Flyback Converter Capacitor Value selection with given ripple voltage limit
\begin{equation}
C&gt;\frac{I_{out}\cdot D_{max}}{V_{ripple}\cdot f_{switching}}
\end{equation}

Dmax is the maximum duty cycle 50% --> 0.5
Vripple is a peak-to-peak value

edit: I found this for you: http://www.ti.com/lit/an/slva559/slva559.pdf