VHF Laptop Power Supply (DART) - Page 1
Forum section: electronics / general

author: polar8
author_rank: Contributor
timestamp: January 08, 2014, 10:33:07 pm
content: Ok, so it's not on Kickstarter yet (company predicts this spring) but it was recently launched at CES and has been getting lots of press. Thoughts?http://www.finsix.com/index.html

author: tom66
author_rank: Super Contributor
timestamp: January 08, 2014, 11:40:52 pm
content: Technical information:http://www.finsix.com/files/FINsix_Tech.pdfIt sounds like they've basically taken the SMPS and kicked it into the tens of MHz range. I would have thought power transistor losses at that point would not make it worth it but apparently not, as they address that.If they can make it practical and cheap enough it looks like it could be quite a winner, though I doubt we will see converters like this on the average PCB, must be using RF capable PCB with known impedances etc. Maybe could work for laptop/computer motherboards though as they already need controlled impedance for RAM, PCI, etc.

author: AG6QR
author_rank: Frequent Contributor
timestamp: January 09, 2014, 12:16:37 am
content: I wonder about the RF implications of this. It says that it meets applicable standards for conducted and radiated EMI, but that's not a guarantee of problem-free operation, especially for those of us who like to play with radios.However, it might be good news. By shifting into VHF, they'll be above the most interesting frequencies for us ham radio operators. The range from roughly 1.6MHz to roughly 30MHz is where weak signals can most easily bounce around the world via the ionosphere. A lot of switching power supplies pollute this range, largely with harmonics that produce broad-spectrum hash across the shortwave bands. I'd love to see the switching power supplies move above this area. The higher frequencies are normally of use mostly for short range communications anyway, and they tend to be less susceptible to interference. But they're not entirely immune...They're talking about switching frequencies in the range of 30MHz to 100MHz, and I'd assume that harmonics would extend much higher. That 30-100MHz range covers some land mobile and police radios, plus part of the FM broadcast band. Harmonics might extend into aircraft navigation and voice communications, terrestrial TV, and other services at higher frequencies.If this works, I think it'll catch on big time, and eventually be copied by many. The advantages sound too good to pass up.

author: Rufus
author_rank: Super Contributor
timestamp: January 09, 2014, 01:58:51 am
content: Quote from: polar8 on January 08, 2014, 10:33:07 pmIntel's switch mode regulators integrated in the die of Haswell processors are even more ridiculously small, high power, and high frequency.Not sure how easy it is to get extremely high efficiency which is required to manage heat in the small packages or how economical it is.Strange they seem to be only offering product to end users who are going to have to throw away a PSU they already have. You would think there would be plenty of interest and more business for them from OEMs so maybe it is too expensive (except for apple customers who will pay a large premium for anything, but, I'm sure apple could do this themselves and probably will if it is practical).

author: tom66
author_rank: Super Contributor
timestamp: January 09, 2014, 09:29:21 am
content: I'm going to guess the first generation of this product will cost at least $100. I don't see RF power transistors being cheap especially if rated for 500V. Probably too expensive for laptop OEMs to include by default, but could be an option that's available for purchase at the same time.If finsix have patents on it, then they might license the technology to Apple, or make power supplies to Apple's requirements.How do you rectify the output of a 30MHz SMPS? What kind of efficiency will these have? Will the output be cleaner, given the lower filter requirements? Will they be repairable?

author: vk6zgo
author_rank: Super Contributor
timestamp: January 09, 2014, 11:05:32 am
content: Quote from: AG6QR on January 09, 2014, 12:16:37 am6 metres, 2metres,& 70cm all are bastions of weak signal work.If it goes from 30MHz to 100MHz,it covers 6m directly,& probably 2m & 70cm on harmonics.6m can hardly be regarded as "short range".It's not a matter of noise propagated from far away,it's the guy next door!

author: Marco
author_rank: Super Contributor
timestamp: January 09, 2014, 03:15:43 pm
content: An old paper describing the technology they used (more detailed than their website) :"A Very High Frequency dc-dc Converter Based on a Class ?2 Resonant Inverter".

