Ultrasonic Transducer Amplifier Interface With Resonant Voltage 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, and existing class-D amplifiers are not compatible with ultrasonic transducers or parametric loudspeaker systems.
Innovation Solution
The proposed amplifier architecture replaces the traditional capacitor with the natural capacitance of the ultrasonic transducer, creating 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, making low-cost class-D audio amplifiers compatible with ultrasonic signals and loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional audio amplifiers are used for ultrasonic signals, then the amplifier cost is reduced, but the amplifier cannot drive ultrasonic transducers due to frequency and load mismatch
Solution Approach 1:
The patent changes the operating parameters of the class-D amplifier by replacing the traditional output capacitor with an inductor, transforming the filter topology from a standard low-pass filter to an under-damped low-pass filter. This parameter change enables the amplifier to operate effectively at ultrasonic frequencies while maintaining compatibility with the capacitive load of ultrasonic transducers.
Solution Approach 2:
The patent introduces an inductor as an intermediary component between the amplifier and the ultrasonic transducer. This inductor serves as a mediator that transforms the amplifier's output characteristics to match the requirements of the ultrasonic transducer, enabling effective power transfer at ultrasonic frequencies.
2Use of energy by moving object
If class-D amplifiers are used for ultrasonic frequencies, then the amplifier efficiency is improved, but the amplifier cannot provide sufficient voltage boost in the ultrasonic frequency band
Solution Approach 1:
The patent exploits resonant vibration principles by designing an under-damped low-pass filter that creates a resonance peak in the ultrasonic frequency band. This resonance effect naturally provides voltage boost at the desired frequencies without requiring additional active amplification stages, thereby maintaining high amplifier efficiency.
Solution Approach 2:
The patent changes the damping parameter of the low-pass filter by replacing the capacitor with an inductor, creating an under-damped system. This parameter change enables the system to exhibit resonant behavior that provides voltage boost in the ultrasonic frequency band while maintaining the efficiency benefits of class-D amplification.
3Device complexity
If standard class-D amplifier modules are used, then the device complexity is reduced, but the amplifier produces high-frequency switching artifacts
Solution Approach 1:
The patent converts the harmful high-frequency switching artifacts into a beneficial resonance peak. By designing the output filter as an under-damped low-pass filter with an inductor, the switching frequency components are transformed into a constructive resonant effect that provides voltage boost in the ultrasonic band rather than appearing as unwanted artifacts.
Solution Approach 2:
The patent uses resonant vibration to convert the switching artifacts into a useful signal. The under-damped filter creates a resonance peak that amplifies the switching frequency components at the desired ultrasonic frequencies, transforming what would normally be harmful artifacts into the desired output signal.
4Stability of the object's composition
If traditional output filter capacitors are used in class-D amplifiers, then the amplifier is stable, but the amplifier cannot achieve voltage boost in the ultrasonic frequency band
Solution Approach 1:
The patent inverts the traditional approach by replacing the capacitor with an inductor in the output filter. This inversion changes the filter characteristics from a standard low-pass response to an under-damped response that provides voltage boost in the ultrasonic frequency band while maintaining overall system stability through feedback control.
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 allows for efficient and cost-effective amplification of ultrasonic signals, achieving a strong resonance peak and voltage boost in the desired frequency range, making ultrasonic transducers compatible with standard class-D amplifier modules, while reducing current draw and eliminating high-frequency switching artifacts.
Implementation Method 1
employs relative impedance magnitudes to create an under-damped low-pass filter that boosts voltage in the ultrasonic frequency band of interest
Implementation Method 2
one or more inductances coupled between the switching amplifier and the ultrasonic transducer
Implementation Method 3
The ultrasonic transducer has a transducer capacitance
Implementation Method 4
The processing circuitry is configured to correct the output level of the ultrasonic transducer in response to variations in one or more values of the one or more inductances and the transducer capacitance
Data Source
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.