How to find IC for boosting voltage - Page 1
Forum section: electronics / beginners

author: Noobiq
author_rank: Contributor
timestamp: December 15, 2022, 08:55:01 am
content: Hello,i need 35V output for 50W audio amplifier from car battery. My idea was to find suitable IC, and check datasheet for circuit. So i picked LM317, soldered some parts and tested it to find out it wont output more then battery voltage. So i read datasheet to realize it is probably for step-down. I didnt really find any hard evidence., mostly quess based on my tests.So i opened my preffered shop and started looking for new IC only to realize i dont know how to easily tell if IC is for boosting voltage. sometimes i couldnt figure it out. lot of potentional candidates are out of stock for long time, my latest choice was LT1339, then LT1680 - kinda complicated circuit. but i was unable to find anything else.so the main question is how to easily tell if my IC can boost voltage or not?Thanks.

author: semir-t
author_rank: Regular Contributor
timestamp: December 15, 2022, 09:08:47 am
content: The one you have selected is the LDO Regulator. For your purpose you would need Switching Boost regulator (Their application schematic will have inductance).

author: wasedadoc
author_rank: Super Contributor
timestamp: December 15, 2022, 07:32:16 pm
content: Quote from: semir-t on December 15, 2022, 09:08:47 amThe schematic having an inductor or transformer is a necessary but insufficient condition for recognising a boost converter. Those components are also found in buck converters. Those give a lower output voltage than the input.The OP's requirement is probably better and more easily met with a ready built module. Such ashttps://www.ebay.com/itm/400442469292

author: Siwastaja
author_rank: Super Contributor
timestamp: December 15, 2022, 07:54:52 pm
content: Quote from: semir-t on December 15, 2022, 09:08:47 amLM317 is not "LDO regulator". LM317 is so-called "linear regulator", and definitely not low-dropout.

author: mariush
author_rank: Super Contributor
timestamp: December 15, 2022, 08:12:47 pm
content: Linear regulators can only reduce an input voltage to a lower voltage. They have a dropout voltage which varies from model to model - this means the regulator's output voltage will be at most input voltage - the dropout voltageTo get a higher voltage, you need a boost regulator. Some call them step-up regulators.You can go to a distributor of components like Digikey, Mouser, Newark/Farnell and select that particular section and then filter results to show only step-up / boost regulators.For example, here's Digikey's section of switching regulators :https://www.digikey.com/en/products/filter/power-management-pmic/voltage-regulators-dc-dc-switching-regulators/739From there, you can go on the Function column and select only the entries that contain "Step-up" keyword and then click on Apply. Or, you can select only the lines that have the keyword "Boost" from the Topology column and hit apply.Next, as you claim it's for a car, you would want the input voltage the chip can handle to be at least around 15v, because a car's battery will be charged at around 13.8v, maybe more.So you could try to filter the results by selecting maximum input voltage ... in this case, I would probably select all options from 18v and higher.You can then filter further with maximum output voltage ... since you want 35v out, set the maximum voltage a bit higher, so let's say filter to show only regulators that can output up to 36v or moreFrom there, you can try filtering more... you will need a chip that can do a decent switching current. Your input will be 10-14v and you want 50w out, so at around 90% efficiency that means your converter will probably take in around 55-60w - that's around 5A of current at the input.At 35v output and 50 watts, that's around 1.5A of current, so the regulator must be able to handle a higher current value than thatand you get something like this (filters applied as described above) :https://www.digikey.com/short/htj7tc93As an example from that list, MC33167 is available from both digikey stock and marketplace sellers. here's some linkshttps://www.digikey.com/en/products/detail/onsemi/MC33167THG/1479127https://www.digikey.com/en/products/detail/onsemi/MC33167TVG/1479129Here's datasheet :https://www.onsemi.com/pdf/datasheet/mc34167-d.pdfOn page 11 you'll see an example schematic of step-up mode, boosting 12v to 28v at 0.9A - you can probably change it to go to 35v and maybe close to 1A of current, so around 35 watts in total ... but 50 watts is unlikely.You'll have to check the formulas and explanations in datasheet .The datasheet also has an example circuit board with recommended placement of partsThis switching regulator is basically a beef-ed up MC33063, I think the formulas are pretty much the same and there's online calculators for MC33063 and MC34063 and even Dave made a video showing how to use the formulas to determine what parts you needBecause this step-up regulator chip runs at low frequencies (under 72 kHz), the inductor will be big, bulky.. and you'll also need input and output electrolytic capacitors. The regulator will also be only around 80% efficient.But on the upside, it's VERY beginner friendly in the sense that it's available in a to-220 package, and all the other components can be through hole so you can make the circuit at home.

