What is a Resonant Inverter, and why is it commonly used in high voltage supplies?
A resonant inverter is the term applied to the combination of the switching transistor stage, its output circuitry and the transformer. When a step up transformer is employed, it generally has a large distributed capacitance due to the large quantity of the wire on its secondary and the close proximity of the turns. By arranging the circuit so that it is tuned to resonance, this capacitance no longer becomes an issue and does not waste any power. Resonant designs utilize a transformer core gap, core ferrite and secondary winding scheme to make them resonant at a particular frequency. Then, the switching frequency of the driver circuit is adjusted so that it is close to the natural resonance of the transformer. Under these conditions, the drive current into the transformer falls to a very low level when the transformer is unloaded. The resulting waveform applied to the transformer is a sine wave.
