Voltage regulation circuit 12V to 5V in 5A range

[Demon]

I just noticed the LM1084-ADJ is claimed to "provide 5 A at high efficiencies and very low drop-out." I just ordered a few from Digikey.

Ioannis, will the TPS565208 or TPS56339 voltage drop when I add load?

Current consumption so far:
- 800mA, ICs and 4 LCDs
- 510mA LED strip 1
- 510mA LED strip 2
- 510mA LED strip 3

I'm at 2.330A and I have a few other ICs to add, hence why I target a power supply that can manage 5A.

The thing with the LED strips is that they can be dimmed from 0 to 100%, that's a respectable load change.

(I'll be limiting the LED strips to 350mA or so, but still, I want to be safe if they get stuck "full ON").

[Demon]

Piece of crap 7V wall adapter worked 10 minutes...

https://www.amazon.ca/dp/B091YHX8RY

[Ioannis]

Piece of crap 7V wall adapter worked 10 minutes...

https://www.amazon.ca/dp/B091YHX8RY

Noname chinese rubbish... They don't even have the proper distances or creapage on the PCB...

Prefer good brands like Mean Well or Sunny.

Ioannis

[tumbleweed]

That's what I said in the second part about getting more than 2A out.

You can't get 5A out if the adapter can only supply 2A

[Demon]

That's what I said in the second part about getting more than 2A out.

You can't get 5A out if the adapter can only supply 2A

The 2A wall adapter was a quick fix to be able to continue testing.

The 9V 2A is holding up for now.

[Demon]

Received the LM1084-ADJ, still waiting on the recommended caps (to properly test ripples), but it's already running nicely with what I have on hand.

Also got a thermal imager to help identify hotspots. Looks like I fried 2 PICs with those 12V and 7V bursts (lesson learned).

LM1084-5V on right, supplies PICs, ICs and LCDs, essentially everything that is "always ON", with a slight tweak on ADJ pin to get it slightly above 5V to compensate for voltage drop.

LM1084-ADJ on left, supplies LED strips, cooling fans (to be determined) and anything else that doesn't care about ripples.

(HIKmicro E02)



No thermal compound yet, this was a temporary setup to help prevent forest fires.



I'm sure there's better ways to skin a cat, but this was the simplest technique I could come up with. It remains to be seen if the ripples are "manageable" for the ADC on the PIC circuit.

[Demon]

Wasted so much time trying to figure out why I STILL had a lot of ripples with the LM1084.

I checked directly on the wall adapter:



GIGO; can't expect the LM1084 to do miracles with that.


So I pulled out a 12V-5A Fqcmogu AL-1250 adapter (no idea what it's for):



Definite improvement.


This is the LM1084-5V running at 5.0V (LED strips and whatnot):




This is the LM1084-ADJ running at 5.2V (PIC, LCDs and other ICs), note that is had less ripples as stated in the specs:

[amgen]

Yes, all of these SMPS do have that high frequency transformer and do isolate the secondary. Few have poor isolation.

....
....
wow, looks like you were trying to take 100 amps from that little power supply..... (just kidding)
.
adding..... should probably never try to use a power supply at it's full rating, maybe 1/2 of rating is safer.







9

[richard]

chinese amps are quite a bit smaller than normal ones. 0.75 seems close

[Aussie Barry]

chinese amps are quite a bit smaller than normal ones. 0.75 seems close

ROFL...
Good one, Richard!

[tumbleweed]

I just noticed the LM1084-ADJ is claimed to "provide 5 A at high efficiencies and very low drop-out." I just ordered a few from Digikey.

The only difference between the LM1084-ADJ and the fixed output LM1084-5 is the latter already has the resistors to set the output voltage built inside it. You will only get 5A out of it if you have the input > the Vdo drop out voltage spec, and stay within the max power dissipation. With no heatsink you're not going to get anywhere near 5A out, not with 12V in.

You said the output voltage of the LM1084-5 dropped when you added a load. That shouldn't happen as long as you're within the datasheet specs.

If you're trying to get 2.5A out, with your 12V adapter that gives a Pd = (12v-5v) x 2.5 = 17.5W !!

Yeah, I'm waiting for a 9V 2A wall adapter to help reduce the waste heat. I'm getting 7V 2A wall adapter tomorrow to reduce that even more.

You'll need an adapter with more than 2A out if you want 2.5 or 5A out of the linear regulator.

[Ioannis]

Not so tumbelweed.

With Linear regulators, your Input current is the same with the output current! Beware of that! Plus the current of the regulator of course, though this is small enough.

The opposite happens with SMPS. In that case wattage is the same plus the losses in the regulator itself.

The voltage drop with increased load is called Load Regulation and is there in the specs. And of course it is different for every regulator, either linear or SMPS. Besides that spec, which is typically small enough (less that 1% for the TPS565208), the voltage will drop for many other reasons, like design of PCB, part selection, thickness of wires and the point where output voltage sample is taken for the regulator to compensate for. the drop.

More output current, more copper on PCB and thicker wires are needed. After all, the regulator will have the nominal voltage on the output but if your wire is 10 meters long, you will have voltage drop on the cable, right?

I think TPS565208 is one of the easiest to handle and very good in terms of cost, pcb estate, output noise and efficiency.

Ioannis