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Selecting The Optimum Inductor to Best Match The Requirements

How to Select the Right Inductor for DC-DC Converter:

  1. Current Rating
    2. Current through a DC-DC converter inductor is always changing throughout the switching cycle and may change from cycle to cycle depending on converter operation, including temporary transients or spikes due to abrupt load or line changes. This peak-to-average ratio makes specification of current ratio difficult. If one takes the highest possible instantaneous peak current as "current rating" for an inductor, the inductor is likely to be spoiled for the application. If one takes the average current as "current rating", the inductor may not perform well when passing the peak current. The way to solve this problem is to look for an inductor that has two current rating factors.
    • The first factor is Isat which to deal with possible core saturation from the peak current.
    • The second factor is Irms which to deal with possible heating that can occur due to the average current.

  2. L (Inductance)
    3. In most design procedures, inductance is the first and main parameter to be calculated the desired circuit function. Inductance is calculated to reduce output current ripple and to provide a certain minimum amount of energy storage (or volt-microsecond capacity). Using much greater or much less inductance may force the converter to change between continuous and discontinuous modes of operation. Using less than the calculated inductance causes increased AC ripple on the DC output. Most DC-DC converter applications do not require extremely tight tolerance of inductance which ±20% is suitable for most converter applications.

  3. DCR (DC Resistance)
    4. DCR is simply a measure of the characteristic wire used in the inductor and is based strictly on the wire diameter and length. Normally this is specified as a “max” in the catalog but can also be specified as a nominal with a tolerance. Typically to reduce the DCR means having to use larger wire and probably a larger overall size. So optimizing the DCR selection means a trade-off of power efficiency, component size and allowable voltage drop across the component.

  4. SRF (Self Resonant Frequency)
    5. The frequency at which the winding self capacitance resonates with the inductance. For most converters, it is best to operate the inductors at frequencies well below the SRF. This is usually shown in the inductor data as a "typical" value.

  5. Isat (Saturation Current)
    6. The amount of current flowing through an inductor that causes the inductance to drop due to core saturation.

  6. Irms (RMS Current)
    7. In physical meaning, the RMS (Root-Mean-Square) is offten called the effective value or DC-equivalent value of a current is an equivalent of a DC current, which has the same heat dissipation as the real current on any resistor. Irms is the amount of continuous current flowing through an inductor that causes the maximum allowable temperature rise. In this case the data sheets almost always provide a rating based on application of DC or low frequency AC current.

Conclusion:

It can be seen that inductors for dc-dc converters can be described by a small number of parameters. However each rating may be thought of as a "5th element" based on one set of operating conditions which may need to be augmented to completely describe expected performance in application conditions.

General Information of SMD Power Inductors

How to Quickly Search Inductor for all of the Characteristics?

Searching and comparing data sheets of inductor manufacturers can be time consuming. DeMint's Parameter Sorting Search Mode allows selection of inductors based on different parameters.
By entering just the inductance value,
By sorting parameter to narrow down searching range,
Or by enter keyword / part number / size dimensions L*W*H to partial or exact searching.

Leading-Edge Technology:

DeMint Electronics brand passive component specializes in standard and custom solutions offering the latest in state-of-the-art low profile high power density inductor components. DeMint provides cost-effective, comprehensive solutions that meet the evolving needs of technology-driven markets. In working closely with the industry leaders in chipset and core development, we remain at the forefront of innovation and new technology to deliver the optimal mix of packaging, high efficiency and unbeatable reliability. Our designs utilize high frequency, low core loss materials, new and custom core shapes in combination with innovative construction and packaging to provide designers with the highest performance parts available on the market.

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Find Your Inductor - SMD Power Inductors
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Find Your Solution - Selecting The Optimum Inductor to Best Match The Requirements
Selecting the correct inductor solution will not only save you time, but it will give you a competitive edge. At DeMint, we are committed to helping you find the most efficient alternative for your power design. Our inductor and power supply design experts can help you make that selection.

Please forward us:

  • A brief description of your particular application's requirements.
  • Details of an existing solution that you’d like to replace, enhance or find an alternative.
  • Inquiries for feasibility to tailor a power transformer or inductor to your specific application.

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