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Constant Current Source

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prasad_newaskar

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Friend please help me for making a constant current source circuit.
I have 2 make a CC source which can provide constant current though variations in temprature occurs(Parameters-Current can be adjustable between 0-1A, variation in temp can be 25degree to 90 degree, voltage should change according to temp. to achieve const. currrent)...
 
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Have you considered using the LM117 or LM317 configured in a current mode? The data sheet gives a few examples. Read the linked to data sheet.

Ron
 
This sounds like a homework / schoolwork assignment. If you want to approach building a constant current source using discreet components I suggest you start looking at circuits using an operational amplified driving a transistor. You make no mention of why the use of a LM317 would not be practical?

Current can be adjustable between 0-1A, variation in temp can be 25degree to 90 degree, voltage should change according to temp. to achieve const. currrent)...

Convert the voltage out from a temperature sensor to drive the input of an op-amp that in turn drives a transistor. You will likely need a linear voltage change as opposed to temperature.

Ron
 
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Thank u so much Ron. This is very helpful for me....
Can u please tel me which transistor 2 use for following specificaton.
Collector Current Ic= 50mA
Vmax= 350volts
Power dissipation= 150Watts
 
I saw your other thread. I am sorry but now with this:

Collector Current Ic= 50mA
Vmax= 350volts
Power dissipation= 150Watts

I do not know what you are trying to do? Initially I assumed incorrectly a low voltage current source of 0 to 1 Amp. Now I have no idea exactly what you are trying to do?

Ron
 
50mA at 350V is only 17.5W, not 150W.
For 150W, you must use many transistors, a huge heatsink and maybe a fan, not just one transistor.
For 150W at 350V then the current is 429mA, not just 50mA.
 
Sounds like an off-line mains PSU? For LED driving maybe? There are better ways to get a regulated 50mA current than running direct from rectified 240v mains!
 
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