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UCC28742: Can the UCC28742 IC operate in quasi-resonant mode?

Tsvetan Ginin
Intellectual 470 points
Part Number: UCC28742
Other Parts Discussed in Thread: TIDA-01505, UCC28C43, UCC28722

Tool/software:

Hi team,

Can the UCC28742 IC operate in quasi-resonant mode? If so, why does it not have a QR input?

Regards,

Tsvetan Ginin

  • 0
    TI__Guru* 86286 points

    Hello,

    The UCC28742 is a DCM ZCS flyback controller.  At full load the converter will operate close to QR.  That is why the device does not have a QR pin.  However, the UCC28742 uses Valley switching and frequency foldback.  This gives the UCC28742 the ability of being more efficient with load variation compared to QR.  At max load the efficiency will be roughly the same.  At lighter loads the UCC28742 will be more efficient compared to QR controllers.

    Regards,

  • 0 in reply to Mike O'
    Intellectual 470 points

    Hi Mike,

    I want to expand my question by asking if it is possible to combine the following reference designs: TIDA-01505 from which to borrow the transformer T1 (WA8759-AL), as well as the management of the SIC MOSFET transistor Q6 along with the bipolar driver (Q13 and Q16), and as a QR controller do I use the UCC28742 for more efficient control and, as a result, to get an output voltage of 12V/4A? The final design will be calculated with the design calculator for the UCC28742. Will other settings be needed? Even the group of the linear regulator Q11 will be removed, as the UCC28742 works with voltages up to 38 volts.

    Best regards,

    Tsvetan

  • 0 in reply to Tsvetan Ginin
    TI__Guru* 86286 points

    Hello,

     

    The Tida-01505 uses a UCC28C43 CCM flyback controller.  So, the transformer that was designed for CCM will not work for a QR or a DCM flyback designing using the UCC28742.

     

    If you need full power with an input of 40 V to 1 kV you would be better off using UCC28C43 in a flyback converter over the UCC28742.  The current sense leading edge blanking control law generally limits the input range roughly to 9 to 1.  The following link will bring you to an application note that discusses how to design the UCC28722 for wide input range designs.  The UCC28722 is a DCM flyback controller with a similar control law to the UCC28742.   This application note explains the limitations of the device and why it should be designed for an input range of roughly 9 to 1.

    https://www.ti.com/lit/pdf/slua781

     

    Regards,