4.2V to 220V inverter | 40W Inverter using | TTC5200

Transistor inverters can either be self oscillating, or driven by a separate oscillator. In the self oscillating type, the transformer itself provides the positive feedback required to cause oscillation. However, loading and transformer design will affect operation to a certain degree. Where frequency stability is important, the inverter

a separate oscillator to drive the switching transistors. The oscillation frequency is thus independent of loading.
Over the years, I have built both types of inverter. The self oscillating type is of course attractive because of its extreme simplicity, and is perfectly adequate for many applications.

Circuit Diagrams