Choice of inductor for buck converter
Choice of inductor for buck converter
(OP)
I am implementing a MPPT solar battery charger (buck converter). The type of converter design have been discussed in my previous post http://www.eng-tips.com/viewthread.cfm?qid=350101
I have finally decided to implement a Interleaved buck converter with 4 leg. With separate driver and mosfet pairs.
My Design Specs:
12V - 500 Watt Charger (That gives a max current of 41.67A)
Current per converter - 41.67A/4 = 10.42A(per converter)
Vinmax- 18V
Vinmin - 15V
Vout - 11V
Iout - 15A/leg (4 leg in parallel therefore 60A in total, well above the max current produced from panel to be safe)
Freq - 500KHz
Iripple - 1A
Substitute the values here http://schmidt-walter.eit.h-da.de/smps_e/abw_smps_... for inductance calculation
Inductance - 8.759x10-6 H
I have chosen the inductor http://in.mouser.com/ProductDetail/Coilcraft/SER29...
Questions:
I have finally decided to implement a Interleaved buck converter with 4 leg. With separate driver and mosfet pairs.
My Design Specs:
12V - 500 Watt Charger (That gives a max current of 41.67A)
Current per converter - 41.67A/4 = 10.42A(per converter)
Vinmax- 18V
Vinmin - 15V
Vout - 11V
Iout - 15A/leg (4 leg in parallel therefore 60A in total, well above the max current produced from panel to be safe)
Freq - 500KHz
Iripple - 1A
Substitute the values here http://schmidt-walter.eit.h-da.de/smps_e/abw_smps_... for inductance calculation
Inductance - 8.759x10-6 H
I have chosen the inductor http://in.mouser.com/ProductDetail/Coilcraft/SER29...
Questions:
- Is my choice of inductor good?
- Do i only have to worry about the max current in the inductor (Isat) or do i have to worry about the voltage across an inductor too?
Thanks
Regards
Gokkul
RE: Choice of inductor for buck converter
You may meet saturation, but that seems unlikely with your 18 V max in and 11 V out specification. You are running at 500 kHz, so your maximum voltsecond surface will be 14 microvoltseconds (at near 100% conduction). I don't find any data for absorbed voltseconds in the data sheet. But, since your operation is in "the lower left corner" in most of the diagrams, I wouldn't worry. If you see saturation, you can easily increase the switching frequency.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Choice of inductor for buck converter
Frequency response and Isat are the critical factors for this inductor, rather than voltage drop (since the first two determine the latter). With the caveat about Isat tolerance, the inductor looks like a good choice for the application.
RE: Choice of inductor for buck converter
Will keep that in mind :).
Thanks
Regards
Gokkul
RE: Choice of inductor for buck converter
Does this mean each inductor can operate only at a specified power level?
If so how do i know if the inductor i have chosen can operate at my required power level.
PDF attached.
Thanks
Regards
Gokkul
RE: Choice of inductor for buck converter
You know yours is okay because you've done the calculation yourself, and satisfied the Isat limits and frequency response.
RE: Choice of inductor for buck converter
That is reassuring.
Thanks for the response.
Thanks
Regards
Gokkul