Apparently Connected Advanced USB Charger Survey

[Gallymimus]

how well does it respond to abuse? (shorted output, shorts between gnd and data, shorts between v+ and data, 12v down the 5v line )

Good question.

It will be very robust against shorted output.  It's not fused but the LDOs on each output have internal current limits at 3A.

Shorts between V+ and data, data to data and data to ground shouldn't present any problems as they should be able to survive up to a diode drop above VCC.

12V down the 5V line is a little tougher and we haven't testing this yet (only have a few prototypes and don't want to start destructive testing yet).  The real point of risk is whether the LDOs can be back fed at that voltage.  Their inherent transistor structure is rated for much higher voltages but the back feed might not play nice. 

We've considered whether putting some transorbs or zeners on the output makes sense.  The down side to this is that in most scenarios they would just burn up if a high voltage (with some current behind it) is placed across the output.  It would give us an indication that the product was abused but it doesn't do a lot for the consumer.

[free_electron]

Do you support PD charging ?

[Gallymimus]

Do you support PD charging ?

I wish .  If we can get this product off the ground we'd definitely like to be one of the early to market suppliers of a USB charger that supports the Power Delivery specification.  I'm not even sure a muliport charger for PD would make sense (at least if you tried to do 4 ports at 100W each you'd have a really hard time keeping any reasonable form factor). 

 

[Harvs]

Totally un-related to this, I did some IV plots of some USB chargers I had lying around the other day, all here http://www.electronicsinoz.info/usb-charger-iv-plots/

A "trend" that is noticeable is the voltage out of these chargers is more like 5.2V, I can only assume to compensate for lead resistance.  Personally I particularly liked how the Samsung charger actually ramped up the voltage WRT current draw, again presumably to compensate for their known lead resistance.  Possibly you could implement something like that.

This is the sort of thing that if I needed a charger now, it was on a shelf next to a bunch of others in a shop and it was a bit more than the rest (maybe $20-30) I might just decide it to buy it. Unfortunately when I'm in front of a computer with time on my hands, I'm far too pragmatic about what I do with my money.  Therefore I can't see myself buying this online.

[free_electron]

Do you support PD charging ?

I wish .  If we can get this product off the ground we'd definitely like to be one of the early to market suppliers of a USB charger that supports the Power Delivery specification.  I'm not even sure a muliport charger for PD would make sense (at least if you tried to do 4 ports at 100W each you'd have a really hard time keeping any reasonable form factor).

It would be nice to have 1 port be PD compatible.

[Gallymimus]

Totally un-related to this, I did some IV plots of some USB chargers I had lying around the other day, all here http://www.electronicsinoz.info/usb-charger-iv-plots/

A "trend" that is noticeable is the voltage out of these chargers is more like 5.2V, I can only assume to compensate for lead resistance.  Personally I particularly liked how the Samsung charger actually ramped up the voltage WRT current draw, again presumably to compensate for their known lead resistance.  Possibly you could implement something like that.

This is the sort of thing that if I needed a charger now, it was on a shelf next to a bunch of others in a shop and it was a bit more than the rest (maybe $20-30) I might just decide it to buy it. Unfortunately when I'm in front of a computer with time on my hands, I'm far too pragmatic about what I do with my money.  Therefore I can't see myself buying this online.

Thanks for the feedback.  Actually you raise a good point.  We are probably going to include a user selectable "turbo" mode which pushes the voltage to the limit of the USB spec.  It should give a 10% charge speed boost.  It is similar to the line resistance compensation that you are talking about.

I like you am very pragmatic and don't dig on spending a lot on accessory products.  Sometimes though I do buy some really really nice things, especially if I use them every day.    Personally I'd be more inclined to have something like this on my desk rather than a little bundle of cables from wall warts.   My wife is certainly going to like this on the nightstand better than the power strip I have now hahahaha

I think audiophiles may go for it too after we get all the data on audio quality.

Thanks for sharing your findings on the IV curves.  Very cool.  Would it be okay to reference your work?

[Gallymimus]

Do you support PD charging ?

