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TNY280 High leading edge current spike

Posted by: Jesper on Wed, 09/29/2021

I´m doing a design based on the DI-152 Ultra wide input design note with TNY280. We have universal input 20-250VDC, 80-230VAC with multiple outputs. The design is working fine, but during startup the leading edge current spike is a bit high when supplied with 230VAC. At most we have measured spikes up to 3.5A with a period of about 400nS. The spike is a damped sine wave and only first spike is this high. I know this is above the absolute maximum of 2.55A, but since we have not seen any problem with this with previous products having the same PSU we were thinking that maybe we could use this anyway. Do you have any opinion on this? 
When the power is up and running the spikes are below max rating.

From what I can understand the leading edge spike comes from capacitance in the transformer and getting rid of them would include designing a new transformer with lower capacitance? Is there something else we can try to do? I have played a bit with rectifiers, damp-circuit etc. but nothing as an effect on the leading edge current spike. 

Attached is an image of the current and voltage during normal operation. During startup the waveform looks the same, but with higher amplitude.



Attachment Size
230VAC_VDS_Id_500nS.png 39.26 KB


Submitted by PI-Jodec on Tue, 10/12/2021



Thank you for using powi products. For your query, May I see your schematic for this as well as your transformer design. Can you also attach the startup waveform for drain voltage and drain current. Thanks!



PI Jodec