Tiny 1:50 Transformer Help

Discussion in 'Power Electronics' started by airplane100000, Sep 1, 2016.

  1. airplane100000

    Thread Starter Member

    Aug 2, 2016
    I am in need of an extremely flat transformer for a pcb project I'm working on, to step-up voltage.
    I have the following transformer: http://www.coilcraft.com/LPR6235.CFM (The 1:50 version)

    I would like to know how to best utilize it.
    I have only had success modeling it in the simulator with the flyback converter scheme:

    My Questions are as follows:
    1. Is my example in the image above good use of the transformer, as in, are there any changes that should be made to improve output/efficiency.
    2. Why is my negative peak lower than my positive peak...I can't seem to solve this.
    3. At what frequency should this transformer run at? The datasheet says tested at 100khz, but it doesn't give a range. How can I estimate what the lowest/highest frequency would be, and how would it effect performance?
    4. I understand the isolation voltage to be the maximum allowed difference between primary and secondary voltage. What happens if I exceed this? What if it is only or a brief moment?
    5. What should the cap values be in the above example? Just from my own testing, when I put the cap on the secondary in resonance with the inductance listed in the datasheet and the given frequency, it works best. For the primary capacitor I just put a random value...
    6. And lastly, does anybody know of a similar small transformer that can be used to achieve better results (My goal being highest current through the load)?

    Assistance with any of these points is much appreciated.
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    1-There is something wrong with the voltage on the FET and the 5 volt signal.
    There is no feedback to control the voltage.
    2. maybe the input as statated above?
    3. I think below the self resonant frequency.
    4. arcs and sparks.
    Take a look at this one. Flyback converters can be difficult.
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
  4. ScottWang


    Aug 23, 2012
    The ntb30n20t4g was designed for the high voltage as 200V and the current 30A, this kind of mosfet always has a higher Rds(sat), if you want to using the low voltage to drive the transformer then you can using logic level Vgs as 4.5V, but you didn't mention the current, so I can't give you the properly number of mosfet.