Low Power 240V AC SMPS <30W flyback or forward?

[Jagd.Panther]

There are 2 other possibilities left which seem interesting, build a half bridge/full bridge smps and the rectify the output to get 100-320V DC by changing DTC.

Yep by saying connect two ATX trafo's together I was referring to this idea. Just add one addtional transformer, an inductor and few diodes with a cap to an ATX power supply and that's all.

Another more interesting option is a pure sinewave inverter which seems close to those variable AC PSU they use in pro labs to build and test smps. Nice ideas to explore for the future.

you can have buck converter with AC output using very little parts. I'll upload a schematic to illustrate an idea in few minutes.

 

[Jagd.Panther]

here are the files.

the PWM modulator could be replaced with an SG3525 and pnp/npn emitter follower could be removed, the high side drivers on the schematic like put them aren't really usefull, and pos/neg cycle detection could be done using a comparator to reduce crossover distortion.

 

[zeus_threat]

Hi sorry for late reply. Thanks a lot for the schematics really useful. I am currently going ahead with my 50Hz version. I have all components lying around and I just did a successful test. The only thing I had to change was to add a voltage regulator in front of the sG3525. By changing the 12V feeding the SG3525 I was able to change the output square wave amplitude. I will post schematic soon.

 

[zeus_threat]

inverter partial schematic

Attached is schematic sorry just started drawing it I need to add some more elements and recheck but at least it gives an idea what am after. If it works out fine i'll put a separate thread on it. most people here as I did test smps using lamps in series some others variac, maybe very few like I did use back to back transformers. In case this can help anyone else it'll be nice.

 

[zeus_threat]

New attempt at flyback

I have gone back to the books and slowly checked out what I was missing. I ended up designing a 12V 1A SMPS using UC3845 . Attached is the simetrix v8.0 file I simulated. Any feedback is welcome.