[Basic course series on passive components (LC)] Basics of LC ~Part 7 What is a coupled inductor?

Narrow down by specifying conditions

現在1888件がヒットしています。check

Basic Analog Discrete Würth Elektronik

Inductors and capacitors are essential components in electronic circuits. I will explain the basic role of its operation.

The contents of this time will be Part 7 "What is a coupled inductor?"

If you want to see other articles, there is a summary page, so please take a look there.

Click here for a list of basic courses on passive components (LC)

What is a coupled inductor

A typical inductor has a single winding on a single iron core. On the other hand, as shown in Figures 1 to 3, inductors with two windings on one iron core are called coupled inductors.

Transformers and common mode choke coils have the same configuration, but inductors mainly used to configure SEPIC, Cuk, ZETA converters, etc. are called coupled inductors.

Depending on how they are used, they can also be used as transformers, common mode choke coils, or single inductors.

Figure 1: Appearance example of a coupled inductor

Example of internal structure of coupled inductor

Figure 2: An example of the internal structure of a coupled inductor

Figure 3: Example schematic

Usage example of coupled inductor

A SEPIC converter is used as an example to illustrate the use of coupled inductors. A SEPIC converter is an abbreviation for Single-Ended Primary Inductor Converter, and is a power supply circuit that can both step up and step down.

Figure 4 shows a circuit example of a SEPIC converter.

Figure 4 SEPIC converter circuit example

From the Analog Devices LT3580 datasheet

As shown in Figure 4, the SEPIC converter uses two inductors. It is also possible to configure using coupled inductors here, and circuits using coupled inductors have a polarity mark as shown in the circuit example.

Advantages of coupled inductors

As can be seen from Figure 4 2 A coupled inductor that consists of two inductors 1 can be configured with a single inductor because the ripple current is shared 2 Half the inductance is required to obtain a ripple current similar to that of a single chip.

Based on these features, the use of coupled inductors has the following advantages.

・Size can be reduced
・Cost can be reduced
·loss (DCR) can be suppressed

Application examples of coupled inductors

Coupled inductors can be used in addition to SEPIC, Cuk and ZETA converters. It can also be used with a flyback converter with a turn ratio of 1:1, making it possible to configure a circuit smaller than a general transformer. Here are six applications of coupled inductors.