I am trying to find the way to arrive at a suitable electrolytic capacitor that would serve the purpose of retaining the powersupply at the working voltage level for a predefined time. I am not successful in making use of the t=RC, or the E =0.2C.V.V , or the E = I.I.R.t where t is the time for which I wish to have the voltage remain at the working level, R the load resistance, C the electrolytic capacitor, V the DC voltage, I the load current. Say I want to achieve a 100ms of retention of the voltage from the instant of the source shutdown. The attached ckt dgm, wavefm dgm should give you an idea i wish to simulate. Request your comment in where in my calculation and in the simulation part I am commiting mistake.