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UCC27211: H bridge application where the same driver keeps failing

Jerry Frank97
Prodigy 220 points
Part Number: UCC27211
Other Parts Discussed in Thread: LM5101A

Hello,

Please look at the attached circuit. U5 gets hot and fails. U4 seems to be functioning normally.

Measured dead time is 35 ns.

Frequency of operation is 125 kHz.

+BRIDGE voltage = 48V. 

16VDC supply for the UCC27211 is clean with less than 2V of ripple.

C9 and C10 are DC blocking caps to prevent core flux walking. Test load is 2700 ohms.

I would be grateful for any insight.

Thanks!

  • 0
    TI__Mastermind 21965 points
    Hello Jerry,
    I am an application engineer supporting the UCC27211 and will work to help resolve your concerns.
    I reviewed the datasheet of the IRFL4315 looking at the gate charge, and the 1st comment I have is to review the HS to HB capacitance.
    The LM5101A datasheet give guidance on selecting the bootstrap and VDD capacitance. The link is www.ti.com/.../lm5101a.pdf
    Section 9.2.2.1 gives guidance on selecting the bootstrap capacitor.
    First you determine Qtotal including MOSFET Qg and driver quiescent current. Qtotal=Qg + IHBS(Dmax/Fsw)
    Which is Qtotal= 19nC + 0.1mA(.5/125kHz)= 19.4nC
    Then determine Cboot by total charge and allowable HB cap voltage drop.
    Cboot=Qtotal/deltaVHB. For 1V drop on HB Cboot would be 19.4nF, 2V Cboot would be ~10nF.
    I would recommend increasing C4 and C5 from 5600pF to at least 22nF which will result in less HB capacitor voltage drop from charging the MOSFET gate charge.
    This may help with the issue and recommend testing.
    If this does not help with the issue, I would need to see some scope plots to assist further.
    Can you record HO, LO and HS of each driver U4 and U5 to be able to examine the driver and switch node timing?
    Record on plot with several switching cycles, and record other plots with the timing zoomed in to see the LO and HO switching transition details, and dead time.

    Regards,
    Richard Herring
  • 0 in reply to Richard Herring
    TI__Guru**** 189399 points
    Hi Jerry,

    It's been a while since we've heard from you, so we must assume you've resolved your issue.

    If possible, please post how it was resolved for others to learn from.

    If not, let us know, and we will work with you to resolve it.