Ultrasound Amplifier Interface Using Transducer Capacitance Boost

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Solution Overview

Problem

Amplifying ultrasonic signals is challenging due to the high frequency range and capacitive load requirements, which are beyond typical audio amplifier capabilities, leading to the need for custom-made amplifiers for specific applications.

Innovation Solution

The proposed amplifier architecture replaces the traditional capacitor with the natural capacitance of the ultrasonic transducer, using relative impedance to create an under-damped low-pass filter that boosts voltage in the ultrasonic frequency band, and includes a secondary feedback loop to ensure correct output voltage levels, allowing low-cost class-D audio amplifiers to be compatible with ultrasonic signals and loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a traditional class-D audio amplifier is used, then cost is reduced and availability is improved, but compatibility with ultrasonic transducers is lost due to frequency and load impedance limitations

Engineering Contradiction:

Improveamplifier cost and availabilityVSAvoidcompatibility with ultrasonic transducers

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the electrical parameters of the amplifier system by replacing the traditional output capacitor with the ultrasonic transducer's own capacitance, and by introducing an inductor to create a low-pass filter with a cutoff frequency in the ultrasonic range. This allows standard class-D amplifiers to operate effectively at ultrasonic frequencies by modifying the filter characteristics rather than changing the amplifier core architecture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent makes a universal class-D audio amplifier module capable of driving both traditional audio speakers and ultrasonic transducers by adding a passive LC filter network. The same amplifier module can serve multiple functions across different frequency ranges, eliminating the need for custom-designed ultrasonic amplifiers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Power

If the amplifier output filter capacitor is replaced with the ultrasonic transducer capacitance, then voltage boost in ultrasonic frequency band is achieved, but high frequency artifacts from switch mode amplifier remain

Engineering Contradiction:

Improvevoltage boost in ultrasonic frequency bandVSAvoidhigh frequency artifacts

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an inductor as an intermediary component between the switch-mode amplifier and the ultrasonic transducer. This inductor, combined with the transducer capacitance, forms a low-pass filter that mediates the signal transmission by allowing ultrasonic frequencies to pass while blocking higher frequency switching artifacts.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs feedback control to monitor and adjust the amplifier output, ensuring that the voltage boost in the ultrasonic band is achieved while maintaining suppression of high-frequency artifacts. The feedback loop allows real-time optimization of the filter characteristics.

Inventive Principle:

Principle #23Feedback

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

This solution enables efficient and cost-effective amplification of ultrasonic signals by creating a voltage boost in the desired frequency range, making standard class-D amplifiers compatible with ultrasonic transducers, while reducing current requirements and allowing for practical use with thin-film ultrasonic transducers.

Implementation Method 1

The inductance value of the inductor and the capacitance value of the ultrasonic transducer form a low-pass filter for removing high frequency artifacts produced by the switch mode type amplifier

Methodology Applied

Scientific EffectLow-pass filter: Filter (electronic)

Implementation Method 2

employs relative impedance magnitudes to create an under-damped low-pass filter that boosts voltage in the ultrasonic frequency band of interest

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS10869127B2Amplifier interface and amplification methods for ultrasound devices

Publication Date: 2020.12.15 POMPEI FRANK JOSEPH

AI summary

Amplifier architecture that allows low-cost class-D audio amplifiers to be compatible with ultrasonic signals, as well as loads presented by thin-film ultrasonic transducers. The amplifier architecture replaces the traditional capacitor used as an output filter in the class-D amplifier with the natural capacitance of the ultrasonic transducer load, and employs relative impedance magnitudes to create an under-damped low-pass filter that boosts voltage in the ultrasonic frequency band of interest. The amplifier architecture includes a secondary feedback loop to ensure that correct output voltage levels are provided.