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Inductor current rating and temperature
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jbb:
Note inductors often have 2 current ratings: the saturation current (above which available inductance drops off rapidly) and thermal current. Saturation currents are often higher and thus may be used for marketing...
Jay_Diddy_B:

--- Quote from: jbb on April 05, 2019, 01:18:26 am ---Note inductors often have 2 current ratings: the saturation current (above which available inductance drops off rapidly) and thermal current. Saturation currents are often higher and thus may be used for marketing...

--- End quote ---

I agree.

In the case of the Pulse datasheet, it is defined in note 3:



Jay_Diddy_B
Siwastaja:
The datasheet only lists ratings based on DC copper loss, which is only relevant when passing a DC current through the inductor.

In a switching converter, there is an additional AC loss, caused by copper AC loss (skin effect) plus core loss. Sometimes the AC loss is negligible; sometimes it's dominant! It's highly dependent on the material properties of the inductor core. Some core materials are completely unsuitable for switch mode converters. Some are so freaking good that you can ignore the AC loss completely and simply work with the datasheet DC current rating.

But, with no data about the AC loss in the datasheet, your only way is to measure, which is basically what you have done (based on temperature measurement), and found the inductor unsuitable.

Nowadays, many inductor manufacturers do provide AC loss analysis software (often web based), based on their measurements and modeling. If available, use such software to find the total loss.
smbaker:

--- Quote from: smbaker on April 05, 2019, 12:59:53 am ---I received my LM2596 150KHz switching regulators today! Pictures of the regulator and the switching waveform are attached!

I saved so much money buying these on eBay rather than digikey.

--- End quote ---

I'm surprised nobody commented on (what I believe to be) fake LM2596. Maybe it flew under the radar. ;) I've received fake vintage ICs before, most notably the SP0256A-AL2, but this is the first time I've received a fake on something as mundane as a voltage regulator. The IC is clearly marked LM2596, but the waveform appears to be 50KHz, not 150KHz. Can someone confirm my logic that this has to be a fake?
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