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- How to Select an Inductor for a DC-DC Converter
NG Electronics · ISO 9001:2015 Certified Company
How to Select an Inductor for a DC-DC Converter
A practical guide on how to select an inductor for a DC-DC converter, written by the applications team at NG Electronics, an ISO 9001:2015 certified inductor manufacturer in Pune.
- Buck, boost, buck-boost
- Ripple-first method
- Worked 12 V to 5 V example
- Free sample for approval
ISO 9001:2015Certified company
Since 2017Manufacturing in Pune
50+ peopleIn-house winding team
100% testedEvery unit, electrically
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Drum Core Inductors
How to select an inductor for a DC-DC converter: the short version
Knowing how to select an inductor for a DC-DC converter comes down to four checks made in a fixed order: inductance, peak current, heating and stray field. The inductor stores energy while the switch is on and releases it while the switch is off, so its value decides how far the current swings in each cycle.
DC-DC converter inductor selection goes wrong most often when a part is picked on inductance alone. Two inductors marked 22 µH can differ widely in saturation current, DCR and core loss, and those three figures determine whether the converter survives a load step or an overload. A datasheet value is also measured at small signal with no DC bias; under load current the inductance is lower, sometimes considerably so with a small core.
This guide walks through the reasoning in words, with one worked buck example, so you can apply it to your own input voltage, output voltage, load and switching frequency. Where a catalogue part does not pass all four checks at once, NG Electronics winds drum core and toroidal inductors to order in Pune and supplies a sample for evaluation on your board.
- Inductance follows from the ripple current you choose, not the other way round
- Saturation current is checked against peak current, including the current limit
- Rated current and DCR are checked against RMS current and allowed temperature rise
- Shielding and package are settled last, from the layout and switching frequency
ISO 9001:2015 certifiedWound & tested in Pune
Specifications
Quick reference: DC-DC inductor parameters
Each row is a figure you will meet on an inductor datasheet or in a converter calculation, with a note on how to use it.
| Inductance (L) | Sets the ripple. Calculated from input voltage, output voltage, switching frequency and target ripple. |
|---|---|
| Inductor ripple current (ΔI) | Peak-to-peak swing in each cycle. Typically chosen as 20% to 40% of full load current. |
| Peak current | Average inductor current plus half the ripple. Compare it with saturation current. |
| Saturation current (Isat) | DC level at which inductance has fallen by a stated percentage. Keep it above peak current with margin. |
| Rated current (Irms) | Thermal limit, typically the current giving a stated temperature rise. Compare it with RMS current. |
| DCR | Winding resistance in mΩ. Copper loss is RMS current squared multiplied by DCR. |
| Shielding | Shielded parts confine stray field near sensitive traces; unshielded parts typically give more current per size. |
| NG Electronics range | Drum core 1 µH to 1 mH; toroidal 10 µH to 10 mH standard, up to 25 A |
Figures such as saturation current and DCR depend on the design and are confirmed on the technical quotation for your part.
Applications
Where this selection method is used
The same four checks apply to any non-isolated switching stage; only the governing limit changes from one application to the next.
LED driver current sources
The inductor carries a near-constant DC current for hours, so temperature rise from DCR usually becomes the limiting check before saturation does.
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Solar and battery boost stages
In a boost converter the inductor carries the input current. Peak current is greatest at the lowest panel or battery voltage.
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Telecom point-of-load converters
Low output voltages at high switching frequency call for small inductance values, low DCR and a shielded part placed close to signal circuitry.
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Drum Core Inductors from our catalogue
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Have a converter inductor specified for you
Email your input range, output voltage, load current and switching frequency to sales@ngelectronics.in, or call or WhatsApp +91 83290 52861, Monday to Saturday, 9am to 7pm.
Design guide
Buck converter inductor calculation, step by step
For a buck stage in continuous conduction, the inductor sees the output voltage in reverse while the switch is off. From V = L di/dt, the ripple is ΔI = Vout × (1 − D) / (L × fsw), where the duty cycle D is roughly Vout / Vin. Take 12 V in, 5 V out, a 2 A load and 300 kHz. D is about 0.42. Choosing 30% ripple gives a ΔI of 0.6 A, and rearranging the relation gives roughly 16 µH, so 15 µH is the practical choice.
