Toroidal Transformer Output Stage for Low-Distortion Audio Amplifiers
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Solution Overview
Problem
Audio amplifiers face challenges in achieving low distortion and accurate signal reproduction, particularly in applications where high distortion leads to an inaccurate representation of the input signal, which is undesirable for sophisticated listeners.
Innovation Solution
The audio amplifier design incorporates first and second amplifying elements driven by 180-degree out-of-phase control signals, coupled with toroidal transformers in push-pull configurations to prevent magnetic saturation and operate in Class A mode, utilizing vacuum tube or solid-state devices, and includes non-polarized capacitors to maintain signal integrity and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transformers are used in the output stage, then the amplifier can drive speakers, but magnetic saturation occurs leading to high distortion and inaccurate signal reproduction
Solution Approach 1:
The patent divides the single transformer function into two separate toroidal transformers, each handling specific current paths. This segmentation prevents magnetic saturation by distributing the magnetic flux load across two independent cores, thereby reducing distortion and improving signal reproduction accuracy.
Solution Approach 2:
Instead of using a conventional transformer configuration that is prone to saturation, the patent inverts the approach by using two transformers with secondary windings connected in series rather than parallel. This inverted connection topology, combined with push-pull operation, reverses the magnetic flux direction periodically, preventing saturation and reducing distortion.
2Use of energy by moving object
If Class AB or Class B operation is used to improve efficiency, then power consumption is reduced, but distortion increases and signal accuracy deteriorates
Solution Approach 1:
The patent implements Class A operation where both amplifying elements conduct continuously throughout the entire signal cycle, ensuring continuous useful action. This continuous conduction eliminates the crossover distortion inherent in Class AB/B operations, maintaining high signal reproduction accuracy while the push-pull transformer configuration manages the power efficiency aspect.
3Device complexity
If single-ended configuration is used, then the circuit is simpler, but distortion is high and frequency response is limited
Solution Approach 1:
The patent segments the amplification function into two separate amplifying elements operating in push-pull fashion, each handling opposite phases of the signal. This segmentation improves frequency response and reduces distortion compared to single-ended configurations, while the dual-transformer setup manages the complexity aspect by providing symmetrical current paths.
Solution Approach 2:
The push-pull configuration implements periodic action where the two amplifying elements alternately conduct in opposite phases. This periodic switching improves frequency response and reduces distortion by canceling even-order harmonics, while the symmetrical transformer connections manage the circuit complexity.
4Measurement precision
If toroidal transformers with series-connected secondary windings are used, then distortion is reduced and frequency response improves, but the circuit complexity increases
Solution Approach 1:
The patent segments the transformer function into two separate toroidal transformers with series-connected secondary windings. This segmentation reduces distortion and improves frequency response by preventing magnetic saturation, while the modular nature of using two identical transformers manages the complexity through standardization.
Solution Approach 2:
The patent changes the connection parameter of the secondary windings from parallel to series configuration. This parameter change increases the output voltage and improves frequency response while reducing distortion, and the use of two identical transformers with standardized parameters manages the overall circuit complexity.
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 configuration achieves low distortion and accurate signal reproduction by preventing magnetic saturation and maintaining efficient coupling, resulting in improved frequency response and output impedance, suitable for high-quality audio applications.
Implementation Method 1
Magnitudes of current supplied by the constant current sources may be balanced to prevent magnetic saturation of the first and second toroidal transformers over a predetermined frequency range
Implementation Method 2
a first toroidal transformer with first and second primary windings coupled together at center terminals to a common voltage source and coupled in push-pull configuration to the first and second amplifying elements, and with first and second secondary windings that are coupled in parallel across output terminals
Data Source
AI summary
An audio amplifier includes an output stage including a first toroidal transformer with a first pair of secondary windings that are coupled in parallel across an output terminal. The output stage further includes a second toroidal transformer with a second pair of secondary windings that are connected in a series combination that is coupled across the output terminal.