I test this circuit using only fake chinese NE555 and TC4420. The result is a flat 5v signal with small HF oscillations during switching. The TC4420 start getting warm above 1A in output. I think it would be better with original parts , like CMOS 555 and a mosfet driver with dead-time and high power mosfets.
-Fixed max duty cycle
-Fixed minimum frequency
-Soft-Start
I recommended: LMC555 , IR21834, IRF3205
