Fluorescent lamp inverter

Fluorescent lamp inverter

This inverter is very easy to build, reliable, and even powerful enough to power a 15W fluorescent tube (if you cool the transistors well). The only hard-to-find part is the so-called yellow inverter transformer. It's a miniature high-frequency transformer with a 25mm x 20mm x 5mm ferrite core, 30 turns primary, 15 turns feedback, and 250 turns secondary, all concentrically wound on a plastic frame and then wrapped with 'yellow' tape. If you can't find it at your local electronics store, search for old portable rechargeable fluorescent lamps, as they all have at least one yellow inverter. Of course, you can wind a hand-made transformer that does the same thing, but it's a very difficult task when you don't have an original as a reference and still requires a suitable ferrite core.

This is a single-transistor oscillator circuit. Current flowing through the primary winding induces a magnetic field in the core, which feeds energy back to the feedback winding. The delay is determined by the core material and the winding itself. The system then oscillates continuously at a frequency that depends on this timing. You cannot use the 2SD882 with voltages exceeding 4.5 volts. It is only necessary if you intend to power a circuit with only 4.5 volts. The equivalent transistor may not perform as well as the 2SD882 (NEC Electronics, Japan).