Inexpensive and simple solution for wide input range (5-24v) buck-boost? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 04:21:58 am
content: Hello.I need 12V 0.1A output, while input will be changing from 5V to 24V.I checked the datasheets of XL6007 and other similar IC.They do have circuit for buck-boost, but usually for 12V output, they specify 10-18V input. The upper range is limited by IC working voltage and lower input is tied to output current, I guess.So what if I replace XL6007 with XL6009, which has much wider operating voltage range and higher current rating?Or maybe there are other, simple to use and inexpensive buck-boost converters with wide input range?

author: Smokey
author_rank: Super Contributor
timestamp: September 19, 2023, 04:51:48 am
content: https://webench.ti.com/power-designerSet input range from 5V-24V, and output to 12V.Returned 49 designs, with schematics and BOMs.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 05:02:23 am
content: There are two issues with "webench"1. Uses only TI parts.2. They are expensive and real BOM prices nowhere close to that shown in the webench.So I'm looking for something considerably cheaperand preferably, thru hole design.

author: ledtester
author_rank: Super Contributor
timestamp: September 19, 2023, 05:06:34 am
content: On aliexpress you can find offerings for a "LM2577 LM2596 buck boost" or "XL6009 LM2596s boost buck" such as:https://www.aliexpress.us/item/2255800080285270.htmlhttps://www.aliexpress.us/item/3256804916921148.htmland here is a blog post on it with a schematic and some discussion on its operation:https://www.electroschematics.com/converter/The point is that there seems to a standard way of combining a step-up and a step-down converter to create a step-up/down converter.

author: Smokey
author_rank: Super Contributor
timestamp: September 19, 2023, 05:17:47 am
content: Quote from: LinuxHata on September 19, 2023, 05:02:23 amTheir BOM prices are for 1K quantities. They say that on the page.Typically you worry about reducing BOM cost by that last $0.50 if you are going to be making 100K pieces... but who makes 100k pieces using through hole parts these days?Having TI do literally all the design work for you has to be worth the $1 more?

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 05:24:57 am
content: I think, the 78M05 + SX1308 will work best for me in terms of price and simplicity (but, these are not TH)And webench prices are wrong, even for 1K quantities. And they're wrong by magnitude. Just look up for say, that converter, using LM2586 and check parts on digikey and their pricing.

author: Smokey
author_rank: Super Contributor
timestamp: September 19, 2023, 06:05:16 am
content: Quote from: LinuxHata on September 19, 2023, 05:24:57 amDirect from TI's store. Those are items in a cart, in stock.

author: Smokey
author_rank: Super Contributor
timestamp: September 19, 2023, 06:06:02 am
content: Missed an attachment.I'm totally going to get a call from my TI rep asking if I forgot to checkout that cart now

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 06:19:23 am
content: Good, you see that their BOM is wrong.Only price of IC is shown, but other components?transformer, capacitors, diodes, resistors, etc...

author: soldar
author_rank: Super Contributor
timestamp: September 19, 2023, 07:22:08 am
content: For those interested in basic topologies of buck-boost converters:https://en.wikipedia.org/wiki/Single-ended_primary-inductor_converterhttps://en.wikipedia.org/wiki/%C4%86uk_converter

author: Smokey
author_rank: Super Contributor
timestamp: September 19, 2023, 07:54:29 am
content: Quote from: LinuxHata on September 19, 2023, 06:19:23 amThat was the part you were using as an example. It's the only high cost part in the design... Fine. Here is the rest...If you want to play along, do a webench search for LM2586S-12 (Boost) with all the default parameters.Inductor = MSS1210-104KEBTI says $0.81,Coil Craft says 1200 = $1. 00https://www.coilcraft.com/en-us/products/power/shielded-inductors/ferrite-drum/mss-mos/mss1210/mss1210-104/Diode = SS14FLTI says $0.03Mouser says 1000 = $0.08https://www.mouser.com/ProductDetail/Taiwan-Semiconductor/SS14-M2G?qs=mAH9sUMRCttdQeg0L83afA%3D%3DOutput Cap = EEE-FK1C681PTI Says $0.42Digikey says 1000 = $0.28https://www.digikey.com/en/products/detail/panasonic-electronic-components/EEE-FK1C681P/765963Input Cap = UUD1C101MCL1GSTI says $0.09Future says 1000 = $0.10https://www.futureelectronics.com/p/passives--capacitors--aluminum-electrolytic-capacitors/uud1c101mcl1gs-nichicon-4403887Minus the standard R and C compensation parts, that's the whole BOM.TI Webench said the BOM cost was $4.89, and in 1000s you can actually get all that stuff for .... $4.76....

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 19, 2023, 08:36:00 am
content: And everything went in the wrong direction as it happens usually