Diode Pin Connections Inquiry!

Discussion in 'General Electronics Chat' started by smock, Dec 7, 2011.

  1. smock

    Thread Starter New Member

    Jan 29, 2011
    5
    0
    Hello, I have what might be a dumb question. I'm creating a dc converter based on something that I saw here: http://reipooom.files.wordpress.com/2011/09/boost-converterfixed.png
    I'm using different parts including an NTE6240 (http://www.dz863.com/datasheet-810603963-NTE6240_Silicon-Rectifier-Super-Fast-Dual-Center-Tap/) for the diode. I'm not sure if I am connecting it properly. this diode has 3pins. I connected the negative pin (pin 3) to the drain of a mosfet and pin 2 was connected to a cap which is connected to ground. I left pin 1 unconnected.

    Can someone please tell me if that's a correct connection?

    I appreciate any help that I can get.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Sure, that's fine.

    Here is NTEinc's datasheet for the NTE6240 and NTE6244:
    http://www.nteinc.com/specs/6200to6299/pdf/nte6240_44.pdf

    Just a word to the wise:
    NTE Inc does not make their own components. When a manufacturer is getting close to shutting down production on a particular IC, NTE may commission a run with their own markings on them. That way when the part is obsolete, NTE can charge a much higher price for the item.

    I frequently see NTE's parts being priced at anywhere from 2x to 20x the price of an original part.
     
  3. smock

    Thread Starter New Member

    Jan 29, 2011
    5
    0
    Hi

    Thanks for your response. However, I still don't know if i connected it properly. Should I be connecting pin 1 to the drain of the mosfet or pin 3? that's my question. I ask this because i'm having problems with my converter.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You can connect BOTH pins 1 and 3 to the drain, and pin 2 to the cap.

    You didn't tell us about the rest of the circuit; you said you changed some parts.

    It would be best if you marked up the schematic (you can use MS Paint if you'd like) and post the updated version, so we have a better idea of what is going on.

    Having accurate and complete schematics available for review will help get your problem solved much more quickly.

    Also, it will help a great deal to have photos of how your circuit is laid out.

    I'll also say that if you're trying to build this on a breadboard, you will likely have a very hard time getting it to work. Breadboards are not good for high frequency things like this.

    I see that L1 in the schematic is 120uH. With that size inductor, you will need to have your PWM frequency be in the neighborhood of 40kHz to 60kHz, and be operating at 50% duty cycle or less for starters. If you try to operate at too high a duty cycle with a low-rated inductor, the inductor can "saturate" and you will overheat the inductor and your MOSFET.

    For an inductor, being saturated means that the core cannot hold any more magnetic energy, and it's inductance suddenly drops way off; it appears to almost be a short circuit.
     
  5. smock

    Thread Starter New Member

    Jan 29, 2011
    5
    0
    Thanks a lot. It's pretty much the same circuit as I posted except that for the mosfet driver, I use a UCC27424 instead of the MIC4421.
    Also, I've always thought the breadboard would work especially since that experiment also uses a breadboard. I guess I will have to use a PCB or something.
    also, my PWM frequency is about 31000. I'll put up a circuit once I try it all out and still have questions.
     
Loading...