Multiphase PWM Synchronization via Capture Register
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing external synchronization techniques for multiphase pulse width modulation (PWM) signals fail to accurately synchronize the period information, leading to corrupted PWM waveforms due to the loss of sync period information, causing waveform errors and distortion between phases.
Innovation Solution
Incorporating a capture register in the master time base circuit to capture the value of the master time base counter at the rising edge of the external sync signal and using this captured value as the effective PWM period for individual PWM generators, along with soft synchronization that limits re-initialization only when the phase register value is updated, to prevent invalid count sequences and ensure phase relationships are maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing external synchronization techniques are used to synchronize multiphase PWM signals, then phase information can be recovered from the external sync signal, but period information is lost causing corrupted PWM waveforms
Solution Approach 1:
A capture register is introduced as an intermediary component between the master time base counter and the PWM generators. This capture register captures the counter value at the rising edge of the external sync signal, thereby preserving the period information that would otherwise be lost. The captured value is then used to initialize the individual PWM generator counters, ensuring both phase and period synchronization.
2Ease of operation
If the master time base counter is reset by the external sync signal without capturing the counter value, then synchronization can be achieved, but waveform errors occur between multiphase PWM signals
Solution Approach 1:
Before resetting the master time base counter upon receiving the external sync signal, the system performs a preliminary action by capturing the current counter value in a capture register. This captured value represents the precise timing information needed to maintain accurate waveform generation. The counter is then reset to enable synchronization, but the preserved captured value ensures subsequent PWM waveforms remain accurate and free from errors.
3Adaptability or versatility
If individual PWM generators use local time base values independently, then each generator operates autonomously, but waveform distortion occurs between phases
Solution Approach 1:
The system implements a feedback mechanism where the captured counter value from the master time base is fed back to initialize the counters of individual PWM generators. This feedback ensures that all generators start their counting cycles from a synchronized reference point, maintaining consistent phase relationships. The autonomous operation of individual generators is preserved while their initial conditions are coordinated through this feedback loop, preventing waveform distortion between phases.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Waveform errors between multiphase PWM signals caused by external synchronization signals is solved by providing a capture register in a master time base circuit. The capture register is triggered by the external sync signal so as to 'capture' the value of the master time base counter at the occurrence of the rising edge of the external sync signal. This captured counter value is then provided to the local time bases of each of the phase PMW signal generators as the effective PWM period instead of locally stored PWM period values of each PWM signal generator. The captured time base value provided to the individual PWM generator time bases insures that the individual PWM generators remain properly synchronized to the master time base throughout the PWM cycles of all of the phases.