USB charge current limiter

[ben_jackson]

Hello, this is my first post here, and I am hoping somebody can help.
I'm looking to make a USB charging station using a old ATX power supply, that can charge up to 20 Phones/hand held devices from it, but i am not quite sure how to limit the current (and if i really need to)
The PSU outputs about 35Amps at 5v, do I need any safety electronics for charging USB devices from this, and if so what would be the cheapest/simplest way to limit the current?

Kind regards
Ben

 

[tpetar]

Hello, this is my first post here, and I am hoping somebody can help.
I'm looking to make a USB charging station using a old ATX power supply, that can charge up to 20 Phones/hand held devices from it, but i am not quite sure how to limit the current (and if i really need to)
The PSU outputs about 35Amps at 5v, do I need any safety electronics for charging USB devices from this, and if so what would be the cheapest/simplest way to limit the current?

Kind regards
Ben

Hello Ben and Welcome to EDABoard forum,

ATX PSU can be used only as power source not as charger!!!.

You need additional circuit for charger, which will control voltage and current for charging.


Best regards,
Peter

 

[ftsolutions]

To do it "officially", you would use an USB power switch with oercurrent protection IC like an LM3525M (single port) or LM3526 (dual port), with the /EN and FLAG pins connected to a microcontroller so you can control the power on/off to the port and also be flagged when it goes into an overcurrent situation. Check the datasheets - you should use at least a 120uF 35V electrolytic and a small ceramic bypass cap on the output of the device (going to the USB port connector). You will need a sizable electrolytic on the +5V input side of the chip as well. As additional protection, you could put a series PTC thermistor of very small value (0.1 Ohm approx) on the 5V USB power net to the connector.

 

[kam1787]

I presume you are charging the device [and not the battery],

https://www.extremetech.com/computi...ks-or-how-to-avoid-blowing-up-your-smartphone

 

[tpetar]

After my repeated reading of thread question, I realize that You want to charge phones, and other devices, and NOT standalone batteries. Devices such as phones, MP3 players and all other USB devices with batteries have charger inside device.

My answer for this, yes You can use 5V rail from ATX power supply for charging process of devices. No need for any modification or any additional parts for this. I often use PC power supply for project testing and other things.



Best regards,
Peter