DC-DC converter Isolated - Page 1
Forum section: electronics / projects

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 22, 2025, 09:14:29 pm
content: I’m searching for recommendations for DC-DC converters (buck, boost or isolated) that meet these requirements:Complete documentation: datasheet, application notes and preferably manufacturer-provided reference schematics.Programmable / digitally adjustable output: built-in or supported way to change output voltage via I²C, SPI, or digital control signals. If the converter itself isn’t programmable, I’m also open to solutions where an additional stage (e.g., a digitally controlled DAC or a programmable regulator front-end) can be added easily to control the output.Practical resources: evaluation boards, reference layouts, and example designs.Useful details: please mention max output power, input/output voltage ranges, isolation (if any), and any caveats.Goal: study the design in depth and possibly adapt it into my own design or add a digital control layer.Do you know specific manufacturers/models, or can you share links to datasheets, reference schematics, or evaluation boards? Real-world experience and tips are very welcome.Thanks in advance!

author: thm_w
author_rank: Super Contributor
timestamp: September 22, 2025, 09:29:42 pm
content: You can search in the DC DC converter section on digikey:https://www.digikey.ca/en/products/filter/dc-dc-converters/922Look for "isolated" and "adjustable" output.None will have schematics provided.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 22, 2025, 09:48:53 pm
content: When I enable the filters, the list gets restricted and I only find one available option.This option does meet the requirement of being programmable via I²C, but unfortunately it does not fit my voltage range. I need an input of 10–20 V and an output of at least 30 V.

author: Someone
author_rank: Super Contributor
timestamp: September 22, 2025, 11:00:14 pm
content: Quote from: SKYVsebasC20 on September 22, 2025, 09:48:53 pmSo, new information. But you also want isolated? Thats a system level specification rather than chip level.Do you want a module? or chip to design all the circuitry around?Chance of finding a ready to use reference design that meets all your (expanding) requirements is almost zero.

author: Obsidianxenon
author_rank: Contributor
timestamp: September 23, 2025, 01:26:04 am
content: I'm not sure if you need a few of these or just one, but you might want to consider building your own converter if you're up to it.The requirement for a datasheet obviously isn't met here, but you would have the entire schematic.Take this suggestion with a grain of salt if impractical.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 23, 2025, 03:47:23 pm
content: Quote from: Someone on September 22, 2025, 11:00:14 pmI’m working on a hobbyist power supply, and I need its output to be isolated. Ideally, I would like a complete module as a starting point, but if there is a chip with a reference circuit designed around it, that would also work for me.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 23, 2025, 03:50:56 pm
content: Quote from: Obsidianxenon on September 23, 2025, 01:26:04 amSince I don’t have much experience and this would require additional costs, I would like to exhaust all the options available on the market before starting from scratch. This is mainly because of the time involved and the possible design errors.However, if you know of or have access to clear documentation that I could use to design after reviewing all the available market options, that would be extremely helpful.As a beginner, it’s difficult for me to work on something at this level without a manufacturer’s recommendation, such as an evaluation module.

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 23, 2025, 05:19:48 pm
content: Quote from: SKYVsebasC20 on September 22, 2025, 09:14:29 pmWhich side of the isolation is the digital control coming from?QuoteThese are specs you should be providing...Most DCDC controllers which support a digital interface are for fairly specialized applications (i.e. VRMs for CPUs/GPUs, battery chargers, etc). Most of these are non-isolated.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 23, 2025, 07:48:04 pm
content: Quote from: mtwieg on September 23, 2025, 05:19:48 pmThank you for your reply and clarification.To provide the missing details:Input voltage: around 20 V (a nearby range is acceptable).Output voltage: adjustable from about 0.5 V up to 30 V or higher.Output power: up to ~35 W, maximum current around 4 A.Isolation: yes, output must be isolated from the input.Digital control: I would like the programmable/digital interface (I²C/SPI/UART or similar) to be accessible on the output side, since this is for a hobbyist adjustable power supply project.I understand most digital-interface DCDC controllers are non-isolated and targeted for specialized applications, but I would like to explore any existing solutions, modules, or even reference designs that could serve as a starting point.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: September 23, 2025, 09:08:21 pm
content: I have seen power supplies installed on equipment, where the communication protocol is either CanOpen or RS485.

author: Someone
author_rank: Super Contributor
timestamp: September 23, 2025, 11:11:54 pm
content: Quote from: SKYVsebasC20 on September 23, 2025, 03:47:23 pmWhy? lots of those are available at all sorts of price points.https://www.koradtechnology.com/product/83.htmlQuote from: SKYVsebasC20 on September 23, 2025, 03:47:23 pmQuote from: SKYVsebasC20 on September 23, 2025, 03:50:56 pmSo you want a kit where you don't need to design anything?

