Efficiency of DCDC converters

[engr_joni_ee]

Hi, I am wondering how the efficiency of DCDC converters is defined. I have checked the specs of some commercial DCDC converters, they have efficiency between 80% to 90%. What does it means ? If this power efficiency then can we say that the output power is 80% or 90 % of the input power ? the remaining are thermal and switching losses ?

There are two main types of DCDC converters, the Buck converters and the Boost converters. The definition of efficiency is same for both type of DCDC converters ?

 

[KlausST]

Hi,

I´d say - like always: efficiency of converters is P_out/P_in.

the remaining are thermal and switching losses ?

--> switching losses are thermal losses.

The definition of efficiency is same for both type of DCDC converters ?

Why would one invent new definitions?

Klaus

 

[engr_joni_ee]

I understand. Thanks for reply.

Does it also means that the output power (Vout x Iout) is always less then the input power (Vin x Iin) ? And this is true for both Buck and Boost converter ?

 

[KlausST]

Does it also means that the output power (Vout x Iout) is always less then the input power (Vin x Iin) ?

It should be quite well known that any physical conversion causes losses. Electric, electronic, optic, acousitc, mechanic....

Where do you expect the extra energy come from? If you manage to get more out than you put in.. you solved every power problem and you will be come the most rich peroson ever. ..

...thinking about it.. a nuclear plant is one of the rare exceptions .. where it produces more ouput power than you put in.
This is because it transfers mass into energy .... according E= mc^2
But if you consider mass as energy .. then .. it is no exception anymore.

Klaus

 

[Easy peasy]

For DC -> DC converters:

efficiency = output / ( output + losses ) if there are no losses ( even in the wires carrying input and output currents ) then efficiency = 100%

this has not been observed to my knowledge, if the losses are negative, the efficiency can be > 100%, this has not been observed either - to my knowledge.

Virtually all losses in electronic devices manifest as heat - i^2R, core losses, dielectric losses, there is some radio frequency radiation too.

Most wires have resistance, so they will have some loss, this is generally true of all common conductors, there are also dielectric losses in capacitors carrying AC

and core losses in inductors with cores.

Generally the efficiency of any DC/DC converter is less than you hoped it would be at the desired operating points.

 

[dick_freebird]

"Wallplug" (Pout/Pin) is the most relevant to you. But the
best numbers may be had from BOMs you wouldn't make
(like a humongous super-Q input filter, you can claw back
several percent there is you want to go big on parts; we
did that on our eval boards even though space boards
would never want to buy that many high-$ space grade
tantalums and ceramics).

Read the fine print around test conditions if you're trying
to compete the options. They are often not the same, Brand
X to Brand Y. Especially if made for different target applications
/ markets; MIL power supply guys will want to see MIL methods
but commercial, anything goes (even more so if it's a startup
trying to make waves).