Hybrid Multi-Level Converter Loop Filter for Early-Sampling Linearity

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Solution Overview

Problem

Multi-level converter amplifiers suffer from non-linearities due to early sampling of analog integrators, leading to in-band distortion and stability issues.

Innovation Solution

Implement an analog loop filter with a non-linear function applied to the signal path to compensate for non-linearities introduced by early sampling, using a combination of analog and digital loop filters to achieve higher-order noise shaping and correct for errors caused by early sampling of integrators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If early sampling of analog integrators is used in multi-level converter amplifiers, then device complexity is reduced, but non-linearities and in-band distortion increase

Engineering Contradiction:

Improvecomplexity of loop filter systemVSAvoidsignal linearity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The loop filter is divided into two separate filters: an analog loop filter that performs initial filtering and noise shaping, and a digital loop filter that performs additional filtering and compensation. This segmentation allows each filter to be optimized for its specific function, with the analog filter handling high-frequency noise and the digital filter correcting non-linearities introduced by early sampling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A sampler is introduced as an intermediary component between the analog integrators and the digital domain. This sampler converts the analog integrator outputs to digital signals, enabling the digital loop filter to process and compensate for non-linearities while maintaining the benefits of early sampling.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If early sampling of analog integrators is implemented, then power efficiency is improved, but system stability deteriorates

Engineering Contradiction:

Improvepower consumption of amplifierVSAvoidstability of amplifier system

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The digital loop filter receives feedback from the sampler output and uses this information to adjust and compensate for non-linearities. This feedback mechanism allows the system to maintain stability despite early sampling by continuously correcting deviations from linear operation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the sampling parameters and filter characteristics dynamically. The digital loop filter adjusts its processing based on the sampled signals to compensate for non-linearities, effectively changing the system's operational parameters to maintain stability under early sampling conditions.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If higher-order noise shaping is implemented, then in-band distortion is reduced, but device complexity increases

Engineering Contradiction:

Improvenoise shaping accuracyVSAvoidcomplexity of filter system

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The higher-order noise shaping function is segmented between the analog loop filter (providing initial noise shaping) and the digital loop filter (providing additional noise shaping and correction). This division allows the system to achieve higher-order noise shaping without requiring a single complex higher-order analog filter.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system replaces part of the analog filtering mechanism with digital filtering. The digital loop filter substitutes for additional analog integrators, achieving higher-order noise shaping through digital signal processing instead of increasing the analog filter order, thereby reducing overall device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20260081572A1Non-linear function in an early-sampled hybrid multi-level converter amplifier system

Publication Date: 2026.03.19 CIRRUS LOGIC INT SEMICON LTD

AI summary

A system may include an analog loop filter comprising a plurality of analog integrators, the analog loop filter configured to receive an analog signal input and a feedback output signal, at least one sampler for sampling outputs of the analog integrators, a second loop filter coupled between an output of an analog pulse-width modulation driver and a digital pulse-width modulation controller, wherein the second loop filter comprises at least one integrator and is configured to receive sampled outputs of the analog integrators from the at least one sampler and receive a feedback pulse-width modulation signal from the analog pulse-width modulation driver, and a correction subsystem configured to apply a non-linear function to a signal path of the second loop filter in order to compensate for non-linearity introduced as a result of sampling outputs of the analog integrators.