Should I use a BuckConverter or a Diode ?

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1

Hey falks,

I have a question:

Should I use a BuckConverter, or can I use 2 or 3 Diodes (IN4007) to drop the Voltage down ?

I fear, that the Diodes maybe burn out because the 3 ESPs will work 24/7.

Or is there no need at all of using one of these, because the power dissipation is not that high ?

Unbenannt
Unbenannt792×642 6.97 KB

2

If the voltage regulator is rated appropriately to supply the required current why would you need to use diodes or a buck converter ?

One answer would be in order to avoid wasting power by turning it into heat, so avoid that by replacing the voltage regulator with a buck converter with an appropriate current rating

3

Will this be in an enclosure?
If yes, what kind of ventilation will you have?
What is the maximum ambient temperature?
Was the PCB designed with the proper AMS1117 footprint and copper area for heatsinking?

4

Let's do a simple worst case example and see how much heat the 1117 can dissipate.
Max ambient temperature (inside your enclosure): 35° C
Max thermal resistance of 1117: 90°C/W
Max junction temperature: 125°C but lets keep it cool so use 100°C
Max power the IC can dissipate = (100-35)/90 = 0.72W
Your actual power dissipation = (6-3.3) x 0.2 =0.54W
So you should be OK in this particular case, provided there is some kind of air circulation around the IC and there are no other heat sources on the PCB

5

Because I fear, that the AMS1117-3.3 will get too much heat.

okay, in other words: by using a buckConv, there would be no wasting power, right ?

6

By using a buck converter there will be considerably less waste of power, not no waste of power

7

Thanks man :smiley: okay, maybe I should place a copper-field on the PCB which can absorb the the heat from the AMS1117 ? Like you see on the Photo...
Unbenann1

8

Okay Thanks man. Good to know.

9

Yes, that will help quite a bit.

There is information in the data sheet about the copper area.
If you make the area at least 10mm x 10mm and the board is at least 50mm x 50mm with some copper area on the bottom, then the thermal resistance will be around 80°C. The bigger the copper area the better and the bigger the PCB the better, to a limit.

10

I usally make a usage GND-Copper-Field in the back. Maybe I could make a "drill-hole" which connects to the back-Copper-field. The filed is 100x120mm big. And also one the top site (10x10mm) which I can use as soldering point for the AMS-1117. Like you see on the photo...

Unbenannt
Unbenannt636×672 6.26 KB

11

Be careful, the TAB is OUT, NOT ground.
If you make another copper area on the bottom use a couple of Vias like a 3 x 3 array

12

Depends on the package. While op never wrote what package will be used, the pictures shows SOT-223 and that tab is neutral.

13

Okay, I allways thought that this is Ground :smiley: Okay, I will use it as a HeatSink anyway. But I will not connect the TAB to the GND