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DC - DC Conversion

It is relatively simple to build yourself a lower voltage power supply, using the output power of your existing 13.8 volt power supply. There are many ways to do it, but here, I will explain how I have done it. I'm sure there are others ways of doing it, depending on who is doing it.

Look at it this way. We already have the majority of the 5 volt supply available to us. It is our 13.8 volt supply. We will not have to look for a transformer, rectifier, or big filter capacitors.

Take a look at the schematic:

a typical dc to dc power supply schematic

If your need for 5 volts, does not require a lot of current, a few diodes in series, at the positive input of this 5 volt supply, will drop the voltage enough, so as not to create as much heat at the final regulator.

As a rule, a diode will drop voltage across it .4 volts. Series them up to what is needed at the positive input of the regulator.

One can substitute the regulator, with any of the 78xx series, as long as they are lower voltage than the output of your main power supply. Then adjust your diode network accordingly.

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