Higher power ( 30W+ ) Wireless Power Transfer solutions..?  - Page 1
Forum section: electronics / projects

author: mrpackethead
author_rank: Super Contributor
timestamp: April 17, 2015, 10:07:21 pm
content: I'm looking for reference designs for 30W+ wireless power transfer solutions.. All the standard based stuff is a maximum of 15W, with 10W and 5W being more common.Any pointers would be really appreciated.

author: sifu0832fjcm2w3fd
author_rank: Newbie
timestamp: April 17, 2015, 10:19:40 pm
content: Hi,It may not be applicable for your application but have you considered instead of getting yourself larger hummer and whacking even harder, making it with more precision? How about directional antenna that will increase your range?You didn't say anything about the application.

author: mrpackethead
author_rank: Super Contributor
timestamp: April 17, 2015, 10:32:39 pm
content: Quote from: sifu0832fjcm2w3fd on April 17, 2015, 10:19:40 pmNo i didn't. Thanks for your valuable contribution...

author: nctnico
author_rank: Super Contributor
timestamp: April 17, 2015, 10:34:18 pm
content: Those reference designs don't exist. I have built a solution from scratch for one of my customers. Wurth has some excellent high power wireless transfer coils so you can use those as an off-the-shelve solution. Depending on the distance you may need coils with a different number of turns to keep the voltage on the receiving end low.

author: tautech
author_rank: Super Contributor
timestamp: April 17, 2015, 10:54:57 pm
content: Quote from: mrpackethead on April 17, 2015, 10:07:21 pmYou're asking about "inductive" power transfer are you not?Edit you thread name to show this.There have been proposals to charge E-cars just by parking them on a transfer position. That will require significant power transfer so solutions will be out there, other than this sorry I can't be of much assistance.

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 12:56:57 am
content: Actually this technology dates back to Nikola Tesla's wireless power transfer ideas. Only he didn't had the MOSFETs to create a nice push-pull stage to drive a resonant tank circuit.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 18, 2015, 01:04:30 am
content: Perhaps "reference designs" are made by people in the Real World where they understand the kind of efficiency you can get from high-power wireless power transmission and realize that it isn't worth the effort to create using today's technology because the cost/benefit ratio is significantly negative.

author: hli
author_rank: Frequent Contributor
timestamp: April 18, 2015, 02:00:46 am
content: I can give you a German article (from mikrocontroller.net) aboutRoyer Converters. The last paragraph talks about transmitting 300W, with 92% efficiency, over about 4mm. Hopefully Google Translate helps you. If not, there are all the formulas, and many links at the end.

author: calexanian
author_rank: Super Contributor
timestamp: April 18, 2015, 04:40:00 am
content: Inductive coupling is the only practical way that does not waste copious amounts of energy and remember that coupling reduces by the inverse square of the distance.

author: mrpackethead
author_rank: Super Contributor
timestamp: April 18, 2015, 06:07:01 am
content: Quote from: nctnico on April 17, 2015, 10:34:18 pmThat is largely what i've found. Much searching has revealed very little, and i think i'm probably going to have to do what you have done. Design one. I in fact have the Wurth Design kit, although its only 5W. I'm only going to need a few ( 2-3mm ) of separation with the coils. In my application i'm just looking to replace some mechanical connectors because the environment is "hostile". Being able to encase some coils will make a big difference.The "theory" of how these things works seems simple enough, in practice it might be a different situation.Freescale have some "solutions", however they don't seem to have shared them. Power by Proxi have some solutions ( up to 250W ) as well, but they don't really come in the way i need / want to use them..

author: mrpackethead
author_rank: Super Contributor
timestamp: April 18, 2015, 06:12:43 am
content: Quote from: Richard Crowley on April 18, 2015, 01:04:30 am75% is very feasible and for my project, there would be pretty big gains.. Loosing power in this application is'nt a big issue.

