switching regulator efficiency

[sweethomela8]

I'm bringing a board up for the first time, and cannot get an exact amount of current needed on my voltage rail (+3.3V), so I decided to protect myself by getting a switching regulator that can provide up to 10 Amps @ 3.3V.

The data sheet says that the efficiency is about 85 percent if I'm using 2 Amps or more and if I'm using less than that, the efficiency drops to 50% at the lowest.

Will I run into any problems if I go below the 2 Amp consumption point where the efficiency drops to 50%? Or does that simply mean, the regulator dissipates wasted energy as heat?

Thanks.

 

[karesz]

Hi,
You have relative to calculate it pls.
Exactly:
what IMPORTANT is; whats your regulators MINIMUM LOAD(that is what you must consum for a safty working)!?
1,
Efficiency means, if you will consum only i.e. 3.3W(1A), & its legal as minimum load for your regulator, with 50% eff, it will dissipate the second 3.3W_you must checking for poperly cooling....
2,
If you will consume 33W (10A), by 85% eff. =ca.5.8W is as dissipation for properly cooling...
All electronics does dissipate waste energy as heat, question is only: how much, that as in your situation too; can be variing in dependance of used energy range-must not be linear predictable...
K

 

[sweethomela8]

So lets say, I'm using this switching regulator here

http://cds.linear.com/docs/Datasheet/4602hvf.pdf

provides 6A continuously. If my load current ends up being about 0.5A, are you saying the design wouldn't work and I wouldn't measure 3.3 Volts as an output of the regulator?

What are the tradeoffs of getting a switching regulator that can provide plenty of load current? Wouldn't it always be a good idea to get a regulator you know will provide enough current than one that may not provide enough?

 

[karesz]

Hi,
No, I didnt told it, not so (I told; that you must check for minimum needed load & cooling capacity from your switcher!)...
Pls check page4, "Light Load Effi ciency vs Load Current with 12VIN"...
Lot of spec`s are specialIC/type dependend, in these case seems, at 12V in) that from 0.1 A it will have ca. 70 % efficiency, with your load of 0.5A/3V3=1.65W it will dissipate ca.2.37W.
You must check a layout/cooling to soluting these heat capacity with the specially used packaging_as every time!
K.