Over-Current Protecting Circuit for Display Panel Initialization
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Solution Overview
Problem
Conventional display devices fail to detect minute over-currents caused by initialization voltages, leading to potential explosions or fires due to undetected burnt defects, especially during the power-on sequence period.
Innovation Solution
A display device with an over-current protecting circuit that outputs an initialization voltage before the scan clock signal and monitors for over-currents during a power-on monitoring period, using different reference currents and times to differentiate between normal and defective states, thereby preventing shutdowns due to false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional over-current protecting circuits are used, then general over-current protection is provided, but minute over-currents caused by initialization voltages cannot be detected
Solution Approach 1:
The patent applies dynamics by making the reference current variable rather than fixed. The over-current protecting circuit switches between a first reference current (lower threshold) during power-on monitoring period and a second reference current (higher threshold) during normal operation. This dynamic adjustment allows detection of minute over-currents during initialization while preventing false positives during normal display, resolving the contradiction between detection precision and reliability.
Solution Approach 2:
The patent implements preliminary action by performing over-current monitoring during a dedicated power-on monitoring period before normal display operation begins. The initialization voltage is applied first, and the over-current protecting circuit monitors for minute over-currents during this preliminary phase using a lower reference current threshold. This preliminary detection prevents burnt defects from developing into dangerous conditions while distinguishing them from normal operational currents.
2Reliability
If over-current protection is activated during power-on, then safety is improved, but false shutdowns may occur due to normal initialization voltage currents
Solution Approach 1:
The patent resolves this contradiction through dynamic adjustment of the reference current threshold. During the power-on monitoring period, a first reference current (lower threshold) is used to detect minute over-currents. During normal display operation, a second reference current (higher threshold) is used to accommodate normal initialization voltage currents. This dynamic threshold adjustment ensures safety during power-on while preventing false shutdowns during normal operation, maintaining device availability.
Solution Approach 2:
The patent applies segmentation by dividing the operation into distinct time periods: power-on monitoring period and normal display period. Each period has its own reference current threshold and monitoring characteristics. This temporal segmentation allows the system to apply different detection strictness levels appropriate for each operational phase, preventing false shutdowns while maintaining safety.
3Ease of manufacture
If initialization voltage is output before scan clock signal, then proper pixel initialization is achieved, but minute over-currents may go undetected
Solution Approach 1:
The patent implements preliminary action by establishing a power-on monitoring period that specifically monitors over-currents during the initialization voltage output phase, before normal display operation begins. This preliminary monitoring phase uses a lower reference current threshold to detect minute over-currents that occur during pixel initialization. By monitoring during this preliminary phase with appropriate sensitivity, the system maintains both proper initialization sequence and detection sensitivity.
Data Source
AI summary
A display device includes a display panel including a pixel circuit, a display panel driving circuit that drives the display panel, a voltage generating circuit that receives an input power supply voltage when the display device is powered on and generates display panel voltages and driving circuit voltages based on the input power supply voltage, and an over-current protecting circuit that monitors an over-current generated inside the display device and generates a shut-down request signal when the over-current is detected. The voltage generating circuit outputs an initialization voltage at a first time point corresponding to a time point at which the input power supply voltage is received. The display panel driving circuit outputs a scan clock signal at a second time point. The over-current protecting circuit performs a first over-current protecting operation in a power-on monitoring period set between the first time point and the second time point.