Silvio
Well-known member
Dear Members I have been experimenting with SMPS for quite a while now but I have found that when choosing output inductors a few problems occurred especially regarding voltage drop and the output inductor getting hot.
I have been using Excellent IT during my design for half bridge topology and this states the value of the output inductor according to the minimum load and also its value if the smps is being regulated or not. This will change to a higher value if the smps is regulated
I also learnt that the output inductor has to be AIR GAPPED in its construction of the material used.
My experience so far is that I noted considerable voltage drop and one has to allow quite some headroom in the output voltage to compensate for this being in the region of 25% Choosing the right core and its size comes somewhat difficult at times as some compromises has to be dealt with regarding minimum load and maximum voltage drop allowed at full load, and also the size of the core as these tend to get rather hot. When they do it may seem that they will tend to change their value and I don't really know if they tend to saturate or not.
There are a lot of different ferrite cores available on line but choosing the right one comes to get me scratching my head and could not make up which is the right one
My Questions.
1) How can I determine the right core physical size for the output inductor according to the output current?
2) Having a split output say 50-0-50v is it best to have a single ring core (common mode choke) or a separate core for each leg?
3) Why these core get so hot when loaded at high current say 8-10 amps?
4) Is it best to wind these core with Litz wire or solid enamel copper wire?
5) Any suggestions regarding color code and frequency of operation SMPS normally are working in the region of between 20 and 150Khz more or less?
6) Can anyone suggest where can I get hold of some kind of chart or list specifying material and what is it suitable for etc?
Regards, Silvio
I have been using Excellent IT during my design for half bridge topology and this states the value of the output inductor according to the minimum load and also its value if the smps is being regulated or not. This will change to a higher value if the smps is regulated
I also learnt that the output inductor has to be AIR GAPPED in its construction of the material used.
My experience so far is that I noted considerable voltage drop and one has to allow quite some headroom in the output voltage to compensate for this being in the region of 25% Choosing the right core and its size comes somewhat difficult at times as some compromises has to be dealt with regarding minimum load and maximum voltage drop allowed at full load, and also the size of the core as these tend to get rather hot. When they do it may seem that they will tend to change their value and I don't really know if they tend to saturate or not.
There are a lot of different ferrite cores available on line but choosing the right one comes to get me scratching my head and could not make up which is the right one
My Questions.
1) How can I determine the right core physical size for the output inductor according to the output current?
2) Having a split output say 50-0-50v is it best to have a single ring core (common mode choke) or a separate core for each leg?
3) Why these core get so hot when loaded at high current say 8-10 amps?
4) Is it best to wind these core with Litz wire or solid enamel copper wire?
5) Any suggestions regarding color code and frequency of operation SMPS normally are working in the region of between 20 and 150Khz more or less?
6) Can anyone suggest where can I get hold of some kind of chart or list specifying material and what is it suitable for etc?
Regards, Silvio