I wish .  If we can get this product off the ground we'd definitely like to be one of the early to market suppliers of a USB charger that supports the Power Delivery specification.  I'm not even sure a muliport charger for PD would make sense (at least if you tried to do 4 ports at 100W each you'd have a really hard time keeping any reasonable form factor).

It would be nice to have 1 port be PD compatible.

That's kindof what I was thinking too.  I don't think it would make it in this version of the product but I think that would make an outstanding V2.... Assuming PD takes off.  I hope that it does.

[Gallymimus]

Hey, I just want to thank everyone again for the thoughtful comments and criticisms.  We really appreciate it.

[Harvs]

I like you am very pragmatic and don't dig on spending a lot on accessory products.  Admittedly this isn't a product for me.  It's a product for an executive, business traveler, and the guy who has a putting green in his office .  I think audiophiles may go for it too after we get all the data on audio quality.

In a way I am your target audience, as I guess I'd fall into the "business traveller" category a lot.  I'm not saying I wouldn't buy it, but it's exactly the sort of thing I'd buy while I was traveling.  I'll be on my way to some S*@t hole somewhere, we'll realise we don't have a USB charger for some kit we need to use and if it happened to be there I could well choose it even if it was the most expensive one.  It's just not the sort of thing I would buy while shopping online at home.  Just some food for thought about potential distribution, I reckon airport stores would be a good target.

Thanks for sharing your findings on the IV curves.  Very cool.  Would it be okay to reference your work?

Of course, it's a website, you don't have to ask permission for that.

[Gallymimus]

I like you am very pragmatic and don't dig on spending a lot on accessory products.  Admittedly this isn't a product for me.  It's a product for an executive, business traveler, and the guy who has a putting green in his office .  I think audiophiles may go for it too after we get all the data on audio quality.

In a way I am your target audience, as I guess I'd fall into the "business traveller" category a lot.  I'm not saying I wouldn't buy it, but it's exactly the sort of thing I'd buy while I was traveling.  I'll be on my way to some S*@t hole somewhere, we'll realise we don't have a USB charger for some kit we need to use and if it happened to be there I could well choose it even if it was the most expensive one.  It's just not the sort of thing I would buy while shopping online at home.  Just some food for thought about potential distribution, I reckon airport stores would be a good target.

Thanks for sharing your findings on the IV curves.  Very cool.  Would it be okay to reference your work?

Of course, it's a website, you don't have to ask permission for that.

I gotcha, thanks.  Fancy airport stores would be a good place for it.  Where do I find the eevblog equivalent of sales and distribution forums

[Harvs]

We are probably going to include a user selectable "turbo" mode which pushes the voltage to the limit of the USB spec.  It should give a 10% charge speed boost.  It is similar to the line resistance compensation that you are talking about.

Have you had a chance to test that hypothesis?  I'd be interested to know if the majority of phone/tablets continue to pull a constant current across the 4.5-5.5Vin, or if they switch over to a constant power draw at some point in that range.

It would just seem a little odd to me, if a charge circuit was capable of charging at 10% higher rate by raising the input voltage within spec, why wouldn't a manufacturer like Samsung already do it?

[Gallymimus]

We are probably going to include a user selectable "turbo" mode which pushes the voltage to the limit of the USB spec.  It should give a 10% charge speed boost.  It is similar to the line resistance compensation that you are talking about.

Have you had a chance to test that hypothesis?  I'd be interested to know if the majority of phone/tablets continue to pull a constant current across the 4.5-5.5Vin, or if they switch over to a constant power draw at some point in that range.

It would just seem a little odd to me, if a charge circuit was capable of charging at 10% higher rate by raising the input voltage within spec, why wouldn't a manufacturer like Samsung already do it?

No I haven't tested it yet.  UGH so many things to test still

You are right.  It's hard to say whether it would work or not.  It really depends on if the SMPS front end in the phones is power regulated or current regulated.  If they limit the current drawn rather than power drawn it JUST MIGHT WORK!

It will be a tricky test.  Making sure the phone or tablet is off so that background tasks don't artificially impact the charging rate and making sure that the phone battery is discharged to a consistent level each test cycle will be important.  I need an intern!

