# Deciphering current transformer output waveform problem!

#### crutschow

Joined Mar 14, 2008
29,528
So the addition of this extra diode allow a path for the "return" current, and thus allows transformer reset and thus avoids transformer saturation. Do I have that right?
Yes.
is the resistor necessary?
If you mean the 1 ohm is series with the return diode, no.

#### SiCEngineer

Joined May 22, 2019
390
Yes.
If you mean the 1 ohm is series with the return diode, no.
Hi All,

Revisiting this thread as still having issues with the transformer. I notice in the schematic you sent, Crutschow, that there is not a 10Kohm resistor. Do I need that? I have placed two diodes now, and the large voltage across the transformer is much improved, but I still get some terrible distortion on the output signal across the current sense resistor. I was not sure whether the inclusion of the extra diode removes the need for the 10K resistor.

Does it also matter about the position of the second rectifying diode? Note in some designs the diodes are connected slightly different... see attached/.

A TI document shows current transformer topologies, and again they often only have the single diode: https://www.ti.com/seclit/ml/slup114/slup114.pdf. So I'm still fairly confused about what's happening in this circuit!

SiC

#### Attachments

• 17.2 KB Views: 3
Last edited: