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Choke (electronics) 1

Choke (electronics)

A choke, with two 47mH windings and rated to

handle 0.6A

A choke is a coil of insulated wire, often wound on a magnetic core,

used as a passive inductor which blocks higher-frequency alternating

current (ac) in an electrical circuit while passing signals of much lower

frequency and direct current by having an impedance largely

determined by reactance, which is proportional to frequency. Chokes

are typically used as the inductive components in electronic filters.

The name comes from blocking —"choking" —high frequencies while

passing low frequencies. It is a functional name; the same inductor is

often called a "choke" if used to block higher frequencies, but a "coil"

or "inductor" if, say, part of a tuned circuit.

Types and construction

An MF or HF radio choke for tenths of an

ampere, and a ferrite bead VHF choke for several

amperes.

Chokes used in radio circuits are divided into two classes  –  those

designed to be used with power and audio frequencies, and the others

to be used with radio frequencies.

Audio frequency coils, usually called A.F. chokes, usually have

ferromagnetic iron cores to increase their inductance. Chokes were

used as filters, in conjunction with large electrolytic capacitors, in

power supplies; working at low power-line frequencies they were

large, heavy, and expensive, but more effective and power-efficient

than resistor-capacitor hum filters. Modern components and circuits,

with very large and cheap electrolytic capacitors and electronic circuits

which suppress hum, have long made chokes obsolete in

mains-frequency power supplies, although small and inexpensive

inductors are used in high-frequency switch-mode power supplies.

Chokes for higher frequencies often have iron powder or ferrite cores (see Ferrite bead). They are often wound in

complex patterns (basket winding) rather than regularly to reduce self-capacitance. Chokes for even higher

frequencies have non-magnetic cores and low inductance.

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Choke (electronics) 2

Common-mode choke

Common-mode chokes, where two coils are wound on a single core, are useful in a wide range of prevention of 

electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for

prevention of malfunctioning of electronic equipment. They pass differential currents (equal but opposite), while

blocking common-mode currents.[1]

A typical common-mode choke configuration. The common mode currents, I1 and I2, flowing in the same direction through each of the choke

windings, creates equal and in-phase magnetic fields which add together. This results in the choke presenting a high impedance to the common mode

signal.[2]

References

[1] http:/    /  www. murata.  com/  products/  emc/  knowhow/  pdf/  26to30.  pdf 

[2] "Understanding Common Mode Noise" (http:/  

 /  

www. 

pulseelectronics. 

com/  

download/  

3100/  

g019& 

ei=NN-NT9WtDMuugQfI3LT8DQ&usg=AFQjCNG7o36UcFFK_bblUwgluE2GUM74ZQ&  sig2=htX-bGkrbazkg-hWQgWcPA). Pulse. . Retrieved 17 April 2012.

External links

• Chokes Explained (http:/   /  www. aikenamps.com/  Chokes. html)

• Common Mode Choke Theory (http:/   /  www. butlerwinding. com/  store. asp?pid=28349)

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Article Sources and Contributors 3

Article Sources and ContributorsChoke (electronics)  Source: http://en.wikipedia.org/w/index.php?oldid=501430329 Contributors: A930913, Amallam, Armstrong1113149, Bushben, CaptainTickles, Chevymontecarlo, DV8

2XL, DanielDeibler, Dcshank, Denisarona, Dicklyon, DieSwartzPunkt, Erodium, Foobaz, Frap, FredYork, Hooperbloob, JJ Harrison, Jmeden2000, Keenan Pepper, Kinkreet, KnightRider, Lukit,

Man pl, Mike1024, Nnh, Nsaa, Omegatron, Peak, Pol098, Prari, Quibik, Rabogliatti, Reddi, Redheylin, Richmond8255, Shaddack, Ssd, Steve carlson, SvNH, Thorseth, Tprentice, Utcursch,

Vhann, WordSurd, Yves-Laurent, 44 anonymous edits

Image Sources, Licenses and ContributorsImage:Choke electronic component Epcos 2x47mH 600mA common mode.jpg  Source:

http://en.wikipedia.org/w/index.php?title=File:Choke_electronic_component_Epcos_2x47mH_600mA_common_mode.jpg  License: Public Domain Contributors: Mike1024

File:Two ferrite beads.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Two_ferrite_beads.jpg  License: Creative Commons Attribution 2.0 Contributors:

http://flickr.com/photos/oskay/ 

File:Common-mode-choke.png  Source: http://en.wikipedia.org/w/index.php?title=File:Common-mode-choke.png  License: Public Domain Contributors: CaptainTickles, Hazard-SJ,

Ww2censor

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