Differential Transformer Audio Amplifier for Noise and Distortion Cancellation
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Solution Overview
Problem
Existing audio signal amplifiers face issues with noise, distortion, and sensitivity to external electromagnetic fields due to galvanic isolation methods, which often require additional shielding or transformers that induce signal distortions and increase noise sensitivity.
Innovation Solution
An amplifier circuit using a transformer pair with opposite magnetic flux and differential amplifiers to cancel noise, suppressing common mode noise and transformer distortion without additional shielding, and enhancing low-frequency response using small transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used to galvanically isolate the input stage from the amplifying stage, then galvanic isolation is achieved, but signal distortions are produced due to non-linear magnetic field
Solution Approach 1:
The patent divides the single transformer into two separate transformers (first transformer and second transformer), each handling a different differential signal. This segmentation allows each transformer to operate with reduced magnetic flux, minimizing non-linear distortions while maintaining galvanic isolation functionality.
Solution Approach 2:
The patent uses two transformers with opposite polarity windings that generate counteracting magnetic fields. The first transformer processes signals with one polarity while the second transformer processes signals with opposite polarity, causing their non-linear distortions to cancel each other out, thereby reducing overall signal distortion.
2Object-affected harmful factors
If additional shielding is used to reduce sensitivity to external noise, then noise resistance is improved, but device complexity and cost increase
Solution Approach 1:
The patent converts the inherently non-linear magnetic field of transformers, which normally causes distortion, into a beneficial effect. By using two transformers with opposite polarities, the non-linear distortions generated by each transformer cancel each other out, turning a harmful effect into a solution that reduces noise sensitivity without requiring additional shielding.
3Object-affected harmful factors
If optical transmission system is used for galvanic isolation, then noise resistance is improved, but additional active electronic components and power supply isolation are required
Solution Approach 1:
The patent replaces the optical transmission system (which requires active electronic components and power supply isolation) with a purely magnetic coupling system using two transformers. This substitution eliminates the need for additional active components and power supply isolation while achieving the same noise resistance through magnetic field cancellation.
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 provides a noise-free, distortion-free audio signal amplification with improved signal-to-noise ratio and reduced sensitivity to external electromagnetic fields, achieving robust galvanic isolation.
Implementation Method 1
The amplifier circuit comprises a transformer. The transformer includes a primary winding and a secondary winding
Implementation Method 2
The first transformer includes a first primary winding, a first secondary winding and a first set of opposite polarity windings. The second transformer includes a second primary winding, a second secondary winding and a second set of opposite polarity windings
Data Source
AI summary
An amplifier circuit (1) for amplifying an audio signal, includes: an input stage (I) for receiving a first input signal representing the audio signal; a transformer (T) including a primary winding (L1) and a secondary winding (L2), defining a first terminal, a second terminal and a middle terminal; a differential amplifier (U), having a first input (U+), connected to the first terminal of the secondary winding (L2); a second input (U−), connected to the middle terminal of the secondary winding (L2), and an output (Uout), connected to the second terminal of the secondary winding (L2); an additional transformer (T′) including an additional primary winding (L1′) and secondary winding (L2′), defining a first terminal, a second terminal and a middle terminal; an additional differential amplifier (U′), having a first input (U+′), connected to the first terminal of the additional secondary winding (L2′), a second input (U+′) connected to the middle terminal of the additional secondary winding (L2′) and an output (Uout′) connected to the second terminal of the additional secondary winding (L2′); an output circuit (O) for receiving as input the output signals from the differential amplifier (U) and from the additional differential amplifier (U′) to generate a differential output signal (Vout).