Basic Regulated Power Supply

The task often comes up where a project needs a quick simple regulated supply voltage, Most of the time this is from a battery to supply a microcontroller or various other logic circuitry. This is quick little circuit i use when efficiency is not important and up to 1.5A is needed.

This circuit uses the very popular LM7805 voltage regulator, while this is not a new regulator and most designers have used it at some point in time it still proves very useful. The basic circuit that i use is adapted and simplified from the datasheets. The following is the layout used:

Basic Regulated Power Supply

This circuit is used either as is in a lot of my designs or modified to have better filtering or current boosting. There are numerous voltage regulators that are interchangeable with the 7805 to obtain different output voltages. Some of these are:

  • LM7812
  • LM7815
  • LM7818
  • Low Dropout Equivalents

One important thing to note when using these regulators is the more current drawn from them the greater the input capacitance needs to be, this helps reduce ripple when regulating from a rectifier. Another important thing to note is the input voltage must not be too much higher than the regulated output voltage as this excess voltage is essentially burnt off as heat and hence the higher the input voltage the hotter the regulator will get. However the input voltage needs to be around 2v higher than the output voltage, and 1v higher for low dropout regulators.

As with any electronic device you should consult the data sheets for the specific requriements, and usually you can also find example circuit applications.

Final thoughts, This may not be the world’s most efficient power supply but it certainly has its place and shouldn’t be disregarded just because it’s a linear regulator.

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