Re: Smps Inductor Loss Reduction

D from BC wrote:

On Tue, 06 Mar 2007 23:54:51 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:


D from BC wrote:


On Tue, 06 Mar 2007 23:29:45 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:



D from BC wrote:



----Data----
Circuit: continuous mode smps
Inductor current: 1.5amps average with 400mA of peak to peak ripple.
Current ripple waveform: triangle at 100khz
Rdc: 0.3ohms
Wire d: 0.6mm
L: 2.6mH

I'm not entirely sure about the following:
Does the proximity effect and skin effect only occur as a result from
the 400mApp ripple current through the inductor?

The 1.5A average current through the inductor doesn't affect the AC
resistance..
If so...It looks like I can ignore these effects due to I^2Rdc loss
dominating.

Therefore, I'm free to fatten up the inductor windings until I get
close to the AC winding resistance..
How is this commonly balanced? Is it 50 50? (The inductor AC resistance and the DC resistance.)
D from BC


Usually I spec a core that has enough worst case saturation reserves and then select a wire gauge that crams it pretty full but not to an extent that it makes production difficult.


Let's say it's a toroid...
When you mean full..do you mean multilayer windings for a big fat
donut? Or full single layer?


For switchers in the few hundred kHz class it's often the big fat donut, for RF filters it's single layer with an isolation layer on the core. Many times switchers will also contain a single layer winding but that is because there comes a point when increasing the wire diameter doesn't buy you much anymore, other than a hard time soldering it in.


Cool...Thanks.. I'll go multilayer on the toroid.
To reduce Rdc, can I dodge ordering fatter magnet wire by doubling up
thinner wire (#23) in some way?
Maybe wind a twisted pair on the toroid? Ill effects?
D from BC


I have doubled up wire without problems on switchers. But not for series production as that increases cost.

--
Regards, Joerg

http://www.analogconsultants.com
.

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