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UCC28730: Maximum frequency of UCC28730

Part Number: UCC28730


I am designing a Flyback-converter and am cuurently planning to use the UCC28730.
How does the controller behave, when the maximum duty cycle is reached at a lower frequency then the 83kHz maximum frequency of the controller? For example, how will the controller react in this point, if there is a slight overload and the voltage drops on the output?

Kind regards
Ludwig Jostes

  • Hi Ludwig,

    Based on the control law of UCC28730, it will not reach to a maximum duty a low frequency. as the load increasing, the primary current reaches the peak current , then frequency will slowing increase . in this way , both of turn on duty cycle and demagnetizing duty will increase too. once the demagnetizing duty cycle touch the maximum threshold (0.432) , the controller will entry constant current mode , the output voltage will drop.