Ratiometric Multiphase PWM Synchronization Across Variable Frequencies
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Solution Overview
Problem
Existing power conversion technologies face challenges in generating phase-shifted pulse width modulation (PWM) signals that maintain duty-cycle and phase relationships over a range of frequencies, requiring significant computational resources and struggling with synchronization issues, especially when external synchronization signals vary widely.
Innovation Solution
Implementing a programmable modulo arithmetic circuit that generates count enable pulses for PWM generation logic, using an accumulator to compare values and adjust the time base, allowing for frequency and phase variations while eliminating the need for divide computations and enabling automatic synchronization with external sync signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard digital PWM signal generation is used, then fixed frequency operation is achieved, but variable frequency operation capability is lost
Solution Approach 1:
The patent implements dynamic frequency adjustment by using a variable prescaler divider that can change its division ratio based on the desired output frequency. The system transitions from fixed-frequency digital PWM generation to variable-frequency operation by dynamically reconfiguring the clock division stages, allowing the PWM carrier frequency to be adjusted while maintaining signal generation capability
Solution Approach 2:
The patent changes the operational parameters of the PWM generator by modifying the prescaler division ratio and accumulator scaling factors. By varying these parameters, the system achieves different output frequencies while maintaining the core digital PWM generation architecture, thus adapting to variable frequency requirements without complete system redesign
2Speed
If accumulator-based frequency scaling is used, then PWM frequency is reduced, but the scale factor must be reduced to increase PWM period which is undesirable
Solution Approach 1:
Instead of reducing the scale factor to increase the PWM period, the patent inverts the approach by using a programmable modulo arithmetic circuit that generates count enable pulses. The system uses division by successive subtraction where the accumulator is compared to a programmable threshold, and when exceeded, the accumulator is reduced by the threshold value. This allows the PWM period to be extended without reducing the scale factor, maintaining ease of operation
Solution Approach 2:
The patent performs preliminary frequency division using a prescaler circuit before the main PWM generation process. By pre-dividing the clock frequency and using programmable division ratios, the system prepares the timing signals in advance, allowing the main PWM generator to operate with optimized scale factors while achieving the desired extended PWM period
3Reliability
If external synchronization is implemented, then PWM signals can be synchronized to external signals, but synchronization problems occur when sync signal period and phase vary widely
Solution Approach 1:
The patent implements feedback mechanisms where the synchronization system continuously monitors the external sync signal characteristics and adjusts the PWM generation parameters accordingly. The programmable modulo arithmetic circuit provides feedback control by comparing accumulator values to programmable thresholds and adjusting count enable signals to maintain synchronization even when sync signal period and phase vary widely
Solution Approach 2:
The synchronization system is made dynamic by allowing real-time reconfiguration of the prescaler division ratio and accumulator threshold values. This dynamic adaptation enables the PWM generator to track and synchronize with external signals that have varying periods and phases, maintaining synchronization reliability across a wide range of sync signal conditions
4Adaptability or versatility
If present technology multiphase PWM generation is used, then phase-shifted PWM signals are generated, but significant computational resources are required for frequency variation
Solution Approach 1:
The patent segments the PWM generation process into independent modular stages: a prescaler division stage, an accumulator stage with programmable modulo arithmetic, and a PWM output stage. Each phase-shifted PWM channel can be generated independently using the same hardware resources, allowing multiphase operation without proportionally increasing processing power requirements
Solution Approach 2:
The patent creates a universal PWM generation core that can produce multiple phase-shifted outputs using shared hardware resources. The programmable prescaler and accumulator circuit serve multiple phases simultaneously, and the system can generate any number of phase-shifted PWM signals from a single generator unit, significantly reducing the processing power needed compared to dedicated generators for each phase
Data Source
AI summary
Groups of phase shifted Pulse Width Modulation signals are generated that maintain their duty-cycle and phase relationships as a function of the period of the PWM signal frequency. The multiphase PWM signals are generated in a ratio-metric fashion so as to greatly simplify and reduce the computational workload for a processor used in a PWM system. The groups of phase shifted PWM signals may also be synchronized with and automatically scaled to match external synchronization signals.