Inductor

Basic Equations¶

Peak current¶

$I_{peak} = \frac{V \times T_{ON}}{L}$

V = Voltage
L = Inductance

From https://daycounter.com/Calculators/Inductor-Current-Power-Calculator.phtml

Saturation current¶

$I_{sat} = \frac{ B_{sat} \times A_e }{\sqrt{ L \times A_L }}$

I_sat = Saturation current
B_sat = Saturation flux
A_e = Core effective area
L = Inductance required
A_L = Inductance per turns²

From http://pigeonsnest.co.uk/stuff/core-saturation.html

Permeability¶

The relation between the magnetizing field H and the magnetic field B can also be expressed as the magnetic permeability²: $\mu = \frac{B}{H}$ or the relative permeability: $\mu _{r}= \frac{\mu}{\mu _{0}}$ where μ₀ is the vacuum permeability.

Power Inductor Checker¶

From http://elm-chan.org/works/lchk/report.html Power inductor checker

2SK2886 - N-channel MOSFET details¶

Datasheet: https://datasheet.octopart.com/2SK2886-Toshiba-datasheet-13713628.pdf
R_DS(ON) = 14 mΩ
V_DSS = 50 V
V_GSS ±20 V
Gate threshold voltage - V_gsth - 2 V

IRFZ44N can be used instead, though its resistance is 17 mΩ.

Ferrite Transformer¶

A_L - inductance factor / inductance per turn / inductance per square turn.
N - Number of turns

$A_L = \frac{L}{N^2}$

If A_L is known, then inductance can be calculated with¹:

$L = A_L \cdot N^2$

To find number of turns require for a give inductance:

$N = \sqrt{\frac{L}{A_L}}$

Common Values¶

Saturation flux, B_sat¶

Iron core
- Usually in the range of 1.6T to 2.2 T²
Ferrite core
- Usually in the rage of 0.2–0.5 T²

Toroid Core Materials and Properties¶

Core-2 - Red-Clear¶

Permeability: 10

Core-2

Core-8 - Yellow-Red¶

Permeability: 35

Core-8

Core-14 - Black-Red¶

Permeability: 14

Core-14

Core-18 - Green-Red¶

Permeability: 55

Core-18

Core-26 - Yellow-White¶

Permeability: 75

Core-26

T50-26¶

Core area, A: 0.112 cm²
Inductance per turn, A_L: 33 nH/N²

Common values:¶

1μH
- Number of turns: 5.5
- Saturation current: 92.481 A
4.7μH
- Number of turns: 5.5
- Saturation current: 42.6583 A
10μH
- Number of turns: 29.245
- Saturation current: 17.4078 A
33μH
- Number of turns: 31.6228
- Saturation current: 16.0989 A
47μH
- Number of turns: 37.7391
- Saturation current: 13.4897 A

Core-38 - Gray-Black¶

Permeability: 85

Core-38

Core-40 - Green-Yellow¶

Permeability: 60

Core-40

Core-45 - Black-Black¶

Permeability: 100

Core-45

Core-52 - Green-Blue¶

Permeability: 75

Core-52