[Harvs]

I don't think you need to get that complicated to start with.  Just hook up a lab supply to USB cable with an ammeter. With the phone off, and not fully charged vary the input voltage between 5 and 5.5V and see what happens to the current draw.  It'll be pretty obvious, either it'll stay flat or will drop with input voltage.

The tricky part is getting your hands on a reasonable sample set of phones so you can offer customers some degree of confidence as to the expected outcome.

[Gallymimus]

I don't think you need to get that complicated to start with.  Just hook up a lab supply to USB cable with an ammeter. With the phone off, and not fully charged vary the input voltage between 5 and 5.5V and see what happens to the current draw.  It'll be pretty obvious, either it'll stay flat or will drop with input voltage.

The tricky part is getting your hands on a reasonable sample set of phones so you can offer customers some degree of confidence as to the expected outcome.

Well you are right that's a perfectly good starting point, though in the experiments we've done so far current consumption is pretty inconsistent in general.  Nexus 7 2013 for instance draws 0.9 amps for a bit, then 1.15A for a bit and switches back and forth, though I should be able to adjust the voltage and look for an increase in those quantal states.

Maybe we should launch a donate your phone thread!

[Harvs]

My observations testing this theory (note test just done with shorted data lines.)

2013 nexus 7 - 5.1V and above (at the cable, so probably 5V at the device.)  It seems to draw a constant current.  No significant change to charge current across 5.1 to 5.5V.  If the voltage is reduced to 5V or below, there is a sharp decline in charge current.  Possibly it uses this as safety mechanism.

Galaxy S3 - Appears to be a constant power draw.  Once charging at a stable "high" current, the current reduces proportional to increases in voltage.

So yeah, bit of a mixed bag.  Need more phones to test.

[scientist]

For the techies out there it also reports voltage and current so you can be certain your expensive device is getting the precise clean charging power it deserves.

Wouldn't want any of that dirty charging power going into your pretty gold iPhone, would you now? 

I kid, I kid... but the market for this kind of thing doesn't seem very large.

[Gallymimus]

My observations testing this theory (note test just done with shorted data lines.)

2013 nexus 7 - 5.1V and above (at the cable, so probably 5V at the device.)  It seems to draw a constant current.  No significant change to charge current across 5.1 to 5.5V.  If the voltage is reduced to 5V or below, there is a sharp decline in charge current.  Possibly it uses this as safety mechanism.

Galaxy S3 - Appears to be a constant power draw.  Once charging at a stable "high" current, the current reduces proportional to increases in voltage.

So yeah, bit of a mixed bag.  Need more phones to test.

Sorry for the late response, I didn't seem to get an auto-notify?!?!

Cool, thanks for checking that out.  That is interesting.  I guess we'll have to get a hold of a bunch of different popular devices to check out.

[Gallymimus]

For the techies out there it also reports voltage and current so you can be certain your expensive device is getting the precise clean charging power it deserves.

Wouldn't want any of that dirty charging power going into your pretty gold iPhone, would you now? 

I kid, I kid... but the market for this kind of thing doesn't seem very large.

hahaha, no really that is the point!  There are a lot of people who want the best simply because it's the best.  I agree it is going to be a small market but that's the intention.  We want to fill a need that isn't being serviced by Anker, Belkin, and the chinese no-names.  Plus, we don't want to have to reduce the quality of our design trying to play the price cutting game with those entities.

  We're not looking to get rich, we're not looking to compete with chinese chargers and honestly we're not interested in spending time shaving 1/4 cent off the cost of a capacitor so that we can improve our margin.  We are interested in high end toys with high end parts.  We're engineers right?  We want to use the best performing designs and techniques which are rarely the cheapest.  If we can do that, and provide some nice things to a small group of appreciative people and make enough to cover the cost of engineering, we'll be happy as clams

Maybe we should sell gold plate coatings for iphones now that you mention it

[Gallymimus]

I have a Qi charger at my home and use it for my tablet each night.  It's OK, but hardly awesome.  It definitely serves it's purpose and for slow lazy charge overnight I love it.

