Well, I have wrote earlier in topic called "push-pull SMPS overshoot problem", but now I have completely different PS type and that topic went in other direction.
So I am designing a small DC-DC inverter, whole 5W of power..
Check out schematic and waveforms:
Waveforms as follows:
1. Secondary
2. Primary, first end
3. Primary, second end
4. Primary, center tap after choke
This schematic came from nowhere, I just thought it could work.. And it does!
The problem is, that this is a part of my university's term work and I need lots of theory. I have talked with my project manager (professor in university) and he has no clue how it works... Thats unfortunate.
So now I need some theory to answer these questions (for myself):
1. How does it work _exactly_?
2. When I load it to 5W, frequency decreases in about 30%. Why?
3. How is frequency influenced by transformer's primary? I have noticed, that this SMPS oscillates because of ferrite core saturation. Am I mistaken?
4. Theory on choke calculations?
5. Theory on secondary voltage calculation. Secondary😛rimary ratio has no sense, because everything is in resonance. S😛 ratio says I should get 90V, but there is 150V instead. Burned my fingers a few times...
6. Where does fourth waveform comes from? I mean that absolute value of a sinus.
My observations:
1. Frequency decreases when loaded;
2. Secondary sinewave gets perverted when loaded (resistor);
3. Stability heavily decreases when choke inductance is decreased. With current components it is very stable.
So, any link to useful information would be really appreciated. Useful comments are welcome as well.
So I am designing a small DC-DC inverter, whole 5W of power..
Check out schematic and waveforms:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Waveforms as follows:
1. Secondary
2. Primary, first end
3. Primary, second end
4. Primary, center tap after choke
This schematic came from nowhere, I just thought it could work.. And it does!
The problem is, that this is a part of my university's term work and I need lots of theory. I have talked with my project manager (professor in university) and he has no clue how it works... Thats unfortunate.
So now I need some theory to answer these questions (for myself):
1. How does it work _exactly_?
2. When I load it to 5W, frequency decreases in about 30%. Why?
3. How is frequency influenced by transformer's primary? I have noticed, that this SMPS oscillates because of ferrite core saturation. Am I mistaken?
4. Theory on choke calculations?
5. Theory on secondary voltage calculation. Secondary😛rimary ratio has no sense, because everything is in resonance. S😛 ratio says I should get 90V, but there is 150V instead. Burned my fingers a few times...
6. Where does fourth waveform comes from? I mean that absolute value of a sinus.
My observations:
1. Frequency decreases when loaded;
2. Secondary sinewave gets perverted when loaded (resistor);
3. Stability heavily decreases when choke inductance is decreased. With current components it is very stable.
So, any link to useful information would be really appreciated. Useful comments are welcome as well.
from memory it has a positive feedback system that makes it oscillate. the inductance of the winding and the capacitor across the transformer set it's resonant frequency.
I can send you some theory on it that i have (back issues of magazines).
give me your email address if you are interested.
I can send you some theory on it that i have (back issues of magazines).
give me your email address if you are interested.
Just an FYI regarding the Royer oscillator:
At my place of employment, we have a textbook that talks briefly about the Royer oscillator, and in the schematic in this book, there is a third winding (on the primary side, low number of turns) that controls the two gates of the switching FETs. Your schematic has the gates of the FETs controlled by the primary itself.
Not saying yours is wrong at all, just thought I'd point this out.
At my place of employment, we have a textbook that talks briefly about the Royer oscillator, and in the schematic in this book, there is a third winding (on the primary side, low number of turns) that controls the two gates of the switching FETs. Your schematic has the gates of the FETs controlled by the primary itself.
Not saying yours is wrong at all, just thought I'd point this out.
Yes, I have found some schematics with feedback winding (few with double feedback winding) on the internet, with BJTs. I have modified them o use FETs, then saw that they might work without feedback winding, and finally rid off all diodes and relatively high power (1-2W) resistors to drive BJTs. And you see what has left..rtarbell said:
Can you post a title, year and author of that book? I'll try to find it online or in our local library. Thanks.
Thanks, found it on eMule.rtarbell said:
No idea, I have no way to measure output power.. My "Fluke 177" multimeter does not measure such frequency voltage/current.areza said:
When not loaded, it draws about 45mA (from DC 5V).
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