Planar Inductor Layout for Low Cross-Talk Class-D Audio Amplifiers
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Solution Overview
Problem
Planar inductors in class D audio amplifiers with air gaps cause significant magnetic flux leakage, leading to unwanted cross-talk between nearby inductors, which is mitigated by spacing them far apart, resulting in large amplifier footprints, limiting multi-channel systems to single-channel applications.
Innovation Solution
Implementing feedback loops between class-D amplifiers and reconstruction filters with magnetically coupled planar inductors to reduce magnetic coupling and distortion, allowing channels to be positioned closer without unacceptable cross-talk, enabling compact multi-channel amplifier designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If planar inductors are spaced far apart to reduce magnetic coupling and cross-talk, then cross-talk between channels is reduced, but the amplifier footprint increases
Solution Approach 1:
The patent implements feedback loops that sense the output signal and feed it back to the class-D amplifier to actively cancel magnetic coupling effects between adjacent planar inductors. This feedback mechanism allows channels to be positioned closer together while maintaining cross-talk performance, thereby reducing amplifier footprint without sacrificing signal isolation.
2Stability of the object's composition
If planar inductors with air gaps are used to linearize inductance change, then inductance linearity is improved, but magnetic flux leakage and cross-talk increase
Solution Approach 1:
The feedback loops detect and compensate for magnetic flux leakage from air-gapped planar inductors by injecting corrective signals into the class-D amplifier. This allows the beneficial inductance linearity from air gaps to be maintained while actively canceling the harmful magnetic coupling effects between adjacent inductors.
Solution Approach 2:
The patent converts the harmful magnetic flux leakage from air-gapped planar inductors into a manageable signal through feedback. The feedback system captures the leaked magnetic flux effects and uses them to generate compensating signals, thereby transforming a harmful phenomenon into a controllable parameter that can be actively managed.
3Area of stationary object
If multiple channels are positioned close together for compact design, then amplifier footprint is reduced, but cross-talk between channels increases
Solution Approach 1:
Each audio channel is equipped with a feedback loop that independently senses and compensates for cross-talk from adjacent channels. This per-channel feedback approach enables compact multi-channel amplifier designs by actively maintaining signal isolation even when channels are positioned in close proximity, thereby achieving both compact footprint and low cross-talk performance.
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 feedback loops effectively reduce cross-talk between audio channels, allowing for compact, multi-channel class D audio amplifier systems that can be mounted in confined spaces while maintaining signal integrity at least 54 dB below the signal level, overcoming the limitations of large footprints and single-channel restrictions.
Implementation Method 1
The feedback loops effectively reduce cross-talk between audio channels, allowing for compact, multi-channel class D audio amplifier systems
Implementation Method 2
The first and second reconstruction filters have corresponding first and second planar inductors, with the second planer inductor being magnetically coupled to the first planar inductor
Data Source
AI summary
An apparatus for providing an audio signal to drive a speaker system includes first and second audio channels. The first audio channel has a first class-D amplifier for receiving an input signal, and a first reconstruction filter for receiving an output from the first class-D amplifier and reconstructing therefrom an output audio signal for driving the speaker system. The second audio channel has a second class-D amplifier for receiving an input audio signal, and a second reconstruction filter for receiving an output from the second class-D amplifier and reconstructing therefrom an output audio signal for driving the speaker system. The first and second reconstruction filters have corresponding first and second planar inductors, with the second planer inductor being magnetically coupled to the first planar inductor.