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Slope Compensation for UC3825

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fethiyeli

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Hi. I am confused at slope compensation for UC3825. In application note of UC3825, normal sense resistor has been used but i need to use current transformer because of high primary current. In formula in application note, sense resistor has been used for slope compensation but there is no sense resistor in case of using current transformer. I only saw a resistor at output of the current transformer in book. So how can i find sense resistor in order to use for calculation ? Should i really need it ?
 

Orson Cart

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you will have burden resistor on the CT you use for current sensing, to add slope comp to the signal from this resistor there are myriad ways in the literature to do this. Slope comp of current signals is only required for pwm >49%.
Regards, Orson.
 
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fethiyeli

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In application note of UC3825, slope compensation has been used for 85% duty cycle for push pull topology but i dont know why they chose greater than 85% duty cycle in push pull topology. Can we use greater than 85% duty cycle in push pull, half bridge or full bridge topology ? My topology is full bridge and i know that i can only select 50% duty cycle at most in full bridge.
 
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