Probably...
I would probably put one on the source of the upper FET and another on the drain of the lower FET. This way you catch a short during each half cycle. Since the currents are 180 degrees out of phase (forces the core to reset) you can use 1 CT transformer and pass both wires through the center of the CT. Be sure you phase the current through the wires correctly so that the directions oppose and the core can reset during each cycle. Use a UF diode brdge to add the burden resistor to the output.
The cheapest OCP latch I can think of would be a TL431 as a voltage reference and a comparator with a diode across the feed back to latch the comparator one it trips. Normally I would use a FET latch with a DIODE/cap as hold up tomake sure everything stays off after a trip.
You can also use the TL431 itself as the Comparator/Voltage reference and add an external two transistor latch (this is what I normally do).
Good luck.
I would probably put one on the source of the upper FET and another on the drain of the lower FET. This way you catch a short during each half cycle. Since the currents are 180 degrees out of phase (forces the core to reset) you can use 1 CT transformer and pass both wires through the center of the CT. Be sure you phase the current through the wires correctly so that the directions oppose and the core can reset during each cycle. Use a UF diode brdge to add the burden resistor to the output.
The cheapest OCP latch I can think of would be a TL431 as a voltage reference and a comparator with a diode across the feed back to latch the comparator one it trips. Normally I would use a FET latch with a DIODE/cap as hold up tomake sure everything stays off after a trip.
You can also use the TL431 itself as the Comparator/Voltage reference and add an external two transistor latch (this is what I normally do).
Good luck.
Hello.
I read all these 31 pages. Built a SMPS. The one is almost this: http://www.diyaudio.com/forums/attachment.php?s=&postid=1660581&stamp=1226919676
I have a problem, the switching with no load (80ohm load resistor) is like a sine wave in about 150Khz.
My specs:
f=50Khz
Vin=220Vac
core=4.6 cm2
prim=19 turns
sec= 3+3
2x mur460 fets
ir2110 driver and sg3525
Vout=~14V
Its an automotive ps.
First, i though it should be some slow diodes I had used. But I changed with no improvement.
Any idea?
I read all these 31 pages. Built a SMPS. The one is almost this: http://www.diyaudio.com/forums/attachment.php?s=&postid=1660581&stamp=1226919676
I have a problem, the switching with no load (80ohm load resistor) is like a sine wave in about 150Khz.
My specs:
f=50Khz
Vin=220Vac
core=4.6 cm2
prim=19 turns
sec= 3+3
2x mur460 fets
ir2110 driver and sg3525
Vout=~14V
Its an automotive ps.
First, i though it should be some slow diodes I had used. But I changed with no improvement.
Any idea?
There is a 470pF and 47ohm resistor in primary.
I did the transformer myself, this really can be the problem!
It's 4 cores EI33 same widding. Maybe my turns are wrong because wrong data or something. I'll take some pics. I just blow up more 2 IRFP460 and one IR2110.
The sine really disapear when I used a 8ohm load, but it drove that fets to heaven in 2 or 3 seconds. I thought about dead time, there is 33ohm resistor like the link I posted, but don't know what to do anymore.
I did soem testes with series lamp, and with load, the lamp starts to turn on, (of course) but there ware some noises that I dont know if it is right.
Some TEC TEC from transistors.
Thanks Chas and Luka for reply.
I did the transformer myself, this really can be the problem!
It's 4 cores EI33 same widding. Maybe my turns are wrong because wrong data or something. I'll take some pics. I just blow up more 2 IRFP460 and one IR2110.
The sine really disapear when I used a 8ohm load, but it drove that fets to heaven in 2 or 3 seconds. I thought about dead time, there is 33ohm resistor like the link I posted, but don't know what to do anymore.
I did soem testes with series lamp, and with load, the lamp starts to turn on, (of course) but there ware some noises that I dont know if it is right.
Some TEC TEC from transistors.
Thanks Chas and Luka for reply.
http://www.qrp4u.de/docs/en/smps_new/
I built mine with an ETD39 core.
Loaded it up to 25A (with fan cooling) and it looks OK.
However, if you're going to use a larger core, the number of turns suggested will not be suitable!
I built mine with an ETD39 core.
Loaded it up to 25A (with fan cooling) and it looks OK.
However, if you're going to use a larger core, the number of turns suggested will not be suitable!
Some pics:
Primary:
Sec1:
Sec2:
Is that sine normal?
Just bought other pair of IRFP460 and took these pics.
I had to rewind the trafo.
Now I changed the core, I'm using just a 1cm^2 Ae toroid. Just to make some tests. Can this core burn the fets?
Before, I was using 4 cores EI33 from ATX PS. Now, learning calculations about cores.
Thanks for repling
Primary:
An externally hosted image should be here but it was not working when we last tested it.
Sec1:
An externally hosted image should be here but it was not working when we last tested it.
Sec2:
An externally hosted image should be here but it was not working when we last tested it.
Is that sine normal?
Just bought other pair of IRFP460 and took these pics.
I had to rewind the trafo.
Now I changed the core, I'm using just a 1cm^2 Ae toroid. Just to make some tests. Can this core burn the fets?
Before, I was using 4 cores EI33 from ATX PS. Now, learning calculations about cores.
Thanks for repling
Now with 10ohm gate resistors.
470ohm dead time
irf840 (cheapper!!!!!!!!!)
Forgeting about ringing... I'm wating my ETD59 core from internet!
With 15A load, output rectifiers ware a problem.
One of them blow up. Maybe not sharing current correctly?
Burned fets, IR2110 and primary bridge rectifier.
It was 4 schottky diodes, MBR2045 in paralel, just one failed.
I thought it could be more than 45V because my output inductor ware made without any measurement and calculations.
Now i'm building a indutance meter.
Please advice!
470ohm dead time
irf840 (cheapper!!!!!!!!!)
Forgeting about ringing... I'm wating my ETD59 core from internet!
With 15A load, output rectifiers ware a problem.
One of them blow up. Maybe not sharing current correctly?
Burned fets, IR2110 and primary bridge rectifier.
It was 4 schottky diodes, MBR2045 in paralel, just one failed.
I thought it could be more than 45V because my output inductor ware made without any measurement and calculations.
Now i'm building a indutance meter.
Please advice!
