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UCC28700-Q1: Burst Mode on light load

Tobias Fernandes
Prodigy 90 points
Part Number: UCC28700-Q1
Other Parts Discussed in Thread: UCC28700,

Hello Folks,

I have a question regarding the control of the UCC28700. First I would like to tell our application. We are using the controller as main power supply for our application (Flyback 400V to 17v) and in our design, we operate with light load in some scenarios and this can stay for longer time.

From the measurements, I have see that the controller in the light Output condition is operating in quite same as a "Burst mode" and the output ripple also increased at this condition.

I would like to know, if the controller has designed to operate in this "burst" mode and if there is any problem to stay longer on that.

Thanks in Advance,

Tobias

  • 0
    TI__Guru 66135 points

    Hello,

    The UCC28700-Q1 does not have a burst mode.  It actually uses an FM/AM/FM modulation scheme to control the duty cycle.  Please refer to figure 13 of the data sheet to show how the FM/AM/FM modulation scheme works.  Also note that the design also requires some pre-load for no load operation.  Equation 28 describes how to set the preload resistor.

    Regards,