there are so many designs available which design is the best and economical to charge?
i dont know sorry
Buy a charger for your phone from a $1 dollar store.
that or get a lm7805 and wire it to the charger
....which is not going to be "best" by any means, a 7805 needs at least 7V on the input to get 5 out, and phones take 100mA to charge, so you are wasting power needlessly, not forgetting the transformer's dissipation.
Why not pay the dollar ?
how much power do you really waste?
you waste 2v+ at 1.5 amps, so that's 3 W wasted and really, how often do you charge your phone? 1-2 hours every week?
if you used it for a year, you would waste 336W every year, and that costs: $0.06