12V push pull SMPS

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#86
two stupid questions

is possible drive a mosfet gate whith a pull-down low resistance <100R and PNP to 12V which base at open colector at tl494??

is possible make a push-pull converter whitout isolation between pri and sec, earth at center-tap and 12V at primaries extremes. Secondaries = primaries plus more turns in the same wire - self-transformer??. Gate drive via gate trafo in this case??

hihihi
 
#88
What simulation software do you use if I may enquire? Lets assume you did not have this software or any other software would you still know how to calculate the filters?
Click to expand...

Good tutorial about push-pull SMPS by National Semiconductor is here

Wery good FAQ about SMPS

Compleate answer about software simulation of SMPS
I tried hard to find the POWER 4-5-6 program, but all my attempts finished unsucsessful...
For simulation of some stages of SMPS or other analog or digital stuff I`m using Altium Designer 6 for analog, and Proteus 7.2 for sirquits with microcontrollers.
 
#89
😀
Hi Luka

I did use a snubber between the primary windings. I followed the procedures outlined by Ray Ridley as to measuring the ringing frequency with a scope and then calculating the components needed.

His suggestions were not to far off albeit I had to play around with component types and values.
 
#92
What about raising the frequency to 100khz or higher to avoid saturation?

Also, if you get a larger toroid core, would that help?


Also another idea I was thinking about was dual toroids, with each it's own rectifiers, then parallel after the rectifiers.....

BTW GREAT job on your SMPS!!!

Also, check out these MOSFETS from OnSemi.... TO264, over 120A a piece!!! :hot: 😱 :hot:
https://www.onsemi.com/PowerSolutions/product.do?id=NTY100N10
 
#93
Check IRF2907Z and other parts from IR. On-Semi doesn't seem to have real high performance stuff for this application. TO-264 parts are not recommended due to the higher package inductance, a pair of TO-220 works better.
 
#94
EWorkshop1708 said:
.....Also another idea I was thinking about was dual toroids, with each it's own rectifiers, then parallel after the rectifiers.....

BTW GREAT job on your SMPS!!!

Also, check out these MOSFETS from OnSemi.... TO264, over 120A a piece!!! :hot: 😱 :hot:
https://www.onsemi.com/PowerSolutions/product.do?id=NTY100N10
Click to expand...

The NTY100N10s are brutes! 100A drain current and only 9mW Rds(on)! Be careful driving them- they have over 10,000pF gate capacitance! Use a PWM chip with high-current totem-pole outputs, or a separate driver buffer between the PWM chip and the MOSFETs.

Toroids: Each primary should be driven by its own MOSFET pair, while the secondaries can be connected in series (now no longer a center-tap) before the output rectifiers, forcing equal current-sharing. I will try to attach an image of said power stage as soon as the server problem uploading the pic disappears.

Steve
 
#98
what i can get from this troid

i have a 40mm outer diameter troidal core.
what would be the best swithching fr. and max. power assuming the primary is 5+5 with 5x0.5mm(diameter) wire and secondary 11+11 3x0.8mm wire. the core data is here
troid data
or can you reccomend any of the catalog on this site

cheers
 
#100
Well,

in the article of ESP project89 it is mentioned that a core with 4cm diameter and cross section of about 1 cm2 is suitable for around 200-250W continuous RMS so mine is with the same diameter, but larger cross section(window area) 1.28 cm2. it should be slightly more powerful i guess???
and what about the primary. are 5x0.5 mm diameter wires not enough for about 30A current (max power)???

Cheers
 
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