits modify resistance values to restore VGH line voltage to safe levels, using parameter transformation to handle stress conditions
3Reliability
If detection and adjustment circuits are added to the DC voltage conversion circuit, then protection during EOS tests is achieved, but the manufacturing cost increases
Solution Approach 1:
The detection circuit serves multiple functions: it detects VGH line voltage under normal operation, detects over-voltage conditions during EOS tests, and provides feedback for both routine voltage regulation and emergency protection. This multi-functionality reduces the need for separate dedicated protection components, lowering overall manufacturing cost
Data Source
AI summary
The DC voltage conversion circuit includes a booster circuit and a protection circuit. When the booster circuit is under EOS test, a detection circuit of the protection circuit obtains a second detection voltage from the voltage on the VGH line. A first adjustment circuit produces a third signal based on the comparison result of the second detection voltage and a reference voltage. A second adjustment circuit produces a fourth signal based on the comparison result of the second detection voltage and the reference voltage. The third and fourth signals adjust the equivalent resistances of a first and a second feedback circuits to a third and a forth equivalent resistances, respectively. Through the adjustment of the equivalent resistances of the first and second feedback circuits, the voltage of the VGH line is restored to that when no test signal is applied.