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Original question:

UCC3895: UCC2895D

UCC3895: UCC2895D

MOR DIOP
Prodigy 40 points
Part Number: UCC3895

Tool/software:

Hello ,

First, many thanks for your reply. 

About the control mode, I think that with my application I would use voltage mode control. It's a high ratio converter (x30) and for the closed loop regulation, the voltage reference is the input voltage. 

The variation range of the input voltage is between 10 and 80V. Do you think that the voltage mode regulation is suitable? 

When you talk about the transformer, do you mean the current transformer ? Do you have an idea about DC blocking capacitor value in series with the transformer to prevent transformer saturation ? 

  • 0
    TI__Guru 73495 points

    Hello,

    I can see why you want to do a voltage mode control design with wide input range.  If you are designing for voltage mode control I would use a PWM ramp of 1.8 V, instead of 700 mV.

    In regard to the DC blocking capacitor this was in regards to the main transformer that transfers the energy primary to secondary.  This was not in regards to the current sense transformer.

    The transformers main purpose is to block DC voltage and pass AC voltage.  Based on reactance (Xc) and switching frequency, you could select a blocking capacitor (CBlocking) value that would produce a voltage drop of less than 5% of the primary voltage.

    Xc = 1/(2*314*fsw, CBlocking)

    Ic*Xc < Vinmin*0.05

    The peak current and RMS currents in the blocking capacitor would be the same as the currents in the primary of the transformer.

    Regards,