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

[amgen]

2 cents....... the LCD and LED's stuff aren't that badly affected by slight power supply fluctuations ... slight. The PIC's and IC's need good stable power 7805 or similar on their own circuit.

[Ioannis]

Are you sure you need 5Amps at 5 volts? That is 25 Watts of power.

And about 35 Watts of power loss on the Linear regulator. This means that you will need a monster heatsink like intel CPU with a fast spinning fan. Not anything close of what you posted.

Better use seperate linear regulator as amgen said for the PIC and a switcher for the power hungry LED and Displays.

Or check these:

Vin 4.5-24, Iout 3A: https://www.ti.com/product/TPS56339

Vin 4.5-17, Iout 5A: https://www.ti.com/product/TPS565208

Following the design examples you may have less or equal to 20mV noise. For me good enough even for PIC using ADC.

Ioannis

[Demon]

2 cents....... the LCD and LED's stuff aren't that badly affected by slight power supply fluctuations ... slight. The PIC's and IC's need good stable power 7805 or similar on their own circuit.

Yup, I'm thinking of running a dual system.

Are you sure you need 5Amps at 5 volts? That is 25 Watts of power. ...

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.


I'll probably need 2A, but I hate running stuff at peak power, hence why I said 5A.

A component running near max is generating more heat than another running at 50% power; that's not good for long life.

[Demon]

I did encounter a problem with the LM1084-5. Voltage drops when I add load.

I expected a specialized IC like the LM1084 to remain at a stable 5V throughout its workable current range.

I used the bottom of figure 7.2.8 with 2 electrolytic capacitors:

[Ioannis]

That 50 ohm resitor will worsen the regulating output. It forces the upper IC to have higher than 5V output but regulation depends now on the resistor.

Have you had a look at TPS565208? It is a chip with low noise and ripple, easy to use SOT-563 package, very small footprint and cheap. I would not mess with any Linear, heatsinks, wall adapters etc.

Only downside (maybe) is that it accepts only up to 17 volts DC. But if your source is upt to 12volts your are more than good to go.

Ioannis

[Demon]

I only used the bottom regulator on that schematic.

I have 9v 2a wall adapter coming in today, and a 7v 2a coming in tomorrow.

That should reduce wasted heat a lot.

[amgen]

I know you already ordered some things, I have used few of these things..... no other regulator needed. The output voltage is pretty stable.

[Ioannis]

Camparing the various chinese power supplies I ended up with Sunny brand, that is represented in Europe by a reputable firm. https://en.sunny-group.com

Opening one of them reveals that the design is in pretty good level.

Please be very carefull with all these cheap SMPS that are sold at low prices. They can have really catastrophic failures (I was almost hurt by this), with very bad "protection" circuits that fail after the big-bang...!

The idea of having a 5V wall adapter may seem good but there is a risk that the user may by mistake connect a 12V adapter at the 5V entry...

Ioannis

[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

[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

[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.