author: tom66
author_rank: Super Contributor
timestamp: January 09, 2014, 03:30:00 pm
content: If it's as described in that paper, it's of a nonisolated topology which surely means it cannot be used for mains power.

author: ConKbot
author_rank: Super Contributor
timestamp: January 13, 2014, 05:41:23 pm
content: Quote from: tom66 on January 09, 2014, 09:29:21 amThe same way you switch itIf youre getting into efficient SMPS's synchronous rectification is almost a given.

author: Rasz
author_rank: Super Contributor
timestamp: January 17, 2014, 07:47:21 am
content: I dont get it, what are the advantages?I seem to remember Satellites use SMPSes in MHz region to make them small and light. But my laptop bag is not a satellite launching rocket, I wont die if my PSU is 10cm instead of 4cm.

author: AdShea
author_rank: Contributor
timestamp: January 23, 2014, 04:51:38 am
content: A few guys in my lab are working on stuff like this. They're much cleaner than normal hard-switched supplies because they're closer to RF circuitry (Class E into a rectifier) and don't really have as many harmonics in the system.As for losses, they're horrible for losses for the amount of Si they use, but generally you can get away with buying more power switch (to reduce those losses) if you are able to make up the cost/space/losses in the passives. The big win here is that you can drop volume with about the square of operating frequency up to a few MHz then about proportional to frequency above that.As for use, most laptop supplies aren't too awful, but I'd sure like something smaller than they paperback-sized brick that comes with my W520. A beefy i7 and high-end Quadro card sucks down a fair bit of power.

author: Harvs
author_rank: Super Contributor
timestamp: January 23, 2014, 09:06:11 am
content: Quote from: Rasz on January 17, 2014, 07:47:21 amI have a 13" ultrabook that I cart everywhere with me, and I know many others that do the same. It's only slightly larger than then screen size, and about 1.5 samsung galaxies thick. Yet the power adapter is the same sort of size as most other 60W laptop power adapters, read huge in relation to the device. Ultrabooks are a premium product that's relatively expensive and bought by a lot of professionals that travel, if there was a product on the shelf today for $100 that was a third the size of the current power adapter for these I reckon they'd fly off the shelf.

author: Corporate666
author_rank: Unknown
timestamp: April 15, 2014, 06:35:08 am
content: Curious what those more knowledgeable think about this. They are basically using very high frequency switching in an SMPS to get everything smaller, ultimately fitting 65W worth of power supply into a very small plug-in adapter.https://www.kickstarter.com/projects/215201435/dart-the-worlds-smallest-laptop-adapterI am not qualified to know what the shortcomings of such a design are, but off the top of my head I wonder about switching losses, as well as thinking "if it was just as simple as cranking up the frequency, it would have been done lots of times before".So I am real interested in what the folks here think about this project....

author: mariush
author_rank: Super Contributor
timestamp: April 15, 2014, 06:46:56 am
content: Discussed here:https://www.eevblog.com/forum/crowd-funded-projects/vhf-laptop-power-supply/

author: johansen
author_rank: Super Contributor
timestamp: April 15, 2014, 07:07:03 am
content: i bought a 90 watt adapter off ebay for 9$ iirc.then promptly broke it by removing the resistor divider and turning it on... thinking it wouldn't nuke itself. i think i saw 27 volts on the output for a moment.no emi flter, just a fwb into a 400 volt capacitor, then a flyback converter, regulated through an optical isolator.of course, the thought concerns me.. for a laptop, you don't really need clean power going in. why not do away with the output filtering completely and run 120 hz or 100 hz ripple all the way to 50% or whatever it is.. no LF input or output filtering needed.you could even incorporate pfc into the flyback converter with nothing but a .1uF on the input and a 10uF ceramic on the output.in fact i'm fairly certain i could get one 4th the normal volume and 1/6th the normal weight for 60-150 watt adapters at just 500khz and standard semi resonant topology, including pfc input. but it would cost more than its worth.

author: Corporate666
author_rank: Unknown
timestamp: April 15, 2014, 07:19:54 am
content: Quote from: mariush on April 15, 2014, 06:46:56 amThank you! Maybe a moderator can merge threads? I completely missed the other thread.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 15, 2014, 07:43:57 am
content: I think a big potential space-saving trick has been missed for decades.A significant space-hog in any SMPS is the input reservoir capacitor, however for a device that is used for charging a battery, there is no fundamental need to supply continuous DC.If the charging circuitry was designed to accept a 100/120Hz pulsed supply, then it would be possible to use a PSU with minimal smoothing, and eliminate the capacitor.It would also eliminate the need for a seperate power-factor correction converter.

