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UCC28600: Constant output current based on UCC28600

Genik Genik
Prodigy 30 points
Part Number: UCC28600
Other Parts Discussed in Thread: TL431

Hi TI team! My name is Genik.

I try to make SMPS based on UCC28600, (20-150V_DC_IN and 13,8V_DC@7A_Out) and I want to make overload protection (for example 7,5A), which will turn off the controller after reaching certain output current on the output of SMPS, . I tried to short circuit at the output and I have got 1,5V@20A, at the output, but controller still works.  Can you help me to do this? My project file is below in attachment. Thanks in advance!

SLVC104I_20-155V_DC_300vds (2).xls

  • 0
    TI__Expert 4015 points
    Hi Genik, unfortunately the UCC28600 does not have a current limit based on the secondary side current. It does have a primary over current protection feature, but this limits the output power, not the peak current, and as your short circuit power is below the normal max power, the primary overcurrent will not be triggered.

    To limit the output current I would say you need to add a shunt resistor on the secondary side and build a circuit which either pull down on the reference input of the TL431 when the current gets above the desired level, which would result in constant current operation when the current gets too high, or triggers a fault on the primary side through an opto coupler by pulling up on the OVP pin for example.

    You will need a rail-rail input amplifier to amplify the shunt voltage. You would probably also need a separate diode to rectify the secondary winding and create a supply voltage for the amplifier, otherwise the circuit will probably not work in short circuit.

    Hope this helps.
    Thanks
    Billy
  • 0 in reply to Billy Long
    Prodigy 30 points
    Hi Billy, thanks a lot for a quick answer! I thought about current sense on secondary side and OPAMP, and wanted to connect op amp to comparator and then through optocoupler to SS pin of IC. This will work, but controller will be latched off, after overcurrent situation, but I want to do some like in hicсup mode.
    Regarding OVP pin, how to pull up this pin if it under AC voltage? Maybe you can show me some appnote or link to do this. Thanks in advance!