300w mains inverter
Avalanche, Sat Aug 19 2006, 05:01PMHopefully this won't be one of those projects that I end up scrapping as soon as I get it half working.
Anyway I'm aiming for about 300 watts at 230VAC RMS out of this thing, and I also want to add somekind of regulation as the input voltage will be anything between 11 and 13.8 volts.
Once I get the regulation working, I hope to add some finishing touches like over/under voltage shutdown, low battery alarm etc.
So far I have built the transformer, 5 turn primary and 55 turn secondary for roughly the right voltage output with 12 volts into the halfbridge. I'll need to use a GDT on the halfbridge, a bit like an sstc. I suppose I should have made the primary multi filar, but I didn't, it's just 1 thick wire wound round 5 times. Hopefully this won't hurt the efficiency too much. The secondary is 2 filar and should be good for 300 watts, and the core is from a monitor smps.
I've started this mainly so that you lot can point out all the mistakes I make as it's my first real smps project
Re: 300w mains inverter
Wilson, Sun Aug 20 2006, 06:27AM
btw, with monitor cores, don't they have a large air gap in the centre leg? I was under the impression that you wanted minimal air gaps in the core with half bridges, as the gap is there for use in flyback topologies?
Wilson, Sun Aug 20 2006, 06:27AM
btw, with monitor cores, don't they have a large air gap in the centre leg? I was under the impression that you wanted minimal air gaps in the core with half bridges, as the gap is there for use in flyback topologies?
Re: 300w mains inverter
Avalanche, Sun Aug 20 2006, 11:01AM
Yes the core does have a rather large air gap, I wonder if it would be worth filling it with thin steel or something?
I'm going to have to rewind the transformer anyway, not making very fast progress here
I've decided that I want to use a center tapped multi filar primary to simplify the primary drive a bit, and hopefully increase efficiency.
Avalanche, Sun Aug 20 2006, 11:01AM
Yes the core does have a rather large air gap, I wonder if it would be worth filling it with thin steel or something?
I'm going to have to rewind the transformer anyway, not making very fast progress here
I've decided that I want to use a center tapped multi filar primary to simplify the primary drive a bit, and hopefully increase efficiency.Re: 300w mains inverter
Steve Conner, Sun Aug 20 2006, 12:36PM
Why not just use the transformer out of an ATX PC power supply as is? After all you're pretty much doing the opposite of what the PS does
I remember trying one with the ZVS flyback driver circuit and getting good results. I used the big heavy centre tapped winding that would normally be the 5V output, as my centre tapped primary, and rectified what used to be the winding driven by the half bridge. I used a voltage doubler rectifier and got about 300V DC.
Steve Conner, Sun Aug 20 2006, 12:36PM
Why not just use the transformer out of an ATX PC power supply as is? After all you're pretty much doing the opposite of what the PS does
I remember trying one with the ZVS flyback driver circuit and getting good results. I used the big heavy centre tapped winding that would normally be the 5V output, as my centre tapped primary, and rectified what used to be the winding driven by the half bridge. I used a voltage doubler rectifier and got about 300V DC.
Re: 300w mains inverter
Avalanche, Sun Aug 20 2006, 01:55PM
I suppose I could, thinking about it Problem is I can't seem to find any decent ones, they are all tiny compared to this core which is 50mm tall 
The amount of hours I've spent prattling about with this one, might as well finish it
Avalanche, Sun Aug 20 2006, 01:55PM
I suppose I could, thinking about it
Problem is I can't seem to find any decent ones, they are all tiny compared to this core which is 50mm tall The amount of hours I've spent prattling about with this one, might as well finish it
Re: 300w mains inverter
Marko, Sun Aug 20 2006, 05:28PM
Airgap may just make trouble making primary leakage inductance too big. Driven in push-pull you would probably blow your mosfets with overvoltage.
I bet ATX can work as is, driven push-pull with good regulation.
You can double the output to get a better voltage match.
Marko, Sun Aug 20 2006, 05:28PM
Airgap may just make trouble making primary leakage inductance too big. Driven in push-pull you would probably blow your mosfets with overvoltage.
I bet ATX can work as is, driven push-pull with good regulation.
You can double the output to get a better voltage match.
Re: 300w mains inverter
Pihkal, Sun Sept 24 2006, 12:02AM
If you're gonna use a ATX transformer,you'll end up with high frequency AC.
If i understand correctly it supposed to be 230 VAC 50Hz.
Allthough you never specified the output frequency i'm asuming it's 50 Hz.
Greets
Pihkal, Sun Sept 24 2006, 12:02AM
If you're gonna use a ATX transformer,you'll end up with high frequency AC.
If i understand correctly it supposed to be 230 VAC 50Hz.
Allthough you never specified the output frequency i'm asuming it's 50 Hz.
Greets
Re: 300w mains inverter
Marko, Sun Sept 24 2006, 12:17AM
Pihkal,
Output of ATX transformer is first rectified into 320VDC and then chopped with a fullbridge of mosfets into 220V RMS at 50Hz.
Marko, Sun Sept 24 2006, 12:17AM
Pihkal,
Output of ATX transformer is first rectified into 320VDC and then chopped with a fullbridge of mosfets into 220V RMS at 50Hz.
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