Differential Power Amplifier Midpoint Control for Restart Audio Continuity
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Solution Overview
Problem
Conventional power amplifying circuits for car audio systems fail to maintain a desired output waveform when the engine is restarted, causing audio output interruptions due to instantaneous drops in battery voltage from abrupt load changes.
Innovation Solution
A power amplifying circuit with a midpoint potential controlling circuit and fully differential operational amplifiers, which includes feedback resistors and a switching circuit to maintain a constant differential gain and control the output voltage based on the power supply voltage, ensuring a stable audio output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is restarted after idling stop, then the audio output should continue without interruption, but the battery voltage drops instantaneously causing audio output interruption
Solution Approach 1:
The midpoint potential controlling circuit proactively detects the engine restart condition and adjusts the output voltage before the audio output is affected. By monitoring the power supply voltage and preemptively changing the output voltage level, the circuit prevents audio interruption rather than reacting after the problem occurs.
Solution Approach 2:
The circuit dynamically changes the output voltage parameter based on the power supply voltage state. When the engine restarts and battery voltage drops, the midpoint potential controlling circuit adjusts the output voltage from the normal level (e.g., half of supply voltage) to a reduced level appropriate for the lower power supply voltage, maintaining audio output continuity despite the voltage change.
2Reliability
If the output voltage is changed to adapt to power supply voltage changes, then audio output continuity is maintained, but the circuit complexity increases due to additional control circuits
Solution Approach 1:
The midpoint potential controlling circuit serves multiple functions: it monitors the power supply voltage, detects engine restart conditions, determines when voltage change is needed, and controls the output voltage adjustment. By consolidating these multiple functions into a single control circuit, the design achieves audio continuity without proportionally increasing circuit complexity.
Solution Approach 2:
The circuit employs feedback by having the midpoint potential controlling circuit monitor the power supply voltage and automatically adjust the output voltage in response to detected changes. This closed-loop control ensures audio output continuity while keeping the control mechanism relatively simple, as the feedback automatically triggers the necessary voltage adjustment without complex external control.
Data Source
AI summary
A power amplifying circuit includes first and second operational amplifiers. The power amplifying circuit includes first to fourth feedback resistor. The power amplifying circuit includes a fully differential operational amplifier that is connected to the output terminal of the first operational amplifier at a non-inverting input terminal thereof, to the output terminal of the second operational amplifier at an inverting input terminal thereof, to a first signal output terminal at a non-inverting output terminal thereof, and to a second signal output terminal at an inverting output terminal thereof and maintains a constant differential gain. The power amplifying circuit includes a switching circuit. The power amplifying circuit includes first and second input resistors. The power amplifying circuit includes a midpoint potential controlling circuit that monitors a power supply voltage and controls the switching circuit.