Electronics

pyose · Guest

Building a Current sensing circuit using DC-D
converte

Good Afternoon guys

As mentioned at the subject, i really have to build the circuit for m
class project..the problem is i dont know where to start and wha
components should i buy..maybe someone has the practical circuit
could refer to or is there any reference from the internet i shoul
take a look? i really have to start building it right now..than

Pyose
Malaysi

Jan Wagner · Guest

You mean current sensing /for/ a DC-DC converter? There are many
ways, for example if you want to measure the switching current then
a simple toroidal ferrite core with a single winding (lots of turns)
would do. Feed the current carrying wire through the center of the
toroid, place a small resistor accross the toroid winding, and there
you go, output voltage is proportional to the current in the wire
that goes through the toroid.

Example coils
http://www.coilws.com/Current%20Sensse.htm
http://en.wikipedia.org/wiki/Transformer#Current_transformers

If you want to sense DC current, a hall effect sensor could do. If
it doesn't have to be galvanically isolated current sensing, then
you could also use a series resistor ("real resistor" or just a thin
ning slab of copper, circuit board trace, etc) which is placed e.g.
on the ground lead. Then measure the voltage drop accross the
resistance, typically is some millivolts (U=R*I...)

If you want to see how to use the current sensing in a DC-DC
converter, check the application notes for various PWM controllers,
they usually have example circuits that show current sensing, too.

For example
http://www.onsemi.com/pub/Collateral/AN983-D.PDF

TL494, LM3524, UC3864, ...

- Jan

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