Coupled Inductor and Tapped Inductor: Are they transformer?

Photo by Harrison Broadbent on Unsplash

What is coupled inductor?

• A coupled inductor has two or more windings on a common core like a transformer.
• Coupled inductors are a valuable component of nonisolated dc–dc converters that store energy in one cycle and power the load in the other cycles.
• As many applications do not require electrical isolation, the use of coupled inductors provides a helpful alternative boosting technique in dc–dc converters that can be achieved by tapping or simply coupling the inductors.

What is tapped inductor?

• Tapped inductor is 3-pin inductor and it is called as a center tapped inductor. It is not a transformer.

Image of the tapped inductor

Circuit diagram of the tapped inductor

What are differences between tapped inductor and coupled inductor?

• The difference between a center tapped inductor and a coupled inductor is that the center tapped inductor is a single coil around a core with a wire ‘tapped’ at some point in the middle of the coil, and a coupled inductor is two separate coils sharing a common core.
• If the end of one of the coils is connected to the beginning of the other in transformer, this essentially it makes a tapped inductor. So connecting two coils of a coupled inductor (transformer) in serie makes a center tapped inductor (autotransformer).

Examples of tapped inductor and coupled inductor.

1)Both Tapped Inductor and Coupled Inductor Topology

2)Just Coupled Inductor Topology

Why coupled inductor?

• High frequency transformers can be employed to level up the input voltage with the benefit of providing electrical isolation. However, when electrical isolation is not required, using coupled inductors can be a simpler and more flexible solution to boost the voltage level of step-up converters.
• Thus the coupled inductor network can be used in the DC-DC converter to achieve higher voltage gain.
• The coupled inductor network has the flexibility to change the number of turns of its two windings which consequently increase the voltage gain. Therefore, the coupled inductor network provides the better voltage gain with the reduced number of passive elements.
• Based on the concept of coupled inductor, the various network is reported in the literature to date. These networks may be either two winding or three winding.