Today I has 12V to 5V 3A DC converter step down Regulator circuit come to deposit. In sometimes friends have power supply 12V 3A , but want Voltage 5V 3A for digital Circuit. This circuit can meet the demand of friends get , by it uses normal electronic part and have 7805 integrated circuits perform to control Voltage 5V Regulate alone it gives current get just 1A. then must have an assistant is transistor MJ2955 perform enlarge current tallly go up be 3A besides. When be born over load or shot circuit as a result still have LED1 bright warn with. And still make Q2 – BD140 work cause Q3 – MJ2955 stop work with. The circuit then safe have no a problem friends may like this circuit. Because the equipment seeks easy , build not difficult too yes.