author: eneuro
author_rank: Super Contributor
timestamp: April 18, 2015, 08:13:20 am
content: Quote from: nctnico on April 18, 2015, 12:56:57 amBring to reality by HAARP?HAARP Facility Shut Down!It is a fact that theHAARP facility in Gakonawas only apublic relations facadewhich distracted from the larger facility near Fairbanks and the many other "ionospheric heaters" located around the country -- and the world -- that no longer use dipole antennae farms and receive their funding as "black projects", exempt from public scrutiny or review.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 18, 2015, 08:53:27 am
content: Wireless chargers and receivers for cellphones are readily available and very cheap - if the application is low volume and not too space-constrained. simply using multiples of these (or at least multiple coils) might be an option.e.g.http://www.ebay.co.uk/itm/Qi-Wireless-Charger-Pad-Charging-Receiver-For-Samsung-Galaxy-S3-4-5-Note2-3-4Kit-/251781820362?pt=LH_DefaultDomain_3&var=&hash=item3a9f5dafca

author: mrpackethead
author_rank: Super Contributor
timestamp: April 18, 2015, 09:01:50 am
content: Quote from: mikeselectricstuff on April 18, 2015, 08:53:27 amThat is not a bad idea, and perhaps quite a good one. I'm in the thousands of times though

author: mrpackethead
author_rank: Super Contributor
timestamp: April 18, 2015, 09:53:54 am
content: Quote from: hli on April 18, 2015, 02:00:46 amThanks, that helped me find some other really useful papers;http://www.jiep.or.jp/hp_e/journal/6/transaction6_1_32-37.pdfandhttps://www.qualcomm.com/documents/loosely-coupled-wireless-power-transfer-physics-circuits-standards

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 10:59:39 am
content: Quote from: calexanian on April 18, 2015, 04:40:00 amI managed to get close to 70% over a 30mm distance which included power lost in the control circuitry and a (no so efficient) DC-DC converter to convert the receiver voltage into a lower voltage. When using larger coils that efficiency can be improved.

author: eneuro
author_rank: Super Contributor
timestamp: April 18, 2015, 01:41:04 pm
content: Quote from: nctnico on April 18, 2015, 10:59:39 amCould you reveal frequency range used?In one of research projects need to charge AC mosfets switch gate directly using directed radio wave beam, but from a few meter distance to as far as possible-it could be nice to have 1inch2 PCB including receiver antena, so probably 1inch diameter will determine its transmiter operating frequency.BTW: There is nothing (or missed something) in OP problem descripion about distance between transmiter/receiver in requirements for his wireless energy power supply.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: April 18, 2015, 01:53:29 pm
content: You may find this video of interest:

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 04:54:35 pm
content: Quote from: eneuro on April 18, 2015, 01:41:04 pmI used a frequency around 200kHz but this is tuned to optimise the efficiency (copper losses, switching losses and core losses). For your setup you may end up with a different optimal frequency.

author: eneuro
author_rank: Super Contributor
timestamp: April 18, 2015, 07:10:29 pm
content: Quote from: nctnico on April 18, 2015, 04:54:35 pmI have no idea how to find optimal frequency eg. of Tesla Pancake coilAnyway almost finished my genetic alghorithms CUDA (cuGA) engine so I can try to use this approach to solve this optimisation problem using GA's, but need to know first howto estimate efficiency based on so many factors.However, what kind of coil did you used?Started searchingyoutubethere are a lot of videos about this fancy Tesla Pancake coil:There is another comparision and... another ones: Vortex Coil, Tesla Pancake and Standard coils comparision attemptOK, I can write w few lines of code and draw this fancy Tesla Pancake coil and make those tracks on PCB and maybe even put a few such PCBs in parallel to amplify this magnetic field, but there is any advantage in this fancy Pancake coil?Vortex coil is sci-fi for me, but I like for the moment idea to manufacture a few 1inch2 Tesla Pancake coils with thin tracks and small spacing, but is it better than 1inch2 filled with another antena type (eg. rectangular pattern) similar to this Tesla Pankake coil?Probably will try wind small room with w few turns of wire first and... try light up diode anywhere inside the room, while it could have many practical use cases tooBut Tesla Pancake coils?