author: Faranight
author_rank: Unknown
timestamp: December 16, 2022, 06:12:46 am
content: Like others have said, check on digikey, mouser, farnell, TME, etc. Most of these stores have an option to choose a "boost" topology somewhere in the search parameters. Also, see, if you can opt for a synchronous boost converter, it gets rid of the extra schottky diode. You would probably want one with a higher switching frequency (GHz range?) so that the inductor will be much smaller. Also, switching regulators are noisy devices. I'm not sure, if this is going to be a problem for an audio application or not, but you may want to choose one with "spread spectrum" functionality. I think TI have a bunch of those.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 16, 2022, 08:55:42 am
content: Not GHz. Not even MHz.

author: Whales
author_rank: Super Contributor
timestamp: December 16, 2022, 09:07:27 am
content: Quote from: Noobiq on December 15, 2022, 08:55:01 amN.B. as an alternative you can buy pre-made "boost" converters pretty cheaply off greymarket sites like eBay and Alixexpress. You don't necessary have to build it all yourself.Building it yourself can however provide you with better control over the performance, eg keeping output voltage ripple low. Some audio amplifiers are more sensitive to this than others and it can cause noises (humm, hiss, squeal, etc) to come out of your speakers. Audio amplifiers often have a "PSRR" graphed against frequency to tell you how well they handle dirty/ripply input power.Don't trust all of the numbers provided by greymarket sellers. Always divide them (at least) by half. Eg the seller claims this thing is pure magic and perfection with 100W at 96% efficiency for only a few dollars:https://www.aliexpress.com/item/1005001619787228.htmlI wouldn't run it above 50W, and even then I'd lookup the datasheets for the main parts on the board (once I get it) to verify

author: mariush
author_rank: Super Contributor
timestamp: December 16, 2022, 09:51:02 am
content: No, the thing with those claims is that they may be achievable but NOT simultaneously.For example,- you may get 96.7% efficiency but this peak efficiency is when boosting 24v to 26v at 0.5A - 1A .... any wider voltage range would be less efficiency, any higher or lower current would be lower efficiency.- they say 100w, but then specifications give more details : "5.Output Power: 75W (when the input and output voltage greater than 20V up to 128W)"- you may get 75w continuous, but only with added cooling on the heatsinks otherwise the controller chip and mosfets or whatever is used could go into thermal limits.If you want peak efficiency at some output voltage and current range, you would want to optimize the inductor (value, current ratings etc), you'd want to optimize input and output capacitors and diodes etc)

author: bidrohini
author_rank: Regular Contributor
timestamp: December 16, 2022, 09:53:06 am
content: The easiest way is to take a look at the datasheet. If the IC is supposed to step-up voltage, then the datasheet will say 'Step-Up Voltage Regulator' or 'Boost regulator' or 'Inverting Regulator - Buck,Boost, Switching'.You can check LM2577https://www.ti.com/lit/ds/symlink/lm2577.pdf?ts=1671157812398&ref_url=https%253A%252F%252Fwww.google.com%252F

author: semir-t
author_rank: Regular Contributor
timestamp: December 16, 2022, 09:56:25 am
content: Quote from: Siwastaja on December 15, 2022, 07:54:52 pmYou are right, this is not an LDO but linear voltage regulator. Thanks for pointing out.Quote from: wasedadoc on December 15, 2022, 07:32:16 pmYes, but the chip that was selected here could immediately be discarded because it doesn't comply to this rule.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 16, 2022, 11:10:07 am
content: Quote from: Whales on December 16, 2022, 09:07:27 amThose SMD capacitors on the aliexpress module are totally inadequate for the claimed output powers or the OP's requirement.

