Multiphase PWM Synchronization Using Captured Master Time Base
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Solution Overview
Problem
Existing external synchronization techniques for multiphase pulse width modulation (PWM) signals fail to accurately synchronize the period information, leading to waveform corruption and distortion among PWM phases due to the loss of sync period information.
Innovation Solution
Incorporating a capture register in the master time base circuit to capture the master time base counter value at the rising edge of the external sync signal and using this captured value for individual PWM generators, along with selective reinitialization of time base counters based on phase register updates, to ensure synchronized PWM waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external synchronization signal is used to synchronize multiphase PWM signals, then phase information can be recovered, but period information is lost leading to waveform corruption
Solution Approach 1:
A capture register is introduced as an intermediary component between the external sync signal 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 serves as a mediator that bridges the external synchronization requirement with the internal timing mechanism.
Solution Approach 2:
The capture register performs a preliminary action by capturing the counter value at the moment the external sync signal rises. This preliminary capture of the period information allows the system to subsequently use this captured value to properly synchronize all PWM phases without waveform corruption, preventing the information loss problem before it can affect the PWM generation.
2Ease of operation
If individual PWM generators use local time base values, then they can operate independently, but synchronization with external signals causes waveform errors
Solution Approach 1:
The invention merges the external synchronization requirement with the local time base operation by having all PWM generators use the same captured counter value from the master time base. This unifies the timing reference across all independent generators, ensuring they remain synchronized to the external signal while maintaining their independent PWM generation functionality.
Solution Approach 2:
The system is segmented into a master time base unit (with the capture register) and multiple independent PWM generator units. The master unit captures the external sync signal and distributes the captured period value to all slave generators, allowing each generator to operate independently while maintaining synchronization through the shared captured value.
3Reliability
If master time base counter is reset by external sync signal, then synchronization is achieved, but individual generators may sequence through invalid count values
Solution Approach 1:
The captured counter value from the master time base is fed back to all individual PWM generators as their reference period value. This feedback mechanism ensures that each generator uses the same validated period information, preventing them from sequencing through invalid count values and maintaining both synchronization and waveform accuracy.
Solution Approach 2:
The master time base performs a preliminary capture of the valid period value from the external sync signal before distributing it to individual generators. This preliminary action ensures that all generators receive a pre-validated period value, preventing them from using invalid count sequences and maintaining waveform precision.
Data Source
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.