Transformers vs Converters: Weight

Thread Starter

pdavis68

Joined Nov 27, 2013
31
I'm curious why, if I want to buy say a 24V, 75VAC transformer (so a little over 3A at 24V), I'm looking at a pretty chunky piece of iron.
On the other hand, I can find a ~24V laptop power supply that can handle 3+A and it doesn't need nearly as much iron to make that happen. I get that the laptop is doing a converter of some kind, but I assume there's a transformer somewhere in there moving 3A of juice. How can it be so much smaller and lighter?
 

OBW0549

Joined Mar 2, 2015
3,503
Converters operate at much higher frequencies (from tens of kHz up to a MHz or more) than the mains voltage, which allows them to use much smaller transformers.
 

crutschow

Joined Mar 14, 2008
25,247
The amount of magnetic material in a transformer or generator for a given power rating is more or less inversely proportional to its frequency of operation, so a 50-60Hz mains transformer is much larger than a switching power supply operating at a much higher frequency.
That's also the reason aircraft power usually is 400Hz, since it significantly reduces the size of the generators and transformers.
 

Thread Starter

pdavis68

Joined Nov 27, 2013
31
The amount of magnetic material in a transformer or generator for a given power rating is more or less inversely proportional to its frequency of operation, so a 50-60Hz mains transformer is much larger than a switching power supply operating at a much higher frequency.
That's also the reason aircraft power usually is 400Hz, since it significantly reduces the size of the generators and transformers.
I was not aware of that, but I can kind of get a sense for why that might be. I need to go back and read up on transformers. Thanks for the info.
 

MaxHeadRoom

Joined Jul 18, 2013
21,191
What is the purpose of the supply?
Generally the linear supply is a little more sturdy and is more resistant to abuse.
Especially where a regulated supply is not necessary
Max.
 
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