0 12V Power Supply (High Curent)

7812 regulator provides only a maximum current around 1.5A at 12V. Unlike the 12V DC supply, this circuit can provide 5A current (even higher if modified) by just adding transistor and resistor.
high current 12V regulator
7812 pins
Part List:
R1 - 33 ohms 1/2W
Q1 - MJE2955 or similar PNP power transistor
7812 - LM7812 or any 12V regulator IC
C1 - 470uF electrolytic capacitor rated 25V (can be removed)
C2 - 100uF electrolytic capacitor rated 16V (can be removed)
DC input - see AC-DC converter circuit below
AC-DC converter circuit
Part List:
Transformer - 220V-15V or 110V-15V center tap minimum rating 75VA
D - MR751 or any diode with 6A minimum current rating
C - 1000uF (higher the better)  electrolytic capacitor rated 25V

To further increase the current capacity, you can add the circuit below to the circuit above. Just connect the points A for A, B for B and C for C. Every additional of the circuit below is additional 5A current to your regulator. Do not forget to add heatsink and you can add fuse in series to the output of transformer for additional protection. Take note also that you must replace the transformer and diode with much higher capacity if you plan to add the current booster circuit below. Qx is MJE2955 and Rn is 56 ohms 1/2W.
current booster circuit


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