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UCC28700: UCC28700/LM5020 : Similar Part with <50khz operating range

Part Number: UCC28700
Other Parts Discussed in Thread: LM5020


I am looking for a PWM controller similar to that of UCC28700 / LM5020 but with <50kHz switching frequency.

Reason: My operating input is 50V-1500V and so the minimum ON time of the primary side FET will be very small (in ns) if I consider the switching frequency to be in range of ~70kHz.

Looking for an auxiliary winding feedback-based controller with <50kHz switching frequency.



  • Hi Ponkamali,

    Thank you for reaching out.

    UCC28700 can be used for this purpose. The control law maximum switching frequency will be limited by the choice of inductance. A high value of Lm will reduce the frequency of operation and this should be taken care while ensuring the frequency is less than 50khz.

    50-1500V is very big variation in input voltage. Generally the PSR controllers are minimum on time limited on on extreme and maximum duty cycle limitation on the other. So this generally ensures input voltage variation of 9x. Yours is around 30x variation and it will not be possible to achieve using UCC28700. You should try UCC28C56 family of controllers.

    Please post under UCC28C56 as this will be addressed by the expert for this part going ahead.