Abstract

A PD GaN fast charger operates at elevated switching frequency and tends to create high-frequency EMI. The PD GaN fast charger suppresses noise via input EMI filters, snubber circuits and PCB layout. This PD GaN fast charger covers conducted limits, radiated margin and common-mode filter parameters to help pass overseas EMC tests and avoid interfering wireless devices.

1. Origin of GaN High-Frequency Noise

Fast voltage edges of GaN devices inside the PD GaN fast charger create voltage spikes. These spikes of the PD GaN fast charger turn into conducted and radiated EMI. Noise spectrum of the PD GaN fast charger extends to higher frequency bands compared with silicon designs.

2. Input EMI Filter Network Parameters

The PD GaN fast charger uses common-mode inductors, X and Y capacitors at input. Two-stage filtering of the PD GaN fast charger attenuates 150kHz~30MHz conducted noise. Y-capacitance of the PD GaN fast charger must balance leakage current constraints.

3. RC / RCD Snubber Circuits

Snubber networks at switching nodes of the PD GaN fast charger suppress voltage spikes. Snubber components of the PD GaN fast charger cannot introduce excessive power loss and hurt efficiency. Component values of the PD GaN fast charger require iterative tuning.

4. PCB Layout Noise Reduction

High-frequency power loops of the PD GaN fast charger must be minimized. Power ground and signal ground of the PD GaN fast charger use single-point connection to prevent ground loop interference. Good PCB layout is critical for EMC compliance of the PD GaN fast charger.

5. EMC Test Margin Assessment

Design of the PD GaN fast charger reserves more than 6dB noise margin to secure mass-production consistency. EMC pre-scan must run under multiple load conditions.

Conclusion

High-frequency operation creates unique EMC challenges for the PD GaN fast charger. For EMC pre-scan reports of a PD GaN fast charger, contact Simsukian for technical support.

References

1. USB-IF USB Power Delivery Specification

2. IEC 62680-1-2 USB PD International Standard

3. IEC 62368-1 AV and ICT Equipment Safety Standard