The Adafruit Constant Current Boost Converter for LEDs makes driving LEDs easy, whether they're in series or parallel - with a chip that can generate up to 40V and 400mA from 3~5V input. Unlike most of our booster chips that generate a fixed voltage (like 5V, or 12V) the TPS61169 increases the voltage until a set current is being drawn. That makes it excellent for LEDs that are specified in current not voltage.

This is perfect for use with our LED nOOds and filaments, where sometimes you need up to 12V or 24V at 200mA or so. It's also excellent when you have a bunch of 3V LEDs in series, so they add up to a high voltage, but only at 25mA or 50mA.

We've used the TPS61169 in our boards with LED backlights: it's pretty common to see 5 to 7 white LEDs in series and a 30mA current requirement. We like this chip because it has a 1.2A internal switch and automatic over-voltage protection in case the output is disconnected. You can also dim the LEDs via the PWM input pin. It's quiet, efficient, and fairly cool, with 90% efficiency. Since it's constant current it's not good when you need a fixed and stable voltage output like 5V - for those cases, use Adafruit's everyday boosters.

Note that you can get up to 40V and up to 400mA but not at the same time. To figure out the approximate power output you can achieve, use the formula: Iout = (Vin * 1.2A * 0.9 efficiency) / Vout. So for example, with 5V input, and approx. 12V output you can get 450mA out (the board is limited to 400mA on the switches). For a 24V nOOd, you can get about 225mA out. The current is selectable via mini DIP switches - the default is 25mA and each switch adds 25mA/50mA/100mA/200mA for a total of 400mA.

You get one fully assembled breakout with a TPS61169 and required passive components, and a small bit of header. Give 3 to 5V DC on the IN and Ground pins or terminal block. Connect your LEDs on the output port, and you're instantly in business! Note if the output is shorted or opened, you may need to power cycle the chip to get it out of safe-shutdown mode.