1.5-V White Led

Thanks to their high light output and long lifetimes, a white LED is an excellent choice as a replacement for the incandescent bulb in a penlight torch. However, there is a ‘but’. Depending on the current level, white LEDs need a voltage of 3 to 4 V. You thus need a penlight with at least three batteries, which is not exactly what you can call compact. Fortunately, this problem can be remedied using a simple adapter circuit.The design described here allows a white LED to be operated from a single 1.5-V battery. It consists of a simple stepup converter and an oscillator. If the circuit is built using SMD components as much as possible, it will not be difficult to fit everything into the torch.