One of the most common power conversion tasks in industrial electronics is converting a 24V DC control voltage into a regulated 5V supply.

This type of converter can be found in:

• PLC systems
• Industrial sensors
• Factory automation equipment
• Robotics controllers
• Embedded control systems

Although the converter itself may appear simple, selecting the proper inductor requires balancing ripple current, saturation margin, thermal performance, manufacturability, and cost.

In this example, we’ll walk through the engineering process used to design a practical power inductor.

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Design Requirements

Input Voltage:

24V

Output Voltage:

5V

Output Current:

10A

Switching Frequency:

200 kHz

Target Ripple Current:

30%

Maximum Temperature Rise:

40°C

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Step 1: Determine Ripple Current

Most buck converter inductors are designed with ripple currents between:

20% and 40%

of load current.

For this design:

10A × 30%

= 3A ripple current

Why not choose a smaller ripple current?

Because reducing ripple current requires a larger inductance value, which generally means:

• Larger cores
• More copper
• Higher cost

Why not choose a larger ripple current?

Because larger ripple currents often increase:

• RMS current
• Losses
• Output ripple
• Saturation risk

👉 Related Guide:

Ripple Current Explained

Calculate Ripple Current

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Step 2: Estimate Inductance

For a buck converter:

Duty Cycle:

D = Vout / Vin

D = 5 / 24

≈ 0.208

A simplified inductor equation is:

L = ((Vin − Vout) × D) / (ΔI × Fs)

Using:

• Vin = 24V
• Vout = 5V
• ΔI = 3A
• Fs = 200 kHz

Produces:

≈ 6.6 µH

This gives us an initial design target.

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Step 3: Determine Peak Current

Peak current is critical because saturation occurs at peak current—not average current.

Peak Current:

10A + (3A / 2)

= 11.5A

This is the current the magnetic design must survive.

👉 Related Guide:

How to Select the Right Inductor Current Rating

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Step 4: Calculate Energy Storage

Energy storage often drives core selection.

Stored Energy:

E = ½LI²

Using:

• L = 6.6 µH
• I = 11.5A

Results in:

≈ 0.44 mJ

That may not sound like much, but it significantly influences core size and gap requirements.

👉 Related Guide:

How to Calculate Inductor Energy Storage

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Step 5: Select a Core Family

Now we begin comparing candidate cores.

Possible options:

• ETD29
• ETD34
• PQ26
• PQ32

How do we choose?

We evaluate:

• Energy storage
• Window area
• Saturation margin
• Thermal performance

👉 Related Guide:

How to Select the Right Magnetic Core Size

Quick Design Evaluation

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Step 6: Verify Saturation Margin

Suppose ETD29 appears attractive because it is compact.

The next question becomes:

Will it saturate?

Engineers evaluate:

• Peak current
• Air gap
• Core material
• Flux density

👉 Related Guide:

Understanding Magnetic Saturation

Check Saturation Margin

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Step 7: Select Wire Size

Now we evaluate conductors.

Possible choices:

• AWG16
• AWG15
• Parallel AWG18

The goal is minimizing:

• DCR
• Temperature rise
• Cost

while maintaining manufacturability.

👉 Related Guide:

Choosing Wire Gauge for Power Inductors

Evaluate Wire Options

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Step 8: Estimate Losses

Every design generates losses.

Major contributors include:

• Copper losses
• Core losses
• AC winding losses

These losses ultimately determine efficiency and temperature rise.

👉 Related Guide:

Inductor Efficiency Explained

👉 Related Guide:

How Core Losses Are Calculated in Magnetic Components

Estimate Losses

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Step 9: Evaluate Thermal Performance

Industrial electronics often operate continuously.

A design that survives electrically but overheats is not acceptable.

Target:

Less than 40°C temperature rise.

Engineers verify:

• Core temperature
• Winding temperature
• Ambient conditions

👉 Related Guide:

How to Reduce Inductor Temperature Rise

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Step 10: Compare Multiple Candidates

At this stage, several designs may be acceptable.

Example:

ETD29:

• Smaller
• Lower cost
• Higher temperature

ETD34:

• Larger
• Cooler operation
• More copper area

The final selection often depends on the product requirements.

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Conclusion

Selecting a practical power inductor requires much more than calculating an inductance value.

Engineers must balance:

• Ripple current
• Energy storage
• Saturation margin
• Wire size
• Thermal performance
• Manufacturability

The best design is usually the one that balances all requirements rather than optimizing a single parameter.

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Need Help Designing Inductors?

The SolidMagnetics platform automatically evaluates:

• Core families
• Wire sizes
• Saturation margin
• Losses
• Thermal performance

while generating CAD models, engineering drawings, BOMs, and production-ready manufacturing outputs.