Audio Amplifier Bias Clamp for Automotive Overvoltage Protection
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Solution Overview
Problem
In-vehicle audio circuits face challenges in maintaining stable audio signal reproduction under fluctuating battery voltages, particularly when exposed to overvoltage conditions, which can damage the circuit and disrupt audio performance.
Innovation Solution
The audio amplifier circuit incorporates a bias circuit with a clamp circuit that regulates the second reference voltage to prevent overvoltage damage, ensuring the first reference voltage adjusts accordingly to maintain audio signal quality across varying power supply voltages, utilizing a shunt regulator and error amplifier to control the clamp circuit's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the audio amplifier circuit operates with fluctuating battery voltage including overvoltage conditions, then the circuit can adapt to various power supply conditions, but the circuit components may be damaged by overvoltage
Solution Approach 1:
The patent introduces a clamp circuit as an intermediary protective element between the power supply and the audio amplifier circuit. This clamp circuit includes a first clamp circuit connected to the first power supply terminal and a second clamp circuit connected to the second power supply terminal, which actively limit the voltage to safe levels before it can reach and damage the sensitive audio amplifier components, thus resolving the contradiction between adaptability and overvoltage protection
2Device complexity
If the circuit uses a simple voltage regulation approach, then the device complexity is reduced, but the audio signal quality and noise characteristics deteriorate under varying voltage conditions
Solution Approach 1:
The patent divides the voltage regulation function into separate, dedicated clamp circuits for each power supply terminal (first clamp circuit for first terminal, second clamp circuit for second terminal). This segmentation allows each clamp circuit to independently regulate its respective terminal without interfering with the other, maintaining audio signal quality while avoiding the complexity of a single integrated regulation system
Solution Approach 2:
The clamp circuits perform preliminary voltage clamping action before the power supply voltage reaches levels that would degrade audio signal quality or damage components. By proactively limiting the voltage at the power supply terminals, the circuit maintains reliable audio performance without requiring complex real-time regulation mechanisms
Data Source
AI summary
A first voltage dividing circuit receives an internal power supply voltage at an input node. A buffer has an input node connected to an output node of the first voltage dividing circuit. A second voltage dividing circuit receives a power supply voltage VCC at an input node. A voltage of the output node of the first voltage dividing circuit is a first reference voltage VFIL, and a voltage of the output node of the second voltage dividing circuit is a second reference voltage VFILP. A resistor Ro is connected between an output node of the buffer and the output node of the second voltage dividing circuit. The clamp circuit controls the voltage of the output node of the first voltage dividing circuit such that the second reference voltage does not exceed a limit voltage determined to be equal to or lower than the internal power supply voltage.