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 08:01:36 pm
content: I used a standard wireless power transmission coil from Wurth. They key is to have the transmitter and receiver act as a resonating tank circuit with a reasonable Q factor.

author: eneuro
author_rank: Super Contributor
timestamp: April 18, 2015, 08:32:15 pm
content: Quote from: nctnico on April 18, 2015, 08:01:36 pmYep, high Q. They says the same there:https://www.qualcomm.com/documents/loosely-coupled-wireless-power-transfer-physics-circuits-standardsNow its time to make somebased on room dimensions etc

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 08:39:04 pm
content: Reasonable is not as high as possible. At a high Q the bandwidth is small so a minor mismatch between transmitter & receiver will make the energy transfer stop. When dealing with power you need to take into account inductance variation due to non linear behaviour of the ferrite material.

author: mrpackethead
author_rank: Super Contributor
timestamp: April 18, 2015, 10:09:15 pm
content: Thanks as normal there's a lot of knowledge here. The point about having to high a Q is important. In my application I'm really looking to replace mechanical connectors as they are a source of problems as they are submerged up to 6meters of water. My separation only needs to be a few mm and I'm not hugely constrained by coil size. Just enough to to be able to get a layer of plastic moulding over them.The Qualcomm paper ( why I didn't find this first is beyond me ) really provides a lot of useful info.For my app I don't need to have to deal with FOD detection or a lot of the other issues that may occur with a consumer type thing. My tx and tx sides will get placed next to each other ( and likely mechanically heldTogether with a clip or bolt ) so alignment also will be consistent.My load will also be consistent.

author: hli
author_rank: Frequent Contributor
timestamp: April 18, 2015, 10:43:03 pm
content: Btw: Würth has demonstrated a Qi coil powerful enough to power kitchen appliances:http://www.element14.com/community/videos/14016/l/w%C3%BCrth-elektronik-wpc-coil-for-kitchen-appliances(unfortunately the audio is Japanese...)

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2015, 10:56:57 pm
content: Well... you don't need a receiver to heat something. A transmitter works very well as an inductive cooker! During my experiments I held a metal PC slot cover near the transmitter. It got hot pretty quick. This is one of the reasons you need to have the receiver communicate back to the transmitter to at least make sure you don't heat a metal object which happens to be in the neighbourhood. The Qi specs are a good place to start to avoid these kind of problems.

author: eneuro
author_rank: Super Contributor
timestamp: April 18, 2015, 11:12:54 pm
content: Quote from: hli on April 18, 2015, 10:43:03 pmIt looks like it is Würth web subpage with this kind of stuff-they make PCBs too, but claims something like multilayer planar coils with huge density:http://www.we-online.com/web/en/wuerth_elektronik/news_weg/news_archiv_2012_weg/News_Detail_WE_Gruppe_2012_14404.phpThis way you can combine multiple coils to form a magnetic circuit and produce a complex, yet precisely designed transformer element. In various test scenarios, these coils were subject to a current density of up to 30 A/mm² with a conductor fill factor of up to 0.9. Generally that'sfive times more than a conventional wire-wound coilcomponent.BTW: Is it 6.780  frequency (mentioned in Qualcomm paper) for WPT transmiter some kind of standard and not restricted in public places worldwide?

author: mrpackethead
author_rank: Super Contributor
timestamp: April 19, 2015, 01:26:23 am
content: Quote from: alsetalokin4017 on April 18, 2015, 01:53:29 pmThats truly bizarre!

