Low cost lighting when there's no mains supply available

The quest for a battery-powered lamp for lighting in poorer areas has presented an interesting and important design challenge for many years. Such a lamp should ideally be cheap, simple, efficient, and flexible - all at the same time.

With this in mind, the authors have designed a lamp which is made from inexpensive stock parts throughout, runs off a nominal 12V d.c. supply, and will power any ordinary fluorescent lamp between 100mW and 15W. It will power the equivalent of a 60W incandescent lamp for about 80 hours off a standard 12V car battery.

Most d.c.-powered fluorescent lamps use specialized components. While this may not pose a problem in major urban centres, it could pose serious supply problems in more remote areas of the world. The authors therefore searched for a means to unhook the World Lamp from the need for any uncommon or custom-made parts. This is accomplished in the present design through a.c. pulse-width modulation (p.w.m.), which is the core concept of the design.