EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: jeremy on January 26, 2019, 02:23:39 am
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Hi all,
I'm trying to understand the price disparity between inductors which are available for small switch mode power supplies. Datasheets always recommend specific ones, and they are usually relatively expensive. For example, this coilcraft part https://au.mouser.com/ProductDetail/994-EPL3012-472MLB (https://au.mouser.com/ProductDetail/994-EPL3012-472MLB) has the following specs from the datasheet: Shielded, 3x3x1.3mm package, 4.7uH @ 20% tolerance, Isat ~= 1A (at 30% drop), DCRmax = 181mOhm. This part is AU$1.89 in single units (although there are similar parts which are >$3).
However, not much searching turns up lots of parts like this from taiyo yuden (among others): https://au.mouser.com/ProductDetail/Taiyo-Yuden/NRH3012T4R7MN (https://au.mouser.com/ProductDetail/Taiyo-Yuden/NRH3012T4R7MN) which appears to have slightly better specs: Shielded, 3x3x1.2mm package, 4.7uH @ 20% tolerance, Isat ~= 1A (at 30% drop), DCRmax = 130mOhm. Conversely, this part is AU$0.41!
In my experience, both coilcraft and taiyo yuden are both good brands (although I've mostly used taiyo yuden for other non-inductor passives). So why are some parts so much more expensive than others? I've noticed this with many of the commonly recommended brands incl wurth, TDK, coiltronics, etc. Is there some obscure technical reason why this is the case (some kink in frequency response, etc?) or is it just that you are paying for the brand?
Thanks,
Jeremy
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The only difference is that someone wants to sell them a high price to become a milioner fast. If the specs are the same, nothing else matters. A Chinese hobbyist built a 1 million dollar car for 26 000 dollars.
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The coilcraft part has qualified reliability for automotive usecases. Also the winding is fully overmoulded by the ferrite material which makes it better shielded than the alternative part you had linked.
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For RF certain coilcraft parts seem to be hard to match elsewhere. (high self resonant frequency for a given nh)
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Markup.
Coilcraft is generally competitive or cheaper, while offering good products. But you have to buy direct from them -- they don't go through distributors, except for Mouser I think.
Similarly Wurth Elektronik is usually on the expensive side from other distributors, but competitive by direct.
Also, singles costs are largely arbitrary -- there is very little you can read into about them. If you're not buying reels at a time, price is really, really irrelevant.
Yeh, sucks for the home player, but if you wanted bargain basement pricing in those quantities, you'd have ordered something from Ali Express and you'd probably already be complaining about how shite it was... ;D
Tim
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Markup.
Coilcraft is generally competitive or cheaper, while offering good products. But you have to buy direct from them -- they don't go through distributors, except for Mouser I think.
Similarly Wurth Elektronik is usually on the expensive side from other distributors, but competitive by direct.
Also, singles costs are largely arbitrary -- there is very little you can read into about them. If you're not buying reels at a time, price is really, really irrelevant.
Yeh, sucks for the home player, but if you wanted bargain basement pricing in those quantities, you'd have ordered something from Ali Express and you'd probably already be complaining about how shite it was... ;D
Tim
Coilcraft also has the benefits of having AC and DC copper and core loss numbers available on their online wizard. If I'm making a buck converter, need a 2-4.7uh inductor, 2A output current, 500KHz, and know the inductor ripple current will be ~25-30%, I can punch that in get actual numbers and temp rise. Rather than trying to make an educated guess based on what kind of ferrite material is in use, or trying to find actual numbers to do make a core loss estimate myself, along with the usually non-existent thermal resistance numbers of the component.
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Yup, including reasonably accurate SPICE* models for most of their parts, too. :)
*For some values of "SPICE". It's an AC steady state model, which is all but useless in transient analysis, in most tools. Fortunately, it is possible to convert this to an efficient universal model: https://www.seventransistorlabs.com/Calc/Coilcraft1.html (https://www.seventransistorlabs.com/Calc/Coilcraft1.html)
Tim