BUCK电感的设计方法.rar_BUCK 电感_Buck design_buck_buck 计算_buck电路设计

air gap (mm)

210.1

Energy (J)

2). Choose the core and determine the gap based on energy vs air-gap curve

W L I

2

⋅:= I

1). Calculate the energy storage

2. Choose core (Ferrite core design)

Note: The diode need to be considered on some cases especially for low output

f is operation frequency (Hz) Io is output current (A)

Kf is the ripple factor (0.1~0.2 for typical application)

L Vo

1 D−( )

2Kf f⋅ Io⋅

⋅:= VoorL Vin Vo−( )

D

2Kf f⋅ Io⋅

⋅:= Vin

a). Continued mode

Analysing the circuit, we can get the followed equations easily.

2). Calculate inductance

D

The flux swing divided by 2, then go to the core loss curve and find the core loss.

If the core loss higher than 100mW/cm^3, the core is saturation.

*This rule come from Lloyd's technical paper. Actually, if you choose the core and gap

based on this method, the core don't want to saturate.

Where:

∆

B is the flux swing in Tesla

∆

I is the peak to peak current

L is inductance in

H

1). Verify if the core saturation

Normally, the inductor has two limitations: one is the temperature rise, the other one is

saturation of core. So need to verify if these two factors can meet requirement.

5. Verify the design

b). American method

a). Chinese method

4. Determine wire size

Where: le---effective length of core in meter

Ae---cross area of core in square meter

lg---gap length in meter

µ

---permeability of core

µο

----permeability of air

Rg

:=

Rc

From step 2, the core and gap length were determined. Now we can use related factors of

core to calculate turns number.

3. Calculate the number of turns: