24 V Flyback Circuit

Introduction

This circuit can drive any type of flyback transformer without using its original primary, but a self built one, composed by few turns. This very simple device grants a low voltage input, few components, high voltage and high current output.

Construction

The first thing to do is to choose the right type of flyback transformer: the better type has a dish-shaped secundary from old TVs, that has a low capacitance, but any flyback works. If you want very high voltage dc, you must use a VGA flyback that has an integrated voltage multiplier. Now there is to make the windings on the ferrite core:  5+5 turns with 6 mm^2  insulated wire for the primary winding and 2+2 turns with thin wire for the feedback winding.

  

Theory

Well, there's not much to say about this design, it is a simple feedback oscillator: when it is on, the transistors begin to conduct and the primary creates a magnetic field through the ferrite core, that field is converted by the feedback windings in a negative impulse. This turns off the transistors and the magnetic field, so them begin to conduct again, and so on.