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What is the name of this component (circled in red) of a charger?

Image of the charger

What are the uses of this component?

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This EMI Common Mode (CM) choke absorbs noise with lossy ferrite in a cylindrical shape.

In this photo a DC-DC converter, it will be high permeability perhaps optimized in the 1~40 MHz range.

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All VGA cables have to suppress the DAC video pixel noise from 40 to 300 MHz range which affects the choice of ferrite to lower permeability types.

There are hundreds of varieties of ferrite compounds and hundreds of varieties of cylinder shapes. The method of attachment can be assembled by the cable mfg as a cylindrical sleeve, prior to plug attachment and then plastic molded casing is applied to this and the plugs. Similar to the snap-on clamshell perfected by TDK, Tokin and others.

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This is useful for all types of cables with pulse noise to improve integrity of high impedance signals as well as reduce interference of both ingress and egress for passing EMC tests. Their product is precision machined and tightly clampled to avoid acoustic vibrations often requiring epoxy in other designs to avoid vibration.

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It's a ferrite choke, not going to retype it all but here's an article: What are the bumps at the end of computer cables?.

These "bumps" are called ferrite beads or sometimes ferrite chokes. Their goal in life is to reduce EMI (electromagnetic interference) and RFI (radio-frequency interference).

A ferrite bead is simply a hollow bead or cylinder made of ferrite, which is a semi-magnetic substance made from iron oxide (rust) alloyed with other metals. It slips over the cable when the cable is made, or it can be snapped around the cable in two pieces after the cable is made. The bead is encased in plastic -- if you cut the plastic, all that you would find inside is a black metal cylinder.

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It's called a clamp-on ferrite cable filter. It functions as a common-mode choke, reducing the ability for noise generated inside the device being charged to be radiated from the charger cable.

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  • \$\begingroup\$ The choke pictured in the original question is a molded in place choke and the ferrite cylinder inside is highly unlikely to be a split type like one would find in a clamp-on cable filter. I have removed many of these from cables and never saw a molded split ferrite choke. \$\endgroup\$ – Michael Karas Oct 29 '12 at 15:27

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