Flyback Switch Mode Power Supply Circuit

This is a flyback SMPS that will boost voltage a voltage of around 20V to 40V, or more if you change the feedback resistors. It uses an off the shelf transformer from CoilCraft.

The LM3479 is a nice controller because it's frequency of operation can be set by changing R1. At 39K it runs at about 500KHz.

One innovation of the circuit is that the regulator is driven with +5V, a smaller voltage than VPIN. Separating the regulator voltage supply from the supply driving the coil allows VPIN to be nearly any value. Of course you need to have the 5V generated else where.

The circuit also has a non-dissipative snubber circuit on the drain of the MOSFET, to limit the voltage spikes when the transistor turns off.

See our calculators to make modifications to the feedback circuit, or use a different transformer.

Flyback SMPS