Multi-Class Modulation Circuitry With Single-Inductor EMI Control

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Solution Overview

Problem

Existing modulation circuitry, such as class AB and class D amplifier circuits, face challenges in efficiently modulating signals while minimizing electromagnetic interference (EMI) and reducing the need for bulky filter circuitry.

Innovation Solution

The implementation of multi-class modulation circuitry that combines class D and class AB amplifier circuits, utilizing a single inductor (1L) modulation technique to generate an asymmetric differential output, and incorporating feedforward circuitry to compensate for non-ideal linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If class AB amplifier circuitry is used for signal modulation, then linearity is improved, but power efficiency deteriorates

Engineering Contradiction:

ImprovelinearityVSAvoidpower efficiency

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The amplifier circuit is divided into two distinct class D amplifier circuitries (first and second) that operate in parallel, each handling different aspects of the signal modulation. This segmentation allows each circuitry to be optimized for specific functions, achieving both linearity and power efficiency through coordinated operation rather than relying on a single class AB stage.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If class D amplifier circuitry is used for signal modulation, then power efficiency is improved, but linearity deteriorates

Engineering Contradiction:

Improvepower efficiencyVSAvoidlinearity

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

Two class D amplifier circuitries are merged to work together in a coordinated manner. The first class D amplifier circuitry processes the input signal with one modulation approach, while the second class D amplifier circuitry processes it with a different approach, and their outputs are combined to achieve both high power efficiency and improved linearity that neither could achieve alone.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The output of the first class D amplifier circuitry is fed back to the second class D amplifier circuitry. This feedback mechanism allows the second circuitry to compensate for non-ideal linearity in the first circuitry, correcting distortion and improving overall linearity while maintaining the power efficiency benefits of class D operation.

Inventive Principle:

Principle #23Feedback

3Productivity

If traditional modulation circuitry is used, then signal modulation is achieved, but electromagnetic interference increases

Engineering Contradiction:

Improvesignal modulation capabilityVSAvoidelectromagnetic interference

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The circuit generates an asymmetric differential output where the first and second class D amplifier circuitries produce unequal but complementary signals. This asymmetric approach, combined with the feedback mechanism, allows for better control of electromagnetic interference by balancing the differential signals in a non-traditional manner that reduces radiated emissions while maintaining modulation capability.

Inventive Principle:

Principle #4Asymmetry

4Object-affected harmful factors

If bulky filter circuitry is used, then electromagnetic interference is reduced, but device size increases

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoiddevice size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The patent converts the inherently noisy switching operation of class D amplifiers into a beneficial feedback signal. By feeding back the output of the first class D amplifier circuitry to the second, the circuit uses the switching noise and harmonics as part of the control mechanism, allowing for EMI reduction without requiring large external filter components. The feedback loop naturally suppresses unwanted frequencies while maintaining the compact form factor.

Inventive Principle:

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

Data Source

PatentUS20250141412A1Methods and apparatus to modulate signals using multi-class modulation circuitry

Publication Date: 2025.05.01 TEXAS INSTRUMENTS INC

AI summary

An example apparatus includes: class D amplifier circuitry having a first input, a second input, a third input, and an output, the first input of the class D amplifier circuitry coupled to the output of the class D amplifier circuitry; and class AB amplifier circuitry having a first input, a second input, a third input, and an output, the first input of the class AB amplifier circuitry coupled to the first input of the class D amplifier circuitry and the output of the class D amplifier circuitry, the second and third inputs of the class AB amplifier circuitry coupled to the second and third inputs of the class D amplifier circuitry, and the output of the class AB amplifier circuitry.