Polynomial-Interpolator PWM for Low-Distortion Class-D Amplifiers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Class-D amplifiers face challenges in accurately identifying crossing points during sampling intervals, which can lead to spectral components like harmonic distortion in the signal, especially when dealing with digitized signals in portable electronic devices.
Innovation Solution
A polynomial interpolator is used to generate coefficients for a representative polynomial, incorporating a virtual carrier waveform to identify switching output controls, thereby reducing harmonic distortion and improving efficiency in pulse width modulators within Class-D amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional pulse width modulation is used in Class-D amplifiers, then the amplifier can operate with high efficiency and reduced power consumption, but harmonic distortion and spectral components appear in the signal due to inaccurate crossing point identification
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing crossing point values in a lookup table before actual signal processing. The crossing points between the modulated signal and carrier waveform are computed in advance for various signal amplitudes and phases, allowing the system to quickly retrieve accurate switching instants without real-time calculation, thus maintaining both low power consumption and high signal accuracy
Solution Approach 2:
The patent introduces an intermediary element - a lookup table - that mediates between the input signal and the pulse width modulation output. This table stores pre-computed crossing point information and acts as an intermediary structure that enables accurate determination of switching instants without requiring complex real-time computations, thereby resolving the contradiction between simplicity/low power and precision
2Manufacturing precision
If the sampling rate is increased to improve crossing point identification accuracy, then harmonic distortion is reduced, but power consumption and device complexity increase
Solution Approach 1:
The patent uses preliminary action by pre-computing crossing points at a lower sampling rate and storing them in a lookup table. This allows the system to achieve high crossing point identification accuracy without requiring high-speed real-time sampling, as the pre-calculated values are retrieved instantaneously during operation, thereby maintaining precision while reducing power consumption
Solution Approach 2:
The lookup table structure enables the system to serve its own precision requirements without external high-speed computing resources. The pre-stored crossing point data allows the modulator to independently determine accurate switching instants using simple memory access operations rather than complex real-time calculations, achieving self-sufficient high-precision operation at low power
3Manufacturing precision
If a polynomial interpolator is added to improve crossing point accuracy, then harmonic distortion is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies copying by creating a static lookup table that replicates the results of complex polynomial interpolation calculations. Instead of implementing the actual polynomial interpolation algorithm in hardware, the pre-computed crossing point values are copied into a memory structure that can be queried with simple address calculations, thereby achieving high precision without the complexity of real-time polynomial computation circuits
Data Source
AI summary
A modulator using a polynomial interpolator is described herein. In a simple circuit implementation of the modulator, coefficients of a representative polynomial are generated with interpolation filters in the polynomial interpolator. Crossing points may be identified for each sampling period by incorporating a virtual carrier waveform with the representative polynomial to generate a switching output control. Among other applications, the described modulator may be used in a Class-D amplifier. The described implementations may further confer benefits such as micro-power low voltage operation, low sampling rate, and low harmonic distortion.