16A 8x USB Mobile device charger idea advice appreciated!

[JelleN]

Hi,

Trying my hand as a 'Maker' in conjunction with some EE students here in Tacloban, Philippines. We have designed a circuit using a Murata OKX-T/16-D12N-C (DC-DC regulator).

Our goal was to design a multiple USB device charger to run off a solar system. The solar side is straightforward but would love some opinions as to the circuit design.

We designed a circuit with the OKX-T/16-D12N-C to be connected to a 12v lead-acid battery bank, using a 1000uf 16v cap on the Vin side and two caps (1 uf and 10uf) on the Vload side before 8 USB connections all on a PCB (1x with resistors between D- & D+ for charging Apple devices and 7x with resistors for Samsung and other devices).

Questions we'd love feedback on:
1. I assume we connect the Sense pin to the V+ after the last cap?
2. Would the caps we've specified be suitable or are they not necessary at all?
3. Any suggestions or tips on how we might improve the circuit?

For info:

USB circuits:


OKX:
**broken link removed**

Thanks for any feedback or advice!

 

[betwixt]

Its not clear what you intend to do with this.

Firstly, a 16A supply to a USB socket is asking for problems, including possibly fire risk from overloaded copnnectors and cables. The USB circuits are, I think, the internal connection in the Samsung and Apple devices although they may be different from one model to another. USB allows for the DC voltage from the potential dividers to be used to program the charging voltage and current limits in the power source but you can't connect more than one at a time in parallel.

The 16A supply is OK although probably not needed if you have 12V available already but I suspect what you need is 8 individual USB charge controllers so each can feed one load regardless of what device is plugged in to it.

Brian.

 

[JelleN]

Its not clear what you intend to do with this.

Firstly, a 16A supply to a USB socket is asking for problems, including possibly fire risk from overloaded copnnectors and cables. The USB circuits are, I think, the internal connection in the Samsung and Apple devices although they may be different from one model to another. USB allows for the DC voltage from the potential dividers to be used to program the charging voltage and current limits in the power source but you can't connect more than one at a time in parallel.

The 16A supply is OK although probably not needed if you have 12V available already but I suspect what you need is 8 individual USB charge controllers so each can feed one load regardless of what device is plugged in to it.

Brian.

Hi, thanks for your response. To clarify:

We already build a briefcase style solar pack which includes a battery and solar panel and a single cigarette lighter style usb adapter. We hoped to incorporate a circuit that expanded the charging capability to 8 modern usb devices that often require up to 2.1A each.

Our research and observations indicates that the resistors are incorporated into the charge side rather than the devices themselves and as you say, enable faster charging. Our design includes 8 such usb circuits, allowing one device per resistor circuit. We would then connect these in parallel to the output of the regulator.

Our goal is to increase conversion efficiency and decrease costs associated with installing 8 seperate usb charge controllers into our 'Solar briefcase'. Aside from which, adequate supply and stock of reliable components is limited here and we have to order everything from the Capital...

Our inspiration was this project: https://eleccelerator.com/wp-content/uploads/2014/03/SimpleUsbCurrentMonitor.png

Appreciate your input!