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UCC28811: PMP6024

Part Number: UCC28811
Other Parts Discussed in Thread: PMP6024, , TPS92210

Hi,

As mentioned previously I have built a prototype based on the reference design PMP6024 and have some issue with the startup circuitry and the consequence is that the MOSFET Q1 overheated. After adjusting the resistor values of R1 and R2 I could lower the heat level on the Q1 and achieved 50VDC on the secondary side. But the system is not working proper. Q1 seems never be turned off and properly because of the Aux winding level on T1 pin 5-7. I have looked in the Tidu958 but could not find any information about this level. 

Since I don't use MathCAD and it is not possible to have the related data of T1 and I really need som support. Here are some of my questions

What is the level this winding should be? does it really need to have a load on the output (50VDC) to achieve the correct level on the Aux winding? What is the max voltage and current that it can be on this winding since the VAC in is 100- 240V?

Q1 is replaced with STN1HNK60 can it be any issue ?

Is there any specification/datasheet for the T1 ?

Does it any matter if C17 replace with tantalum capacitor?

Is it possible to have the configuration file of the PMP6024 in PDF, i.e exporting from MathCAD Tool?

Thanks in advance!

Br,

Conny

  • Hello Conny,

    Please note this is the first correspondence that I have seen with this title UCC28811:PMP6024. I reviewed you inquiry and the PMP6024 schematic and have the following comments.

    I don’t believe it matters if you use STN1HNK60 or FQN1N60CTA for Q1. The specifications seem close. You mentioned Q1 is burning up. This FET should only be on until switching starts and the aux winding is providing power to U5 and the rest of the discrete circuitry.

    Q1 is supposed to turnoff once the aux winding (P5 and P7) has enough voltage power D12 and U5 and turn on Q3. The voltage at D10 cathode needs to be greater VD12 + VSAT of Q5 and the source of Q1. This will back bias the FET and turn it off. It sounds like the voltage at D10 anode is not going high enough to shut off Q1.

    If you are starting up this converter in a constant current load to simulate the diodes this may be causing the aux voltage not to climb high enough to turn off Q1.

    Are you using the same transformer as the reference design? If it is not this might be part of the problem.

    Using a tantalum for C17 may not be wise without current limiting on Q1. These capacitors have a tendency to become fired hazards when they fail.

    The one thing I don’t like about this startup circuit is that Q1 does not have current limiting. I would add a resistor between Q1’s drain and the input bulk capacitance to limit the current. R > 375V/0.25A should resolve that issue.

    Could you send me a link to MathCAD file that you are talking about?

     

    Regards,

     

    Mike

  • I looked at the UCC28811 product folder and could only find excel design files for buck derived PFCs. This reference design is a single stage flyback for driving LED strings.

    I did find the TPS92210 single stage PFC controller in a flyback for LED strings. This device had and Excel tool that can used to design the transformer so you will not need MathCAD.

    http://www.ti.com/lit/ds/symlink/tps92210.pdf

    http://www.ti.com/tool/tps92210_design_calc

    The TPS92210 is similar device to the UCC28811 and these files should help you in your design process.

    Regards,

  • Hi Mike,
    Thanks for the quick reply!
    You have confirmed my conclusion about the " voltage at D10 anode is not going high enough to shut off Q1"
    I have asked Würth Midcom to supply the transformer and mentioned to them that it is for this reference design.

    I do agree about the current limitting on the Q1's drain, I think this will makes this design more stable.
    I have also tried to add a light load to see if it helps to raise the Aux winding voltage but it is just about 8-9 VDC. When the AC in is 100v.

    I don't have any configuration file of the PMP6024 in MathCAD and asking TI to provide me that. Since I don't use MathCad and ask for You to export the file to PDF. Sorry for my careless written!

    My strategy was to short the development time by to copy the reference design and tried to build a prototype before optimizing it so I used the schematic files and 95% of the BOM on my design.

    In this situation I would need to have all design data of the PMP6024 from TI to verify my design. Could you please check and provide me?

    Br,
    Conny
  • Hi Mike,
    The TPS92210 has limited input <145Vrms. I need universal input 85-265VAC is required!
    Br,
    Conny
  • Hello Conny,

    The TPS92210 can handle 85V to 265V RMS.  Down load the excel design I referenced enable editing and change the input conditions and power conditions to match your design. I doubled checked and you and you can change the inputs to 85 V to 265 V RMS.

    Regards,

    Mike