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Sepic smps current transformer use

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energeio

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I build a Sepic converter around an UC3843 IC. The converter is suposed to work in continuous mode. The primary current, that passes through the Mosfet switch, is continuous. I try to use a current transformer because it is a high current and a sense resistor is unuseable, but current transformers are for AC currents so may be there is my problem. Can anyone give me a hint of how to use the CT. The Sepic is rated to be 500W.
The image depicts the whole circuit. I plan to use the circuit as a power converter for a wind turbine.
 

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Warpspeed

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Its quite likely that the current transformer is saturating due to too high a voltage across the secondary.

It depends on the magnetics design of the current transformer, but many of them struggle to produce much more than 1 volt, and you are probably losing most of that across the series diode.
Check the specifications of your CT, and use a low voltage drop shottky diode.

Your best bet is either to design and wind your own current transformer, or use a Hall effect sensor instead.

The circuit should work, but only if the current transformer can generate enough usable peak output volts to satisfy your controller chip without saturation.
 

energeio

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Thanks Tony, my scope broke two days ago. I will fix my problem and look at your suggestion. However, as you mention the difficulty of CT to produce the necessary voltage, I though to use a current sensor based on hall effect as those produced by allegro, like the ACS 712.
 

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