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UCC21520: Recommendation for gate driver power supply

Lakshmi R21
Prodigy 230 points
Part Number: UCC21520
Other Parts Discussed in Thread: LM25017, LM5030, UC2844, UCC21530, TIDA-00174

Hi,

I am designing a phase shifted full bridge dc-dc converter.

Input voltage: 400VDC; Output voltage: 650VDC; Power: 3500W; Frequency: 200kHz.

Please provide power supply recommendations for UCC21520, used to gate each of the half bridge, preferably one power supply module that can provide 3 or 4 isolated voltages. Also, thoughts on how the design can be completed with minimum number of power supplies are highly welcome. 

The board has a 24VDC bus. 

Regards,

Lakshmi.

  • 0
    TI__Expert 3355 points

    Hi Lakshmi,

    Thanks for your interest in UCC21520.  I work on the applications team in the high power drivers group and can help answer your question.

    Since you're designing for a PSFB and presumably operating at constant 50% duty cycle, have you considered switching to bootstrap supplies for your high side bias? This would eliminate two of the required isolated power supplies. This method is described in section 9.2, part selection in section 9.2.2.2, of the datasheet.

    If you're set on using dedicated supplies for each driver, you'll still need at least 3 isolated voltages. 2 for the high sides, 1 for the low sides. I can't exactly speak to modules, but in this case, we have a reference design which might be of interest to you, using LM25017: http://www.ti.com/tool/PMP10516 . LM25017 has a wide variety of evaluation modules and reference designs for further reading.

    Let me know what you think.

    If this helped answer your question, could you please press the green button?

    Thanks and best regards,

    John Geiger

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

  • 0 in reply to John Geiger
    Prodigy 230 points

    Hi John,

    We don't prefer bootstrap supplies. Hence, need dedicated supplies. Below is my supply requirement. PMP10516 is a good choice, but for the following requirement can you please suggest a better fit (least number of dedicated supplies)? The driver on each half bridge corresponds to UCC21520. 

  • 0 in reply to Lakshmi R21
    TI__Expert 3355 points

    Hi Lakshmi,

    Thanks for sharing this diagram. After interfacing with some of my coworkers, we'd like to recommend looking into LM5030, used as an open loop push pull supply. You can see this device used in the TIDA-00181 reference design, generating isolated rails for IGBT gate drivers. This reference design should still be relevant for this application as well.

    Another option for generating these rails is to use a general purpose PWM controller, such as UC2844, configured as a flyback with multiple output windings. This is a low-cost solution that has been used widely in the industry.

    Since you're planning to operate at 200 kHz/3500W, and need negative bias, I would assume that you're planning on using SiC FETs - correct me if I'm wrong. In this case, you might also be interested in UCC21530. This driver is very similar to UCC21520, but has the added benefit of the DWK package. This package removes the two NC pins between Channel A and Channel B, giving wider ch-ch creepage.

    Feel free to share more on your planned design and main concerns with the proposed bias supplies. Do you also need a recommendation for the 5V rail?

    Thanks and best regards,

    John

  • 0 in reply to John Geiger
    Prodigy 230 points

    Hi John,

    Thank you so much for the recommendations. TIDA-0081 seems a good fit. But we are looking at voltage range of -2V to -5V and since this uses a voltage doubler if I make necessary design changes, the positive rail might go below recommended values.

    I came across TIDA-00174 (TIDU478). Please let me know your opinion about using this reference design. In particular, I wish to know how good the output voltage regulation would be with and without the use of an optocoupler feedback for FlyBuck topology and how does this compare with the performance of a flyback converter.

    Thanks,
    Lakshmi

  • 0 in reply to Lakshmi R21
    TI__Expert 3355 points
    Hi Lakshmi,

    That's an understandable concern.

    This reference design should work as well. Output regulation of a fly-buck with primary side feedback is typically within +/-10%. If the primary side rail is unloaded, it is possible to pull in regulation closer to +/-5%.

    If using an optocoupler for fly-buck feedback, performance will be approximately the same as a flyback with opto-feedback.

    Thanks,
    John