Audio Power Amplifier With Energy Storage for Current-Limited Peaks
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Solution Overview
Problem
Portable two-way radio devices face challenges in amplifying audio signals without exceeding the limited current budget, leading to distortion and reduced intelligibility due to the need for peak instantaneous power that exceeds the battery's current output capacity.
Innovation Solution
A method that boosts the battery voltage to a higher level using an intermediate energy storage circuit, allowing the audio power amplifier to deliver peak power beyond the input power limit by adjusting the gain of a pre-amplifier when energy is depleted, ensuring distortion-free audio amplification within the current budget.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a lower voltage battery (3.6V) is used to reduce weight and volume, then device portability is improved, but available audio power decreases leading to insufficient output in noisy environments
Solution Approach 1:
An intermediate energy storage circuit (capacitor) is introduced between the battery and audio power amplifier. This capacitor stores energy during low-demand periods and releases it during peak power demands, enabling the system to deliver high instantaneous audio power without requiring a larger battery. The intermediary capacitor decouples the continuous power supply from the pulsed power demands of audio amplification.
Solution Approach 2:
The intermediate energy storage circuit pre-charges the capacitor during periods when audio power demand is low, preparing stored energy in advance for subsequent peak power demands. This preliminary energy accumulation allows the system to respond instantly to peak power requirements without exceeding the battery's current limits.
2Reliability
If conventional audio power amplification is used with current limiting, then battery current limit is respected, but peak clipping occurs causing significant distortion and reduced intelligibility
Solution Approach 1:
The intermediate energy storage circuit acts as a buffer between the current-limited battery and the audio power amplifier. During peak power demands, the capacitor supplies additional current to the amplifier, preventing peak clipping and maintaining audio fidelity. This intermediary solution allows the system to exceed the battery's instantaneous current output capacity without violating the overall current budget.
Solution Approach 2:
The system dynamically changes the effective voltage parameter by charging the intermediate capacitor to a voltage higher than the battery voltage. This voltage boost enables the audio amplifier to deliver peak power levels that exceed what would be possible with direct battery connection, while the battery itself never exceeds its current limits.
3Power
If a higher voltage battery (7.2V) is used to increase available power, then audio power capability is improved, but battery weight and volume increase two to four times
Solution Approach 1:
Rather than using a larger high-voltage battery, the patent uses an intermediate capacitor to achieve voltage boosting. The capacitor is charged to a higher voltage than the battery through a boost converter, and this elevated voltage is used temporarily during peak power demands. This approach achieves the power benefits of a high-voltage battery without the weight and volume penalties.
Solution Approach 2:
The system operates in periodic cycles, alternating between charging the intermediate energy storage element during low-power periods and discharging it during peak-power periods. This periodic charge-discharge pattern enables high instantaneous power delivery while maintaining a small, lightweight battery for continuous operation.
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
This solution enables distortion-free audio amplification in noisy environments by providing peak power levels that significantly exceed the input power limit, maintaining audio fidelity and intelligibility while adhering to the current budget constraints.
Implementation Method 1
boosting a voltage level of a battery to a boost voltage level across a storage capacitor at an output of a boost stage
Data Source
AI summary
A method and apparatus for amplifying audio signals without exceeding an input current limit budgeted for the audio power amplifier circuit includes an intermediate energy storage between a battery and the audio power amplifier which provides an energy reserve to support amplifying peaks where the peaks have a peak power that is greater than the power that can be drawn from the battery due to the input current limit. Speech signals, which include substantial periodic content having short peaks relative to a pitch period, can be amplified without depleting the intermediate energy storage, allowing the intermediate energy storage to recover after a peak and before occurrence of a next peak. When an audio signal is amplified that results in depletion of the intermediate energy storage, a depletion recovery circuit reduces the overall audio gain to reduce the power demand of the audio power amplifier so as to substantially avoid distortion.