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UCC28C45: TL431 will be demanged when the output power is over than 300W in dual tube flyback topology of UCC28C45

Jon WANG
Intellectual 320 points
Part Number: UCC28C45
Other Parts Discussed in Thread: TL431

Tool/software:

The customer use a UCC28C45 designed dual tube flyback power supply with an input voltage of 85-265VAC and an output of 24VDC. If the output power is greater than 300W, TL431 will be damaged and the output voltage will be 0. The transformer flux is sufficient. The following figure shows the voltage waveform of TL431 Reference under 360W output state.

  • 0
    TI__Expert 8591 points

    Hi Jon,

    -What is nominal power that the power supply was designed for? is it lower than 360W?

    -What happen with the output voltage when this issue happens? 

    -Could you please share the following waveforms when this issue is happening for a better debug?

    (VDD-GND), (DRV-GND), (VS-GND), (FB-GND), (CS-GND). Please, probe at the pins of the device. Please specify the VIN and the load current.

    Thank you