Multi-port USB charger - Page 1
Forum section: electronics / projects

author: senso
author_rank: Frequent Contributor
timestamp: January 29, 2015, 02:11:35 pm
content: Good evening, I'm looking for some help/ideas about making a multi-port USB charger, instead of having a dozen "wall warts" my idea is to throw everything inside a nice case with about 10 usb outputs.Here is the actual idea that I have:Use a dedicated dc-dc regulator to power each USB port, with the capability to change current limit on the fly, and the add a shunt right at the ouput and add an INA199 or an INA3221(3 channel with voltage monitor), but I dont really know any dc-dc regulator that can be used for this effect. Using an lcd show the actual current consumption on each port, and probably warning when there is no current going into the device and maybe add an over-current alarm as well.My doubts are mainly about two topics, is there any nice/easy to use dc-dc regulator with external current control/current limit to allow modification, and how do I signal the devices(phones, tablets, either Android and Apple flavored ones).And how do I signal the device that it can sink more than the 500mA that they default to?I have found this IC's from TI, the TPS2514:http://www.ti.com/lit/ds/symlink/tps2514.pdfOr do I "only" need to connect D+ and D- with a 200ohm resistor and then pull them up to 0.6v(read that somewhere... ) to allow the high current charging?EDIT: The somewhere was from this Maxim doc:http://www.maximintegrated.com/en/app-notes/index.mvp/id/4803Best regards.

author: HKJ
author_rank: Super Contributor
timestamp: January 29, 2015, 02:33:30 pm
content: When you buy a multiport charger, they will often run the power in parallel to all port. This is, of course, not a very good idea if one of the outputs get shorted.For 1 to 1.5A you just connect D+ and D-, no need to apply any voltage.For 2A you must use Apple coding and hope the device supports it.Many usb power supplies has some ports with each connection, but you can also get chips that will change automatically.Here are all the coding I know:

author: ajb
author_rank: Super Contributor
timestamp: January 29, 2015, 03:50:25 pm
content: There are purpose-built ICs for exactly this purpose--have a look at "charging port controllers". There are some meant for standalone charge-only ports and others meant to add high power charging features to hub ports.

author: senso
author_rank: Frequent Contributor
timestamp: January 29, 2015, 09:13:44 pm
content: A bit strange, didn't found has much hits as I was expecting, the most glaring ones are the UCS1001 from Microchip/SMSC and the TPS2544 from TI, the later supports two current limit values, the former only accepts a fixed value, I would like to have a couple more steps, or maybe I'm over-engineering this, and two steps is more than enough.EDIT:Forget that there is a whole list of them from TI:http://www.ti.com/lsds/ti/power-management/switch-battery-charging-controller-products.pageBut still, I would prefer something a bit cheaper, but at least there is a bit of choice.

author: cc83
author_rank: Contributor
timestamp: January 30, 2015, 07:01:04 am
content: If you want to do this cheap I've used lm317's from ebay that were a few cents each in current limited configuration, they have built in short and overtemp protection. you can use switches to switch the outup resistors for voltage and current. Look at some of the lm78xx if you want to do this really on the cheap. Of course this won't help with your monitoring and control being built into the regulator, you would have to design a circuit for that.http://datasheet.octopart.com/L7805CV-STMicroelectronics-datasheet-5316848.pdf

author: senso
author_rank: Frequent Contributor
timestamp: January 30, 2015, 09:35:13 am
content: It doesn't have to be super cheap, but all the TI chips on Mouser are over 2€, for 10 ports, thats roughly 100€ in just on IC.I think I found the contender, the ST STCC5021 its just 1.15€ in singles and drops to a nice 90 cents at a quantity of just 10.For the current monitoring I'm about either the INA139 or a 50 cents Zetex sot-23, and just use a micro-controller with lots of ADC inputs and an externel V-Ref of 2.048v.

author: Monkeh
author_rank: Super Contributor
timestamp: January 30, 2015, 12:53:02 pm
content: The UCS1002 is $1.96 in 10 quantity, has programmable current limiting, and current monitoring.

author: senso
author_rank: Frequent Contributor
timestamp: January 30, 2015, 02:16:54 pm
content: Seems like a pretty good contender to the required job.Will worder a couple different chips, make some breakout boards and start testing them.