The higher resistance from emitter to base of the PNP, the sooner it will turn on.Hi I built the circuit & checked. The 7805 is getting too much heat with 1Ohms resistor. How to overcome this?
At 2 A output current, you are dissipating 14 W in the regulator circuit. Changing the value of R1 changes the proportion of how much heat is dissipated in the regulator and how much is dissipated in the transistor, but the total always will be 14 W. Assuming a 50/50 split, 7 W in a TO-220 package with no heatsink will melt fingerprints.
Totally meets your requirements, Suraj143, although, its footprint is, of course, considerably larger than a 7805, even with a heat sink...