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Inrush limitation for X2 capacitors in Offline PFC'd SMPS?

treez

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Hi,
The attached is a FET based inrush limiter for a Boost PFC’s output capacitance.
Is it worth having an inrush resistor for the X2 caps aswell (as shown). For example, for a 250W, 240VAC Boost PFC, a 1R,3W inrush resistor could be used just upstream of the X2 caps.

Or is this not worth it?
The X2 capacitor datasheets don’t allure to inrush protection measures
https://www.illinoiscapacitor.com/pdf/seriesDocuments/MKP series.pdf
 

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  • Inrush into Boost PFC.pdf
    162.3 KB · Views: 3

biswaIITH

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Hi,
The attached is a FET based inrush limiter for a Boost PFC’s output capacitance.
Is it worth having an inrush resistor for the X2 caps aswell (as shown). For example, for a 250W, 240VAC Boost PFC, a 1R,3W inrush resistor could be used just upstream of the X2 caps.

Or is this not worth it?
The X2 capacitor datasheets don’t allure to inrush protection measures
https://www.illinoiscapacitor.com/pdf/seriesDocuments/MKP series.pdf

Only an inrush limiter resistor for Bulk capacitance is enough. The product we have designed in the past up-to (2 to 3 kW) ,we have never faced any issue for X-cap Inrush. However ,you must provide a bleeder resistor to discharge it once disconnected
 

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