PWM Switching Frequency Control for Harmonic and Noise Reduction
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Solution Overview
Problem
Existing PWM systems generate PWM signals with a fixed switching frequency, leading to varying quality of the synthesised analogue signal, particularly in susceptible parts, causing noise and losses due to harmonic excitation in loads like motors.
Innovation Solution
A pulse-width modulator that adjusts the switching frequency during each period of the PWM waveform, varying it based on the gradient or susceptibility of the analogue signal to maintain consistent quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed high switching frequency is used to generate PWM signals, then the synthesised analogue waveform quality is improved, but the device complexity and energy consumption increase
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The clock unit dynamically adjusts the switching frequency during each period of the PWM waveform, changing it according to the gradient or susceptibility of the analogue signal at different time points. This dynamic adjustment maintains high waveform quality where needed while reducing complexity and energy consumption during less critical periods.
Solution Approach 2:
The patent changes the switching frequency parameter throughout each PWM period based on the characteristics of the analogue waveform. By modifying this key parameter dynamically - using higher frequencies when the analogue signal gradient is steep and lower frequencies when it is shallow - the system achieves consistent waveform quality without requiring a permanently high fixed frequency, thus reducing overall complexity.
2Manufacturing precision
If a fixed high switching frequency is used to generate PWM signals, then the synthesised analogue waveform quality is improved, but the energy consumption increases
Solution Approach 1:
The system dynamically adjusts switching frequency to match the instantaneous requirements of waveform synthesis. During periods where the analogue signal has low gradient or low susceptibility to deviation, the switching frequency is reduced, directly lowering energy consumption. During critical periods requiring high quality, the frequency increases to maintain waveform purity, optimizing the energy-quality tradeoff.
Solution Approach 2:
The switching frequency parameter is continuously modified throughout each PWM period based on the analogue signal characteristics. This parameter change strategy ensures high frequency (and thus high energy consumption) is used only when necessary for waveform quality, while lower frequency (lower energy consumption) is used during less critical periods, achieving energy efficiency without sacrificing overall quality.
3Use of energy by moving object
If a fixed low switching frequency is used to generate PWM signals, then the energy consumption is reduced, but the quality of the synthesised analogue waveform deteriorates in susceptible parts
Solution Approach 1:
The patent applies local quality by using different switching frequencies for different portions of the PWM waveform period. Instead of applying a uniform frequency, the system identifies susceptible parts of the analogue waveform (where gradient is high or deviation impact is significant) and applies higher switching frequencies locally to those regions, while using lower frequencies in less susceptible regions, thus achieving high quality where needed without unnecessary energy consumption elsewhere.
Solution Approach 2:
The switching frequency parameter is adaptively changed throughout each PWM period based on the local characteristics of the analogue signal. When the signal gradient is steep or the susceptibility to deviation is high, the frequency increases to maintain quality. When these conditions are not present, the frequency decreases to reduce energy consumption, achieving a locally optimized balance between quality and efficiency.
4Manufacturing precision
If the switching frequency is varied during each period of the PWM waveform, then the quality consistency of the synthesised analogue signal is improved, but the device complexity increases
Solution Approach 1:
The system implements local quality control by adjusting the switching frequency according to the local characteristics (gradient and susceptibility) of the analogue waveform at different points in time. This ensures that each portion of the waveform receives the appropriate level of switching frequency to maintain consistent quality across the entire period, with higher frequencies applied locally where needed and lower frequencies where sufficient.
Solution Approach 2:
The clock unit dynamically adjusts the switching frequency in real-time during each PWM period based on the instantaneous gradient and susceptibility of the analogue signal. This dynamic control mechanism maintains consistent waveform quality throughout the period by adapting to local conditions, achieving quality consistency without requiring overly complex control systems.
Data Source
AI summary
A pulse-width modulator (401) comprising a pulse generator (402) configured to generate, at a switching frequency, a pulse-width modulated waveform for synthesising an analog waveform, and a clock unit (403) configured to control the switching frequency and to, while the pulse generator (402) is generating a series of pulses that represents a single respective period of the analogue waveform, change the switching frequency such that at least one pulse in every series is generated at a different switching frequency from other pulses in that series.