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A question about LED Driver Snubber circuit

None_feiyu
Expert 1320 points

HI Ti,

    I can understand how Snubber circuit it works,but I have question about this:

   Q1: We know the Snubber circuit is composed of  RF Diode (BAP65-02)and Zener diode(DDZ10BSF-7), which takes away all the ringing energy from the circuit by clamping the voltage.

    I want to konw when ringing voltage exceed the clamping voltage,so at that time,it will have same current flow into the ILLUM_HEX_LED. The ILLUM_HEX_LED is the dcdc output,so it seem like the current either flow into ILLUM_HEX_LED or flow output ILLUM_HEX_LED. all right?

   Thanks&Regards

    None

  • 0
    Expert 1320 points
    Hi Ti,

    Is there anyone can help me solve this problem.

    Thanks&Regards

    None
  • 0 in reply to None_feiyu
    TI__Intellectual 1680 points
    Hi None

    The snubber circuit consists of the RF diode and the 330pF capacitor. Zener diodes are usually slower. Zener diode clamps the node to a voltage as you interpreted. So we are getting a part of the ringing energy back by doing this.
  • 0 in reply to Nithin Jose
    Expert 1320 points
    Hi Nithin,

    thanks.

    so the snubber circuit can reduce the speed of the voltage of the Laser diode,for protect the laser.

    Thanks&Regards
    None
  • 0 in reply to None_feiyu
    TI__Intellectual 1680 points

    Hi None

    Laser diodes are very sensitive to reverse voltage. Here the energy stored in parasitic inductance of the lasers can cause a reverse voltage across the lasers before the mosfet turns on . Also the cds of the mosfet and parasitic inductance can cause ringing. Also the ringing peak voltage can reach a value beyond the absolute maximum voltage for the lasers. The snubber circuit used in the CDK protects the lasers from all these problems. Laser diodes are used to operate at very high speeds, so the speed of voltage across them is fairly lower than their capability.