Variable Isoltated current source modification

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karnel

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Hello,

I have ~20 year old isolated(output floating on 200V) Filament power supply which I need to replace. Can somebody suggest some schematic using todays components (hopefully more simple). The specs are such:

output 0..3A, user variable with DAC and has to be contriolled, Voltage is about few Volts.
Input Voltage 24V.

Here is picture of old PSU which needs to be replaced.
 

You won't change the transformer isolation. I assume, that the load should be supplied by filtered DC rather than midfrequency
AC, you'll use a PWM controller in any case.

So effectively, SG3524 may be replaced by a device that can directly drive the power stage, either push-pull or single ended.
Or use an integrated low side gate driver. The switching frequency can be optimzed according to the acceptable core size.
No serious changes, anyway. You may want to leave it just as it is.
 

Thats what i want to simplify is the input stage. Any suggestions where to look for more modern drivers?
Also the old transformer is of unknown type so I need to replace it also.
I have been looking in to "Power Over Ethernet" transformer which looks to be of acceptable power rating. For example:

**broken link removed**
or
http://www.coilcraft.com/pdfs/fct1xxm22sl.pdf

Any I deas ca i use them?
 

PoE transformers are usually intended for single ended flyback mode operation. The original device requires a symmetrical
push-pull transformer. As mentioned, single ended would be an option to reduce the overall effort. In the 10 - 20 W power range,
a PWM controller with intgrated gate driver should be sufficient, e.g. good old SG3525 or a newer type. Otherwise a driver
like TC427 can be used. An integrated switch PWM controller (e.g. PoE type) would result in minimum part count.
 

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