Reccomend a switching regulator controller. - Page 1
Forum section: electronics / beginners

author: David97
author_rank: Contributor
timestamp: July 20, 2014, 06:25:24 am
content: Hi everyone. I'm working on a robot that that used a external switching regulator to chop the voltage from 8.4V (2s lipoly) and brought it down to 5V-2A for the microcontroller (and other stuff) and 6V-5A for the motors and motor driver.Now I'm trying to reduce weight, so I'm incorporating the step down switching regulators and MCU into a single board. Form the regulators I've pulled apart it seems that they use a switching regulator controller to monitor the input. This then switches the mosfets at the right duty cycle to cut the voltage down. Then just have some generic smoothing stuff after that.So, I need to find a switching regulator controller or 2 that I can use for my robot. Can anyone recommend a good switching regulator controller for my application?Thanks.

author: David97
author_rank: Contributor
timestamp: July 20, 2014, 08:38:12 am
content: Anyone? I've been looking at the tc105, TL5001 or the LTBRZ

author: Bored@Work
author_rank: Super Contributor
timestamp: July 20, 2014, 08:53:29 am
content: Quote from: David97 on July 20, 2014, 08:38:12 amReally, there are thousands of switching mode regulators on the market. Go to any large (or small) semiconductor manufacturer's web site, or your favorite distributor web sites, and search for what you need.

author: AndyC_772
author_rank: Super Contributor
timestamp: July 20, 2014, 08:54:26 am
content: From the wording of your post, I'm guessing you're not yet very familiar with how a switched mode power supply works.I'd respectfully suggest it will be really, really worthwhile for you to do some reading up on how a 'buck converter' works in a lot more detail, before you try and design your own converter. You'll save yourself a lot of frustration in the long run, I promise.The best learning tool I know of for the purpose is LTSpice, from Linear Technology. They make a wide range of converter ICs, and there are simulation models in LTSpice for most if not all of them. Use it to learn about inductor current, power dissipation, parasitic effects, loop stability, ripple current and bulk capacitance.Designing a good switched mode power supply isn't easy; you might well find it's better to just buy a pre-assembled module off the shelf.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 20, 2014, 02:40:29 pm
content: TPS54233?

author: David97
author_rank: Contributor
timestamp: July 21, 2014, 08:55:46 am
content: ThanksDo you think that a MC34063 would be a good choice?

author: mariush
author_rank: Super Contributor
timestamp: July 21, 2014, 08:59:49 am
content: No, a mc34063 by itself is only capable of about 0.5-0.75A, you need much more than that. It's also a lousy chip protection-wise, not really suitable for a project like yours.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: July 21, 2014, 09:55:53 am
content: Go to Texas instrument website, they have a nice web based designing tool , just input you input voltage , output voltage and current, this tool will automatically select the proper controller for your application and give all values of passive component that go with the controller.

author: David97
author_rank: Contributor
timestamp: July 21, 2014, 10:02:08 am
content: Quote from: mariush on July 21, 2014, 08:59:49 amLooking at using this as a buck boost converter with an external mosfet, so current is not a issue (unless I've made a noob mistake). This will only control the mosfet.Thanks.

author: mariush
author_rank: Super Contributor
timestamp: July 21, 2014, 11:45:57 am
content: If you're going to use an external mosfet, go use a proper controller. For example see lm5085, lm5088, lm5116, lm5117 .. they all have solutions in Webench on ti.com's website (may have to create a free account to see the schematic).Do a 6v 7-8A switching regulator and then you could use a linear regulator to get 5v @ 2A - use something like lm1085 (1.5v drop at 3a, 1v at about 2a). You lose 2w at 2A using linear regulator to get 5v@2a from 6v, but a switching regulator won't be much more efficient, you're still going to lose about half a watt to one watt and it's probably not worth the extra pcb space and cost of all parts (mosfets, inductors etc)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 21, 2014, 05:37:18 pm
content: Quote from: David97 on July 21, 2014, 08:55:46 amNo, 34063 is never a good choice, under any circumstances. It's a steaming pile of...Tim

author: nsayer
author_rank: Regular Contributor
timestamp: July 21, 2014, 08:01:59 pm
content: Quote from: David97 on July 21, 2014, 10:02:08 amThe MC34063 has a built-in darlington pair for switching. You can coerce it into controlling an external transistor, but the path of least resistance is to just use a different part designed for an external switch.Someone above mentioned TI's web design tool. I recommend it as well. You do wind up having to tweak the result, as the parts they recommend aren't always the cheapest or most available (they have an obvious preference for TI semiconductors).

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: July 22, 2014, 01:16:25 am
content: Quote from: nsayer on July 21, 2014, 08:01:59 pmMost part can be sampled from ti website

author: XFDDesign
author_rank: Frequent Contributor
timestamp: July 22, 2014, 02:39:01 am
content: Frankly, unless you're up to the task of dealing with the nitty-gritty of switcher designs, and the perils involved with them, I suggest going the canned power module route.TI makes some nice ones:http://www.ti.com/product/lmz22003No magnetics to design for. No compensation networks to muck with. Drop in, set a few resistors, and move on.Linear also makes a module, and they make excellent power parts if you do decide to get into the nitty-gritty.

author: rob77
author_rank: Super Contributor
timestamp: July 22, 2014, 07:17:11 am
content: why not to buy one of those small and lightweight buck converter modules from china ? those are dirt cheap (cheaper than the IC alone in single piece quantity) and meets your spec of 5V/2A.regarding the MC34063 - those are good for many applications, but definitely not for 5V/2A with external transistor.... i'm using the 34063 for low current applications (because it's dirt cheap) - making negative rail , or boosting the supply to have enough gate voltage for high-side n-channel drive.

author: David97
author_rank: Contributor
timestamp: July 22, 2014, 08:03:55 am
content: Thank you everyone!