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UCC28730-Q1: Operation at Duty>50%

Hidekazu Someno
Expert 5130 points
Part Number: UCC28730-Q1
Other Parts Discussed in Thread: UCC28730, UCC28600

Hello, application team,

My customer is considering the application using this part with wide input range(several ten Vdc to 600Vdc). For wide input range,  they is trying to study the operation with Duty>50%.   However, According to section 8.2.2.3  in datasheet,  Dmax seems to be limited by DMAGCC and DCM resonant period.

Is it possible to configure this type of operation(wider duty cycle >50%) with UCC28730?   To achieve it, is there any alternative part to achieve it?

Regards,

H.Someno

  • 0
    TI__Expert 7080 points

    Hello , H.Someno,

    UCC28730 has some limitation on max. duty cycle due to the constant current control scheme. but that not means can't support wide input range application.

    As we know the Dmax not only decided by min.input voltage , but also impacted by the transformer turn ratios selection at lowest input voltage and the output voltage. so choose a little small turn ratios at low line input and let the Dmax meet the controller allowed value. but small turn ratios means high voltage stress on secondary side rectifier at high line input. that is should be considered when you select the turn ratios.

    For a large Dmax , I proposal UCC28600 which Dmax can up to 99% . that is maybe better for you to design the transformer.

    Thanks.