PWM Pulse Phase Variation for Carrier Harmonic Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pulse width modulation methods result in energy being heavily concentrated at multiples of the carrier frequency, making post-filtering difficult and causing interference in current supplies, particularly in multi-use scenarios.
Innovation Solution
The method involves varying the phase position of pulses within the pulse width modulated signal's period to distribute energy across the frequency spectrum, preventing concentration at carrier frequency multiples, and using sigma-delta modulators with feedback loop filters to suppress carrier signals, allowing for effective post-filtering and reduced interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional pulse width modulation with fixed phase position is used, then the amplifier efficiency is improved (over 90%), but the energy concentrates at multiples of carrier frequency making post-filtering difficult and causing interference in current supply
Solution Approach 1:
The patent applies dynamics by making the phase position of PWM pulses variable rather than fixed. The phase position changes according to a dither signal or random variation, which distributes the energy spectrum and prevents concentration at specific harmonic frequencies while maintaining the high efficiency of Class D amplification
Solution Approach 2:
The patent changes the phase position parameter of the PWM signal dynamically. By modulating the phase position according to a dither signal or random sequence, the spectral distribution of the PWM signal is altered to spread energy across a broader frequency range, reducing peak amplitudes at carrier frequency multiples
2Object-generated harmful factors
If phase position of pulses is varied to distribute energy over frequency spectrum, then post-filtering is facilitated and interference is reduced, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent replaces complex mechanical or electronic phase control mechanisms with a simpler digital or signal-based approach. By using a dither signal or random sequence generator combined with simple phase adders, the system achieves spectral distribution without requiring complex control circuitry
Solution Approach 2:
The patent employs periodic dither signals or pseudo-random sequences with specific properties to modulate the phase position. This periodic variation ensures that energy is distributed across the frequency spectrum in a controlled manner, achieving filtering facilitation through regular phase modulation rather than complex adaptive control
Data Source
AI summary
A method and a device are proposed for the conversion of a quantized signal into a pulse width modulated signal, wherein dependent on a signal value of the quantized signal in each case a pulse duration of a pulse is determined within a period of the pulse width modulated signal, in which the pulse width modulated signal assumes a first value, while in the remainder of the period it assumes a second value, and wherein a phase position of the pulse is varied within the period of the pulse modulated signal from period to period in such a manner that energy of the pulse width modulated signal is distributed across a broad frequency spectrum. In one case, this takes place by means of parallel switched SD modulators and a vector controller.