Efficiency measurement of step down switching converter

[powersys]

Sorry if I came off as arrogant. That wasn’t my intent.

Sorrie... you didn't sound arrogant at all to me... Pls don't feel offended... If you did, here's my apologies... you know, my english is away off... Honestly, I really appreciate every single idea you share with us here... Thanks.

I was the same as you my efficiency measurements were way off. For example some people in my class were getting 98% efficiency using my instructor’s procedure. This isn’t likely to happen particularly by a bunch of inexperienced students (Dixon, Middelbrock, Cuk maybe). So I did some more research reviewed my calculation. Noting the input current waveform and came to the conclusion that that is the problem. I want the average value of that wave form. So how do I get it? There is no instrument in the lab that will give it to me directly so I came up with the method above. Using that method brought my efficiency to within 3 to 5 % of calculated. Oddly enough that is the way my instructor trained us to take current measurements rather then use a current probe .Why he felt it wasn’t necessary to use in SMP’s I don’t know. This just makes sense when you calculate the efficiency you use the average value of the input current.

Very similar to my case... I will try your approach... really thanks.

 

[phongphanp]

max0412:

Regarding the standards the app-note above is written by application engineers from national so I think it’s safe to say they are outlining the standard procedure. If you do more digging you can find more on the subject.

Sure, More eliborate schemes must be investigated & take care . And hard to dig .