Switching Amplifier Gain Correction for Power Supply Ripple

Solution Overview

Problem

Class D amplifiers suffer from 0 dB power supply rejection, causing power supply ripple to be directly transferred to the output, which is audible and compromises audio fidelity, while conventional analog feedback loops increase power consumption and chip area, posing challenges in battery-powered devices.

Innovation Solution

A digital correction loop is implemented using an ADC, averaging filter, and digital divider to sample and average the supply voltage, generating a correction factor that adjusts the gain in the digital chain, improving power supply rejection and reducing total harmonic distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional analog feedback loops are used to improve power supply rejection, then power supply ripple rejection is improved, but power consumption and chip area increase

Engineering Contradiction:

Improvepower supply ripple rejectionVSAvoidpower consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent replaces the conventional analog feedback loop (mechanical/electrical system) with a digital correction loop that uses an ADC to sample the supply voltage, a digital signal processor to generate correction factors, and digital filtering stages to compensate for power supply ripple. This substitution of analog components with digital processing reduces power consumption and chip area while maintaining effective power supply rejection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If conventional analog feedback loops are used to improve power supply rejection, then power supply ripple rejection is improved, but chip area increases

Engineering Contradiction:

Improvepower supply ripple rejectionVSAvoidchip area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent replaces the conventional analog feedback loop (mechanical/electrical system) with a digital correction loop that uses an ADC to sample the supply voltage, a digital signal processor to generate correction factors, and digital filtering stages to compensate for power supply ripple. This substitution of analog components with digital processing reduces power consumption and chip area while maintaining effective power supply rejection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If power supply ripple is not corrected, then device complexity remains low, but audio fidelity deteriorates due to audible ripple

Engineering Contradiction:

Improvedevice complexityVSAvoidaudio fidelity

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary action by sampling the power supply voltage and generating correction factors in advance before the ripple affects the audio output. The digital correction loop proactively compensates for power supply variations by adjusting the audio signal based on detected supply voltage fluctuations, preventing audible ripple from reaching the output rather than attempting to correct it afterward.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP4697595A1Switching amplifier with power supply ripple correction

Publication Date: 2026.02.18 NXP BV

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AI summary

An amplifier includes an amplifier chain and a digital correction loop coupled to the amplifier chain. The digital correction loop includes an analog-to-digital (ADC) converter, an averaging filter, and a digital divider. The digital correction loop is configured to generate a correction factor based on ripple or noise in a supply voltage. The amplifier chain is configured to apply the correction factor to an input signal.