Video Signal Clamp Using Horizontal Sync Timing
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Solution Overview
Problem
Conventional clamp circuits for composite video signals are sensitive to noise and inaccurately determine the negative peak of the synchronization signal tip due to non-linear signal amplification, leading to inconsistent clamping of video signals across different standards.
Innovation Solution
A circuit and method that utilize horizontal synchronization timing information to clamp the video signal during the video black level, using an electrode, signal detection and generation circuitry, and clamp circuitry to assert and de-assert control signals corresponding to horizontal synchronization components, thereby maintaining the video signal within specified voltage ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional clamping techniques clamp the negative peak of the signal based on the synchronization signal tip, then the clamping function is provided, but the clamping becomes sensitive to noise causing the negative peak to drift, and the synchronization signal tip height is inaccurate
Solution Approach 1:
The patent applies preliminary action by detecting the horizontal synchronization signal components in advance and using this detection to generate a control signal that triggers the clamping action at the precise moment when the video signal is at the black level. This pre-detection and timing mechanism ensures that clamping occurs at the correct moment without being affected by noise on the negative peak
Solution Approach 2:
The patent introduces an intermediary control signal generated from horizontal synchronization signal detection. This control signal acts as a mediator between the synchronization detection and the clamping action, allowing the system to clamp based on timing information rather than directly on the noisy negative peak voltage level
2Ease of operation
If conventional clamping techniques are used to provide clamping function, then the basic clamping is achieved, but the clamping does not maintain accurate voltage levels as specified by CEA standards due to non-linear signal amplification
Solution Approach 1:
The patent implements feedback by continuously monitoring the horizontal synchronization signal components and using this information to generate a control signal that regulates the clamping voltage. This feedback mechanism ensures that the video signal is clamped to the correct voltage levels (−286 mV to +714 mV for CEA-770.1-C, or −300 mV to +700 mV for CEA-770.2-C and CEA-770.3-C) despite non-linear amplification characteristics
Solution Approach 2:
The system performs preliminary detection of horizontal synchronization components to determine the precise timing for clamping action, ensuring that clamping occurs during the back porch period when the video signal is naturally at the black level, thereby maintaining accurate voltage levels without requiring complex compensation for non-linear amplification
Data Source
AI summary
A circuit and method for clamping a composite video component signal at the video black level by using horizontal synchronization timing information contained within the signal and clamping the signal during a time interval in which it is at the desired black level.