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  • Author Author: Jan Cumps
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Experimenting with Magnetic Components - Boost Converter part 1: Inductor and Calculations

Jan Cumps

I'm reviewing a set of inductors for the Experimenting with Magnetic Components design challenge.

Because it's a design challenge, I'd like to start with a working product. A switch mode DC converter.

It's one of the standard circuits: the boost converter. A design that increases a DC voltage.

 

Goals:

  • 9 - 12 V DC input
  • 30 - 60 V DC output
  • up to 20 mA output current
  • max 200 mV ripple
  • common components
  • no regulation or feedback

 

But first:

 

Post 1#: Introduce yourself and explain what experiments you plan to perform

I live in Schaerbeek, Belgium and have studied electronics, measurement & control techniques, and information systems.

My theme is "grow the love for inductors as LAB project building block".

  • What they do
  • Where you use them,
  • Review the inductors in the kit
  • How to measure, without LCR meter
  • How to use an LCR meter
  • How to roll your own coil, your own little transformer
  • PCB transfo

 

Back to the story:

 

The inductor: Bourns RLB Series 1mH Radial Lead InductorBourns RLB Series 1mH Radial Lead Inductor

 

image: Bourns RLB0914-102KLRLB0914-102KL 1MH inductor with candidate MOSFETs

 

The datasheet is available on element14. All info is taken from that document.

image: the specifications of the 1mH inductor

 

Measurements on the component in my kit:

The datasheet did the measurements at 252 KHz. I'm doing them at the maximum setting of my meter: 100 KHz.

The meter (comparable with GW INSTEK LCR-916) was calibrated before the measurements.

Results (f = 100 KHz)

 

L:955.5µH

Q:  106.5

D: 0.009 (1/Q)

ϕ: 89.4°

ESR: 5.64 Ω

 

The Boost Converter Calculations

 

I'm using the most common boost converter design. Adafruit (and others) posted a calculator online.

I used that, and changed parameters until the design matched the 1 mH inductor.

 

image source: calculation done with the Adafruit boost converter calculator.

 

Whe in I use a switching frequency of 72000 Hz, the calculator suggests exactly 1 mH.

Texas Instruments has an application note on the calculations.

Coursera has an excellent Power Electronics course, from U of Colorado Boulder.

 

Hang on while I'm starting the build.

 

 

Related posts
1. Boost Converter part 1: Inductor and Calculations
2. Boost Converter part 2: Build
3. Boost Converter part 3: Measure the Inductor in action
4. LCR meter experiments
5. SMD transformers experiment gizmo part 1: Build
6. SMD transformers experiment gizmo part 2: Measure
7. Common Mode Choke
8. Make your own Inductor
9. Calculate your own Inductor
10. Boost Converter part 4: Efficiency
11. DIY Inductance Meter
Planar PCB Transformer: GaN Point of Load converter 48V to 1V 50A
Measure Unknown Inductor Value with Function Generator and Oscilloscope
Experimenting with Magnetic Components: About the Competition
Anonymous
Parents

  • My function generator should be up to the job.

     

    It can generate a square wave that's 22 V p/p. I can use it isolated and concider the -11 V as ground level.

    If I use its offset mechanism to make it ground-referenced, I can get a 13.5 V square wave:

     

    I don't worry about the negative shoot-through in offset mode, should not harm the gate.

    But most likely I'll use it in isolated mode.

    In any case. 8 V and more should do it in my scenario:

    source: Sanyo 2SK2632LS datasheet

  • in reply to Jan Cumps

    no regulation or feedback

    Without feedback regulating the output, I think if you take it off load you'll probably see either the Schottky break down or the output capacitor fail.

     

    If you can't manage to get the generator to work with the offset, you could experiment with AC-coupling and clamping the gate side to ground with a Schottky. This seems to work in the simulator

     

  • in reply to jc2048

      wrote:

     

    no regulation or feedback

    Without feedback regulating the output, I think if you take it off load you'll probably see either the Schottky break down or the output capacitor fail.

    Yes. I've soldered the load on proto board. It's all a bit brutal but it should do for the experiment.

     

  • in reply to Jan Cumps

    Hi jan,

    Nice prototyping!

    Btw there's a typo, you mean 72000 Hz but have written 72000 kHz.

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