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LM5045: Schematic for Full-Bridge DC-DC Converter

Yashaswini M N
Prodigy 95 points

Part Number: LM5045

Tool/software:

Hi Folks,

I am designing a full-bridge DC-DC converter with the following specifications:

Input Voltage: 36V - 75V
Output Voltage: 12V
Output Current: 33.33A
Output Power: 400W
Duty Cycle: 30%
Switching Frequency: 100kHz - 200kHz
Efficiency Target: 90%

I am considering using the LM5045 in the full-bridge configuration.

1. Is the LM5045 suitable for this application given the input voltage range, output power, and switching frequency?
2. Can you provide a reference schematic design for a full-bridge DC-DC converter using the LM5045?
3. What are the critical design considerations for achieving the 90% efficiency target?
4. Are there any specific layout guidelines or best practices for this application to minimize EMI and optimize performance?
5. Can you suggest me a transformer for this application?

Thank you for your time and expertise.

Sincerely,

Yashaswini M N
yashaswinimn@gyroscope.one

  • 0
    TI__Genius 10945 points

    Hello Yashaswini,

    Yes, the LM5045 and the Full-Bridge topology can be a good fit for your design. 

    You can search through our Reference Design Library for example designs. PMP31092 is a good reference. You can also use our Webench Circuit Designer for automated schematics. Power Stage Designer is also a useful tool for general calculations. Below is an example with Power Stage Designer using your values:

    90% efficiency should be doable. If component size is not an issue, then 100kHz-200kHz is ok. Decreasing the component size will require increasing the switching frequency and thus increasing switching losses. A Full Bridge will have significant switching losses since it is not Zero Voltage Switching (ZVS). 

    Is the 30% duty cycle a requirement? If not, then I would also recommend the UCC25660 and LLC topology. We typically see LLC used in an offline AC/DC application so the input voltage is ~390V. However, you can scale down the input voltage by adjusting the turns ratio. The power level, efficiency, output voltage and switching frequency are all possible with the LLC topology. The PMP23463 is a good fit for your design. 

    If you would like digital control and flexibility, then the UCD3138A is a good option. We have a HSFB example that closely matches your requirements. 

    Please expect a delay in further responses until January due to the holidays.

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    Prodigy 95 points

    Hi Jonathan,

    Thank you for your response.