# Does current flow through the potentiometers of buck and boost converters?

I'm working on a project where I'm replacing the trimpots on a buck converter and a boost converter with proper potentiometers. The new potentiometers will be wired to the converters instead of soldered directly on, so this poses a problem: What wire gauge should I use?

Let's say my loads will be maximally drawing 10A. Does that mean I need 16-14AWG wire to attach the potentiomters? I don't think so but I don't totally understand these things. My current understanding is that the potentiometer acts as a voltage divider and it is the center pin which tells the chip how to limit voltage or current by being at a certain voltage.

The answer may be that it depends on the converter but I think there is a general pattern here. To give an example though, I'll be working on this Chinese converter (Google translate) Update: This post is the most information I can find on it.

As I understand it, it's based on the UC3842A SMPS controller driving at least one power MOSFET (I also see a big N-channel and then the smaller BU806 NPN.) I don't know if that's enough information to answer my question though. It seems like, if it works the way I think it does, it's pins 2 and 3 on the UC3842A which read the potentiometers.

Another example is the LM2596-based boards. I suspect they work in a similar way (and are a bit easier to understand.) There's one more board/chip that I'm interested in but I don't have any information on it yet since it's not in my possession and there's very little details online. If it's okay, I'll leave the ebay link here.

• To be sure what you're talking about, you should add schematics (or parts of it as image) and links to datasheets. – try-catch-finally Apr 17 '16 at 10:12
• Good point. I added datasheets for the two chips that I know and a link to a post with an unofficial schematic and some explanation. – Anthony Apr 17 '16 at 10:19
• A trimpot cannot take much current let alone 10A which would release the magic blue smoke instantly, so why would swapping them out for external pots require big wire? – JIm Dearden Apr 17 '16 at 10:35
• That's clever; it would not. – Anthony Apr 17 '16 at 11:32
• Variable resistors obey Ohm's law, more or less, as you'd expect, more or less. – Russell McMahon Apr 17 '16 at 12:40

The feedback resistors are also recommended in the $k\Omega$ range, reducing current flow.