BTL Audio Amplifier Load Detection Through Monitor Pins
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Solution Overview
Problem
Conventional audio amplifiers struggle to accurately detect the connection state of electroacoustic transducers, particularly when a DC blocking capacitor is present, and lack the ability to set open/short criteria externally.
Innovation Solution
An audio amplifier with a BTL type configuration, incorporating a first and second amplifier, monitor pins, a current source, and a load state determination circuit that detects the load state based on potential differences between monitor pins, allowing for open state detection and setting of detection criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC blocking capacitor is interposed between the output terminal and the electroacoustic transducer terminal, then the amplifier can block DC voltage, but the connection state of the load cannot be determined correctly
Solution Approach 1:
The patent introduces a monitoring circuit with current source and voltage detection components as an intermediary between the amplifier output and the load. This monitoring circuit can detect the load connection state through voltage measurements without being affected by the DC blocking capacitor, thereby resolving the contradiction between DC blocking functionality and accurate load state detection
Solution Approach 2:
The patent separates the detection function from the power delivery function by introducing dedicated monitor pins and a monitoring circuit. The main amplifier outputs power through output terminals while the monitoring circuit independently detects load state through separate monitor pins, allowing both DC blocking and accurate detection to coexist
2Reliability
If open/short criteria are defined as parameters inside the audio amplifier, then the amplifier can detect abnormalities, but the criteria cannot be set by a designer of an audio output device
Solution Approach 1:
The patent makes the detection criteria dynamic and configurable by introducing external resistance elements that can be adjusted by the system designer. The open/short detection thresholds are no longer fixed internal parameters but can be adapted to different application requirements by changing external component values, thus achieving both reliable detection and design flexibility
Data Source
AI summary
An audio amplifier of a BTL (Bridged Tied Load) type, includes a first amplifier, a second amplifier, a first output pin connected to an output of the first amplifier, a second output pin connected to an output of the second amplifier, a first monitor pin, a second monitor pin, a current source connected to the first monitor pin and configured to be switched on and off, a switch interposed between the second monitor pin and a fixed voltage line, and a load state determination circuit configured to detect a state of a load based on a potential difference between the first monitor pin and the second monitor pin.