Good how to on voltage conversion from 9 VDC to 220 VDC, Pedro writes – “To have a Direct Current Converter on your work bench increases greatly your capability of experimenting within an ample range of electronic components that need over 100 volts to be driven. Among these components we find neon lamps, nixie display numerical tubes, and some kind of triode and pentode valves. Neon lamps open a broad field to build audio oscillators, blinkers and flashers, polarity finders, display decorations, hot chassis checkers…etc. Nixie tubes allow you to construct displays for digital counters, and various types of clocks; and with electronics valves many kind of radio transmitters and receivers can be mounted, among a huge lot of other electronics instruments and equipment. Some of these devices work with voltages between more or less 100 and 200 VDC.”Link.