High Power USB Charger current limiting ( +40 Watts ) - Page 1
Forum section: electronics / beginners

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 04:34:35 am
content: Hello, i'm working on a high current USB charger powered by a 12 volt 100 watt solar panel. I have a basic under standing of electronics and have ordered a lot of the parts for the project except for the Voltage regulator. I am not sure how to the limit current to provide as much current as the devices need, and be able to handle up to 2.5 amps per port. ( 30 mAh led light, or my Ipad at 2.1 Amps) I'm trying to make a device that will have 4 USB ports at 2 - 2.5 amps per port and be able to limit current to what the device requires. I have a basic circuit drawn out and a plan, but need help making a safe and effective device.So far i have ordered a few parts, but not the main components.All of the items are from Digi-KeyDiode: VFT4045BP-M3/4W voltage lost 0.670V 40A max TO-220-22x 2 port usb + ethernet jack with leds: 507-1450-ND200 ? variable Resistor for correct led color: 67YR200LF33,000 UF 16v nichicon cap: UFW1C333MRD4x 100k? variable resistor for correct data voltages: 67WR100KLF25 AMP 125 volt toggle switch: 360-2087-NDI was looking at a LDO voltage regulator that can out put 7.5 amps at +5 volts. I have a large selection of heat sinks to attach the regulator and diode to.5 volt regulator: MIC29750-5.0WWT voltage lost 0.425V 7.5A max TO-247-3Please tell me what else I need to have for the project and if I should use some other way to get 5 volts out instead of a regulator.Thanks for any help you can provide.

author: mij59
author_rank: Frequent Contributor
timestamp: July 14, 2014, 05:14:31 am
content: Hi,You'll need to design the circuit before you order the parts.Powered by a solar panel, so there's no battery ?You've chosen is a linear regulator, a lot of power will be wasted.Best way is to use four separate step-down converters with a 5V output with a current limit set a 2.5A

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 05:38:03 am
content: The circuit will be on a bread board.The solar panel comes with a charger for a 12-24 volt sealed lead acid batteries.basically everything I have is powered by USB, and I have a 20,000 mAh usb battery pack to use. ( if there is a power outage the only thing I will miss is my desktop computer)The step down converters seems like a good idea, will they be smart enough to not over or under current a USB device?Here is my unfinished circuit idea.

author: mij59
author_rank: Frequent Contributor
timestamp: July 14, 2014, 06:13:18 am
content: Quote from: Dr_Taco_Cat on July 14, 2014, 05:38:03 amStep down converter is only a power supply, there's nothing smart about it.I don't know what smart in this context means, the usb powered device has to provide the max current setting to the step down converter somehow.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 06:43:40 am
content: I think i'm going to stick with a voltage regulator. The odds that the solar panel preforms at 12 volts is very unlikely its more around 10-7 volts and the diode + regulator only uses about 1.1 volts in theory. I just need some way to regulate the output current. Any thoughts on a way to easily regulate the output current?

author: jc101
author_rank: Frequent Contributor
timestamp: July 14, 2014, 09:57:09 am
content: You may well run into the problem of getting the device to charge in the first place, the "Battery Charging Specification v1.2" may help you. It isn't just a case of using the +5v and GND rails, you have to also manage the two data lines to signal what type of charger you are. This, naturally, is handled differently depending on the device.There are some neat IC's to handle the device handshaking side of things, and will limit current too if needed, have a look at the UCS1001. You can then generate a stable 5v supply line and have the IC do the negotiation with the device(s) to be charged.

author: mij59
author_rank: Frequent Contributor
timestamp: July 14, 2014, 10:03:48 am
content: Quote from: Dr_Taco_Cat on July 14, 2014, 06:43:40 amThere's an other thread about usb power on the forum, you may want to check it.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 05:38:22 pm
content: Quote from: jc101 on July 14, 2014, 09:57:09 amI looked that chip up, and its perfect. The only thing is I have no idea how to make the correct circuit for it. Looking at the data sheet, it will need quite a few other parts. Would you happen to know how much it would cost to make 4 of the circuits shown on the data sheet? ( about $10 each?)

