Speaker Connection Detection in Class D Audio Output Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for determining speaker connection in class D power amplifiers face challenges due to high-frequency components increasing output current levels, leading to erroneous determinations, and delays in digital-to-analog conversion complicating accurate comparisons between input and output current levels.
Innovation Solution
The sound output device employs first and second low-pass filters to remove high-frequency components from input and output signals, followed by peak detection units to compare peak currents within specific periods, using a comparison unit to determine speaker connection or disconnection based on threshold ratios or differences, with a level check unit controlling comparisons when input levels are low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class D power amplifier with PWM signal is used, then amplification efficiency is improved, but output current increases at high frequencies causing erroneous connection determination
Solution Approach 1:
The patent extracts and removes the problematic high-frequency PWM signal from the output signal before comparison. A filter is applied to eliminate the high-frequency component, leaving only the audible range signal for accurate connection determination. This separates the useful audio signal from the harmful high-frequency component that causes erroneous detection.
Solution Approach 2:
The patent introduces an intermediary filtering process between the power amplifier output and the connection determination logic. The filter acts as a mediator that transforms the PWM signal into a form suitable for accurate comparison, eliminating the direct harmful effect of high-frequency components on the detection accuracy.
2Adaptability or versatility
If digital-to-analog conversion is used in power amplifier, then signal processing capability is improved, but signal delay occurs causing comparison errors
Solution Approach 1:
The patent applies preliminary filtering to both the input and output signals before comparison. By pre-processing both signals through identical filtering operations, the system compensates for the conversion delay inherent in digital-to-analog conversion, ensuring that the comparison is made between equivalent signal representations.
3Reliability
If continuous speaker connection monitoring is implemented, then safety is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing power amplifier multi-functional by integrating speaker connection determination capabilities into the amplifier's existing signal processing path. The same amplifier circuit that performs audio amplification also performs connection monitoring by comparing filtered versions of input and output signals, eliminating the need for separate dedicated monitoring hardware.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a sound output device (100) having a function of accurately determining the presence or absence of a speaker at all times. The sound output device (100) of the present invention includes a controller (110), a power amplifier (60), a low-pass filter (70), and a speaker (80). The controller (110) includes first and second low-pass filters (120, 122) configured to remove high-frequency components of a sound input signal (S2) and a sound output signal (S3), a first peak detection unit (130) configured to detect a peak current (SigInP) of the sound input signal (SigInL) from which the high-frequency component has been removed, a second peak detection unit (132) configured to detect a peak current (SigOutP) of the sound output signal from which the high-frequency component has been removed, and a comparison unit (140) configured to compare the peak current (SigInP) with the peak current (SigOutP) and determine connection or disconnection of the speaker (80) when a level of the peak current (SigInP) is equal to or higher than a certain level.