The Feed Forward transformer is a voltage controlled version of the current controlled flyback transformer. Key considerations are leakage inductance and interwinding capacitance. Typical values for capacitance are <10pF and leakage inductance <40uH. The inductance determines the amount of time that is required for the pulse to collapse to zero. The primary winding of the feed forward transformer typically has an inductor in series with the primary winding or a capacitor in parallel with the primary winding. Both the inductor and the capacitor are used for voltage retention. Voltage storage design parameters, like the flyback transformer include leakage inductance (uH) and DCR.