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Electronics Help Answered

Hi ppl,
I am currently making a variation on this circuit:
http://www.edn.com/article/CA257052.html
http://www.edn.com/contents/images/257052f1.pdf
I understand how it all works but do not understand the principle of the inductor capacitor used (bottom left), if anyone could give a brief explanation of this (links are good too) and also some formulae i would b e very greatful!!

thanks

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usha seelam
usha seelam

7 years ago

hello

can u plz expln me

how to route a video call in automated security system using psoc 3??

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drummer ian
drummer ian

13 years ago

thanks so much for all the replies! really great!!!!

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tech-king
tech-king

Reply 13 years ago

no problem
said the wise electrical wizard

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tech-king
tech-king

13 years ago

the inductor cuts out sudden current spikes. like all inductors, a slow sine wave or square wave can pass, however, a massive spike, being a sudden fast pulse, is converted to a very small sine wave. the capacitor does 3 things: smothes the remaining humps, smoothes the sinewave like form generated by the coil and reduces inrush current from starting ic's (CMOS comes to mind)

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Goodhart
Goodhart

13 years ago

are you referring to the 68 uH inductor and the 100 uF capacitor ?

It looks like it is used in conjuction with the two types of diodes in that block to smooth out any "rogue" spikes in the power line.

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drummer ian
drummer ian

Reply 13 years ago

those are the ones! and yeah i know the function of the diodes just not the cap and inductor, thanks!

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Goodhart
Goodhart

Reply 13 years ago

The capacitor smooths out remaining "bumps" in the signal, as does the inductor, that is why they are with the diodes (in fact, you will see similar configurations, sometimes with a few more caps, in most power supplies of this type).

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Goodhart
Goodhart

Reply 13 years ago

One more thing I forgot, in case you want to do some research on this: the pair of inductor with a capacitor is called an LC filter, an LC pair or and LC circuit.

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guyfrom7up
guyfrom7up

Reply 13 years ago

the diode is to make it so that cureent flow only one way?

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guyfrom7up
guyfrom7up

13 years ago

for boost circuits (and buck) the inductors are used to store the current and diliver it back at higher voltages (I think). With buck circuits it might be just cheaper than a capacitor that can operate at that frequency? I don't really no, I just make the circuits from the datasheets, lol

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drummer ian
drummer ian

Reply 13 years ago

thanks for trying duude at least its something to go on :P