USB Charging controller - Page 1
Forum section: electronics / projects

author: JJalling
author_rank: Unknown
timestamp: April 25, 2016, 09:12:14 am
content: Hi,I'm planning to build a dual port USB charger to mount on the back of a shelve in our livingroom. I have a wall plug with a power output of 15W (5V, 3A) I plan to use.That means roughly 1.5A for each port if they are used simultaneously.Most of the time, only one of the outputs will be used, so ideally I want to be able to draw more than 1.5A pr port.I have been looking around at TI's charging controllers with dual outputs, but the only support setting the output current for each port. What I (think I) want, is to be able to set the maximum available current (3A) and the device should be able to share it between the device(s) connected.Has anyone seen a charging controller that supports this scenario?How would you do it? Just set the max current to 1.5A pr port?BR Jonas

author: Kilrah
author_rank: Unknown
timestamp: April 25, 2016, 09:45:18 am
content: An "USB charger" is just a power supply, the charge controller is in the device you plug to it.So if you've got a 5V regulated supply you have nothing to add to it besides maybe doing the proper connections to signal the devices you'll connect to it that they may draw more than 500mA.

author: JJalling
author_rank: Unknown
timestamp: April 25, 2016, 10:17:27 am
content: Quote from: Kilrah on April 25, 2016, 09:45:18 amWell not quite just a power supply - have a look at ie. TI's TPS2511. You have to apply the correct voltage or impedance on/at the D+/- pins to control the current according to BC1.2.BR Jonas

author: HKJ
author_rank: Super Contributor
timestamp: April 25, 2016, 11:10:11 am
content: Quote from: JJalling on April 25, 2016, 10:17:27 amBC1.2 only talk about shorting D+ and D-, other codings are from various manufacturers. For high end smartphone there is also QC that can increase the voltage. I have never seen any that tries to distribute power between the ports.A usb charger may be an interesting project to build, but it is considerable cheaper to buy one.

author: JJalling
author_rank: Unknown
timestamp: April 25, 2016, 11:26:18 am
content: Quote from: HKJ on April 25, 2016, 11:10:11 amI may be interesting to you, but I find it boring but necessary - unfortunately I can't find any commercially available chargers with mounting holes for mounting behind a drawer or on a shelf. Perhaps you can suggest one?Thanks in advance.bR Jonas

author: HKJ
author_rank: Super Contributor
timestamp: April 25, 2016, 11:32:39 am
content: Quote from: JJalling on April 25, 2016, 11:26:18 amMy interest is more in taking them apart than building them.I would suggest a box shaped one and then make a bracket or replace the box.http://lygte-info.dk/review/USBpower%20Anker%2040W%205-port%2071AN7105%20UK.html

author: JJalling
author_rank: Unknown
timestamp: April 25, 2016, 11:48:29 am
content: Quote from: HKJ on April 25, 2016, 11:32:39 amI know :-) I remember your site from the old dk.teknik.elektronik days - funny.I'll consider you suggestion instead. Thanks.BR Jonas

author: Delta
author_rank: Super Contributor
timestamp: April 25, 2016, 01:01:53 pm
content: Just wire them in parallel - any USB device worth its salt should monitor the voltage presented to it whilst charging, and as the supply voltage drops under load (ie two devices attempting to ramp up to 2.1A) it should knock-back it's current draw.