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Buck-boost converter for telecom

Hi Linear Technologies Support


We have a system that will potentially use the LTC3789 or LTC8392 a step-variable (12/24/48) power supply from Vin 9-36VDC. The output power is 96W maximun.
 

My main quiestion is: it is possible to make the change between the 3 otuputs voltage without modifing the compensation network?  The voltages step will be made adding parallel resistor in the feedback network ( The voltaje value has not to exactly, is more relevant the overcurrent protection and the loop stability).

Best regards 

  • Hi Anto_RF,

    This is possible by slowing the loop down, compensating on the extremes(in this case, 12V and 48V output). Make sure that all the outputs are inside the midband(between 1/RTH*CTH & 1/RTH*CTHP).

     

    By doing this, you will be able to make sure that the phase margin is enough to ensure stability for all of the output voltages. The trade-off is then the converter's response will be slow as it will be overcompensated. The gain margin will also be high on one output and low on the other. Thank you.

    Regards,

    Jhun