Variable-Frequency Triangular Wave Circuit for Low-EMI Class-D Amplifiers

Solution Overview

Problem

Class-D power amplifiers generate fixed-frequency output voltages, leading to electromagnetic interference due to spikes in the spectrogram, which can interfere with electronic devices.

Innovation Solution

A class-D power amplifier with a triangular wave generator that uses control signals to adjust the frequency of the triangular wave, utilizing a variable current source module, energy storage module, comparison module, and control module to generate a variable frequency triangular wave, reducing electromagnetic interference by avoiding fixed frequency harmonics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a fixed frequency triangular wave is used in the class-D power amplifier, then the circuit operation is simple and stable, but electromagnetic interference occurs due to fixed frequency spikes in the output voltage spectrogram

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidtriangular wave generator complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The triangular wave generator is transformed from a fixed-frequency circuit to a dynamically adjustable frequency circuit. The patent introduces a variable current source that can be controlled by external signals to change the oscillation frequency of the triangular wave, thereby making the system adaptive and eliminating fixed frequency electromagnetic interference spikes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the key parameter of the triangular wave generator - the frequency - from a fixed value to a variable value. By controlling the current through the integrator circuit with variable current sources, the oscillation frequency can be adjusted dynamically, which directly addresses the electromagnetic interference problem caused by fixed frequency harmonics.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the triangular wave frequency is made variable to reduce electromagnetic interference, then electromagnetic interference is reduced, but the device complexity increases due to additional control modules

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidcontrol circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The control module serves multiple functions: it generates control signals for the variable current sources, adjusts the triangular wave frequency, and can potentially synchronize with external signals. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby managing complexity while achieving variable frequency operation to eliminate electromagnetic interference.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces a control module as an intermediary between the input signal and the triangular wave generator. This control module processes the input signal and generates appropriate control signals for the variable current sources, acting as a mediator that coordinates the frequency adjustment without requiring direct complex interconnections between all components.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If a fixed frequency triangular wave is used, then the circuit design is simple, but the output voltage produces fixed frequency harmonics that interfere with electronic devices

Engineering Contradiction:

Improvecircuit design simplicityVSAvoidfixed frequency harmonics

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The triangular wave generator is transformed from a fixed-frequency circuit to a dynamically adjustable frequency circuit. The patent introduces a variable current source that can be controlled by external signals to change the oscillation frequency of the triangular wave, thereby making the system adaptive and eliminating fixed frequency electromagnetic interference spikes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the key parameter of the triangular wave generator - the frequency - from a fixed value to a variable value. By controlling the current through the integrator circuit with variable current sources, the oscillation frequency can be adjusted dynamically, which directly addresses the electromagnetic interference problem caused by fixed frequency harmonics.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8872581B2Class-D power amplifier capable of reducing electromagnetic interference and triangular wave generator thereof

Publication Date: 2014.10.28 PRINCETON TECH CORP

AI summary

A class-D power amplifier capable of reducing electromagnetic interference includes an integrator, a triangular wave generator, a comparator, a gate driver, a feedback circuit, and an output stage circuit. The integrator is used for receiving an input signal and potential of ground, and outputting a first voltage. The comparator is used for comparing the first voltage with a triangular wave generated by the triangular wave generator to output a pulse-width modulation signal. The gate driver is used for driving the output stage circuit to output an output voltage according to the pulse-width modulation signal. Therefore, the class-D power amplifier reduces the electromagnetic interference by the triangular wave.