You are still using the standard 7805 to get a stable 5V output?
Well you need 7V (minimum) Input Voltage for the 7805
Let say we need 100mA Output Current.
Which efficiency you will get from the 7805 versus an LDO like the ADP150?
Tip: Datasheet of the ADP150: http://www.analog.com/en/products/power-management/linear-regulators/adp150.html
Solution:
7805
Ptot= (Vin-Vout) *Iout = (7V-5V)*0,1A = 0,2W
Ptot equals to heat you need to distribute.
Pab=5V*0,1A = 500mW
n=Pab/Pzu=500mw/700mW ~71%
ADP150
Vin(min)= Vout+0,4V
Vout=5V
Vin= 5,4V
Ptot =0,4V*0,1A = 0,04W
Pab=500mW
n=Pab/Pzu = 500mW/540mW ~ 92%