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 15, 2014, 09:02:35 am
content: Quote from: mikeselectricstuff on April 15, 2014, 07:43:57 amIndeed.Another method though could be adding additional windings to the SMPS and an additional switch and rely on the output capacitors, I mean, the difference between input and output is so high that an unfiltered 240v AC sine has a differential above 20v for 95%~ of the time...

author: theatrus
author_rank: Frequent Contributor
timestamp: April 16, 2014, 03:48:42 pm
content: https://www.kickstarter.com/projects/215201435/dart-the-worlds-smallest-laptop-adapter?ref=searchSomething tells me this is going to be a bear to get through any certification process. And apparently MIT has a patent on the VHF band.

author: mariush
author_rank: Super Contributor
timestamp: April 16, 2014, 05:08:27 pm
content: Apparently people DON'T KNOW HOW TO USE THE SEARCH BUTTON :https://www.eevblog.com/forum/crowd-funded-projects/vhf-laptop-power-supply/mod ... maybe add DART in the name of that thread so this won't happen so often ?And some people don't know how to use the Report to Moderator button. It's the best way to bring something like this to the attention of a moderator.

author: tom66
author_rank: Super Contributor
timestamp: April 19, 2014, 11:37:43 am
content: Quote from: mikeselectricstuff on April 15, 2014, 07:43:57 amBut a laptop's processor -does- need constant DC. How would you supply that? Most laptops switch all busses to AC power only once it's available. Plus you don't want to be shoving 100Hz/120Hz ripple through a small output capacitor.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 19, 2014, 02:56:35 pm
content: Quote from: tom66 on April 19, 2014, 11:37:43 amFrom the battery, obviously.

author: Marco
author_rank: Super Contributor
timestamp: April 19, 2014, 07:43:33 pm
content: Would using the battery as a smoothing capacitor not quickly destroy it?

author: scientist
author_rank: Frequent Contributor
timestamp: April 22, 2014, 03:05:00 am
content: These twats seriously think patents don't apply to them?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: April 22, 2014, 03:38:01 am
content: Quote from: scientist on April 22, 2014, 03:05:00 amThey own the patent mentioned in the description...or are you referring to something else?

author: scientist
author_rank: Frequent Contributor
timestamp: April 23, 2014, 01:46:31 am
content: Just because they graduated from MIT doesn't mean they own an MIT patent.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: April 23, 2014, 03:01:24 am
content: Quote from: scientist on April 23, 2014, 01:46:31 amhttp://www.google.com/patents/EP2606564A1?cl=enApplicant: Finsix Corporation

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 23, 2014, 05:29:01 am
content: This isn't too exciting but maybe I'm missing some key point to this. It seems to me that an innovative solution would be one that does away with the battery altogether. How about a small butane (or whatever's in a cigarette lighter) powered bank of MEMS generators. Properly shielded and placed where the battery used to go. Go for a month or two on a single fill up. In a pinch a cigarette lighter could be used as a refill.

author: calexanian
author_rank: Super Contributor
timestamp: April 23, 2014, 05:34:56 am
content: WTF??!!!!!! smaller lighter electrons? Did anybody actually watch their video? Holy crap! And these are MIT students? What the hell is going on over there? They say they have put lots of time and effort into this project? Any competent engineer could knock out the basic design and have the gerbers off to the quick turn house in an afternoon!Not to mention...THIS IS A TERRIBLE IDEA!!!!!!Why do you need to go that high in switching frequency? Just the distributive capacitance will kill you at 65 watts in that small of a package! Dielectric heating alone would be a safety hazard. Just the proper filtering alone at these frequencies to cover VHF would be larger and harder to build an tune than a traditional switcher. With new fets and high efficiency switcher designs I see no practical need to go that high in freq. Its all down side and no up. The ferrite size diff in that wattage range from low freq to VHF is not that much. You still need the same size bulk capacitance weather it be on the primary or secondary.Young students with no practical product design experience should go to a grey beard once or twice to get this kind of thing ridiculed so they will think through this stuff before they broadcast their underdeveloped design to the masses.

