Simple 9-18V boost regulator for pedals

[Cliff Schecht]

The idea for this project was simple, eliminate the extra power supply befuddlement required to get 18V for your pestos. I prefer to power everything off of one supply if I can. Specifically I want to be able to power my flanger with a 12V regulator from my clean 9V power supply. While I already have a solution to powering this cleanly, I thought I could come up with a more elegant way of powering whatever effects I want from 18V. I don't like the awkwardness of using isolated power supplies (they are physically large usually) and most of the charge pumps I've seen switch at too low of a frequency even for lo-fi guitar applications (not to mention the low current capability) so I think it's about time we had a tiny boost supply that's small, quiet and easy to use.

A quick peek at TI's website revealed an easy solution in the form of the TPS61170 power management IC. It has a built in 1.2A, 40V low-side FET, switches at up to 1.2 MHz and has all of the amenities one expects from a modern power solution (thermal/overload protection, slope compensation and an easy to use compensation scheme). In a nutshell it looks like a tiny, inexpensive and simple part to use. And you are by no means stuck with going from 9-18V with this part, you can go at least as far as 5-24V (of course sacrificing current by doing so) and maybe further if need be (eventually you max out the duty cycle and need to look at a flyback topology instead for getting higher voltages). Current output should be at least 300mA (constant) and the efficiency is boasted to be up to 93%.

I've already designed a board for this part that's about the size of a nickel (0.675"x0.675"). Most people here probably don't keep 0603 resistors around but it uses four of these, two 0805 capacitors, a SMD inductor and a SMD Schottky diode. If you aren't afraid of a few surface mount parts (the IC will probably need to be put down with a small heat gun) then this will be a fun little project to build. If you aren't good with surface mount parts then this is good practice .

I still need to etch a board and test everything but I have high hopes for this little power supply. The final version will probably be a bit more user friendly with vias for connecting wires (probably need to grow the board size for this!) but I will share the project files as well for anybody wishing to adjust the layout or include this on a board they are making.

I'll keep you guys updated as parts arrive and things progress.

Here's some eye candy for now:
Schematic: http://www.aronnelson.com/DIYFiles/up/9to18_boost_schematic.pdf
Board (real size): http://www.aronnelson.com/DIYFiles/up/9to18_boost_board.pdf

[therecordingart]

I'm in for at least 5 of these.

[Cliff Schecht]

I don't plan on selling anything fwiw, just providing the project files for all to enjoy. I want to make it as easy as possible to build too so any suggestions are welcome, especially when it comes to interfacing to this little guy. As of now I've just left enough space to solder wires right onto the extra fill areas (if you don't have a soldermask) but it wouldn't be hard to add a jack to one side and vias to the other side for connecting a prewired 2.1mm barrel adapter. This would allow you to put this right in-line with whatever effects you want powered on 18V like the Godlyke solution that sells for $30-40 retail.

[Morocotopo]

A cool thing for sure. I think most here would love to buy prefabricated boards. A partnership with someone that makes them, like, hmm, Smallbear perhaps?

[Cliff Schecht]

I'd be glad to assist in having this done. Let me get one working first, then we can talk about having them made professionally .

[rustypinto]

That DFN is not at all easy to install, especially with the thermal pad on the bottom and the fact that its 2x2mm! If you don't mask-off the PCB, place it JUST right, or put the right amount of solder paste on prior to installation; the part could float during re-flow resulting in open-connections to the control pins. You might also shock the part if you use a heat gun.

[Cliff Schecht]

This is doable without a soldermask and with a SMALL heat gun specifically meant for installing SMD parts. I'm lucky enough to work in labs that are equipped to work on SMD stuff so I never shy away from them. For the IC I will put a small amount of solder on all of the pads and hold the part in position using tweezers while I apply the heat. I've done this trick before on non-soldermask boards and it works as long as you don't put down too much solder and leave enough extra pad length to get the soldering iron on both the board pad and the little bit of metal showing on the SMD.