Audio Signal Converter Chopper Circuit for Audible Noise Shifting
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Solution Overview
Problem
Audio amplifiers introduce circuit noise, such as flicker and thermal noise, which degrade the signal-to-noise ratio (SNR) and affect the quality of audio signals in processing devices.
Innovation Solution
An audio signal converter device with a variable gain amplifier circuit, loop filter circuit, and digital-to-analog converter circuit, incorporating a chopper circuit coupled via transistors to perform noise modulation using a single clock signal, reducing noise by relocating it outside the human hearing range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an amplifier is used to amplify audio signals, then the signal strength is improved, but circuit noise (flicker noise and thermal noise) is introduced which degrades the noise-to-signal ratio
Solution Approach 1:
The patent applies noise shaping technology to convert the harmful circuit noise generated by the amplifier into a beneficial form by modulating the noise to high frequencies outside the human audible range. The chopper circuit modulates the noise signal using a clock signal, transforming the low-frequency harmful noise into high-frequency noise that can be filtered out, thereby converting the amplifier's noise generation from a harmful effect into a manageable characteristic that ultimately improves overall audio quality
Solution Approach 2:
The patent changes the frequency parameter of the noise signal through modulation. By using a chopper circuit to modulate the noise with a clock signal at a frequency beyond human hearing (typically ultrasonic frequencies), the noise is shifted from the audible low-frequency range to an inaudible high-frequency range, effectively removing its harmful impact while preserving the amplified signal
2Object-generated harmful factors
If noise modulation is performed using a chopper circuit coupled to output terminals, then noise frequencies are moved outside the audible range, but signal jitter may be introduced
Solution Approach 1:
The patent introduces a buffer stage as an intermediary element between the amplifier output and the chopper circuit. This buffer isolates the signal path from the noise modulation process, allowing the chopper circuit to modulate noise without directly interacting with the amplified audio signal, thereby preventing signal jitter while still achieving noise frequency translation
Solution Approach 2:
The patent segments the signal processing into distinct functional stages: amplification, buffering, and noise modulation. By separating the noise modulation function from the signal amplification function and placing the buffer between them, the system can independently optimize each stage, ensuring that noise modulation does not adversely affect signal integrity
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
The solution effectively reduces overall noise by minimizing signal jitter and quantization noise, enhancing signal quality and performance by modulating noise frequencies away from the audible range.
Implementation Method 1
The chopper circuit is coupled to the plurality of output terminals via the plurality of transistors, and performs a noise modulation according to a first clock signal
Data Source
AI summary
An audio signal converter device includes a variable gain amplifier circuit, a loop filter circuit, a quantizer circuit, and a digital-to-analog converter circuit. The variable gain amplifier circuit amplifies an audio signal to generate multiple first signals. The loop filter circuit generates multiple second signals according to the first signals. The quantizer circuit generates a digital output according to the second signals. The digital-to-analog converter circuit adjusts the first signals according to the digital output. A corresponding circuit in the variable gain amplifier circuit or the loop filter circuit includes an amplifier, which includes an input pair circuit and a load circuit The input pair circuit includes multiple input terminals and output terminals. The load circuit includes multiple transistors and a chopper circuit. The chopper circuit is coupled to the output terminals via the transistors and performs a noise modulation according to a clock signal.