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Need help for UCD9240 on 200V input and 48V output Multiphase Buck Converter

Jack57152
Prodigy 25 points
Other Parts Discussed in Thread: UCD9240

Dear My friends

I am trying to programming my UCD9240 control board using TI fusion GUI for 200V normal operation Vin buck converter and 48V output voltage, however I met one cirtical problem on input voltage configuration. Acturally, from GUI desinger, the input voltage can be defined up to maximal 400V according to the recommendation. In GUI configuration, the Vin warn limit and Vin Fault limit is only allowed to be defined lower than 24V. I can not 100% make sure if UCD9240 really can be applied for this high voltage application. According to my regarding, I think I can use resister divider net to provide required input votlage range, such as deviding 200VDC input to 20VDC and then using another resistor divider net as voltage scaling to configure the required input votlage for hardware. It means I have to lie to GUI software for system configuration. Meanwhile for the output voltage I would like to employ the same resistor divider net.Therefore here I would like to ask friends and TI engineer if I can make such kind of supporting in order to have the same operation condition for high input voltage buck converter???

Thanks for answer and help from friends and TI engineer in advance.

Jack

  • 0
    TI__Genius 13700 points

    The limitations on the voltage ranges supported by the UCD92xx controllers is based on the PMBus specification which was written around low-voltage POL non-isolated power applications.

    I've never tried it but it should be possible to fool the controller/GUI by scaling the resistor dividers to the VIN and EAPx/EANx inputs, the scaling should be the same between these two inputs.  So if you scaled the input to appear in the monitor as 20V instead of 200V then the output should be scaled to appear as 4.8V instead of 48V.  The scaling needs to be the same to allow some of the controller's features to function properly, i.e. pre-bias start-up. 

    So lets say you want the voltage on the VIN/IIN pin to be 2V when the input is 200V then a single resistor divider from the rail input to the VIN/IIN pin would require an attenuation of 0.01 but you would enter 0.1 into the Fusion GUI for VIN_SCALE.  This would cause the monitor to report 20V when the input is 200V. 

    Scaling the output voltage is a little different as the maximum sensed voltage at the EAP/N pins is 1.6V rather than the 2.5V that is sensed at the VIN/IIN pin.  You'll need to leave some headroom to account for any OV condition on the output so using 1.4V for the nominal would be good.  This would require a resistor divider with an attenuation of 0.0292 but again when you enter the VOUT_SCALE_LOOP and VOUT_SCALE_MONITOR in the GUI it would need to be set to 0.292.  This will cause the monitored voltage to report as 4.8V vs. 48V.

    You shouldn't use the automatically generated component value selections for inductance and capacitance and the auto-tune function would not provide the correct compensation values.  But if these can be entered manually then it should work.

  • 0
    TI__Genius 13700 points

    And you would need to have a driver circuit capable of integrating with the output of the UCD92xx and the 200V line.