12v 2amps power supply to 5v

Thread Starter


Joined Nov 27, 2015
I have designed 12v 2amps to 5v power supply design, here used 12V 2amps transformer rectified output goes to LM7805. why we used 12v 2amps for DC Motor 12v 2amps is used.
my clarification is
# LM7805 support 2Amps input ?
# LM7805 output 5v 1amps need for out microcontroller
# 12v transformer rectified output comes 14v some times. how to get 12v constant.

Here attached the circuit please give suggestion.



Joined Nov 30, 2010
Bad design.
D6 will melt.
One end of the transformer winding is shorted to the negative rectified output.
If you use a 12 volt AC transformer, the rectified output will be 17 volts, minus the voltage used up by the diodes (usually 1.1V to 1.5V).
Will an LM7805 support 2 amps? The datasheet says 1 amp.
How to get 12 volts constant: Use a 12 volt regulator chip.



Joined Jun 4, 2013
Ugeshkumar, you may not be aware that one of the reasons for using a voltage regulator is so that the input voltage can vary a lot while the output voltage is maintained at a fixed value. So you don't need to make your 12 Volts constant in order to feed your 5 Volt regulator. However, if you ALSO need a stabilized 12 Volts, then you'll want a separate 12 Volt regulator being fed from the same point in your circuit as your 5 Volt regulator.

Also, all the comments from #12 are correct and should be corrected.