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Basic theory of DC > DC (Boost)

cjdelphi

Oct 26, 2011
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I bought a couple of 5 pins step up, and i don't need with the circuit, easy enough i just can't get my head around it.

I can understand how step down works, eg, take 15volts, oscillate at a high frequency and reduce the voltage coming out and smooth it through a cap....

but going up? All i can imagine is thousands of capacitors or inductors with diodes all aligned to give say 35vdc from 3vdc, and then switch it at high frequency to get the desired voltage out?...

chances are as usual, i'm probably way off lol
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Remember that diode you have to put across a relay?

It prevents damage from that voltage spike that happens when you switch the relay off.

In a boost DC-DC converter this "spike" is used to generate a higher voltage. There are also other ways of doing this, but that's a common one.

An oscillator is used to drive a transistor which alternately allows then prevents current from flowing. When the current is switched off, the spike in voltage is used to charge a capacitor to a higher voltage than the input.
 

BobK

Jan 5, 2010
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Inductors are probably the most difficult of the basic electronic components to understand. Inductors resist a change in current. And to do this, they change the voltage across themselves! So when, as Steve said, you remove the source of a current in an inductor, it will raise it's voltage to keep the current flowing. Where does this "extra" voltage come frome? Well, the same place that it comes from in a generator. A change in magnetic field thorugh a coil of wire produces a voltage. When the current in an inductor is changing, it is producing a changing magnetic field and that field is inducing a voltage in the inducutor.

Bob
 
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