Class-D Amplifier PCB Ground Layout for Low Parasitic Emissions
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Solution Overview
Problem
The increased switching frequency in modern class-D amplifiers leads to higher parasitic emissions of electromagnetic waves, which are not effectively addressed by existing technologies.
Innovation Solution
A class-D amplifier design featuring a single printed-circuit board with a broad output ground pattern extending into all regions, including input and output amplifying circuits and filters, combined with multiple negative feedback circuits to manage high switching frequencies and reduce parasitic emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching frequency of the class-D amplifier is increased to improve amplification efficiency and reduce distortion, then the amplification performance is improved, but parasitic emissions of electromagnetic waves increase
Solution Approach 1:
The patent divides the ground system into separate input ground and output ground regions on the printed circuit board, preventing the mixing of high-frequency switching noise with low-frequency signal references. This segmentation isolates the harmful electromagnetic emissions from the sensitive input stages, allowing high switching frequencies to be used without degrading amplification performance or increasing parasitic emissions in the signal path.
Solution Approach 2:
The patent introduces a ground isolation circuit as an intermediary element between the input and output grounds, typically implemented as a resistor or inductor connection. This intermediary blocks the direct path for high-frequency parasitic currents while maintaining DC ground reference, thereby suppressing electromagnetic emissions without compromising the amplification efficiency gained from high switching frequencies.
2Object-generated harmful factors
If a solid pattern of the output ground extending into all regions is used to reduce parasitic emissions, then electromagnetic interference is decreased, but the device complexity increases
Solution Approach 1:
The patent merges the output ground pattern into a solid, continuous structure that extends across all regions of the printed circuit board where switching components are located. This unified ground structure provides a low-impedance return path for high-frequency switching currents, reducing electromagnetic radiation and parasitic emissions without requiring complex multi-layer designs or additional shielding structures.
Solution Approach 2:
The patent utilizes the planar dimension of the printed circuit board to create an extensive ground pattern that covers all necessary regions. By expanding the ground structure in the two-dimensional plane rather than adding vertical complexity through multiple layers or three-dimensional structures, the patent reduces electromagnetic interference while keeping the device complexity manageable.
Data Source
AI summary
A single printed-circuit board of a class-D amplifier includes an input ground, an output ground, an input amplifying circuit, a modulation circuit, an output amplifying circuit, and an output filter, a solid pattern, a first feedback circuit, and a second feedback circuit. The solid pattern of the output ground extends into all regions of the input amplifying circuit, the modulation circuit, the output amplifying circuit and the output filter. The first feedback circuit executes a feedback where a voltage at a first connecting point is negatively fed back to an inverting input of the input amplifying circuit. The second feedback circuit executes a feedback where a voltage at a second connecting point is negatively fed back to a non-inverting input of the input amplifying circuit.