author: miguelvp
author_rank: Super Contributor
timestamp: April 23, 2014, 07:58:18 am
content: Quote from: Marco on January 09, 2014, 03:15:43 pmQuote from: suicidaleggroll on April 23, 2014, 03:01:24 amOther than name changing and terminology their dc-dc conversion part seems way too close to that paper by totally different authors.instead of multi-stage call it multi-cell, buffer instead of storage, but it gets better, you can hit the prior art in the patent link and well the previous paper is there among others.And look at the schematics too, yeah different they took the auto-transformer and replaced it with a capacitor. Of course a full rectified bridge so it's ac-dc converter instead of a dc-dc converter. Some pulse magic and voila new stuff, but the original paper has it covered with the multi-stage resonant driver and the on/off control.But it doesn't matter if the patent holds I guess, most likely they won't get sued and if the original paper holder from 2008 makes a product I bet they won't try to sue them either.I'm with GiskardReventlov but instead of a butane lighter just plug it in a cow, you get all the methane you need for you a hydrogen fuel cell to power your computer plus free milk! And tasty steaks once you need to replace the cow.

author: scientist
author_rank: Frequent Contributor
timestamp: April 24, 2014, 09:11:00 pm
content: Quote from: GiskardReventlov on April 23, 2014, 05:29:01 amButane is pretty flammable.

author: calexanian
author_rank: Super Contributor
timestamp: April 24, 2014, 10:40:00 pm
content: But why has nobody picked up on the smaller lighter electrons thing? am freaking bugged by that!

author: wraper
author_rank: Unknown
timestamp: April 24, 2014, 11:27:51 pm
content: Quote from: calexanian on April 23, 2014, 05:34:56 amYour arguments contradict one another. First you talk about the gerbers in a one day. If it is that simple why nobody sells them? Then you talk about realization problems. Are you serious at least a little bit?

author: wraper
author_rank: Unknown
timestamp: April 24, 2014, 11:33:24 pm
content: Quote from: calexanian on April 23, 2014, 05:34:56 amSpecially watched that video. She says "smaller, lighterelectronics" Clean your ears before shouting.

author: PChi
author_rank: Frequent Contributor
timestamp: April 25, 2014, 06:25:07 pm
content: Some thoughts:-I hope that it doesn't break the first rule in Power Supply design which is that it must be cheap.It is small so needs to be high efficiency to keep the internal temperatures down which is another challenge. This could conflict with rule one.How does it supply both the laptop and the USB which probably need different voltages?The USB socket cables have no strain relief so doesn't look like a real product.For off line switch mode power supplies the insulation required between the primary and secondary windings for safety cause leakage inductance which isn't helpful for high frequency switching.I wasn't able to download the FINsix_Tech.pdf (internet too slow) but I don't see any new ideas. I'd be frightened of the patented technology claim. What new technology have they created?The losses due to switching equal the loss per cycle times the frequency so at a higher frequency the claim to waste far less energy per cycle is a must.Another problem is high voltage switches have high capacitance. The switch drive circuit is going to loose 1/2 CV squared every cycle. It's another reason off line supplies run at lower frequencies than low voltage switched mode units.

author: calexanian
author_rank: Super Contributor
timestamp: April 26, 2014, 09:54:53 pm
content: Quote from: wraper on April 24, 2014, 11:33:24 pmI know what I many not have actually heard. wait...I would really like to see what harmonics are coming off of that sort of design though.

author: PChi
author_rank: Frequent Contributor
timestamp: April 27, 2014, 11:16:38 am
content: I was able to access the FINsix_Tech.pdf. So they intend to use air cored hence more turns for same inductance and with no core and more turns the leakage inductance will greater. I can envisage getting a non isolated supply to work (not easy and high efficiency difficult) but an isolated supply really challenging.