author: jc101
author_rank: Frequent Contributor
timestamp: July 14, 2014, 06:10:48 pm
content: Quote from: Dr_Taco_Cat on July 14, 2014, 05:38:22 pmTo use the UCS1001 you only need to provide it a 5v supply of sufficient capacity, to run the IC itself it's really just a few passives to set the various limits. Looking at a draft BOM I have it looks like to get 4 ports, including passives and USB connectors, would be under £10 ($17).You can get a dev board from Microchip if you wanted to play around with one (ADM00540 Evaluation Board) for under £20 ($35).One catch is if you set the current limit above 1.5a it will limit using 'trip mode', 1.5a or below it will just limit the current to the device regardless of what it can take. If you just leave it at 2.5a then that will let any device draw as much as it wants to up to the 2.5a limit. Just make sure your supply is beefy enough to supply enough current.The IC is handy, as so far I have not managed to plug anything into it which won't charge at the same rate as it's own supplied charger.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 07:23:44 pm
content: Quote from: jc101 on July 14, 2014, 06:10:48 pmIll get 4 of the chips and make 4 circuits ( 2 ports will each have their own board (2.5 amps each port) , and the last 2 USB's will share 1 board, so using 3 in total and an extra for something else.) Any idea on the parts required to build the circuits? ( the pre-made boards are expensive, and it would a nice learning experience to make the circuits.)

author: jc101
author_rank: Frequent Contributor
timestamp: July 14, 2014, 07:33:55 pm
content: I've sent you a PM...

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: July 14, 2014, 09:23:36 pm
content: Quote from: jc101 on July 14, 2014, 07:33:55 pmI sent you an email with the parts i'm looking at buying.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: August 17, 2014, 09:05:42 am
content: Hello, I have made some progress on the circuit and put it on a solder-less bread board and it does not work correctly. The main issue is that the led's do not turn on when they should. I have included my schematic's of the circuit so far, please let me know if there are any errors on it.I think ditching the 5 volt regulator would be a good idea, if I under stand correctly if I give the regulator 6 Amp's straight from a solar panel it will fry the ic and the USB device attached.(correct me if i'm wrong)If needed I think I will try to find a 200 to 100 watt 5 volt regulated power supply, that has a DC only input. ( Are there any high Amp 5 volt power supply's intended to hook up to a 12 or 24 volt SLA car battery?)

author: jc101
author_rank: Frequent Contributor
timestamp: August 17, 2014, 05:16:59 pm
content: Do devices actually charge?The UCS1001-1 and UCS1001-2 have different meanings for the output pins, so if you want your LED to come on when a device is charging then you need the UCS1001-1, for an 'attach detection' event you need the -2 variant.If you directly short the +5v and Gnd on the USB port, you should get the alert LED come on.

author: idpromnut
author_rank: Unknown
timestamp: August 17, 2014, 09:35:47 pm
content: Also, @ 24V you will be throwing away about 80% of the energy from the PV cells. You would be much better off with a buck design instead of that 5V regulator.

author: wraper
author_rank: Unknown
timestamp: August 17, 2014, 10:23:35 pm
content: Quote from: idpromnut on August 17, 2014, 09:35:47 pmOr just buy off the shelf step down DC/DC converter module.

