InnoSwitch-CE - High Frequency Ripple on DC Output - 5V 15W SMPS
Posted by: HimanshuRai84
on
Hi,
I am designing a 15W 5V SMPS Board for a universal line voltage input (85V-265V). Most of the design works well but I am seeing a lot of High-Frequency Ripple on the Output of the SMPS PCB. See the attached Schematic and Waveforms for the measurements and design.
Please can someone review and advise what I could do to reduce / eliminate this HF Ripple component from the DC output? It increases in amplitude with increase in Line Voltage input at the maximum power output level (3A / 15W).
Files
Schematic for Design
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SDS00061.jpg
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SDS00063.jpg
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SDS00067.jpg
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SDS00071.jpg
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SDS00073.jpg
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Hi HimanshuRai84,
Thank you for using Power Integrations products.
It is possible that the HF spikes you see on the ripple waveform are noise pick-up by the oscilloscope probe. The spikes you showed are in-sync with SRFET switching events and as VIN increases, SRFET VDS also increases.
Are you using a probe with short connection, preferably with a BNC adapter? https://probemaster.com/4987ba-bnc-adapter/
Long wires for the probe are prone to noise pick-up.
Also, can you check if a ceramic capacitor directly at the output terminal helps to reduce the noise?
It appears you have a provision in schematic (C19) but it displays not populated.
Regards,
PI-Spark