author: wraper
author_rank: Unknown
timestamp: April 27, 2014, 11:26:04 am
content: Quote from: PChi on April 27, 2014, 11:16:38 amThey claim the inductance needs to be at 100nH level, so it might be only 1-2 turns.

author: wraper
author_rank: Unknown
timestamp: April 27, 2014, 11:31:58 am
content: QuoteSo it seems that transformer will be PCB itself. Also read somewhere that there will be multiple channels in parallel.

author: calexanian
author_rank: Super Contributor
timestamp: April 27, 2014, 04:41:05 pm
content: air core at vhf is an extremely difficult thing to tune. leakages all oner. not to mention dielectric heating.

author: PChi
author_rank: Frequent Contributor
timestamp: April 27, 2014, 08:16:02 pm
content: The only viable power planar transformers that I have seen were far from cheap. The turns were assembled from multiple layers seperate from the PCB. I have seen attempts to use the PCB but am not convinced they are viable for a good few watts output. They need lots of copper and little insulator, not like a PCB were there is lots of Epoxy and glass fibre but only thin copper.

author: SeanB
author_rank: Super Contributor
timestamp: April 28, 2014, 09:47:08 am
content: You can do a fairly cheap planar transformer using flex PCB, though it will be a massive stack of mylar and a huge spot for a multipole connector to bind the layers together. I have seen some though that wind a flex on the bobbin as the one low voltage winding that has a high current, making the coil, leadouts, sense winding and interwinding shield as a single strip that is wound on in a single operation. That at least used a standard core.

author: Dago
author_rank: Frequent Contributor
timestamp: April 28, 2014, 11:11:08 am
content: Quote from: PChi on April 27, 2014, 08:16:02 pmPlanar transformers using the PCB are very common in the industry. They usually use a stack of PCBs as the turns, like this:I have some multiple hundred watt PSUs using transformers like this.

author: nidlaX
author_rank: Frequent Contributor
timestamp: December 29, 2016, 12:47:48 pm
content: Has anyone gotten their hands on one of these for a tear down / analysis? Arrow Electronics was going to do a write-up / video, but I haven't seen anything posted.

author: riccardo.pittini
author_rank: Regular Contributor
timestamp: January 05, 2017, 04:57:33 pm
content: I'm working in a similar business and I have seen some teardown.The unit is fully potted, with a very hard potting. Not that easy to reverse engineer. But also from measurements on EMI/EMC, it turns out that it is a conventional power supply (no VHF), operating at variable frequency in the 170-300kHz range.So my feeling is that they struggled too much with the vhf technology and they had to fold-back. Here a good design allowed to match the size constrains

author: Richard Head
author_rank: Frequent Contributor
timestamp: February 11, 2017, 12:25:31 pm
content: The figure of merit in this game is power density. The power density here is 21.7W/ cu. inch. That power density is not that unusual today at all, and routinely done at 500Khz. In fact Eltec energy does higher than this at 3.2kW with active PFC at around 100Khz and with EN61000 compliance.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 11, 2017, 12:38:59 pm
content: Quote from: Corporate666 on April 15, 2014, 06:35:08 amI agree. Despite not AC/DC, there's a relatively new (April 2016) DC-DC Buck converter that does the conversion at 10MHz. Looking at its footprint it is very bizarre, but they claim a reasonable efficiency.http://www.ti.com/product/TPS54A20

author: f4eru
author_rank: Super Contributor
timestamp: February 12, 2017, 08:48:38 pm
content: Quote from: mikeselectricstuff on April 15, 2014, 07:43:57 amyep. I did that in a commercial product.80w psu for a product with a motor. I used a typical pfc chip as a flyback controller. No electrolytic at the primary, the secondary electrolytic took all 100hz voltage ripple.advantages: less cost by avoiding pfc hw, prim cap. Emc is a little spread. Smaller design .disadventages: ripple at the output, higher peak current through components, slow regulating response

author: Marco
author_rank: Super Contributor
timestamp: February 12, 2017, 10:05:59 pm
content: Induction hobs do the same thing.

author: f4eru
author_rank: Super Contributor
timestamp: February 14, 2017, 08:42:45 pm
content: And also led psus, at least the good ones (avoiding chemical caps is vital for hot running led psus)