Measure all diodes. If they are ok . But if I am not mistaken your secondary main caps are mounted with wrong polarity!
Acca and all,
If I use double stack EI33 for the output traffo, is the no ot turns still the same per original schematic? (first post). I'm thinking of squeezing roughly 600w and by using TV Horizontal output transistor (TO-247).
Secondly, increasing the output voltage would mean disassembling the original core to add more turns to the secondary winding, am I correct?
Regards,
Albert
If you stack a couple of cores then your trafo becomes bigger and need less number of turns for the primary (volts per turn will be larger) If for example you have one EI 33 core which have 50 turns for the primary then for a couple this number will reduce nearly by half. Do not just half the number as then you have to work out the Cross sectional area (csa) of both trafo stacked together and a new calculation has to be made according to the frequency of operation and the new csa of the trafo. The copper wire csa has to be suited to the new current handling in the primary and secondary current. The secondary turns will be calculated according to the new number of turns in the primary and taken proportionally according to the volts per turn.
For all this you have to disassemble both trafos make a new bobbin to suit the new size and yes you have to rewind it.
Regards Silvio
Hello Albert, If I am not mistaken the gate drive trafo has not been touched and it is one pulled out of an ATX power supply. You only have to play with the feedback winding on the main trafo it could be 2 or 3 turns just check it out on the tread. Try to reverse the polarity from the feedback going to the gate drive. Recently someone was playing with the same circuit and found that R2 was getting hot. it could be that a lot of voltage drop is present on it but this value has to be found out by trial and error as gate transformers vary a little from one another. See that you have adequate voltage around 10v-15v supplying the gates during operation.
Good luck Silvio
Hello Albert, If I am not mistaken the gate drive trafo has not been touched and it is one pulled out of an ATX power supply. You only have to play with the feedback winding on the main trafo it could be 2 or 3 turns just check it out on the tread. Try to reverse the polarity from the feedback going to the gate drive. Recently someone was playing with the same circuit and found that R2 was getting hot. it could be that a lot of voltage drop is present on it but this value has to be found out by trial and error as gate transformers vary a little from one another. See that you have adequate voltage around 10v-15v supplying the gates during operation.
Good luck Silvio
Hello Albert, An ETD 49 is rather a large transformer, and a lot of power can be absorbed from it. At 40Khz you can get 700-900 watts. I do not know if you know the number of turns you have in the primary of the etd49 or you just found it ready made.
I will make some assumptions for you but these may vary as I do not know yet the number of turns in the primary of the etd49
Let us assume you have 20 turns in the primary winding and the switching frequency is 45Khz. The topology used in the circuit is half bridge so half the mains voltage is arriving at the primary winding. The rectified and smoothed voltage is around 310vdc and we will have half of it so we have around 155v.
The turns per volt is 155v / 20 turns = 7.75v per turn. So every turn in the trafo is carrying 7.75v.
I am doing this to calculate the feedback winding voltage. So more or less you will be needing more or less 2 turns in the feedback to get 15.5v
Now we come back to the gate transformer. This is rather a small ferrite ring that you are using and somehow the turns ratio in the trafo will be more as this has a much smaller cross sectional area. However we can use a little less but we have to be careful as there will be a lot of current in it. This is why we use the resistor is series to limit the current.
I do not know what ring are you using but let us say you use 30 turns to carry this voltage. So your ring will have 3 wires in parallel twisted together first then you wind 30 turns with them on the ring. Use different colors for the wires so that you don't mix them up. You will take one wire for the primary. and the other 2 for the gates one for each fet.
Be careful as one of the secondaries must have a different phase according to the other secondary wire. Put a series resistor with the primary of the feedback winding to limit current going to the gate drive trafo as shown it the schematic. Start with a 100 ohm first and see what you get. You can gradually decrease until you have enough voltage at the gates with minimum current.
I hope you understood well. You can experiment with different number of turns in feedback winding say you can try 3 but this will add another 7v to your voltage and hence you will be needing a larger resistor. There is not much room to play with turns as the volt per turn is rather high on the main trafo.
You can also use enameled copper wire of say 0.2mm to wind your gate trafo but be careful as you have a high voltage difference between the high side fet and ground. if the windings tend to short with one another BOOM. See if you can find some kind of telephone wire which is thin and has insulation on it. If 30 turns do not fit in the ring that you have try with less turns. These are only assumptions and 30 turns may be too much.
Make some reserch about gating transformers maybe you can find information how to make them and what material (wire) is suited best for them.
Good Luck in your experiments and please be careful when playing with grid voltage.
Regards Silvio