Sensing Circuit Harmonic Filtering for PWM Signal Accuracy

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Solution Overview

Problem

Harmonics introduced by pulse width modulation (PWM) signals reduce the signal-to-noise ratio (SNR) in sensing operations, affecting the accuracy of sense and related control operations.

Innovation Solution

Incorporation of a filter with zeros at the frequency and multiples of the frequency in the processing circuit to suppress or attenuate harmonic components in the sampled signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If PWM signals are used to drive the circuit, then the circuit can be controlled with high efficiency and speed, but harmonics are introduced that reduce the signal-to-noise ratio and sensing accuracy

Engineering Contradiction:

Improvecontrol speedVSAvoidsensing accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent applies this principle by using a filter specifically designed to attenuate harmonic frequencies generated by PWM signals. The filter converts the harmful harmonic distortion into a benefit by selectively removing these frequencies while preserving the fundamental signal, thereby improving sensing accuracy without sacrificing PWM control efficiency and speed

Inventive Principle:

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

2Productivity

If harmonics are present in the signal, then the PWM control operation can proceed, but the signal-to-noise ratio is reduced affecting measurement accuracy

Engineering Contradiction:

Improvecontrol operationVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies this principle by extracting and removing the harmful harmonic components from the signal using a dedicated filter. The filter is configured with zeros at PWM frequencies and their multiples, effectively separating and eliminating these unwanted frequency components while maintaining the useful control signal and improving the signal-to-noise ratio

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the accuracy of sensing operations by minimizing the impact of PWM harmonics, resulting in more precise impedance measurements and control operations.

Implementation Method 1

a processing circuit having a processing input and a processing output, the processing input coupled to the sense output, the processing circuit including a filter having zeros at the frequency and multiples of the frequency

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS20250370014A1Sensing circuit with harmonics filtering

Publication Date: 2025.12.04 TEXAS INSTRUMENTS INC

AI summary

An apparatus includes: a driver circuit having a driver output, the driver circuit including a pulse width modulation (PWM) circuit configured to provide a PWM signal at the driver output at a frequency; a sensing circuit having a sense input and a sense output; and a processing circuit having a processing input and a processing output, the processing input coupled to the sense output, the processing circuit including a filter having zeros at the frequency and multiples of the frequency.