Silvio, is 10V enough for IRF740 or IRFZ44N to fully turn-on (0.25 ohm for IRF740 and 0.014 for IRFZ44N) ?
Regarding the drive circuit looks very promising and it should be tried in practice for real results.
As for the EI 33 core well it says you should widen the gap and this would lower the inductance of the core. An inductance meter will surly help you here as you can measure the primary inductance and adjust the gap accordingly until the required inductance is achieved.
I have seen videos on Youtube of Robert Balanos doing this method. This guy is a principal reserch engineer and designs SMPS for NASA. He is a very professional person and knows a lot about the subject but he also uses a lot of math and its a bit hard for me to understand at times. If you are patient enough you can see some of his videos. He is very calm and the videos are quite long.
Cheers Silvio
I suggest you download Excellent IT software from diysmps there is a chap named Starichock51 The forum name is called Calculation programs for transformers and inductors
I bought an EE55 core from Aliexpress for a reasonable price.
What I do myself is when I get hold of used cores from old equipment I simply try to look at the pcb where it came from and take note of the oscillator chip. Then I read the resistor capacitor value and make up the frequency it was operating with. This will give me a good guide of the number of turns per volt for a particular frequency.
I get my ETD49 from a broken smps. Yes it has windings and I need to find a way to open it.
I will not use the ready-made primary because there are many windings and I don't know which one is it.
These are bargains:
->click<-- 10 sets = 10$ -> you can get cheap 200W @ 350khz for 1$
->click<-- 5 sets = ~17$ -> you can get cheap 1kW @ 250khz for ~3$ (vertical)
->click<-- 5 sets = ~17$ -> you can get cheap 1kW @ 250khz for ~3$ (horizontal)
but its not said what exactly is:
is it:
- ER 32 / 21 / 11
or its:
- ER 32 / 20 / 11
Too many questions at one go lol
1) Try boiling the core for 5 min see if the resin looses a little bit. (Remove the outer binding tape on the core first). If this would not work try your mum's oven heat the core to around 130 deg celcius and with a pair of gloves or thick cloth grab the cores and try to separate them. Be careful do not go beyond 150 degrees as you ruin the core material. If it does not work either try immersing the core in Acetone or cellulose thinner for 24 hrs. All this is to try to dissolve the varnish which is gluing the core together. Sometimes they put super glue to hold the cores but this should give away with heat.
2) If you still have the old smps try to follow the traces and see which pins where on the half or full bridge mosfets / transistors etc
3) To decide which core it is 32/20/11 or 32/21/11 These are the dimensions of the core. Measure carefully the core and you will know. You can surly judge a 1mm difference.
As for the trafo turns please give more detail of the transistors you are going to use, output diode, your mains voltage at home (the usual you measure) The actual power needed for the amplifier you are going to use. The drive chip.
Try not to go beyond 100Khz with the switching frequency as you will experience a lot of switching losses from your fets.