Multi-Coil Loudspeaker PWM Delay Driving for Higher Loudness
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Solution Overview
Problem
Existing loudspeaker systems in portable devices face challenges in producing high volume audio outputs without increasing physical volume or requiring a boosted power supply, as larger speakers have reduced sensitivity and dual loudspeaker configurations occupy more space.
Innovation Solution
A system that uses a modulator to generate a pulse width modulated (PWM) signal, with a delay element applying a delay to the signal to drive multiple coils in a loudspeaker, forming a finite impulse response (FIR) filter arrangement to suppress out-of-band signals and increase audio output without boosting power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a relatively large loudspeaker is used to generate high volume audio outputs, then the audio output volume is improved, but the sensitivity is reduced and the physical volume increases
Solution Approach 1:
The loudspeaker coil is divided into multiple independent coils (first coil, second coil, third coil) that can be driven by different signals. This segmentation allows each coil to contribute to the overall audio output, enabling high volume output from a compact speaker structure without requiring a single large coil.
Solution Approach 2:
The system uses pulse width modulated (PWM) signals with specific timing relationships to drive the multiple coils. A delay element introduces a controlled time delay between signals to different coils, creating periodic action patterns that constructively interfere to enhance audio output volume from a small speaker.
2Illumination intensity
If two loudspeakers are mounted in a back to back configuration to increase loudness, then the loudness of audio output is improved, but the physical volume occupied increases
Solution Approach 1:
Multiple coils are merged into a single loudspeaker structure, sharing common components such as the magnet assembly and suspension system. This combining approach achieves the loudness enhancement of multiple speakers while occupying the physical space of only one speaker.
Solution Approach 2:
The single loudspeaker structure performs multiple functions by using several coils that can be independently controlled. The system achieves both volume enhancement and space efficiency by making one speaker structure serve multiple acoustic purposes through differential coil excitation.
3Illumination intensity
If pulse width modulated signals are applied to multiple coils with delayed timing, then out-of-band signals are suppressed and audio output is enhanced, but the system complexity increases
Solution Approach 1:
A delay element is introduced as an intermediary component between the signal source and the coils. This simple timing device creates the necessary phase relationships between coil signals to suppress out-of-band frequencies and enhance audio output, adding minimal complexity while achieving significant performance improvement.
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 system effectively increases loudness of audio output from a single loudspeaker without the need for a boosted power supply, reducing physical volume and improving sensitivity, while suppressing unwanted signals and jitter.
Implementation Method 1
a sense coil for sensing the amount of excursion of the loudspeaker cone by detecting a current induced in the sense coil as a result of movement of the loudspeaker cone
Implementation Method 2
a drive coil for driving the cone of the loudspeaker
Data Source
AI summary
A system for driving a loudspeaker having a plurality of coils, the system comprising: a modulator configured to receive an input signal and to output a pulse width modulated (PWM) output signal representative of the received input signal; a delay element for receiving and applying a delay to the PWM output signal to generate a first delayed signal; a first output configured to be coupled to a first coil of the plurality of coils of the loudspeaker, wherein the first output is coupled to the output of the modulator; and a second output configured to be coupled to a second coil of the plurality of coils of the loudspeaker, wherein the second output is coupled to the output of the delay.