loxly
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Hi everyone,
I had to design and construct flyback and forward converters for my Power Electronics course project. After testing and measurements the flyback converter is working like a charm, but I have some issues regarding my forward converter.![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Here are some specs:
Input voltage 25V
Primary to secondary windings ratio 1:1
Primary to tertiary windings ratio 2:1
Duty cycle 0.5
Output inductor 1.2 mH
Output capacitor 690 uF
Output resistance 47 Ohm
Switc frequency 100 kHz
According to my calculations (and Simplorer simulations) MOSFET voltage waveform in stationary state should be:
but instead, scope measurements showed this
As you can see, the voltage spikes are definitely too high, and the thing is that spikes are getting higher as I'm raising duty cycle and lower as I'm lowering it. That shouldn't happen! Changing duty cycle should only vary spikes width, not the amplitude.
So I'm asking You, what could be the problem?![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I ruled out some possible issues like not properly connected tertiary winding or inductor issues.
I'm suspecting the primary leakage inductance is too high. Transformer was wounded by hand. I don't have protective RCD circuit cause I thought I wouldn't need one
(and most of them don't have it in practice as I have seen)
Please help
Thank you in advance![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Lovro
I had to design and construct flyback and forward converters for my Power Electronics course project. After testing and measurements the flyback converter is working like a charm, but I have some issues regarding my forward converter.
Here are some specs:
Input voltage 25V
Primary to secondary windings ratio 1:1
Primary to tertiary windings ratio 2:1
Duty cycle 0.5
Output inductor 1.2 mH
Output capacitor 690 uF
Output resistance 47 Ohm
Switc frequency 100 kHz
According to my calculations (and Simplorer simulations) MOSFET voltage waveform in stationary state should be:
![](https://obrazki.elektroda.pl/14_1341141509_thumb.png)
but instead, scope measurements showed this
![](https://obrazki.elektroda.pl/24_1341141509_thumb.jpg)
As you can see, the voltage spikes are definitely too high, and the thing is that spikes are getting higher as I'm raising duty cycle and lower as I'm lowering it. That shouldn't happen! Changing duty cycle should only vary spikes width, not the amplitude.
So I'm asking You, what could be the problem?
I ruled out some possible issues like not properly connected tertiary winding or inductor issues.
I'm suspecting the primary leakage inductance is too high. Transformer was wounded by hand. I don't have protective RCD circuit cause I thought I wouldn't need one
Please help
Thank you in advance
Lovro