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LM5160: Isolated IGBT Gate-Drive Fly-Buck Power Supply with LM5160

Yi-Lin
Intellectual 545 points
Part Number: LM5160

Hi,

I am developing Three-Phase Inverter Gate Drive circuit.

I design the Isolated IGBT gate drive power following TIDA-00199 reference design, but changing Zener diode "BZX84J-B15,115" to "BZX84-B15".

Schematic is down below:

The output of secondary side will got a strange ripple (about 1V).

 

C1 is the SW output of LM5160

C2 is the voltage between PB15 and PB-8 ( Measured by isolated voltage probe)

How can I reduce this ripple?

Does diode "BZX84-B15" cause this problem?

Thanks a lot

Yi-Lin

  • 0
    TI__Mastermind 35080 points
    I am not sure that its the diode as the are very slight differences between the two diodes in question. It could be caused by the layout? It is unlikely Did you follow the layout of the ref desgin? Do you see a strange ripple on the primary? If so, the issue can be related to the ripple injection on the primary/Noise? Can you try reducing C73 from 10nF to 4.7nF?
  • 0 in reply to David Baba
    Intellectual 545 points

    Hi David

    Sorry for late reply.

    I reduce C73 to 4.7nF.

    I measure the SS pin of LM5160 and Vout(C80) on primary side.

    The strange ripple exist  on primary side.

    Picture 1: Before reducing C73 to 4.7nF

    Signal 1: Vout(C80) on primary side

    Signal 2: SS pin of LM5160

    Picture 2: After reducing C73 to 4.7nF

    Signal 1: Vout(C80) on primary side

    Signal 2: SS pin of LM5160

    Yi-Lin

  • 0 in reply to Yi-Lin
    TI__Mastermind 35080 points
    Is your supply loaded? Can you measure the primary side inductor current by placing a loop on the primary side of the inductor?
  • 0 in reply to David Baba
    Intellectual 545 points

    Hi David,

    C79 and C80 are electrolytic capacitor, will this cause the problem?

    I change C79 to 10uF and add a 22uF Tantalum capacitors on Vout of primary side

    The ripple of Vout on primary side can be reduced

    C1: Vout on primary side(C80)

    C2: SW pin of LM5160

    But sometime the LM5160 will be unstable, with multiple ON-time bursts followed by a long OFF-time.

    I add a dummy load 2k Ohm resistor the primary side.

    and the circuit works  

    Thanks a lot

    Yi-Lin