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Need clarification regarding Active clamp - TIDA 00951

Ramesh Palanisamy
Intellectual 620 points

Hi Ram,

This is related to TIDA-00951 : 2kW, 48V to 400V,Isolated Bidirectional DC-DC Converter.

Regarding active clamp circuit, I would like to clarify below points which i could not find in the related documents.

1, What is the design criteria of clamp capacitor? I could not find in the document -TI Designs: TIDA-00951.2-kW, 48- to 400-V

2,Pls refer your schematic diagram for TIDA-00951.
As the clamp capacitor is to handle around 30A peak current, providing the following 1210 pack-X7R type capacitor is sufficient?
C4,C11,C13,C18,C19,C21 = 2.2 uF,100V
How the above capacitors will handle higher currents?
Also,100V rating is sufficient for active clamp capacitor?

3, what is the purpose of diode D1 and capacitor C61 connected in parallel with active clamp MOSFET Q5?
   Is the capacitor C61 helps in achieving ZVS condition?
   C61 = 2600 pF,500V  D1 = 100V,1A

Looking forward to your reply,

regards,

Ramesh P

  • 0
    TI__Intellectual 2815 points
    Hi Ramesh,

    1. The clamp capacitor design criteria is based on the allowable "AC swing" in the clamp voltage during the period when the entire input current is flowing through the clamp circuit. I will try to send you a link to a paper shortly.

    2. Upto 30Amps these 6 capacitors are good enough. We looked for the thermal rise on them at full load.

    3. The capacitor C61 and diode D1 are used to adjust the clamp resonant frequency. This needs to be only mounted if required in your design.

    Best Regards,
    Ram
  • 0 in reply to Ramkumar S
    Intellectual 620 points

    Hi Ramkumar,

    Thanks for your quick reply.

    Kindly send the reference link for active clamp which you followed in your design.

    Also,pls share the firmware for TIDA 00951.

    regards,

    Ramesh P

  • 0 in reply to Ramesh Palanisamy
    TI__Intellectual 2815 points
    Hi Ramesh,

    Plesae find below the link to active clamp capcitor design calacualations. It is mainly driven by the delV you want to allow. Use the clamp current ripple and allowable clamp voltage ripple to arrive at the minimum value you need.

    ieeexplore.ieee.org/.../stamp.jsp

    For the firmware, please send the request from the TI Design page.