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

[Demon]

EDIT: Figured I'd concentrate my power supply circuit here instead of my MSFS thread.

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Figures that I would hit a roadblock after wiring an ammeter to be able to see current and voltage in real-time. That DC-DC converter under the meters has too much noise on VDD and VSS for stable ADC readings.




I made a 7805 circuit for testing, but it's only rated for 1.5A.




I wish I had seen the LM1084 before; it can handle 5V up to 5A, more than enough for my design. At least it's a piece of cake wiring a through-hole LM1084 with some caps instead of the DC-DC converter.

[tumbleweed]

I wish I had seen the LM1084 before; it can handle 5V up to 5A

Just be aware that if you're starting with 12V VIN then the regulator is going to dissipate roughly 5W with 700mA out (from your other thread).
Pd = (12V-5V) x 0.7 = 4.9W

That's going to get quite hot... over 100degC rise depending on the package type.

[Ioannis]

Well, the SMPS you used are crap and although they say it is a LM25xx in fact they are just bad copies. Also the caps and inductors are crap too.

I would design my own SMPS and make sure to follow the manufacturer advices (either TI or Microchips). Having a goal of 20mV p-p is totally acceptable and doable.

Linear regulators will get too hot and while DC output, if well designed, may be clear enough, it is wasting too much power. You will need a big (and expensive) heat sink also, with ventilation holes on the final product.

Ioannis

[Demon]

I had 2 options originally:

- stay under 500mA and use USB power
- use a wall adapter and add a voltage regulator component.


USB power is no longer an option with the 4 LCDs. I don't have any "simple" design for a SMPS that would have noisy power.

The LM1084 "should" be as clean as the 7805 (I hope).

I can use the TO-220 package with cooling fins, and even add a tiny cooling fan. Tests will confirm how much heat I will generate with everything.

[Demon]

I bought a bunch of these a while back; aluminium heatsink with double-sided tape.

It fits just right on the back of a IRFZ44N (TO-220). I don't seem to have to bother with a screw/nut (unless you highly recommend a model with a fastener).




Aliexpress:

8.8 x 8.8 x 5, I tried removing the fin once attached, and it doesn't come off unless I usetools.

https://www.aliexpress.com/item/1005004079109702.html


My alternative was this screw/nut model with thermal paste for maximum efficiency:

https://www.aliexpress.com/item/32882672963.html

I'd just prefer in bare aluminium; I don't like paint on a cooling surface, seems counter productive to me.

[Ioannis]

Paint on heatsinks is not for cosmetic reasons. Black heatsinks radiate more IR energy than bare aluminum ones.

As for the power loss on the regulator (either 7805 or 1084 or 317, it does not matter which), it depends on the Vin and the current you will need on the load.

Example:
Vin 12 volts
Vout 5 volts
Max current 1A

The power loss on the regulator will be (12-5)*1A=7 Watts.

According to datasheet Power dissipation diagram, at about 35 degrees celsius ambient temp, you will need better than 10°C/W heatsink. So if you opt for 50°C ambient temp, then around 5°C/W maybe just enough.

How this 5°C/W translates to a physical heatsink part? something like this https://www.mouser.ca/ProductDetail/...jU4NS4xNi4wLjA.

Just tested a 7805 with 1A load and 12 volt input, roughly 7 watts of heat and the 7°C/W I used, is over 80°C with just 24°C ambient !!!

So, you will need a large and expensive piece of aluminum heat sink...

Better use a SMPS, I insist on this.

Ioannis