With 15 µH the ripple becomes about 0.65 A, so the peak current is 2 A plus half of that, close to 2.3 A. The saturation current should clear this with margin, and should also clear the controller's current limit, because that is what the inductor carries during a short circuit or a hard start-up. RMS current is only slightly above the 2 A load figure, and that is the number to set against rated current and DCR.
- Fix the operating cornersList minimum and maximum input voltage, output voltage, full load current and switching frequency. Buck ripple is highest at maximum input voltage, so calculate there.
- Choose the ripple and calculate LPick a ripple between 20% and 40% of load current, apply the ripple relation and round to a value that can actually be wound or bought.
- Check saturation at temperatureCompare peak current, and the current limit, with saturation current at the hottest core temperature expected. Ferrite saturates earlier when hot.
- Check heatingMultiply RMS current squared by DCR for copper loss, add an allowance for core loss, and confirm the temperature rise suits your ambient.
- Settle construction and testDecide shielded or unshielded and SMD or through-hole from the layout, then confirm on the bench that the current ramp stays straight at full load.
About NG Electronics
How NG Electronics supports your inductor choice
A calculation gives you a target; a wound part has to hit it every time. NG Electronics is an ISO 9001:2015 certified company that winds and tests inductors under one roof in Pune. Every unit is electrically tested for inductance, DCR, Q factor, saturation current and hipot, so the figures you designed around are the figures measured on the parts that arrive.
If the calculated value falls between catalogue parts, send us the converter details instead of compromising. You receive a technical quotation within 24 working hours and a free sample to approve in your own lab, typically within 7 to 10 working days for a custom design. We ship across India from Pune, and enquiries from overseas design teams are welcome.
ISO 9001:2015 certifiedQuality system audited and documented
Wound and tested in-houseNothing outsourced, nothing rebadged
100% electrical testingInductance, DCR, Q, saturation, hipot
Batch traceabilityRecords back to material and date
Engineer-to-engineer supportDesign help from specification to sample
India and export deliveryExport documents and test certificate
How it works
From your requirement to tested delivery
Share specification
Call, WhatsApp or use the form with inductance, current and quantity.
Technical quotation
Price, lead time and datasheet within 24 working hours.
Free sample
Sample built in-house for your lab testing and approval.
ISO production
Production with 100% electrical testing under ISO 9001:2015.
Delivery + certificate
Packed with a test certificate, shipped across India or exported worldwide.
Frequently Asked Questions
Answers about how to select an inductor for a DC-DC converter from NG Electronics, an ISO 9001:2015 certified company
Work in order. Choose a ripple current, typically 20% to 40% of load current, and calculate the inductance from input voltage, output voltage and switching frequency. Check that saturation current exceeds peak current and the controller's current limit. Check that rated current and DCR keep temperature rise acceptable. Then decide on shielding and package from the board layout.
A ripple of 20% to 40% of full load current is the typical starting range. Lower ripple needs more inductance, which means a larger part and a slower response to load steps. Higher ripple shrinks the inductor but raises peak current, output capacitor ripple and core loss.
No. Inductance falls as DC current rises, gradually in powder cores and more abruptly in gapped ferrite as it nears saturation. It also carries a tolerance, typically ±10% or ±20%. Run the ripple calculation with the lowest inductance you expect at full load and maximum temperature, not the nominal figure printed on the datasheet.
The method is the same but the currents differ. In a boost stage the inductor sits at the input, so its average current is the input current, which exceeds the load current by roughly the step-up ratio divided by efficiency. Size saturation current for the lowest input voltage, where input current is greatest.
Not automatically. More inductance lowers ripple, but in the same package it means more turns of thinner wire, so DCR rises and saturation current falls. It also slows the response to load changes. Staying near the calculated value and spending the margin on saturation current is usually the sounder choice.
Yes. Drum core inductors are wound from 1 µH to 1 mH in SMD, radial and axial formats, and toroidal power inductors from 10 µH to 10 mH as standard, with custom values beyond that. Share your voltages, load current, switching frequency and footprint, and a technical quotation follows within 24 working hours.
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