Inexpensive micropower buck-boost converter with wide input range? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 25, 2024, 05:23:53 am
content: Hello.I'm looking for INEXPENSIVE (This means NO Linear or No Maxim products), single inductor, buck-boost converter, which can output around 100mA at 12V, with input voltages in range of 5-30V (higher is better). No BGA or DFN packages, SOIC/SOT-23 etc. -are ok.The main issue is with available solutions that they're mostly low input voltage, like one pictured, but I want higher input voltage and I don't want to use something like 78M05 to not convert power into heat).Any ideas?

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2024, 05:55:36 am
content: You should probably give what price you consider to be inexpensive, or rather, a fair price given your expected BOM cost.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 25, 2024, 07:37:29 am
content: <$1 per controller itself.There are numerous IC in that price range, but they either are low voltage, as one above, or use dual/coupled inductors and have range like 9-18V input for 12V output.

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 25, 2024, 07:40:00 am
content: If it´s intended for battery operation then you could think about an inverting buck/boost converter. It´s practically a non-isolated flyback, it uses one inductor and there are hundreds of cheap controllers available for this. For the power range of slightly over 1W it´s not a bad topology.

author: ArdWar
author_rank: Frequent Contributor
timestamp: September 25, 2024, 07:49:13 am
content: You can even use normal buck converter in inverting mode if inverted Vout is acceptable. For example LMR51606 gives you 53V max Vin at -12 Vout.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 25, 2024, 10:22:01 am
content: Unfortunately, no, I need non-inverted output.

author: daisizhou
author_rank: Super Contributor
timestamp: September 25, 2024, 10:38:15 am
content: Do you plan to select the chip and make your own PCB? If so, your PCB layout and inductor placement will have a bearing on your power conversion efficiency.This usually requires experience and trial and error.

author: ArdWar
author_rank: Frequent Contributor
timestamp: September 25, 2024, 11:14:04 am
content: Bit the bullet and design a zeta converter. Or maybe even literal back to back buck-boost if you still insist on single inductor. Two inductors or two ICs should be still much cheaper than integrated 4-switcher.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 25, 2024, 12:05:34 pm
content: Yes I will make my own PCB. I do have some experience in power pcb topology.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: September 26, 2024, 03:44:29 pm
content: Following because I'm also interested in this for my own project.The XLSemi XL6008 kinda fits the criteria, but (to my knowledge) it requires 2x inductors and the package is a TO252-5L, which is about the size of SOP-8, which may be too large.The XLSemi XL6007 is in the SOP-8 package but supports only 3.6V to 24V. Technically you could do a low-cost LDO before the XL6007 to get that 30v range. Some LDO's that I've looked into only drop 0.5v (or less) at 100mA.If you haven't already, consider looking through lcsc.com and using their filters to find the exact part that you want. They offer a bunch of Chinese switching converts which are generally cheaper than what's available at Digikey/Mouser.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 27, 2024, 04:13:42 am
content: I already tried XL6007, as well as some other XLSEMI products.They all have a specific issue - if power source (battery, etc) has high internal resistance, so at startup, when output mosfet opens, source voltage drops for a moment, mosfet will stay open, cause short to the ground, voltage drop, so UVLO circuit will stop it's driver, but mosfet remains open, so depending on your power source energy, you will get either burnt chip or burnt battery or other, undersirable audiovisual effectsregarding the LCSC, the above shown IC was found on their website, but as you can see, all such designs have very limited input-output ranges. Adding LDO is not a good idea at all - if I can add LDO and tolerate huge losses on it, than I'll use something like 7812 directly

author: Andy Chee
author_rank: Super Contributor
timestamp: September 27, 2024, 09:09:02 am
content: Hysteretic control ok? Then the LM3485/9 is for you.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: October 02, 2024, 08:41:33 pm
content: Cand find them to be used with my requirements....