Buck Converter (DC-DC)


Alright! So hello everyone! Long time user, follower, commenter but first time iblest here! So for my first instructable I thought I’d share a recent simple project I made; a Buck Converter.

Buck Converters are great! I use them all over the place in many of my nerdy, techy, geeky hobbiest projects. They also can commonly be referred to by other names, a DC-DC converter or a switching regulator. Essentially what it does is take some higher voltage in (higher than what you want for your project), chops it up, and pieces together a lower voltage. It might help to think of it as a transformer for DC circuits… only without the giant iron block… and without the long coils of wire… and with only 3 pins.

Buck Converter (DC-DC)

Ok ok so it might not be like a transformer electrically speaking but it does take a voltage in and transform it to a lower voltage. It achieves this by taking the higher source voltage and “chops” it. The Buck Converter integrated circuit (IC) switches the higher voltage on and off very very quickly. It then passes this through caps and inductors and filters it down to a desirable lower voltage. Essentially if you increase the “on” time you increase the voltage out and vice versa.

So you may be wondering why use the more complicated Buck Converters when a simple voltage regulator serves the exact same function with no external circuitry. The answer? Buck Converters are WAY more efficient. They achieve their purpose at around 90-95% efficiencies. Regulators get their lower voltage by bleeding off the excess voltage as heat. So if you need 10V from 12V a regulator would probably be just fine and heat worries are probably not a concern. But if you have 16V (from a li-ion battery pack) and need 3.3V (to power various IC’s) a regulator would have to bleed off about 13V! That’s a lot of voltage to turn to heat! A buck converter solves this problem without the need for big and bulky heat sinks.

So now if you’ve decided to make a Buck Converter circuit, let’s get to it!

Step 1: Gather the Materials!

Gather the Materials! Buck Converter (DC-DC)

So with any prototyping project this really shouldn’t be the first step… But we’re gonna go ahead and do it cuz it’s just so darn fun! Just a little disclosure, we’ll be using the ACT4088 picked because it’s cheap and has an adjustable VOut along with a max of 1.5A out. Of course if you need different characteristics chances are, there’s a chip out there for you! The circuit we’ll build is taken straight from the IC’s datasheet and works very well!

List of parts:

Notes: Alright, now to address some design notes.

  1. All parts are surface mount for two reasons. 1: Our project will take up much less space once completed. 2: SMD parts are generally cheaper nowadays. 😛
  2. The inductor listed is shielded as speced in the datasheet however I got an unshielded one and the circuit works just as well and it’s about $0.20 cheaper.
  3. The two resistors listed are speced for a 3.3V out however you are more than welcomed to change them to whatever values you want! The resistor selection is how you change VOut to whatever is desired. The datasheet recommends keeping the 49.9 kΩ resistor and changing the 16.2 kΩ resistor. This being said with a little imagining you can see how a potentiometer can be used to make your very own $2 variable power supply! Which I have done and will show you at the end of this instructable.

For more Details: Buck Converter (DC-DC)

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