test circuit for switching power supply. Not using a ready-made IC! It is based on PNP transistor, and coil from a CFL.
Efficiency is not so good but not too bad, the transistor does not heat up, dumping 6 volts into 22 Ohms, from 20 Volts.
The circuit makes some noise!
And it is not the latest technology…actually based on a LM317. Modified it a little so the current can be reduced. Input current is lower than output current! 70mA -> 200mA (20v -> 6v).
this is the coil I used at the beginning. Very bad, everything gets hot, transistor burned out. Wrong inductivity!
This is how the circuit looks now! The coil really was taken from a CFL circuit board. Smaller inductors are not so good for this circuit…Output is adjustable!