Suggestion:Which Currentmode PWM controller, Vin 3-6V? - Page 1
Forum section: electronics / projects

author: Yansi
author_rank: Super Contributor
timestamp: May 08, 2019, 08:33:22 pm
content: Hello!I have just sifted through 38 pages on Mouser, trying to find a current-mode pwm controller, capable of running from 3 to 6V, unfortunately unsuccessfully.What I am aiming for is a battery powered (4xAA alkaline) boost converter, just couple of W, but rather higher voltage, than usually available chips --> hence external mosfet required.The closest I came around was MCP1632, unfortunately, 6V absolute maximum is I think not safe for use with 4 AA cells. (something like UC3843, however for <4V operational voltage would be sooo nice!). Am I asking for just too much?Thank you for any suggestions! Cheaper the better!

author: Buriedcode
author_rank: Super Contributor
timestamp: May 08, 2019, 08:39:44 pm
content: What output voltage? If it is only slightly higher than the max output voltage, coupled inductors 1:1 are widely available in a range of inductance and will half the peak switch voltage.

author: Yansi
author_rank: Super Contributor
timestamp: May 08, 2019, 08:43:13 pm
content: Coupled inductors forbidden. Too pricey & I am too lazy to wind any such. And I am trying to avoid designing this around the old steaming pile 34063...It is just a one-off project for a friend, output voltage needs to be 80V and reasonably clean (quite sensitive stuff will be supplied with it). Hence why I wanted a PWM controller, not hysteretic controller like 34063, which are little factories for big interference.

author: mariush
author_rank: Super Contributor
timestamp: May 08, 2019, 08:55:29 pm
content: Maybe checkLT8361 ... barely... 5v or higher preferred.LT3482 ... up to 90v output voltage, with low input voltage.Both chips around 3.5$ if you buy 10-25... something like that.

author: Yansi
author_rank: Super Contributor
timestamp: May 08, 2019, 09:34:25 pm
content: Waaaaaay to pricey for what it is. I can't get those under $10 a pop. I could make a whole bunch of different solutions for that price, including the coupled inductor one.I have not considered using IC with integrated switch, due to exactly this pricing. :-/ So just looking for a controller IC, or one that an external mosfet may be connected to.

author: Buriedcode
author_rank: Super Contributor
timestamp: May 08, 2019, 10:26:16 pm
content: Quote from: Yansi on May 08, 2019, 08:43:13 pmNo need to wind any. As I said 1:1 are widely available and not much more than a single winding inductor. For 80V out that gives you 40V max on the switch node. Of course that won't matter much if you're going with external FET. For just the controller, I'm surprised you haven't found anything suitable. First result for TI's search:http://www.ti.com/product/LM3478

author: Yansi
author_rank: Super Contributor
timestamp: May 09, 2019, 08:17:53 am
content: Nice catch! I may not have found anything, because Mouser listed like what.. 120+ pages of those ICs and I have only gone through 38 of them manually (the parametric search sucks as always).That one also can be obtained for friendly price, indeed, how could I have missed that one? Whatever...But thanks for tip! If anyone else finds anything similar, pls let me know!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 09, 2019, 08:21:46 am
content: A literal one-off? Pfft, suck it up, you've spent more time talking and reading about it than a hundred inductors are worth!The economics of low quantity products are very different and I find I have to remind myself constantly.Regarding voltage but not current ratings: you don't need a controller for that. Consider cascoding the switching transistor. As much voltage range as you like, and the regulator doesn't know the difference. Obviously, doesn't work with internal diode type regulators, shop accordingly.This approach doesn't show up very often but IIRC, some of the ADUM family isolator-converter chips used such a method for higher output voltage/power from a 5 or 10V chip.Tim