External Speaker Connection Detection Using Ultrasonic Audio Signals
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Solution Overview
Problem
Existing portable audio appliances face challenges in detecting external loudspeakers reliably and inexpensively due to limited space, which affects sound quality and requires costly and complex current measurement methods.
Innovation Solution
Incorporating a detection frequency component outside the audible spectrum in the electrical signal between external terminals, using a class D amplifier and an inductor tuned to this frequency for current detection, and adjusting signal gain based on loudspeaker connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power supply current measurement methods are used to detect external loudspeakers, then detection reliability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The invention extracts the detection function from the power supply current measurement system. Instead of measuring power supply current to detect external loudspeakers, the patent uses a separate detection circuit that monitors the audio output signal for the presence of external loudspeakers. This separation simplifies the overall system while maintaining detection reliability.
Solution Approach 2:
The invention introduces an intermediary detection circuit between the audio output and the external loudspeakers. This circuit includes a capacitor connected in parallel with the audio output terminals, which serves as an intermediary element to detect voltage changes caused by external loudspeaker connection, eliminating the need for complex power supply current measurement.
2Reliability
If power supply current measurement methods are used to detect external loudspeakers, then detection reliability is improved, but manufacturing cost increases
Solution Approach 1:
The invention uses simple, inexpensive components for the detection circuit, including a capacitor and voltage measurement circuitry. These cheap components replace expensive and complex power supply current measurement systems, significantly reducing manufacturing cost while maintaining adequate detection reliability through the voltage change detection method.
3Strength
If additional loudspeakers are added to improve sound quality, then sound rendering is improved, but appliance dimensions and space requirements increase
Solution Approach 1:
The invention segments the audio playback system into two independent parts: a portable appliance with internal loudspeakers for portability, and a separate external loudspeaker system for enhanced sound quality. This segmentation allows the portable appliance to remain compact while enabling high-quality audio playback when external loudspeakers are connected, resolving the contradiction between size and sound quality.
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
Enables reliable and cost-effective detection of external loudspeakers, allowing for automatic gain adjustment to enhance sound quality without user intervention and maintain ergonomic operation.
Implementation Method 1
the means for detecting a current flowing between the external terminals comprise an inductor tuned to the detection frequency and connected between an amplifier of the appliance and one of the external terminals, together with means for measuring the voltage across the terminals of said inductor
Data Source
AI summary
An audio appliance includes two external connections for connection to external loudspeakers, and includes means for establishing an electrical signal between the external terminals that is representative of an audio source in order to inject an excitation electric current into each external loudspeaker. Means are provided for incorporating a component at a “detection” frequency that is situated outside the audible spectrum in the electrical signal that is established between the external terminals, together with means for detecting an electric current flowing between the external terminals and having a frequency corresponding to the detection frequency. This is applicable in particular to systems comprising a mobile appliance and a fixed docking station incorporating a woofer and designed to receive the mobile appliance.