DC_DC power supply inductance calculation

鬼谷清泉

DC_DC power supply inductance calculation [Copy link]

Overview :

There are two main topologies of non-isolated DC-DC power supplies that are most commonly used in our onboard power supplies: BUCK and BOOST. Inductance is a key parameter. This article briefly introduces the selection and calculation of inductors for these two power supplies.

1. Main parameters and significance of inductance

The following parameters need to be considered when selecting a DC-DC peripheral inductor: inductance L, self-resonant frequency f0, internal resistance DCR, saturation current Isat, and effective current Irms.

Inductance L: The larger L is, the stronger the energy storage capacity is, the smaller the ripple is, and the smaller the required filter capacitor is. However, the larger L is, the larger the inductor size is usually required, the DCR increases, and the DC-DC efficiency decreases. The corresponding inductor cost will also increase.

Self-resonant frequency f0 : Due to the presence of parasitic capacitance in the inductor, the inductor has a self-resonant frequency. When it exceeds this f0 , the inductor behaves as a capacitor effect, and when it is lower than this f0 , the inductor behaves as an inductor effect (impedance increases with frequency).

Internal resistance DCR: refers to the DC impedance of the inductor. This internal resistance causes I2R energy loss, which reduces the efficiency of DC-DC and is also the main cause of inductor heating.

Saturation current Isat: usually refers to the DC current value corresponding to a 30% drop in inductance.

Effective current Irms : usually refers to the equivalent current value when the surface temperature of the inductor rises to 40 degrees.

PowerAnts

Effective current Irms: usually refers to the equivalent current value when the surface temperature of the inductor rises to 40 degrees.

"Rise to 40 degrees" should mean a temperature rise of 40 degrees

鬼谷清泉

PowerAnts published on 2019-9-11 19:58 Effective current Irms: usually refers to the equivalent current value when the surface temperature of the inductor rises to 40 degrees. "Rise to 40 degrees" should be...