Cool 5V stabilized power supply.

A 5V Switching Mode Power Supply (SMPS), replaces a 7805 (= linear 5V stabiliser).

In applications with e.g. a PIC, an SD/MMC card reader, an Ethernet interface based on the ENC28J60 and an RS232 interface based on the Max232, the current drawn from the 5V power stabiliser becomes rather high. A heat sink is required for the stabiliser IC (usually an 7805, fed from an transformer via a bridge rectifier and a buffer elco). Things get worse if more components are added to the circuit: the heatsink must become bigger and bigger. Of course one can take a number of mesures to make the input voltage of the 7805 as low as possible (but not too low: stabilisation must still be possible), but even then the dissipation problem persists.

This circuit poses a solution to that problem.

Circuit diagram


This type of power supply has the following characteristics: The main components in the circuit are: There are also versions of the LM2575 for other output voltages (o.a. 3.3V).