author: wyphy
author_rank: Contributor
timestamp: August 17, 2014, 11:54:43 pm
content: Have you actually measured the solar cell output in actual open circuit and load conditions in your real-world usage setup?The voltage and current out of the panel will vary a lot depending on whether it has a load, how much light it receives, the angle of the panel to the sun, and the temperature of the cells.If you got an inexpensive system from a place like Harbor Freight, consider that they may have used the absolute best case spec and used some fuzzy math to rate the system; par for the course when marketing gets involved.What you will actually get out of the system may be considerably less than you think. (Seriously, think 50%-80% less than the box says)It appears that your pots are not connected correctly to the LEDs, unless you are just using them for their nominal value, in which case you'd be better off with standard resistors; much cheaper too.Even if you are wiring them correctly and just drew them wrong in your schematic, it'd still be cheaper to use standard resistors, unless you have some special reason you need to vary the brightness of the LEDs. Don't know what that would be, perhaps you could fill us in?You'll also need a resistor for the LED with the fans.You must be using a seriously massive heat sink with big fans to dissipate that 140+W of power the 5V regulator will be generating at full load. A switching regulator would be much more efficient and generate almost no heat. Don't know how much power the 12V regulator is dissipating, but easy for you to calculate as you should have the specs on the fans.A better way to go would be to use a 12V switching regulator to run the fans, and as a pre-reg for the 5V reg. You'll be dissipating about 50W that way, but that's still a lot of wasted power.Might want to watch Dave's video on thermal design and figure out how hot that junction will be and if it's within the spec of the regulator. I'd bet not, at least in the current setup, but you haven't given enough detail to even get close to a WAG.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: August 18, 2014, 03:45:27 am
content: Quote from: jc101 on August 17, 2014, 05:16:59 pmThe circuit will charge devices and other USB things. I have accidentally shorted the USB ( I purposely shorted it this moment, it sparked and shut off) and the led still does not come on, but the whole circuit will shut down until I disconnect then reconnect the power supply. I have tried giving it low voltage and over voltage, but the led still does not come on. (2.2 volts in and powering the device at 2.2 volts, but the led remain off, the same for over voltage ) It still does not work with a pull up resistor on the current limiting pin (ILIM) or directly to VDD. The schematic says that it requires a pull up resistor, but I guess i'm not sure what that would be if its not the current limiting one. Both of the led's do not light up when they should, any ideas on what to do?

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: August 18, 2014, 05:07:19 am
content: The regulator and diode will have there own heat sink, the regulator is on a x812722-001 rev B Xbox 360 heat sink, and the diode on a smaller heat sink. The regulator's part number is MIC29750-5.0WWT and it will never come close to the maximum 7.5 Amps its rated for, only about 5 Amps and 14 volts at the absolute maximum. The diode's part number was VFT4045BP-M3/4W, but I managed to blow it up by accident, and have moved to another brand APT60S20BG-ND. ( They are total over kill, but that's besides the point. Me and my father are still puzzled on how it blew up connected to the 12 volt rail of a 85 watt computer power supply that can only deliver 2 Amps before it automatically shuts off, at least it did not fry the $20 regulator )I still have not bought the solar panel, here is the link to the one I am looking at:http://www.ebay.com/itm/Solar-Panel-100W-Watts-Solar-Panel-Off-Grid-12V-RV-Boat-Home-Solar-System-/281279985045?pt=LH_DefaultDomain_0&hash=item417d97f595I estimated that a sunny day would give out about ~ 10 volts and ~ 5 amps ( I expected it to be about +/- 50% efficiency from the start )I wired the pots correctly, but they are shown incorrectly on my drawing. I am using a RJ-45 port with 2 USB connectors and the integrated led's with a UCS1001-2 circuit on each USB port. ( part number: 507-1450-ND ) I have a green 12 volt led along with a board that accepts up to 4 fans and a speed controller that I used then modding my Xbox 360 and reclaimed it once it could not be repaired any more. (Red ring of death about 5 times before it could not be fix by a reflow )I have all the parts in the schismatic shown and lots more, as well lots of extras. (I planned on making 5 of the charge controller circuits and bought enough for 10 of them, i'm down to 7 IC's now. I bought 2 of the 5 volt regulators and only 1 diode, as well as some 5 volt step up converters.)

