Buck Converters? [closed]

Question

All I need to do is step-down my 12V power supply to 8V to power an Arduino, and I've been told a buck converter is the easiest way to do this; I see some buck converters online that look like this:

Which are obvious as to how there used, but then I also see much smaller and cheaper ones that look like this, which from reading their datasheets seem to require capacitors and all sorts in order to work:

And yet others that have 3 pins, 4 pins, even 16 pins?

Can anyone please explain (or provide a guide) as to what the difference is? Which type should I use, and if one of the smaller more complicated ones are better, how do I actually get it to do what I want?

Thank you all :)

Answer 1

The first picture shows a Buck Converter Module. It has the required external circuitry and facilities on-board so you can use with with minimum effort.

The second picture shows an integrated circuit (IC in short). As the name suggests, it integrates multiple stuff (e.g. sub-circuits, controller blocks, logic, etc) inside a tiny chip.

but then I also see much smaller and cheaper ones that look like this, which from reading their datasheets seem to require capacitors and all sorts in order to work:

What you have seen are quite possibly Buck Converter controller ICs or Buck Converter ICs. The key difference between them is the latter houses a switch as well whilst the former doesn't (you'll need to select/use a MOSFET or another semiconductor switch).

If you want to design a custom stuff, you can use ICs and design the external circuitry by following the guidelines given in the datasheets and/or the application notes. This is a bit of a hassle and requires some theoretical background because you'll end up with selection of a lot of components such as inductors, capacitors, resistors. Note that you can't use any type of inductors or capacitors in a buck converter or a switching converter, in general.

And yet others that have 3 pins, 4 pins, even 16 pins?

Generally, the more functionality and customisation the controller offers, the more pins it'll have. If you want to define a custom soft-start time or brown-out level or OVP level etc, there are many different ICs available in the market.

Which type should I use, and if one of the smaller more complicated ones are better, how do I actually get it to do what I want?

First you need to know your requirements i.e. output voltage (fixed or adjustable), maximum output current (continuous, pulsed, etc), input voltage range, ambient temperature range, etc. Then, you decide which direction to go:

• Design your own converter,
• Or buy a module and carry on

The latter is the easiest. Once you know your requirements, all you need to do is search the market (Digikey, Mouser, RS etc) and buy the module. You may also want to read the tutorials and reviews, if available, before buying a module.

Make sure the specs fit your requirements. As stated in another answer, if your maximum continuous current requirement is, say, 1 Amp then select a module that is able to deliver a higher level (e.g. 3 Amps).

Answer 2

To add to the other answers, the picture of the buck regulator board in the question looks like that in Counterfeit LM2596 Regulator Boards.

See also the answer in Step down converter LM2596 with voltage spike on output when powering up, destroys subsequent circuits which notes "cheap "LM2596" modules" are usually fake and counterfeit contains:

Eventually the low quality, high-ESR output cap will die and output voltage ripple will go out of control, but that shouldn't happen when it's new.

I.e. worth avoiding online market places which may supply products of unknown quality.

Answer 3

The easiest thing you were told is to buy something, and you were told to buy a ready made buck regulator module.

The chip you show is only a buck converter chip, and to make it work, it needs external componets like inductors and capacitors and everything else you need to make a working buck regulator.

The module already contains the chip and everything else needed for it to work. So you don't need to design it yourself or calculate component values or buy the other components.

Also the simplest way is to just use a linear regulator, and depending on Arduino model and what you do with it, it might work with 12V as well.