Qi Chargers from China, what's your experience? - Page 1
Forum section: electronics / projects

author: quanttrom
author_rank: Regular Contributor
timestamp: December 22, 2013, 11:32:32 pm
content: Hello guys,I purchasedhttp://dx.com/p/wpc-qi-standard-wireless-charger-for-nokia-lumia-920-lg-nexus-4-samsung-i9300-n7100-white-217772with the hopes of using it to charge my Nexus 4 phone.The charger is extremely unreliable and it only draws about half an amp @ 5V.My understand is that the power receiver (phone) determines the current when charging. What is your experience with that? Is the charging current typically in that range for Qi chargers? It seems like they should be able to charge with up to 5W..What's your experience?

author: Psi
author_rank: Super Contributor
timestamp: December 22, 2013, 11:37:26 pm
content: My experience with deal extreme is you get what you pay for.Although for US$20 i would have expected it to charge properly

author: peter.mitchell
author_rank: Super Contributor
timestamp: December 23, 2013, 04:20:14 am
content: I have that specific model, or at least, so similar you can't tell; from the outside.Make sure you have a decent 5v source plugged into it and you position your phone correctly. Aside from that, i have no idea. I have used it with a samsung galaxy note 2 (n7100) and a verizon branded lg g2 with no issues, draws about 2A when charging.

author: quanttrom
author_rank: Regular Contributor
timestamp: December 23, 2013, 06:06:49 am
content: Quote from: peter.mitchell on December 23, 2013, 04:20:14 amyeah I am powering it with a benchtop power supply capable of 6A. More than enough.I've opened mine up and it seems like a very simple design. Have you had a chance to see what's inside yours??

author: peter.mitchell
author_rank: Super Contributor
timestamp: December 23, 2013, 08:39:55 am
content: Pretty simple too, from memory, just a Ti wireless charging IC, a boost converter (and associated Passives) , some LEDs and the coil.Took another look; for more info, it had a Ti wireless charging IC, a boost converter (and associated passives), a dual fet package, a vqfn-16, some leds and the coil.

author: dannyf
author_rank: Super Contributor
timestamp: December 23, 2013, 01:05:30 pm
content: QuoteI am too poor to buy cheap stuff.

author: amyk
author_rank: Super Contributor
timestamp: December 23, 2013, 03:40:58 pm
content: 500mA sounds too right of a value to just be a random choice - it's the maximum current available from a standard USB port and a standard USB charger, so maybe they limited it to that unless it detects it's plugged into a charger that declares a higher current standard? The presence of a TI IC in it would suggest that, at least, it's not just a dumb oscillator driving a coil.

author: quanttrom
author_rank: Regular Contributor
timestamp: December 23, 2013, 08:14:21 pm
content: I will take some pictures of the unit but it doesn't seem to contain nearly as many components as peter.mitchell's charger.It has a chip labelled Tesla TS1001S(not an OpAmp), and a TI LM224(Quad OpAmp) and a bunch of passives. Rather small board really..

author: quanttrom
author_rank: Regular Contributor
timestamp: December 23, 2013, 08:14:40 pm
content: Quote from: dannyf on December 23, 2013, 01:05:30 pmYou sir are 100% correct !

author: quanttrom
author_rank: Regular Contributor
timestamp: December 23, 2013, 11:17:46 pm
content: So, I have access to a bq51013EVM-725. This is one of the TI Evaluation Modules for QI . When I place the receiving module on the transmitter, it occasionally comes up but isn't very reliable. When it comes up, and I get power on the receiving end, things seem to be working fine until I load it.I am using just a simple resistive load of 20 ohms. (250mA) and the TI receiver module will shut down.After some testing I realized I can increase the power supply voltage to 7V or so and it will maintain a 5V output with the 250mA load but the output voltage starts dipping.Anyways, this is junk as far as I can see. I will take some pics and then see what kind of voltage it can handle ! After all more volts solves all problems !!

author: quanttrom
author_rank: Regular Contributor
timestamp: December 23, 2013, 11:46:33 pm
content: So this is the Tesla Chip. It has 4 transistors hooked up to it, so I am assuming some sort of H-Bridge. I will post pics of the whole thing in a bit.

author: quanttrom
author_rank: Regular Contributor
timestamp: December 24, 2013, 06:30:05 am
content: More picsThe board is loaded only on one side. What is see is all there is to it !

author: peter.mitchell
author_rank: Super Contributor
timestamp: December 24, 2013, 09:01:03 am
content: Quote from: quanttrom on December 24, 2013, 06:30:05 amWow, that is shit.I got mine and a flex pcb with a pcb antenna, passives and a bq51013B all for $20!Looks like you got a chinese knock off of a chinese knockoff!

author: amyk
author_rank: Super Contributor
timestamp: December 24, 2013, 12:52:44 pm
content: Number of parts is not really indicative of anything here... you don't need many as most of it has been integrated into an IC.Odd that there is practically no mention of the "Tesla" brand or that part number anywhere else on the Internet, although TI has a Qi charging IC series they call bqTESLA.Would be interesting to RE that, but might be hard since it looks like 4-layer PCB.And a bq51013B is areceiver...

author: peter.mitchell
author_rank: Super Contributor
timestamp: December 24, 2013, 03:31:15 pm
content: Quote from: amyk on December 24, 2013, 12:52:44 pmI know the number of parts isn't directly indicative of much, but there are some primary requirements.This is what i think i see on that board;a tl431 regulating the power to that tesla chip or providing a reference.the tesla chip, driving an led and driving 4 transistors4x transistors, driving the tank circuita lm324 opamp, probably with a shunt resistor to stop the thing cooking if a metal object is placed on it directly. IF *IF* is actual wireless charging chip, also probably driver for coil communication.Nah, none of the TI wireless transmitter products come in a package like that. I had a pretty thorough search for that chip too, all of the tesla related results returned refer to and old ic manufacturer, and i couldn't find a single wireless tx chip for this application, in that package.Also, yes, i know the bq51013b is a receiver, it was on a flex pcb with a pcb antenna for retrofitting into an existing device or something. I got this in addition to my charger for free.

author: quanttrom
author_rank: Regular Contributor
timestamp: December 24, 2013, 03:40:14 pm
content: Yeah, I had a good look at TI's wireless power portfolio and found nothing.Then I though that the TS would be indicative of Triune Systems chip but they don't have any reference to it either..http://www.triunesystems.com/wireless-power/transmitters

author: all_repair
author_rank: Frequent Contributor
timestamp: December 24, 2013, 03:53:11 pm
content: Quote from: Psi on December 22, 2013, 11:37:26 pmQuality of DX seems to be at the lowest ends. It maybe the margin that DX asked and the recourse from buyers are absent. It could be the rejects of already low quality products that DX are selling, from my own purchase experiences.