author: idpromnut
author_rank: Unknown
timestamp: August 19, 2014, 07:56:29 pm
content: I did a quick test of the computer PSU to power supply conversion that I did a couple of years ago, and obviously this isn't the same supply, but I was easily able to load the supply up to the rated current (10A+ on the 12V rail). By contrast, I noticed that the supply voltage drooped below the stated 12V very quickly, at about 1-2A it was already at 10V rather than 12V. So I'm not sure if mine is just a super crap supply (highly likely as it was a dumpster dive) but I guess these supplies aren't all that fantastic.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: August 19, 2014, 08:37:16 pm
content: Quote from: idpromnut on August 19, 2014, 07:56:29 pmThe computer power supply will shut its self off when over 2.5 Amps are used on the 12 volt rail. The current computer PSU i'm using is only 85 watts, and its pretty crappy, but it was free. It is definitely not in spec as it hovers at 10.8 volts on the 12 volt rail, its almost 20 years old but it still works. (none of the caps are bad or any cracked traces) I have some other ones around, but they are not cheap junk that i'm willing to destroy. I have a CORSAIR CX600 from my old computer laying around, but that's still $70 at risk.About the buck converter, is there a good direction you can point me in? (something that can go down to ~7 volts DC and up to ~ 25 volts DC and handle about 10 Amps?

author: jc101
author_rank: Frequent Contributor
timestamp: August 19, 2014, 09:29:18 pm
content: Regarding the LED's, just noticed you have the LED's backwards. The ADET and ALARM pins are open drain, active low. They do not produce any voltage but connect to ground when active.You need to go +5V - Resistor - LED - Alert pin, then they should work as you expect.Note, it looks like it can sink up to 8ma on each pin from the data sheet.

author: Dr_Taco_Cat
author_rank: Contributor
timestamp: August 19, 2014, 11:07:27 pm
content: Quote from: jc101 on August 19, 2014, 09:29:18 pmThe led's work now, but the circuit is spazzing out and flashing or just plane not working. The output voltage has giant spikes with the led's flashing. I removed the 180 UF electrolytic capacitor and it works. I removed the cap and put it in back words( the wrong direction), and the led's still flash and voltage spikes. I remove the cap and it works fine. I threw out the first cap and put a new one in only to see that both the alert and detected led light up and stay on. The circuit works without the cap, but the voltage spikes from 5.00 to 5.15, when the cap does work it is from 5.05 to 5.08 volts. Any ideas on why the capacitors are doing that?

author: idpromnut
author_rank: Unknown
timestamp: December 28, 2014, 03:06:23 pm
content: Watch out for reversing the polarity of electrolytic caps... bad things can happen if you do that (explode, leak, fizz, silently fry, etc).

author: LukeW
author_rank: Frequent Contributor
timestamp: December 28, 2014, 03:44:54 pm
content: To charge devices like an iPad you will need some sort of negotiation device to "identify" the USB power-supplying charger with a current supply capability of 2.1A.I was going to suggest using the TPS2543 from TI, but somebody has suggested the UCS1001 above - I haven't seen this one before, but it looks like a similar chip and it's cheaper.Of course, you are going to have to learn to solder the little QFN chip onto a PCB - this could pose a beginner's challenge.As far as the regulation is concerned, to produce a >2.1A output at 5V from an input voltage up to 24V you absolutely do want a buck regulator - a linear regulator will be wasting a huge amount of energy, generating lots of heat.You can get absurdly cheap basic reference boards using LM2596s from China these days, try one of those as a regulator or a pre-regulator if you don't want to build one yourself. Even if there is a 50% chance they sell you a piece of dirt painted to look like an LM2596 it still seems like good value.http://imall.iteadstudio.com/im130731002.html

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 28, 2014, 03:53:30 pm
content: QuoteAnd for USB 3.1....QuoteYou seem to be designing something that uses USB connectors at higher currents than they were designed for. Beware of the safety/heat/fire implications.