PLL Phase Selection for Pixel Clock Alignment Under Sync Shift
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Solution Overview
Problem
Phase-locked loops in video display devices are unable to instantaneously adjust the pixel driving clock due to a phase shift in the horizontal synchronization signal, leading to errors in pixel alignment across rows.
Innovation Solution
A phase-locking method and loop that dynamically adjusts the phase of the output signal using a phase/frequency detector, generating multiple oscillation signals and selecting the appropriate one based on a detection result to compensate for phase shifts, ensuring accurate pixel alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the phase-locked loop uses conventional frequency locking method, then the frequency of the pixel driving clock can be stabilized, but the phase shift in the horizontal synchronization signal cannot be compensated, causing pixel alignment errors
Solution Approach 1:
The patent applies dynamics by making the phase-locked loop adaptive to phase shifts through multiple oscillation signals with different phases. The system dynamically selects the appropriate phase based on detection results, transforming a static frequency-locking system into a dynamic phase-compensating system that can adapt to varying synchronization signal conditions.
Solution Approach 2:
The patent changes the phase parameter of the output signal by generating multiple oscillation signals with different phases (first through fourth phases) and selecting the appropriate phase based on detection results. This parameter change enables the system to compensate for phase shifts in the horizontal synchronization signal while maintaining stable frequency locking.
2Manufacturing precision
If the phase-locked loop responds slowly to phase shifts, then the system remains stable, but pixel alignment errors occur due to uncorrected phase shifts
Solution Approach 1:
The patent applies preliminary action by pre-generating multiple oscillation signals with different phases before phase shifts occur. When a phase shift is detected, the system can immediately select the appropriate pre-prepared signal, eliminating the need for gradual phase adjustment and achieving instant correction of pixel alignment errors.
Solution Approach 2:
The patent uses feedback by continuously detecting the phase of the horizontal synchronization signal and using this detection result to select the appropriate oscillation signal phase. This closed-loop feedback mechanism ensures that pixel positioning precision is maintained by constantly adapting the output phase to match the incoming synchronization signal.
Data Source
AI summary
A phase-locked method includes: generating a selection signal according to a detection result of a phase/frequency detector (PFD) of a phase-locked loop (PLL); generating a plurality of oscillation signals according to at least a first oscillation signal generated by the PLL, wherein the plurality of oscillation signals respectively correspond to a plurality of phases; and from the plurality of oscillation signals, selecting an oscillation signal as an output signal of the PLL according to the selection signal.