Which devices / wireless charger are you using?  I find it's a pain to align my tablet over the coil on the charger, maybe you don't have that problem with yours.  Do all of your devices support the wireless charging pad you are using?

Sounds like a sucky charger. I have a few, all better than yours. I have a Nexus 5 charger that is magnetic, so the phone aligns itself naturally. I have an LG charge pad that fits into a car holder so the phone is always in the right place. I have a Panasonic Qi pad that uses a motor to position the charge head under the device automatically. Finally I have a cheap no-name charging pad and for some reason don't have a problem aligning stuff over it.

Oh yeah, your's sound much better.  I got one of the early ones and it was on sale.  I got it just to try it and tear it down and learn about it. 

[Gallymimus]

USB charging is going to be around for a while, Especially since the new charger spec (USB Power Deliver Spec 1.0 http://www.usb.org/developers/powerdelivery/) will support 12 and 20V and up to 5A.  We will likely see monitors and notebook computers powered via the new USB specs.  Wireless won't be getting there for some time.

So what you are saying is your device will soon be obsolete? Only kidding, but rather than spending so much time trying to shave a few minutes off charging phones and tablets you should think about adding more useful features. Stick a Qi compatible wireless charging pad on the top, or maybe two. Design an ultra-low power standby mode so it can be kept plugged in all the time. Panasonic offer that feature on some of their battery chargers, and it seems to use the voltage of the battery itself to turn on before switching to mains power. You could do the same with 5V USB power available from many devices.

Harsh

We'll look at the Qi.  It would eliminate the possibility of having an aluminum case as you'd dump all the antenna energy into it.  It would have to be a different product.

Great idea on the super low power mode.  That's actually something we were looking at doing so it's good to hear it's a potentially desired features.  Since we are going to have a micro in this we can put a lot of stuff to sleep and periodically "look" to see if anything is attached, and then bring things back online.

You don't happen to have a sense of what power consumption levels are desired for chargers when idle do you?  I can look up the energy start specs but I've actually not checked that out yet.

[PointyOintment]

A very small solar panel of the kind used for calculators could easily suffice, with a moderate size super capacitor.

Just use the supercap, and when it gets low, start up the converter briefly to recharge it. Either way, it's probably going to save only a few cents worth of energy per year.

[Balaur]

Hey, potentially interesting device if implemented correctly. I would not mind buying one or two.

I may have a few question (I've quickly gone through the thread, but didn't managed to find the info):

• What kind of power input is needed? 12V, 19V, 12 to 24V? If 19V, then that's interesting since you can use a notebook charger (assuming the plug works), and the 12V could be nice for car usage.
• BTW, do you intend providing a primary PSU bundled in the package? It would nice to be able to buy the kit or just the charger.
• Any chance for an extra "direct" 5V output on a better connector for power distribution (I would like to suggest a PowerPole, but that could get me lynched on some forums), with adjustable current limit?
• Any plans for a travel version with maybe two outputs and a smaller primary PSU?

Thank you and best regards,
Dan

[nathancrum]

Patrick  can better answer the input power limits question than I, but I believe the multi-phase buck converter we're using is capable of accepting anything from 12V up to 40V input power.  Any notebook charger or vehicle power should certainly work.

We planned to include the PSU for all orders because we're largely dependent on a quality PSU for safety and it is the only way we could reliably get enough quantity to offer it at a reasonable price.  However - the way it is designed, the output power quality is largely independent from the PSU and we could potentially offer it without one if there's enough interest.  Most people however - prefer a turnkey product.

A "direct" 5V output is not a bad idea - although a USB adapter output cable would be even easier to implement.

A travel and/or battery powered version is definitely in our sights for a next step, but we're trying to tackle this one design at a time.

Thanks for the questions & feedback.

[Gallymimus]

It's the principal. Standby wastes a lot of power, and even if it is only a small amount we should make an effort to avoid it. Whatever solution Panasonic came up with seems to be very low cost and very effective.

It's funny,

I actually saw a small USB wall wart... I think from AT&T, that was super low power and quoted 0 standby current.  It actually had a relay inside that clicked on when the charger was operating.

[Balaur]

...

Hey Nathan. Thank you for your quick and informative reply. Appreciated!