Decent boost converter for battery powered project - Page 1
Forum section: electronics / projects

author: Pacjunk
author_rank: Newbie
timestamp: April 20, 2023, 05:22:59 am
content: Hi,I currently have an Arduino project that operates from 2xAA cells and 3.3V modules. This works well down to about 2.7V when the GPS module cuts out (the uController is fine down to 1.8V). In order to get some more capacity from the cells I am looking at small boost converters. I have tried this module:but the efficiency is terrible!With newish batteries (3.15V), my project draws 65mA. If I wire the above boost converter in, the output voltage jumps to 3.3V as expected, but the current from the battery jumps to 130mA!So I'm wondering whether the extra I could squeeze from the battery is worth the circuit drawing double the current when the batteries are fresh? I might get twice the battery life, but at double the current, is it really worth it?Does anyone have any recommendations for small modules that are more efficient than this?Thanks,

author: mariush
author_rank: Super Contributor
timestamp: April 20, 2023, 08:19:46 am
content: The easiest fix would be to use 3 AAA batteries.Use synchronous rectifier regulators, which don't need a diode and therefore you have less parts and less losses.Look for minimum voltage below 2.4v (2 rechargeable AA batteries would peak at 1.35v but be around 1.2v for most of their life), frequencies at least 300-500kHz if you want small inductors and ceramic capacitors (but too high frequency can mean less efficiency and higher idle power consumption), and you may just be able to get a fixed output voltage 3v / 3.3v / 3.6v , even 2.85v is a common voltage so you may be able to get one.some suggestions :MCP16251 (adjustable )https://www.digikey.com/en/products/detail/microchip-technology/MCP16251T-I-CH/4079881MCP1640 (adjustable, just lower output current than previous) :https://www.digikey.com/en/products/detail/microchip-technology/MCP1640T-I-CHY/2258569TPS63030 (adjustable, high switching freq, around 2.4 mhz )https://www.digikey.com/en/products/detail/texas-instruments/TPS63030DSKR/1972182Another option - especially if the actual voltage is not critical, as long as it's above some threshold - would be to use charge pump regulators.They can be much more efficient, up to let's say 97%, and basically double the input voltage.For example, see LM2660MX :https://www.digikey.com/en/products/detail/texas-instruments/LM2660MX-NOPB/366876though for the voltage doubler mode, the datasheet says a minimum of 2.5v is required, so if you use 2 rechargeable AA batteries it could be a problem (page 15 in datasheet :https://www.ti.com/lit/ds/symlink/lm2660.pdf)

author: RoGeorge
author_rank: Super Contributor
timestamp: April 20, 2023, 08:41:42 am
content: Sometimes I replace 2-3 series rechargeable cells (1.2V) with a single Li-Ion cell (3-4.2V), no extra regulator.Li-Ion has much lower self discharge rate. Even the ones used in former mobiles phones, 5-10 years ago, are still better than NiMH or NiCd. They may have lost some 20-50% of their nominal C, but still have enough storage capacity left, and in terms of self discharge rate they are still better than low self-discharge NiMH.

author: Pacjunk
author_rank: Newbie
timestamp: April 22, 2023, 02:24:09 am
content: Thanks for your help, but I was looking for premade boards. Using 3 batteries means I will need regulators or buck converters and then I will have the same issue. Also the batteries will still need a reasonable overhead for the regulator to work.I think I'll just have to try the various cheap boost converters and go with the best one. I would be happy with the 80-85% they advertise, but not the 50% I get in reality.Cheers,

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 22, 2023, 02:37:47 am
content: Quote from: Pacjunk on April 22, 2023, 02:24:09 amJust make sure it doesn't have a diode on it like the one you first posted has. (SS14 diode) That's a dead give away. Also, look for boards that use the chips mentioned by mariush. Or when looking at the board, if you can determine what chip it uses, look up it's datasheet and make sure it uses active rectification instead of a diode.

author: Psi
author_rank: Super Contributor
timestamp: April 22, 2023, 02:59:10 am
content: +1 for something with synchronous rectification.For ultra low voltage stuff you need this or the efficiency is terrible

