Switched-Mode Audio Amplifier Load Limiting Across Impedances
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Solution Overview
Problem
Conventional audio amplifiers are limited in their ability to adapt to varying load impedances, resulting in inefficient use of output power and the need for multiple discrete amplifier models to accommodate different impedance configurations.
Innovation Solution
An audio amplifier with a switched mode output amplification stage and a limiter device that adjusts the intermediate signal based on load impedance, allowing for flexible adjustment of output power without changing the internal supply voltage, and incorporating a control unit to manage the limiter device for optimal power delivery across a wide range of impedances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the amplifier is designed for a specific output power and load impedance, then the amplifier can operate efficiently at that specific configuration, but it cannot adapt to different load impedances and requires multiple discrete amplifier models
Solution Approach 1:
The patent implements dynamic adaptability by introducing a limiter device that can adjust the intermediate signal level based on the connected load impedance. The amplifier transitions from a static, fixed configuration to a dynamic system that automatically adapts its output characteristics. The control unit detects load impedance and adjusts the limiter accordingly, enabling a single amplifier model to serve multiple impedance configurations without requiring multiple discrete models.
Solution Approach 2:
The patent changes the operating parameters of the amplifier by adjusting the intermediate signal level in the limiter device based on load impedance. Instead of changing physical hardware configurations or supply voltages, the system modifies the signal parameter (intermediate signal level) to match different load conditions. This allows the amplifier to maintain optimal performance across varying impedances while keeping the hardware configuration constant.
2Ease of manufacture
If the amplifier uses a fixed internal supply voltage, then the design is simplified, but the output power cannot be adjusted for different load impedances
Solution Approach 1:
The patent introduces an intermediary element - the limiter device - that sits between the fixed supply voltage and the output stage. This intermediary component allows the system to maintain a simple, fixed internal supply voltage while still achieving output power adjustment for different load impedances. The limiter acts as a mediator that translates the fixed voltage into variable output power based on load conditions, preserving design simplicity while enabling adaptability.
3Power
If the amplifier operates at maximum power for low impedance loads, then the output power is maximized, but the amplifier cannot provide appropriate power levels for high impedance loads
Solution Approach 1:
The patent implements a feedback mechanism where the control unit detects the load impedance and adjusts the intermediate signal level in the limiter device accordingly. This closed-loop feedback system ensures that the amplifier delivers appropriate power levels for different impedance loads. The feedback allows the amplifier to sense the load conditions and automatically adjust its output characteristics, preventing both overload and underutilization across the impedance range.
4Reliability
If the amplifier is designed with high output power capability, then it can drive low impedance loads effectively, but it may overload high impedance loads
Solution Approach 1:
The patent applies preliminary action by adjusting the intermediate signal level in the limiter device before the power stage amplifies the signal. By pre-limiting the intermediate signal based on detected load impedance, the system prevents potential overload conditions before they occur in the final output stage. This preliminary adjustment ensures that high impedance loads are protected from excessive power while maintaining flexibility in load configuration.
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 flexible adaptation of output power to any load impedance, eliminating the need for multiple amplifier models and protecting loudspeakers from overload, while maintaining high efficiency and cost-effectiveness.
Implementation Method 1
The output amplification stage is designed as an amplifier that is operated in the switched mode to amplify an intermediate signal into the output signal
Implementation Method 2
a limiter device (4) is integrated in the audio amplifier (1), which is programmed and/or electronically configured to generate the intermediate signal on the basis of the input signal, wherein the level of the intermediate signal always lies below a maximum level
Data Source
AI summary
The invention relates to an audio amplifier (1) for amplifying an input signal into an output signal, comprising an output amplification stage (6), wherein the output amplification stage (6) for the amplification of an intermediate signal into the output signal is designed as an amplifier operating in switching operation, and further comprising a limiter device (4), which from a programming and/or a circuit design point of view is designed to generate the intermediate signal on the basis of the input signal, wherein the level of the intermediate signal is always limited by a maximum load as a function of a settable maximum output and a load impedance which is coupled and/or can be coupled the audio amplifier or equivalent parameter thresholds such that the output signal does not exceed the maximum load at the load impedance, or the equivalent parameter thresholds, independently of the input signal.