author: eneuro
author_rank: Super Contributor
timestamp: April 19, 2015, 10:37:57 am
content: Quote from: nctnico on April 18, 2015, 10:56:57 pmProbably you had desent amount of magnetic flux througth itTried to make some kind of feasibility study of my concept and used also thisMIT Inductance and Magnetic Energyguide, than wrote a few lines of code to compute mutual inductance as well as other self-inductance of each coils: transmiter 3m in diameter put on room ground and small 1inch receiver and numbers doesn't look great at 1MHz 1 meter above ground 3m diamater transmiter coilCode:wpt: freq: 1.000 wpt: w0: 6283185.307 [rad/s]wpt: r1: 1.500 wpt: r2: 0.013 wpt: z: 1.000 wpt: wire: A: 2.500 [mm^2]wpt: copper resistivity: p: 1.724e-08 [ohm * m]wpt: n1: 1wpt: r1: 1.500 wpt: l1: 0.004 wpt: n2: 1wpt: r2: 0.013 wpt: l2: 0.004 wpt: R1: 0.065  wire length: 9.425  diameter: 1.784 wpt: L1: 2489.357  C1: 10.175 wpt: R2: 0.001  wire length: 0.080  diameter: 1.784 wpt: L2: 0.178  C2: 141947.629 wpt: M: 0.122262891 wpt: k: 0.000005801wpt: RL: 0.001 wpt: n: 0.409146416 [%]I used 2.5 mm2 copper wire and only 3 turns on transmiter and 9 in receiver.However, when recalulated at 27.120 MHz also around 1 meter above tramsiter coil it looks much better:Code:wpt: freq: 27.120 wpt: w0: 170399985.531 [rad/s]wpt: r1: 1.500 wpt: r2: 0.013 wpt: z: 1.000 wpt: wire: A: 2.500 [mm^2]wpt: copper resistivity: p: 1.724e-08 [ohm * m]wpt: n1: 1wpt: r1: 1.500 wpt: l1: 0.004 wpt: n2: 1wpt: r2: 0.013 wpt: l2: 0.004 wpt: R1: 0.065  wire length: 9.425  diameter: 1.784 wpt: L1: 2489.357  C1: 0.014 wpt: R2: 0.001  wire length: 0.080  diameter: 1.784 wpt: L2: 0.178  C2: 192.996 wpt: M: 0.122262891 wpt: k: 0.000005801wpt: RL: 0.002 wpt: n: 56.750921923 [%]However, didn't calculated Q factor yet, only guessing from this MIT guide that lowering R in receiver coil will improove this Q factor.When we change receiver coil to 0.5 in diameter numbers are much better even at 1MHzBTW: According to thishttp://en.wikipedia.org/wiki/ISM_bandand this threadhttps://www.eevblog.com/forum/projects/6-78-mhz-ism-band-worldwide/6.780 MHz is marked assubject to local acceptance, while 27.120 MHzworldwide, however it require more sophisticated equipment and faster switching.Anyway it is interesting what happends at 1MHz, 6.790 Mhz and 13.560 MHz or 27.120 MHz-higher frequency.Huge coil means that coupling coeficient will be small if we put inside small loop relative to much bigger transmiter, so probably inductive heating will not be a problem, but much bigger to notice any energy transfer effects at all between big and small coil.Now its time to see moreyoutubevideos while, we know how mutual inductance is affected by coils geometry and its distance between each other used in this kind of experiments.Quick calulation shows, that distance between coils makes a huge difference, so no ssupprise what we see on tricky youtube WPT demosUpdate: Another story is transmiter power limits even on those worldwide ISM band radio frequency, so 30W+ isn't too much?Update2: Now realized, that I might have bug in this software and need read again how mutual inductance is derived in those documents-maybe those numbers will look better-not sure if number of turns in coils is taken into account-my solenoid estimated self-inductance uses number of turns and need to verify how those equations for mutual inductance were derived-with one only turn in coilor more, but at least some hints how to deal with WPT...Update3: Yep, Qualcomm document assume single-loop coils, so calculated again and updated previous output code and now, wow: at 27MHz we get at distance 1m close to 60% maximum theoretical efficiency at optimal RL load?probably time to debunk those theories and usehttp://en.wikipedia.org/wiki/Joule_thiefin receiver to see what happends in real world experiment