author: mariush
author_rank: Super Contributor
timestamp: April 22, 2023, 07:50:15 am
content: Quote from: Pacjunk on April 22, 2023, 02:24:09 amThey're a bit more expensive, but you can look at "Development boards" for such regulators at stores like Digikey, mouser, newark/farnell etc or even directly at the manufacturer.They won't necessarily be the most efficient boards, because as development boards they would have for example inductors selected to work well with a wide range of input voltages and output voltages, but they'll work for your needsAn example of such board is here, using a sync rect. chip TPS63070 :https://www.digikey.com/en/products/detail/sparkfun-electronics/COM-15208/10187090You can use a LDO regulator (linear regulator) to reduce 3 x (1v...1.65v) down to 3.3v or 3v, they make such regulators with as little as 10-20mV voltage drop.For example :ablic S-1740A33-M5T1U4 IC REG LINEAR 3.3V 100MA SOT23-5 :https://www.digikey.com/en/products/detail/ablic-inc/S-1740A33-M5T1U4/9489530It has 20mV voltage drop at 10mA, probably a bit more at 100mA but not by much.So you can give it 3 x 1.2v = 3.6v and it will output 3.3v ... that's 3.3 / 3.6 = 91.6% efficiency, more than what you'd get with switching regulator, even synchrounous rectifier ones will have a hard time reaching this efficiency.The regulator will output less than 3.3v if the input voltage is lower, for example if the batteries discharge down to 3.020v, the regulator should still output around 3v and your gps module should still work.ablic S-1740 series3.0v 100mA "A" version :https://www.digikey.com/en/products/detail/ablic-inc/S-1740A30-M5T1U4/85741473.0v 100mA "C" version :https://www.digikey.com/en/products/detail/ablic-inc/S-1740C30-M5T1U4/85741593.3v 100mA "C" version :https://www.digikey.com/en/products/detail/ablic-inc/S-1740C33-M5T1U4/9641995This series has a 2nd output, which (for the models above) is Vin / 2. It can enabled by setting a pin high in the case of A version, or low (tied to ground) for the C version.So for example, you could have 3 x (1v ..1.5v) as input as you'll have 1.5v.. 2.25v on the 2nd output of these regulators.njm12888 :https://www.digikey.com/en/products/detail/nisshinbo-micro-devices-inc/NJM12888F33-TE1/10671834fixed 3.3v up to 300mA output, 0.1v dropout voltage at 100mA (less than 0.2v at 300mA)it will also work like the others with less than 3.3v input, graph at page 9 in datasheet shows it with input voltage as low as 3.1vLDCL015MR adjustable output voltage, up to 150mA , 0.1v dropout voltage :https://www.digikey.com/en/products/detail/stmicroelectronics/LDCL015MR/2793103In theory, with the right battery holder, you could have the 3 batteries in series and have a wire going from the 2nd battery to give your circuit 2 x (1v...1.65v) and a wire from the 3rd battery to have 3 x (1v...1.65v) for the GPS module.So you could have your arduino consume a few mA from the 2 batteries and enable the regulator to produce 3.3v or 3v for the gps module only as needed. For example let's say you start the gps module for around 10-20 seconds every 5 minutes, just enough to find the gps network and retrieve location, and then you shut it down to save power.

author: SouthCoding2
author_rank: Newbie
timestamp: April 23, 2023, 12:58:46 am
content: Do you know how to post? I'm new to the forum and i can't find the post button? Do I have to wait untill someone allows me to post?Thanks

author: tunk
author_rank: Super Contributor
timestamp: April 23, 2023, 12:00:43 pm
content: Have you tried to run from one AA cell - the efficiency may be better at lower voltages.

author: Pacjunk
author_rank: Newbie
timestamp: May 06, 2023, 05:34:34 am
content: Hi, I took your advice and ordered two different modules that don't have the diode on them.The first one (which didn't even have an inductor) turned out to be 48% efficient (Vout=Vin) - so not good!The second one (inductor, but no diode) gave me 82% efficiency which is acceptable for my application.The IC used is a 2188A (for those playing along at home!)Cheers,Quote from: Kim Christensen on April 22, 2023, 02:37:47 am

author: mino-fm
author_rank: Regular Contributor
timestamp: May 06, 2023, 08:14:10 am
content: Maybe I'm too late but a RP2040 Pico-board would offer Arduino 'feeling' for software and a 1.8 - 5.5 Vin regulator with 3.3 V output for your GPS-module.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 06, 2023, 12:26:11 pm
content: I am not entirely sure, but I think there are step up regulators that can be used in a very low power "pass through" mode. The idea is that the regulater just shorts it's input to it's output as long as your batteries deliver enough voltage, and it only starts boosting the voltage when your battery voltage is too low to power your circuit directly.

author: Pacjunk
author_rank: Newbie
timestamp: May 13, 2023, 11:41:17 am
content: Quote from: mino-fm on May 06, 2023, 08:14:10 amLooks good, but I wanted to drop the boost converter into an existing circuit. I'll certainly keep the pico in mind for future projects.

author: Pacjunk
author_rank: Newbie
timestamp: May 13, 2023, 11:46:28 am
content: Quote from: Doctorandus_P on May 06, 2023, 12:26:11 pmThat would be ideal, but I didn't see anything like that in the premade boards that I saw. The one I'm using now increases my project's battery life from ~5 hours to ~27. The GPS module cut out at 2.7 - 2.8V, so the batteries had a lot left in them at this stage. The boost converter, while not perfect, gave me a lot of extra battery life.