12V CT push-pull series secondaries

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E

eseemann

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Joined 2006
#1
this is the test circuit that Im making
-SG3524
-trying current pulse limit (refered on other thread, from Bob Blick circuit)
-trafos are 2X EI33 from AT PSU (inductance measured for test)
each:
PRI= 7+7 turns
SEC = 20+20 turns

40KHz
regulated at +-44V

Is it aparently correct?

thanks!!
 

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#4
Swap the halves of the secondaries on the transformers so if there's an unbalanced load, it would not make an asymmetrical load on the transformers and require them to be derated. (In other words, make each side of the rectifier connect to a secondary on each transformer.)
 
#6
eltonseemann said:
sorry about draw

secondaries of each single trafo is conected, im draw this wrong

each leg of each full-wave rectifier is on one extreme of series secondarie
Click to expand...
Consider what each transformer would see as load if one of the outputs is loaded more than the other. It would become asymmetrical and cause problems.
Connect one transformer with a center tap and split the other transformer so each secondary is in series with each end of the other transformer.
 
#10
PCB broke track

This morning I did find an stupid error on pcb. One colector at sg3524 are not at 12V (broke track at pin 12). The converter was playing on only one leg :bigeyes:. capable of 50W load

Now results are more satisfactory

Im working on current limit, this work well.
I impement an idea found on other thead, thanks Eva, rectifying primary legs to supply driver circuit
 
#12
yeah I will adopt your way.
Supply now absorbs many amperes, drop on cables and connectors was huge. Tests at 150W was OK, but at 300W I experience problems on conectors. Voltage at CT drops to 7.7V🙁
Plastic plug melted.

circuit modified at current sense
 

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#13
Re: PCB broke track

eltonseemann said:

I impement an idea found on other thead, thanks Eva, rectifying primary legs to supply driver circuit
Click to expand...

Your MOSFETs will run cooler due to the reduced Rds-on at higher Vgs, however, be careful to not exceed 20V at the gates under any circumstances.
 
#14
Re: Re: PCB broke track

Eva said:


Your MOSFETs will run cooler due to the reduced Rds-on at higher Vgs, however, be careful to not exceed 20V at the gates under any circumstances.
Click to expand...
20v gate drive is too high for most MOSFETs. Most gate drive circuits work with voltages of 12v or so. However, driving the gates slightly negative when turning off can increase efficiency. (It counteracts stray capacitance that couples the rising drain voltage which slows turn off of the MOSFETs.)
 
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