Flyback transformer design

[ahilis]

Hi, fellow enthusiast!

I am new to EDboard and a newbie to SPMS, and i have difficulties in flyback converter design. If someone could clarify a few things that i don't understand i would be most gratefull.

My idea is to make a FLYBACK converter, for charging a capacitor in my eletric fence design. I have made a flyback converter but i am not sure if it operates according to my needs.

Spceifications for flyback DC-DC converter are:

Vin=12V
Vout=600V
Iprimary=2A (max)
Isecondary=0.2A (max)
frequency=14kHz

I have made a 555 based driver for MOSFET with a duty cycle of approximately 51%. Problem is in flyback transformer design. I have constructed a flyback transformer of E32 ferrite core, N87 material, without airgap. I have wound 10 turns on primary and 115 turns on secondary. When i tested it, the results haven't been satisfaying. I have 120V on secondary instead of 600V and transformer seems to ring (EMI).
I dismantled the transformer and put a layer of eletrical tape on every layer of secondary winding. I also put a lot of attention to formly shape the turns on bobbin. So when a hooked it back for testing, I got 632V on my secondary but my MOSFET got really hot. What am I missing here? Any help would be most welcome.

 

[ahilis]

Anyone?

I have made 2 small transformers. Based on E32 ferrite core. I have tested both but my DC-DC converter can not charge my 50uF 12'Vdc heavy-duty motor cap in 2s. I havbe made transformers from E32 ferrite core, with 0.5mm - 10 turns of primary wire and 0.2mm - 110 turns of secondary wire. I don't have an airgap? Is that a problem? If I add airgap to these transformers, how should I do that? I have read somewhere that a piece of isolating material like cellotape is used for making an airgap.

 

[ahilis]

If I add an airgap, should I increase my primary and secondary turns of the transformer?