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UC2844: Find suitable socket to replace UC284x

Sulyn ZHANG
Expert 8700 points
Part Number: UC2844
Other Parts Discussed in Thread: LM5021

Hi Team,

My customer is looking for new socket to upgrade UC284x. They hope the new sockets have decrease the switch frequency when light load. For example the switching frequency can decrease to 35kHz or can be set to 35kHz, can you help recommend one, thanks!

Best regards,

Sulyn Zhang

  • 0
    TI__Expert 3260 points

    Hi Sulyn,

    Thanks for reaching out. Just few questions before we can find the best solution for your customer:

    • Is your customer looking for general purpose PWM controller for multiple topologies? or just for flyback?

    • Any other concerns expect for the light load efficiency?  Why 35kHz for any particular reasons?

    - LM5021 has the skip-mode operation to increase the light efficiency, but it does not rely on switching frequency reduction to achieve high efficiency.  

    • What is the application and input / output requirements for your customer? We can help you to find the reference design that is close to their application.

    Thank you.

    Best Regards,

    Wei-Hao Chen

  • 0 in reply to Wei-Hao Chen (TW-FAE)
    TI__Expert 8700 points

    Hi Wei-Hao,

    Thanks for your support, for your question, pls find below:

    1.Input/Output conditions: 

           Input: 200V-1300V DC        

           Output:

            5V         0.8A

            15.3V       1A

            6.45V     0.15A    

            6.45V     0.15A

            6.45V     0.15A

           Considering the application, Need to consider 3W output when input 200V or 1300V input situation.

    2. Customer use flyback topologh;

    3. For the switching frequency, customer need to select 35kHz switching frequency because they need this switching frequency to better match their 1700V MOSFET     and also they can decrease the power consumption as well.

    Do we have suitable device here for recommendation? Thanks.

    Best regards,

    Sulyn Zhang

  • 0 in reply to Sulyn ZHANG
    TI__Expert 3260 points

    Hi Sulyn,

    It looks like your customer is using IGBT for high voltage purpose which also limits the switching frequency. Maybe we can use a cascode MOSFET configuration to reduce the voltage stress on single FET, that way we will have more freedom on the switching frequency and also reduce the cost for an additional IGBT driver.

    I am working with the team to find the closest reference design for you and will get back to you soon.

    Thanks.

    Best Regards,

    Wei-Hao