Class-DG Amplifier Sensing With Common-Mode Compensation

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Solution Overview

Problem

Class-DG amplifiers experience inaccuracies in sensor measurements due to changes in common-mode voltage when switching between different power rail supply voltages, affecting output current or voltage sensing.

Innovation Solution

A system with a sensing stage and a common-mode compensator that generates a sense signal and compensates for changes in the common-mode voltage of the differential supply voltage, specifically designed for Class-DG amplifiers with multiple signal-level common modes, using both analog and digital compensators to correct for these changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a Class-DG amplifier uses multi-level output stage with variable power rail supply voltages to improve power efficiency, then power efficiency is improved, but common-mode voltage changes cause inaccuracies in sensor measurements

Engineering Contradiction:

Improvepower efficiencyVSAvoidsensor measurement accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent introduces a common-mode voltage sensing circuit as an intermediary that specifically measures the common-mode voltage component separate from the differential signal. This intermediary sensing path allows the system to detect common-mode changes without being affected by them, enabling accurate measurement of the actual output signal despite power rail switching.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements feedback by using the sensed common-mode voltage to generate a compensation signal that is subtracted from the output signal. This feedback mechanism continuously corrects for common-mode voltage changes, ensuring that sensor measurements remain accurate even as power rail voltages change to optimize power efficiency.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If Class-DG amplifier switches between different power supply voltages to reduce wasted power, then power efficiency is improved, but step changes in common-mode voltage are introduced affecting sensing accuracy

Engineering Contradiction:

Improvewasted powerVSAvoidsensing accuracy

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by pre-sensing the common-mode voltage before it affects the output signal measurement. The common-mode sensing circuit continuously monitors common-mode voltage levels, allowing the system to prepare compensation signals in advance that will correct for upcoming common-mode changes when power rail switching occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of common-mode voltage steps into a beneficial measurement. By sensing the common-mode voltage separately and using it to generate compensation signals, the system transforms the previously problematic common-mode changes into useful information that enables accurate output signal measurement despite power rail switching.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If multi-level pulse-width modulation with variable duty cycle is used to achieve rail-to-rail digital output, then output range is improved, but common-mode voltage variations increase affecting current- or voltage-sensing circuitry

Engineering Contradiction:

Improveoutput rangeVSAvoidsensing circuitry accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent segments the output signal into differential and common-mode components. By separating these components through differential sensing and common-mode sensing paths, the system can independently measure and compensate for common-mode voltage variations, allowing the full rail-to-rail output range to be utilized without compromising measurement accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by optimizing the sensing circuitry for specific measurement needs. The differential sensing path is optimized for measuring the output signal, while the common-mode sensing path is optimized for measuring common-mode voltage variations. Each sensing path has tailored characteristics that make it locally optimal for its specific measurement function.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11811370B2Common-mode compensation in a multi-level pulse-width modulation system

Publication Date: 2023.11.07 CIRRUS LOGIC INC

AI summary

A system for sensing an electrical quantity may include a sensing stage configured to sense the electrical quantity and generate a sense signal indicative of the electrical quantity, wherein the electrical quantity is indicative of an electrical signal generated by a Class-DG amplifier configured to drive a load wherein the Class-DG amplifier has multiple signal-level common modes and a common-mode compensator configured to compensate for changes to a common-mode voltage of a differential supply voltage of the driver occurring when switching between signal-level common modes of the Class-DG amplifier.