Audio Modulation Circuit With One LC Filter for Low EMI
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching amplifiers require two sets of LC filters to meet electromagnetic interference (EMI) requirements, increasing silicon space, complexity, and cost, while mismatches in inductance between filters introduce undesired harmonics, and existing modulation circuits either worsen switching loss or harmonic distortion.
Innovation Solution
A modulation circuit using a single LC filter generates a switching transition totem pole signal, reducing silicon space and cost, and improving switching loss and total harmonic distortion (THD) with effective EMI management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If two sets of LC filters are used to meet EMI requirements, then EMI performance is improved, but silicon space and device complexity increase
Solution Approach 1:
The patent extracts and eliminates one of the two LC filters from the traditional switching amplifier architecture. By removing the second LC filter while implementing a specific modulation technique that ensures clean switching transitions, the design achieves EMI compliance with only one LC filter, thereby reducing silicon space and device complexity while maintaining EMI performance.
Solution Approach 2:
The patent changes the modulation parameters and switching transition characteristics to achieve cleaner spectral content. By modifying the modulation approach and ensuring proper zero-crossing alignment of switching transitions with the audio signal, the design reduces EMI emissions enough to satisfy requirements with a single LC filter.
2Object-affected harmful factors
If two sets of LC filters are used to meet EMI requirements, then EMI performance is improved, but silicon space increases
Solution Approach 1:
The patent extracts and eliminates one of the two LC filters from the traditional switching amplifier architecture. By removing the second LC filter while implementing a specific modulation technique that ensures clean switching transitions, the design achieves EMI compliance with only one LC filter, thereby reducing silicon space and device complexity while maintaining EMI performance.
3Device complexity
If inductance values of LC filters are mismatched, then device complexity is reduced, but total harmonic distortion increases
Solution Approach 1:
The patent converts the potential harm of inductance mismatch into a benefit by designing a modulation approach that is inherently robust to such variations. The switching transition technique ensures that even with mismatched inductors, the spectral content remains clean and harmonic distortion is minimized, eliminating the need for precise inductance matching.
4Loss of energy
If existing modulation circuits are used to improve switching loss, then switching loss is reduced, but total harmonic distortion worsens
Solution Approach 1:
The patent changes the modulation parameters and switching transition characteristics to achieve a balance between switching loss and harmonic distortion. By carefully controlling the timing and shape of switching transitions to align with zero-crossings of the audio signal, the design reduces switching losses while maintaining low harmonic distortion, unlike conventional modulation approaches that trade one for the other.
Data Source
AI summary
Methods, apparatus, systems, and articles of manufacture are disclosed to generate a modulation protocol to output audio. An example apparatus includes a modulation circuit including a first input, a second input, a first output, and a second output; a first gate coupled to the first output of the modulation circuit; a second gate coupled to the second output of the modulation circuit; a first multiplexer including a first input coupled to the first output of the modulation circuit, a second input coupled to the output of the second gate, and an output coupled to a first switch; and a second multiplexer including a first input coupled to the second output of the modulation circuit, a second input coupled to the output of the first gate, and an output coupled to a second switch.