Splitting 12v output

[pointjg]

Hi guys,

First time post here. I'm trying to fit some electronics into a case and wanted to get your guys thoughts on the following:

I have an external power adapter that is outputting 12V 3.33A. The device (LCD panel) it is powering has "normal power consumption" listed at 20W for typical operation. What I'd like to do is build a board that takes the power adapter's output, and allows me to utilize it for a 5V 2A device as well.

Could this be done? I've done soldering, basic circuit boards, etc, but never really anything like this.

The external power adapter has a DC plug on the end, so I'd like to utilize the same size jacks and make the "box in the middle" a plug-and-play unit.

Thanks in advance!

 

[Gryd3]

You can use the 12V supply to power a 5V regulator easily enough.
You may have problems pulling 2A on the 5V line though, as the LCD will be pulling 1.6A.

 

[pointjg]

Hi Gryd3, thank you for the quick reply. I just checked the manufacturer of the 5V device specifies that their device draws 1-1.5A in normal usage.

Could you recommend a regulator for this specific case? Would a MP2307 do the job (if so, would I just be placing a resistor to limit the MP2307 to 1A?)

Thanks again

 

[(*steve*)]

Your best option would be a switching regulator. For 2A at 5V it should draw under 1A from 12V

 

[KrisBlueNZ]

Just use a switching converter to convert the 12V down to 5V. As the voltage is reduced, the current is increased. Input power is equal to output power divided by efficiency, which is typically around 80%. So 1.5A at 5V = 7.5W, divide by efficiency gives 9.4W.

If your LCD panel, which is powered directly from 12V, draws 20W, add your 9.4W to get 30W and calculate the current by dividing that by the voltage. 30 / 12 = 2.5A load on your power adapter.

This method also avoids most of the heat dissipation due to wasted energy that you would get with a linear regulator.

Suitable buck switching regulators are available preassembled for a few bucks on eBay.

 

[pointjg]

Thanks everyone,

Did some searching around and some different things are coming up for the Buck Switching Regulators. Would something like the MP2307 UBEC work?

 

[KrisBlueNZ]

Yes, the MP2307 looks fine.

 

[pointjg]

Sounds great, thanks again guys!