Need a DC-DC converter circuit

Job ID: 35085137

Budget: $30 – $250 USD

30Vdc to 27.4Vdc Battery charger (no-stages)
UPS output with battery cutoff at 22Vdc
no reverse polarity protection
no short circuit protection

Must use IRFZ44N with op-amp and basic components
Must regulate to max 5A to Batteries, no higher.