Pico Speaker Sigma-Delta Modulation Power Reduction
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Solution Overview
Problem
Existing systems for operating picospeakers face challenges in terms of noise, dynamic range, harmonic distortion, and latency, while also having prohibitive electrical power draw, especially in mobile and portable applications.
Innovation Solution
A speaker device that generates an audio signal by modulating an ultrasound signal, using an electronic driver device that supplies two electrical signals: one for generating the ultrasound signal and another for generating a modulation signal, which operates the membrane and shutter to produce an acoustic audio signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If state of art approaches are used to operate the picospeaker, then the picospeaker can generate audio signals, but the electrical power draw becomes prohibitive
Solution Approach 1:
The patent replaces traditional digital-to-analog converter (DAC) and analog filtering circuits with a sigma-delta modulation approach that uses 1-bit PWM signaling. This substitution of the driving mechanism eliminates the need for complex analog circuitry, significantly reducing power consumption while maintaining audio quality through oversampling and noise shaping techniques
Solution Approach 2:
The patent changes the operating parameters by using ultra-high sampling rates (e.g., 384 kHz or higher) and 1-bit quantization in the sigma-delta modulator. This parameter change allows the system to achieve high-fidelity audio output with minimal power consumption by pushing quantization noise to ultrasonic frequencies where it can be easily filtered
2Object-affected harmful factors
If traditional driving circuits are used, then the picospeaker can operate, but noise and harmonic distortion increase
Solution Approach 1:
The patent extracts and removes the need for complex analog filtering circuits and DACs by using sigma-delta modulation. The noise shaping function extracts quantization noise and relocates it to ultrasonic frequencies, where it can be easily removed by simple low-pass filtering, thereby reducing both noise and circuit complexity
Solution Approach 2:
The patent introduces a sigma-delta modulator as an intermediary between the digital audio source and the picospeaker driver. This intermediary performs noise shaping and 1-bit PWM generation, effectively separating audio signal processing from power amplification and reducing harmonic distortion through the inherent low-pass filtering of the acoustic system
3Loss of time
If complex electronic circuits are used to drive the picospeaker, then audio signals can be generated, but latency increases
Solution Approach 1:
The patent replaces complex analog signal processing circuits with a direct digital-to-acoustic path using sigma-delta modulation. The 1-bit PWM output can be directly driven by a simple amplifier or even directly by the picospeaker, eliminating multiple analog processing stages and their associated delays, thus reducing latency while simplifying circuitry
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
The solution improves the performance of picospeaker systems by reducing noise, enhancing dynamic range, minimizing harmonic distortion, and lowering latency, while also reducing power consumption, making it suitable for mobile and portable devices.
Implementation Method 1
The membrane is configured to oscillate at a combination of frequencies with at least one frequency effective to generate an ultrasonic acoustic signal
Implementation Method 2
A shutter and blind are positioned proximate to the membrane. The shutter is configured to move in reference to the blind... The resulting modulated ultrasound signal has a lower acoustic frequency sideband which corresponds to the frequency difference between the frequency of the ultrasound acoustic beam and the modulation frequency
Implementation Method 3
A driver device is provided which includes a membrane driver configured to generate an electrical signal... and a modulator driver configured to generate a modulation signal
Data Source
AI summary
Techniques described herein generally relate to generating an audio signal with a speaker. In some examples, a speaker device is described that includes a membrane and a shutter and driver device is configured to receive an audio signal, modulate it and generate electric signals to operate the speaker and generate an acoustic audio signal.