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Capacitor Selection help

Posted by: mohan.n2293@gm… on

Hi All,

Myself Mohan,

Im design a 60 W fly back converter ,my output ripple im getting is 10.6A but please help me to findout correct value of capacitor

Comments

Submitted by PI-DATA on 11/20/2017

Hi Mohan,
It depends on what kind of ripple voltage you are getting if it low or high frequency ripple or both. For low frequency ripple and your minimum input voltage is 90Vac, the input bulkcapacitor would be 2-3 times the output power(i.e. for 60W the input bulk capacitor should be atleast 120uF).

For high frequency ripple, the value of the capacitor at the output is highly dictated by the ESR of the capacitor. ESR (Equivalent series resistance) is shown at the data sheet of the manufacturer. In your case, you should be using very low ESR in the rang of milli ohms.
Example: Vripple=ESR x Io Vripple=50mV Io=2A
50mV=ESR x 2A
ESR=0.025 ohms or lower