author: SCSKITS
author_rank: Regular Contributor
timestamp: September 23, 2025, 11:24:22 pm
content: A simple transformer will provide primary to secondary isolation. Then any adjustable power supply regulator should work. You can use a DAC to control the output.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 24, 2025, 10:03:19 am
content: This is agreat projects site. 320volt.com/enSee thishttps://320volt.com/en/sg3525a-0-30v-0-20a-smps/I've put a tanslated version of the pdf at the end of this reply.You can drop them a line herehttps://de.elv.com/contactTechAndhttps://320volt.com/en/0-2v-80v-0-10a-adjustable-switched-mode-power-supply/Commercially available DC-DC converters (isolated or not) are usually niche products aimed at a particular application. Current, voltage and efficiency dictate construction. So input and output ranges are quite narrow. One of the greatest problems is getting isolated feedback working when the output voltage is low. Optocouler in the feedback loop requires enough voltage to drive it's LED. So you end up needing an auxillary isolated supply to sense the output voltage and current.You might also consider running a non-isolated variable DC-DC conveter from a fixed isolated DC-DC converter.BTW....https://www.aliexpress.com/item/1005007995649022.html?spm=a2g0o.productlist.main.29.2a2aKSxNKSxNwe&algo_pvid=62f888c7-cef2-41b7-97f3-cf3bceec36c8&algo_exp_id=62f888c7-cef2-41b7-97f3-cf3bceec36c8-28&pdp_ext_f=%7B%22order%22%3A%22396%22%2C%22eval%22%3A%221%22%2C%22fromPage%22%3A%22search%22%7D&pdp_npi=6%40dis%21GBP%215.48%214.93%21%21%217.19%216.47%21%402103205217587057446034751ed065%2112000043196937977%21sea%21UK%213100120370%21X%211%210%21n_tag%3A-29919%3Bd%3Affe2652f%3Bm03_new_user%3A-29895%3BpisId%3A5000000187068828&curPageLogUid=p24yz4F4qRjB&utparam-url=scene%3Asearch%7Cquery_from%3A%7Cx_object_id%3A1005007995649022%7C_p_origin_prod%3A

author: temperance
author_rank: Super Contributor
timestamp: September 24, 2025, 10:24:17 am
content: QuoteIf the input voltage is around 20 V, does it mean the power supply is powered from an isolated source? Why would you need an extra isolated converter? It just creates more noise.Forget about an input voltage of 20 V with an output range of 0...30 V, fully adjustable voltage and current limit. You will need a buck boost converter and if you don't know how to design the control loop you will probably never get it to work properly and performance will be poor anyhow for a bench power supply. Stick with current mode controlled buck converters and make the output voltage lower than in the input voltage.So people here suggest a hobbyist to build an off line switching power from scratch while the OP doesn't know how to change any "normal regulator" into an adjustable regulator over SPI or something similar by adding some external components.Prepare for some smoke, fire and probably never seen again after a while.

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 24, 2025, 12:07:56 pm
content: Quote from: SKYVsebasC20 on September 23, 2025, 07:48:04 pmI'm not aware of any off-the-shelf DCDC controllers which have a digital interface suitable for such a wide operating range.I'd suggest breaking the design into two stages: an isolated DCDC with a fixed output voltage of ~35V (a bit higher than your maximum Vout), followed by a nonisolated stepdown with adjustable Vout. You can probably find lots of off-the-shelf options for the fixed isolated stage. For the adjustable output, it's unlikely you'll find something which satisfied your wide adjustment range requirement, you will have to do some analysis and design on that part yourself.For the adjustable output, I'd suggest looking at special DACs like DS4432 or LTC7106, they are specially designed for what you're doing (not sure if their resolution is sufficient for you though). Both are compatible with an I2C interface.

author: Psi
author_rank: Super Contributor
timestamp: September 24, 2025, 12:45:43 pm
content: Sadly as soon as you want both isolated and more than a few watts the options are very slim for off the shelf modules.I second the idea to have a single isolated module followed by a non-isolated module to get the final voltage.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 25, 2025, 11:40:17 pm
content: Quote from: Someone on September 23, 2025, 11:11:54 pmI would like a kit that helps shorten the design process, since I am developing this hobbyist power supply together with something already developed. My goal is to add a new device whose output I can adjust through a digital signal, with its corresponding GUI.For this reason, buying a power supply is not useful to me, and it would also be much more expensive.

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 25, 2025, 11:45:49 pm
content: Quote from: SCSKITS on September 23, 2025, 11:24:22 pmI don’t know what the implications are of adding a transformer to my design, since for this I usually rely on evaluation modules from some manufacturers.

author: Someone
author_rank: Super Contributor
timestamp: September 25, 2025, 11:51:21 pm
content: Quote from: SKYVsebasC20 on September 25, 2025, 11:45:49 pmIf you want an isolated design but are unfamiliar with transformers, then the project is simply beyond your capability as isolation at those power levels is almost always done with magnetics (transformers) and the alternatives (piezoelectric or optical) are even more complex. If there is no time pressure then it's possible to go back to the "books" and learn the basics first.Quote from: SKYVsebasC20 on September 25, 2025, 11:40:17 pmAs has been mentioned in the thread already power supply design (particularly with your requirements) is hard, and there is not simple circuitry or reference design that will be close to what you want.Experience says you will not save money by building a one off or small volume device, when there is a volume production device which already does the job.What is the goal? What are the constraints that make you think you MUST design a circuit to do the task?

author: SKYVsebasC20
author_rank: Newbie
timestamp: September 25, 2025, 11:54:23 pm
content: Quote from: Terry Bites on September 24, 2025, 10:03:19 amI understand everything you’ve explained, and it was very helpful. However, could you please elaborate a bit more on this option, as it could be very interesting?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 26, 2025, 08:33:33 pm
content: Quote from: SKYVsebasC20 on September 23, 2025, 07:48:04 pmAs others mentioned a single unit that does all you need is rare,but you can split the tasks as Terry suggestsEghttps://www.aliexpress.com/item/1005007980654262.htmlOr similar have your digital control and wide output and even has a display and MCU.Quote from: SKYVsebasC20 on September 23, 2025, 07:48:04 pmIf you want isolated and Vo > Vin you need a simple DC-DC step up unit that isolates and has the right ratio.A quick search finds one’s like this 9-36vin to 24vohttps://www.aliexpress.com/item/1005007360763059.html

author: Psi
author_rank: Super Contributor
timestamp: September 27, 2025, 11:10:29 am
content: Anything from aliexpress wont met OPs requirement for complete documentation.Aliexpress is usually "You get what you get and you don't get upset" hehe.Lots of useful stuff but not all that tested and documented.