Here is a very old unregulated (1960's) dc to dc converter (switching mode power supply) circuit using two 2N3055 transistors to generate about 300 volts from a
6 volt battery. This circuit uses a standard 60-Hz transformer, and the switching frequency (determined by the resistor and transformer inductance) is several hundred Hz.
http://www.wbnoble.com/WN_articles/CD-ignition-SK.pdf
This evolved into the Delta Mark Ten kit about 1968. The Delta kit had a pot core transformer instead of a standard 60-Hz transformer.
http://www.selectric.org/delta/index.html
Bob S