EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ant17 on September 02, 2013, 08:19:37 am
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hi in all the time i have been playing around with circuits i have never understood the concepts of current limiting in transistor circuits i want to build a common emitter amplifier switching at about 200hz low frequency at 60volts 1amp now its pretty hard to get a 60watt resistor i don't even know if its the right choice current limiting but what other choices are there maybe inductive reactance a coil i don't know what normal and best way to limit current so it doesn't burn up the transistor if you guys could tell me whats normally the best practice i would be really greatful thanks anthony cosier
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post a basic schematic of what you have at the moment and what you want to drive and what supply you would like to use.
It's not hard to create a 60W resistor... Use either a bigger (100W?) resistor or several smaller ones (3x 25W).
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did attach it but at the moment not able to draw schematics but i attached a circuit similar to that to drive a igbt cm300ha pwrx brick
the bias resistors are 100k at the top a 47k at the bottom and 1k emitter resistor but as for using a load resistor like in the schematic i am not sure do all you guys allways uses power resistor to limit current through a transistor
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For high power applications you probably don't want to use that circuit configuration. Take a look at Shahriar's excellent tutorial here for some hints:
http://thesignalpath.com/blogs/2013/02/04/tutorial-on-the-design-and-characterization-of-class-b-and-ab-amplifiers/ (http://thesignalpath.com/blogs/2013/02/04/tutorial-on-the-design-and-characterization-of-class-b-and-ab-amplifiers/)
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I remember I used a 6.3V/250mA bulb between the emitter and ground of a transistor, in a simple high voltage variable power supply (0-120V) I made years ago. Of course not the best regulation. It had a very soft "knee" but it worked! Maybe you could try one of those 50W halogen bulbs. Normally, the pins on these bulbs takes solder easily.
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Maybe you could try one of those 50W halogen bulbs. Normally, the pins on these bulbs takes solder easily.
However, the operating temperature of such bulbs is way above the melting point of solder. So if the bulb lights up the solder connections will fail...
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Maybe you could try one of those 50W halogen bulbs. Normally, the pins on these bulbs takes solder easily.
However, the operating temperature of such bulbs is way above the melting point of solder. So if the bulb lights up the solder connections will fail...
Permanent current limiting! 8)
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say i wanted to build a transistor circuit that limited the current so the power was limited to 100 watts over the transistor how would something like that be achieved in a single transistor circuit
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hi ant17, posting someone elses schematic and making everyone figure things out from a text description won't engender help from this community.
Why don't you restate what your trying to do a little differently, perhaps?
"I've got an inductive device X (specification here) that I want to switch from a 60v supply at 200Hz. I think that the X will need current limiting at 1A." then avoid opening another thread by saying "could I use an IRS2153?"
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sorry i i have irs2153 but i can measure with the scope on bottom igbt gate drive output and ground a square wave but between vs the top gate drive output i get no signal it does not drive the two cm300ha igbt pwrx so i am wondering if i need a bipolar supply to instead of 60vdc and ground i have attaced a drawing from the datasheet with my comments on values in red which is the values i used in that circuit