author: Terry Bites
author_rank: Super Contributor
timestamp: December 16, 2022, 08:04:28 pm
content: You might start off with an online design tool. eg TI's web bench, LT Powercad, Onsemi WebDesigner+ etc.It will be cheaper to just buy an off the shelf module or two for the price of an IC!egwww.aliexpress.com/item/4001359096981.html?spm=a2g0o.productlist.main.19.7a3d2ddcmC8c6R&algo_pvid=a8f99468-edf8-40a9-a8c6-fdc749cbb90e&aem_p4p_detail=202212161203052948065358140960006635336&algo_exp_id=a8f99468-edf8-40a9-a8c6-fdc749cbb90e-9&pdp_ext_f=%7B%22sku_id%22%3A%2210000015796744902%22%7D&pdp_npi=2%40dis%21GBP%217.71%216.56%21%21%21%21%21%400b09b6c616712209851311578d0701%2110000015796744902%21sea&curPageLogUid=VqfzMSUZrquv&ad_pvid=202212161203052948065358140960006635336_2&ad_pvid=202212161203052948065358140960006635336_2

author: EPAIII
author_rank: Super Contributor
timestamp: December 17, 2022, 05:59:17 am
content: Try here:https://www.ti.com/design-resources/design-tools-simulation/webench-power-designer.html

author: Terry Bites
author_rank: Super Contributor
timestamp: December 17, 2022, 02:24:12 pm
content: Yep.Great resource, deseves to be more widely known.Beats the crap out of LTs powercad.

author: Noobiq
author_rank: Contributor
timestamp: December 19, 2022, 08:19:08 am
content: Thank you all for replyes.sorry im late, i was off grid for few days.im building 50w amp.but knowing how loud is just 20w, i doubt i will really need 50w, more like 20w if not less.my work include (manual) tht and smd assembling, so price is not an issue as most parts are readily avalible for me, i just need to buy main ic.im aware of those"chines solutions", but where is the fun in that? parameters of these items are questionable. besides, i could learn thing or two building my own. In fact, its my first time i made my own inductor (I am probably underqualified for this project).big inductor is not an issue, plenty of space.im getting my parts from tme.eu, i wanted that MC33167 but its out of stock for long time.I found by chance spare LT1170, What do you think of that? "typycal application circuit" in datasheet doesnt look complicated.i will check those design tools later.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 10:58:25 am
content: Why don’t you share key info like what your available supply voltage is, and what kind of amp you were planning to use?

author: Noobiq
author_rank: Contributor
timestamp: December 20, 2022, 10:47:43 am
content: i am Sorry but im not sure what more i can tell here then what i alredy wrote.Input: 9-15V,Output: 35V 1,5A - audio amp rated 50Wpower source is car battery, so i expect 9-15V. though i don't think i could start car at 9v.. While driving, its mostly 14,4-14,7V.I want to use it for audio amp (i have yet to build it) which main parts are TL074, TIP111/116/34B/33B

author: mariush
author_rank: Super Contributor
timestamp: December 20, 2022, 12:30:34 pm
content: There are lots of class-D amplifier chips which can run straight from 12v.Seems like a waste of energy for debatable benefits - you're gonna lose some power as heat in the step-up regulator, and then you'd lose maybe half the power as heat in those transistors.For example, get a couple TPA3122, one for each channel :https://www.digikey.com/en/products/detail/texas-instruments/TPA3122D2N/1841855In BTL mode, 12v is enough for the chip to produce around 10w with THD <=1% .. see figure 21 in datasheet :https://www.ti.com/lit/ds/symlink/tpa3122d2.pdfWith 24-28v, the maximum output power goes to 30-40 watts.It would much easier to find some step-up regulator to boost 10-14v to 24-28v instead of 35vOn page 15 you have figure 19, how to use the chip in BTL mode.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 20, 2022, 12:54:33 pm
content: Quote from: mariush on December 20, 2022, 12:30:34 pmYou cannot state amplifier output power without knowledge of the speaker impedance.

author: mariush
author_rank: Super Contributor
timestamp: December 20, 2022, 08:11:12 pm
content: Quote from: wasedadoc on December 20, 2022, 12:54:33 pmYou cannot state amplifier output power without knowledge of the speaker impedance.I linked to the datasheet.That particular chip can work with 4 ohm speakers in SE mode, or 8 ohm in BTL mode.

author: Noobiq
author_rank: Contributor
timestamp: December 21, 2022, 08:15:34 am
content: its 4ohm speaker i extracted from some older set.