Diode's junction capacitance related to frequency

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snvl0228

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I'm designing PSFB converter. so, I'm using SiC diode.

It's switching frequency is 100kHz.

If I change frequency 100kHz to 20kHz, diode's junction capacitance will decrease? or increase?
 

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Capacitance "should" not depend on frequency
but your -measurement of it- may, as Rs is in
there and could affect "simpleminded"
current-for-applied-AC-voltage methods. A
VNA / s-param pull would give you the
component values for Cj and Rs.
 

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Capacitance increases with power rating as Rs decreases. SiC material has a much lower RsC=Tau material time constant but other factors affect Tau (Figure of Merit) such as PIV which raises Rs or RdsOn in FETs or Rce in BJT's or IGBT's. There isn't a precise constant yet there is a consistent trend for diodes with these variables of semi- material, geometry and power rating or chip size.

However frequency is a parameter that does not change the capacitance structure of the insulation between conductors hence the value does not significantly change in this range.
 
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Thanks. It helped me a lot.
 
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