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UCC 2803 current sense threshold

Christophe SCHOENENBURG
Prodigy 40 points
Other Parts Discussed in Thread: UCC28740, UCC28710, UCC28700

We are using UCC 2803 in a flyback converter application.

The current sense threshold (at pin 3) is defined (in the datasheet) as being comprised between 0.9 V and 1.1 V, over temperature range. Typical value is 1 V.

We need a current regulation which should be more accurate than +/- 10 %.

Is there a solution ? 

  • 0
    TI__Expert 5900 points

    Hi Christophe,

    what is your input range? output power?

    TI has some new ICs for flyback which could achieve +/- 5% current regulation.

    You can search for UCC28700/ UCC28710/UCC28740.

    Regards 

  • 0 in reply to Kening Gao
    Prodigy 40 points

    Hi Kening,

    Thank you for your answer.

    Input voltage is 5V, output voltage is 400V and output power is approx. 4W.

    The current sense amplitude is 160 mV, I use following biasing circuit found in an application note :

    Unfortunately, the circuits you suggest do not work under 5V.

    I believe there will be no other solution than to add a trimmer, in series with RA or RB. This would allow to set an accurate current, at room temperature. But, I wonder what would be the temperature drift, I can't find this information. The datasheet says the current regulation is +/-10% over temperature range, but I don't know which is the part of construction and which is the part of temperature drift. Can someone help ?

    Best Regards