Most commercial LED flashlightsuse three AAA or AA batteriesin series that produce 4.5V. The batteriesthen drive four white LEDs that connectin parallel. These LEDs can workat voltages as low as 2.7V ...
It’s a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage. Normally, if you want to light up a blue or white LED you need to provide it with 3 – 3.5 V, like from ...