PWM Control Circuit Frequency Phase Adjustment for Display Stability
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Solution Overview
Problem
In digital television systems, the phase and frequency tracking of PWM signals relative to vertical synchronization signals is crucial for maintaining display stability, as deviations can cause water ripples or flickers due to varying panel characteristics and lack of advance knowledge of the PWM signal period, leading to transient frequency differences and phase changes.
Innovation Solution
A signal processing method and electronic device that detect changes in the input period of the vertical synchronization signal, adjust the frequency and phase of the PWM signal to match the synchronization signal within acceptable ranges, ensuring a stable relative phase relationship by using a processor-controlled PWM control circuit to perform frequency and phase adjustments in stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PWM control circuit adjusts the PWM signal frequency and phase dynamically to track the vertical synchronization signal, then the display stability is improved and water ripples/flickers are prevented, but the device complexity increases due to the need for continuous detection and adjustment mechanisms
Solution Approach 1:
The PWM control circuit continuously detects the period of the vertical synchronization signal and compares it with the current PWM signal period. Based on this feedback, the circuit dynamically adjusts the PWM signal frequency and phase to maintain synchronization, thereby preventing display instability, water ripples, and flickers while adapting to period changes in real-time
Solution Approach 2:
The PWM control circuit autonomously performs detection of the vertical synchronization signal period and self-adjustment of the PWM signal parameters without requiring external intervention. The circuit automatically identifies frequency deviations and phase differences, then corrects them through integrated control logic, reducing the need for additional external control mechanisms
2Measurement precision
If the PWM signal period is adjusted to match a longer vertical synchronization signal period, then the frequency tracking accuracy is improved, but the brightness adjustment capability deteriorates due to increased bright band time causing panel flicker perception
Solution Approach 1:
The system implements dynamic adjustment of the PWM signal period based on the detected vertical synchronization signal period. When the Vsync period changes, the PWM circuit adaptively modifies its period to maintain frequency tracking accuracy. The bright band time is dynamically controlled within acceptable ranges to prevent panel flicker while ensuring accurate frequency synchronization
Solution Approach 2:
The PWM control circuit changes the signal period parameter dynamically in response to detected Vsync period variations. By adjusting the PWM period to match the Vsync period while maintaining the bright band time within acceptable ranges, the system achieves both accurate frequency tracking and stable brightness output, preventing both frequency deviation and panel flicker
3Measurement precision
If the PWM control circuit performs both frequency adjustment and phase adjustment stages, then the signal synchronization accuracy is improved, but the adjustment time increases due to the multi-stage process
Solution Approach 1:
The synchronization adjustment process is segmented into two distinct stages: frequency adjustment stage and phase adjustment stage. In the frequency adjustment stage, the PWM period is adjusted to match the Vsync period. In the phase adjustment stage, the phase alignment is refined. This segmentation allows systematic achievement of high synchronization accuracy while managing the complexity of the adjustment process
Solution Approach 2:
The frequency adjustment stage is performed as a preliminary action before the phase adjustment stage. By first establishing correct frequency alignment, the system creates a stable foundation for subsequent phase adjustment. This preliminary frequency synchronization reduces the complexity and time required for the final phase alignment, achieving overall high synchronization accuracy efficiently
4Adaptability or versatility
If the PWM signal frequency is adjusted to track a changing vertical synchronization signal, then the adaptability to different panels is improved, but the transient frequency difference causes water ripples during the adjustment period
Solution Approach 1:
When a period change of the vertical synchronization signal is detected, the system performs preliminary frequency adjustment before phase adjustment. This preliminary action of establishing correct frequency alignment first prevents the generation of water ripple distortions that would occur if phase adjustment were attempted during frequency mismatch, while still enabling adaptability to different panel characteristics
Solution Approach 2:
The system applies preliminary anti-action by detecting period changes and proactively adjusting the PWM frequency to match the new Vsync period before any phase adjustment occurs. This preemptive frequency alignment prevents the harmful water ripple effect from occurring during the adaptation process, allowing smooth transition to different panel configurations
Data Source
AI summary
A signal processing method for maintaining a signal relative relationship and an electronic device thereof are provided. The signal processing method includes: detecting that a current input period of a vertical synchronization signal changes relative to a previous input period; determining whether a frequency difference between a pulse width modulation signal and the vertical synchronization signal is within an acceptable range, and when the frequency difference is not within the acceptable range, performing a frequency adjustment stage to adjust a period of the pulse width modulation signal to be close to the current input period; selectively performing a phase adjustment stage to adjust a phase of the pulse width modulation signal to a phase of the vertical synchronization signal; and maintaining a relative phase relationship between the pulse width modulation signal and the vertical synchronization signal.