Decide between two inductors for a DC / DC converter

Discussion in 'General Electronics Chat' started by Glebiys, Sep 22, 2019.

  1. Glebiys

    Thread Starter New Member

    Mar 11, 2019
    13
    0
    Hi,

    I am designing a power board based on the LM2596.

    Board specifications:
    1) Input - 12V
    2) Outpuit 5V, 2.5A

    At the output, I need to put an inductor. I examined many options and settled on two:

    1. TDK - 33uH, RC 3.2A, DCR 47.4 mOhm, Isat 3.2A

    [​IMG]

    2. TAITEC - 33uH, RC 6A, DCR 65 - 75mOhm, Isat 8A

    [​IMG]

    What prevents to determine:
    1) Is TAITEC better than TDK in terms of shielding? There will be signal lines near the inductor and I would like to minimize the influence of the inductor.
    2) If TAITEC has better shielding, then in comparison with TDK it has a high DCR. 47.4mOhm vs 65mOhm. As far as I understand, the lower the DCR, the better. Is 65mOhm too high?

    How to be?
     
  2. ci139

    Active Member

    Jul 11, 2016
    609
    87
    it would guess the option 1 has grater "flux leakage" near "air gaps" -- but it likely takes to compute it out with some 3d grid model ...
    i'm not really into this topic now
    /// a while ago - i noticed while rewinding iron core transformers that using the Litz wire on secondary !likely gained a better efficiency ... likely → https://www.researchgate.net/public...s_Design_of_a_100_kHz_Inductor_with_Litz_Wire , (https://www.ieee.li/pdf/viewgraphs/fundamentals_magnetics_design.pdf)
    ← returned by https://www.google.com/search?q=flu...ube+bobbin+ferrite+core+inductor+flux+leakage
     
    Last edited: Sep 22, 2019
  3. crutschow

    Expert

    Mar 14, 2008
    23,089
    6,849
    Can't tell for sure from the pictures.
    You need to look at the data sheets.
    It's a matter of efficiency.
    At 2.5A, (ignoring the inductor current ripple) the TAITEC will dissipate 6.25 * 65mΩ ≈ 400mW, while the TDK will dissipate 6.25 * 47.4mΩ ≈ 300mW.
    Is this 100mW difference important to the efficiency you want?
     
  4. MrSoftware

    Senior Member

    Oct 29, 2013
    1,494
    480
    You can download TI Switcher Pro application to help you calculate all sorts of things. Of course it's targeted at TI products, but you can create your own inductors and see how they behave at different switching frequencies, etc..

    http://www.ti.com/tool/SWITCHERPRO
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,768
    2,862
    I would go with the one with the higher Isat.
    Have you simulated the circuit to see peak inductor current? I always worry about that.
     
    BobTPH likes this.
  6. ci139

    Active Member

    Jul 11, 2016
    609
    87
    there are not many occasions where the higher R.ser of the inductor can be preferred - but some of such may be ? the voltage drop at the inductor (that would otherwise draw the supply down compromising the operation of the circuit) ? to reduce ringing of the mosfet at high dv/dt (? slow down operation to enable fly-back diodes to follow up at lower voltages) ? to limit whatsoever I/O (to/from inductor) peak current (so smaller filter caps can be used) ← but this is like a last measure to consider . . . ((the high currents need to be "stored" somewhere and routed to the inductor with minimum losses))
     
  7. BobTPH

    Senior Member

    Jun 5, 2013
    1,940
    537
    I agree with @ronv. The max current the inductor sees will be higher than the continuous output current. The first one may very well go above saturation at peak current.

    Bob
     
    ronv likes this.
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