# Flyback converter primary and secondary sides power calculation

The problem is as below.

Input DC voltage is at 12V, transformer inductances are: Lp = 60uH, Ls = 240uH, switching behaviour is controlled by a single NMOS with switching frequency at 60kHz.

For ideal case, is it correct that power at primary winding is equal to the power at secondary winding, and that is the equation for this power.

• Yes, and in terms of basics, you need Lenz's Law to help find the power. – Brian Drummond Oct 30 '18 at 7:56

• @Electronicsnewbie Power = energy x frequency and $0.5\cdot L_P\cdot I_P^2$ is the stored energy in the inductor. So, if all that energy is transferred to the secondary then so is all that power (assuming zero losses.) – Andy aka Oct 30 '18 at 11:39
• Follow JonRB's link to the section called "VBUS to VOUT transfer ratio" and you'll see that your 2nd formula should be $F_{SW}^2$ in the denominator. – Andy aka Oct 30 '18 at 11:45