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How to measure the current flowing thru the inductor...

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powersys

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How to measure the current flowing through the inductor (i.e. L1 in the figure below) in a buck converter?

The switching frequency of the LT1074 controller is 100kHz. Most of current sensors (isolation type, e.g. hall effect sensor) cannot measure up to 100kHz (bandwidth). Therefore, I plan to use current sense resistor. But where should I install the current sensing resistor, before L1 (near sw) or after L1 (near output)? Will the additional current sensing resistor alter the performance of the buck converter?
 

I would measure the voltage and calculate the current.

V = L*dI/dt
dI/dt = V/L

Or the slope of I is V/L. At steady state, I is periodic. Use these two things to derive the current based on the voltage across the inductor.
 

You can measure after the diode on the input of the inductor, use 10 resistors 1R in parallel as a current sense and multiply the scope reading times 10.
That should work.

Tornado
 

Tornado said:
You can measure after the diode on the input of the inductor, use 10 resistors 1R in parallel as a current sense and multiply the scope reading times 10.
That should work.
Click to expand...
Do u think the additional resistors will alter the performance of the buck converter? Thanks.
 

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