Elektor Article: Led Booster for Microcontrollers

There’s many a time when you want to connect a white LED to a microcontroller operating from a 3 V supply voltage. Unfortunately, this doesn’t work and your nice white LED only lights up feebly or not at all.

Elektor Article_ Led Booster for Microcontrollers

Why does it work perfectly with red and green LEDs, but not with white? A bit of data sheet research reveals the reason: white LEDs have a forward voltage of 3.2 V, so a 3 V supply is simply not enough to let them light up properly. The advice you often see in online forums is to use a boost converter to generate a higher voltage, along with a transistor switch to control the LED. For just a single LED, this seems like a lot of overhead.

The good news is that there’s an easier way. And it only needs one inexpensive component: an inductor, which costs next to nothing. 

Operating principle of a boost converter

Take an inductor L (a coil) and connect one end to the input voltage UIN and the other end to a switch S tied to ground. When the switch S is closed, a gradually rising current flows through the inductor L, creating a magnetic field. When the switch S is opened a bit later the magnetic field collapses, generating an inductive voltage over the coil (Figure 2), the same as an ignition coil in a car.

Read more: Elektor Article: Led Booster for Microcontrollers

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