Class D Modulator Feed-Forward Loop for Lower Power Dissipation

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Solution Overview

Problem

Conventional class D amplifiers dissipate significant power, leading to heat generation and reduced battery life in portable systems, as they process both signal and error content in their feedback loops.

Innovation Solution

Implementing a digital feed-forward loop in an analog feedback class D modulator that separates signal content from error content, allowing the feedback loop filter to process only error content, thereby reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the feedback loop processes both signal content and error content, then the modulator maintains accurate signal reproduction, but power dissipation increases significantly

Engineering Contradiction:

Improvesignal reproduction accuracyVSAvoidpower dissipation

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent segments the feedback loop processing into two distinct paths: a digital feedback path that processes only error content (quantization noise) and an analog feedforward path that processes signal content. This segmentation allows the high-power analog feedback loop to handle only the low-power error signal while the digital path handles the full-bandwidth audio signal, thereby reducing overall power dissipation while maintaining signal reproduction accuracy.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If conventional analog feedback loops process full signal bandwidth, then signal fidelity is maintained, but power consumption increases

Engineering Contradiction:

Improvesignal fidelityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent extracts the error content (quantization noise) from the full signal bandwidth and processes it separately through the analog feedback loop. The main signal content is processed through the digital feedforward path. This extraction allows the analog feedback loop to operate at lower power while the digital path maintains signal fidelity, resolving the contradiction between signal quality and power consumption.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the modulator uses high-power analog feedback for error correction, then distortion is reduced, but heat generation increases

Engineering Contradiction:

Improvedistortion reductionVSAvoidheat generation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent introduces a digital-to-analog converter (DAC) as an intermediary element that converts the digital error signal back to analog form for feedback processing. This intermediary allows the system to use digital processing for the majority of the signal path (reducing heat) while maintaining analog feedback for error correction (reducing distortion), thereby resolving the contradiction between distortion reduction and heat generation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11916707B2Power efficiency in an analog feedback class D modulator

Publication Date: 2024.02.27 ANALOG DEVICES INT UNLTD CO

AI summary

Systems and methods are provided for architectures for an analog feedback class D modulator that increase the power efficiency of the class D modulator. In particular, systems and methods are provided for an analog feedback class D modulator having a digital feed-forward loop. The digital feed-forward loop allows for removal of signal content from an input to an analog-to-digital converter, such that the ADC processes just noise and/or error. Using the techniques discussed herein, the loop filter is low power as it processes error content but not signal content.