MicrosiM
I am glad that you have time to answer my questions. I am total noob this is my first smps and I have to learn a lot.
If you would like give me some ideas and I can test them, the work can go bit quicker. What would you think about protection with resistor at lower mosfet ?
Yes I have managed to get over load protection working, with the short circuit at secondary winding (I am shorting it with set of the car bulbs for safety) the smps is turning off quickly and with no hiss.
With the schematic from post 1 --> the protection was not workin correct, the spikes were causing the smps to oscillate and make the hisss noise.
The key to the success was to put 2.2k resistor in between the gate of thyrystor, and it really maters. The current sense trafo is: 1 turn primary and 2x25 turns secondary, load resistor is 10R but i had to change it with 4,7R (and maybe I will have to reduce 2x25 turns to 2x15 turns and recalculate it) to get higher load capability. The main problem was hiss noise when protection was in action.
The good solution in my opinion would be to connect a small bipolar transistor and mosfet BS170 ''thyrystor wise'' instead MCR100.
I have putted 8R resistor across secondary winding in smps. The mosfet gate resistors I putted 33R
One question:
Does the oscillation present on secondary winding (5,17A load) has to be sorted out --> inductor after diodes or somethin else ??
The filtering cap is 680uF only for now.
I am here to learn and to help as much as I can. I always answer when I have time.
I am glad that you have success with the over current circuit working. How do you reset the SMPS when it enters protection?
I don't like the idea of using resistor at lower mosfet, cos it will not work all the time, some times it will miss, and will cause the SMPS to blow. I tested that years ago.
The only way of testing short circuit is to SHORT the output of the SMPS, also you have to short the SMPS output and then power up, and if those tests passed, then GOOD!
In the last few days, I blown many mosfets testing, the thing that makes me interested into the IR2153 as SMPS controller, it works like magic, but making it as full SMPS is a complex task indeed, Mosfets running cool, Even when the SMPS is loaded 400W, they become just warm. witch is perfect! also its very cheap, very simple. a few parts and you run!
I dont understand the (Hiss sound) you mentioned, why you hear it when the SMPS enters protection? can you upload a small video?
Your waves looks very nice at the 5.17A, I dont think you need to worry about the waves for now, all can be sorted out with Snubbers, witch is last worries.
** Opps, I saw 20.4MHz on scope, I am sure that the oscillation is happening, can you post a picture of your SMPS?
Regards