- #1
girts
- 186
- 22
Hi, I was thinking about smps power supplies and for the record I have built a few myself, so normally in a more powerful smps you want to implement a PFC stage for both "grid health" and efficiency, although I assume usual linear supplies with a mains transformer and a bridge rectifier with filter caps at the secondary also suffers the same problems and would benefit a PFC stage? I do realize it would be impossible to implement such a stage because the input AC isn't rectified into DC.Now my main question is this, and it basically asks can something like that work and has it been tried.
So Instead of having the usual rectifier and filter caps at the smps input and then chopping up the DC to make a high frequency pulse AC to feed into the ferrite transformer, can't I just take the input bridge rectifier and then take it's output which would be in the form of half sine waves and put that directly into a switch (MOSFET/IGBT) which is driven with a carrier wave frequency and then feed this signal into the transformer?
The idea is essentially much like AM modulation, the AC sine wave has low frequency so would be of no use for a small smps transformer, but if I chop up the sine wave into individual peaks and feed those into the transformer I have achieved pulsed operation of the transformer so now at the secondary I can put a capacitor across the windings and since the time inbetween the fast pulses would not be enough to discharge the capacitor I would get back a 50hz sine wave.My idea is basically that since such an approach uses equally every part of the sine wave that would increase efficiency and would not require additional PFC stage or filter caps, the drawback that I can think myself is that the transformer would need to be larger for the same power because rectified DC pulses have all equal potential while here the individual pulse potential is dependent on its place in the sine wave.
I would like to hear some comments about this idea, thanks
So Instead of having the usual rectifier and filter caps at the smps input and then chopping up the DC to make a high frequency pulse AC to feed into the ferrite transformer, can't I just take the input bridge rectifier and then take it's output which would be in the form of half sine waves and put that directly into a switch (MOSFET/IGBT) which is driven with a carrier wave frequency and then feed this signal into the transformer?
The idea is essentially much like AM modulation, the AC sine wave has low frequency so would be of no use for a small smps transformer, but if I chop up the sine wave into individual peaks and feed those into the transformer I have achieved pulsed operation of the transformer so now at the secondary I can put a capacitor across the windings and since the time inbetween the fast pulses would not be enough to discharge the capacitor I would get back a 50hz sine wave.My idea is basically that since such an approach uses equally every part of the sine wave that would increase efficiency and would not require additional PFC stage or filter caps, the drawback that I can think myself is that the transformer would need to be larger for the same power because rectified DC pulses have all equal potential while here the individual pulse potential is dependent on its place in the sine wave.
I would like to hear some comments about this idea, thanks