Power supply is needed for  all of electronic circuits. Say you have  a 12V power supply  and you want to use it as a 5V power supply. Then use this 12v to 5v dc-dc converter circuit diagram to convert 12 volt to 5 volt. This DC converter circuit provide 5V, 1Amp at output. Here is the small schematic circuit diagram of 12volt to 5volt converter.
Circuit Diagram of 12VDC to 5VDC converter:
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| Fig: 12 volt to 5 volt dc converter circuit schematic | 
This DC-DC converter is based on IC LM7805. The LM 7805 is a 3-terminal fixed output positive voltage regulator IC.  The output current of this circuit is up to 1Amp . Use a heat sink with LM7805 to protect the IC from overheating.


 
 
 
 
 
 
 
