Group-Aware Current-Limited Amplifiers for Stereo Brownout Control
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Solution Overview
Problem
In larger mobile devices with multiple amplifiers, independent peak current limit decisions by each amplifier can degrade stereo imaging and the audible experience, as they respond to local battery voltage and program material without coordinating with other channels, leading to inconsistent power supply and potential reset events.
Innovation Solution
A group of amplifiers share a common audio interface and communications bus to coordinate current draw and manage audio degradation, using intra-chip or inter-chip communication protocols to calculate cumulative peak current usage, with a master/slave relationship and 'open loop' configuration to control audio feeding to each amplifier based on precise voltage and tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each amplifier makes independent peak current limit decisions based on local battery voltage and program material, then current protection is provided, but stereo imaging is degraded and the audible experience is deteriorated
Solution Approach 1:
The patent merges the decision-making process of multiple independent amplifiers into a coordinated group decision. The brownout controller in each amplifier communicates with other amplifiers in the group to share information about current draw and audio content, allowing them to make unified peak current limit decisions that protect against brownout while maintaining stereo imaging integrity.
Solution Approach 2:
The system implements feedback mechanisms where each amplifier's brownout controller monitors its own current draw and receives information from other amplifiers in the group. This feedback loop enables dynamic adjustment of gain and current limits based on the cumulative current demand of the entire amplifier group, resolving the contradiction between protection and audio quality.
2Reliability
If amplifiers respond to local battery voltage variations due to tolerances and IxR drops, then individual protection is achieved, but inconsistent power supply conditions cause difficulty in managing low battery operation
Solution Approach 1:
The patent creates a virtual equipotential system where all amplifiers in the group share a common reference for battery voltage status. Through communication between brownout controllers, each amplifier becomes aware of the power supply conditions experienced by other amplifiers, allowing them to coordinate their protection actions despite local variations in voltage and current draw.
3Reliability
If a common current limit is applied to prevent brownout, then reset events are prevented, but audio peaks are excessively limited and degrade the audible experience
Solution Approach 1:
The system dynamically adjusts the current limit threshold based on real-time conditions. The brownout controller in each amplifier continuously monitors the cumulative current draw of the amplifier group and the detected audio content, adjusting the gain and current limits dynamically to allow peaks when safe and prevent brownout when necessary, thus resolving the contradiction between protection and audio quality.
Data Source
AI summary
A group-aware, current limited amplifier system including a group brownout control bus and a number of current-limited amplification channels coupled to the group brownout control bus. In an example embodiment, each current-limited amplification channel includes an amplifier, an amplifier power supply developing a current level signal that represents the amount of current being drawn by the amplifier, a brownout controller responsive to a digital audio input, the group brownout control bus, and the current level signal, and operative to develop a control signal; and an audio digital-to-analog (D/A) converter responsive to the digital audio input and to the control signal and operative to develop an analog audio output that is coupled to an input of the amplifier.