having 2 Computer PSUs in here (parts) , and wanna build my
1st small (about 100watt) car SMPS out of those parts..
parts includes : transformers, KA7500B, DBL494 (=TL494), LM339N SMPS Controllers..etc.
i just need it as simple as possible and gives out the desired
output power..
any help plz??
1st small (about 100watt) car SMPS out of those parts..
parts includes : transformers, KA7500B, DBL494 (=TL494), LM339N SMPS Controllers..etc.
i just need it as simple as possible and gives out the desired
output power..
any help plz??
Find the data sheet for the switchmode controller and design you powersupply based on the one on Elliots site... http://sound.westhost.com/project89.htm substituting in the **494 controller IC.... you will need to buy a pair of mosfets... the transistors used in a computer powersupply are not suitable... you will probably have to rewind the transformer, unless you can come up with a way to use it as it is, but in reverse.... hey, thats a good idea, I'm going to try that some time.. 
you will need to buy a pair of mosfets... the transistors used in a computer powersupply are not suitable...
you'll probably find that those transistors *are* quite suitable, provided you don't expect to run get 250W+ from the PSU
The ones I've taken out of old PC PSU's are all high voltage BJT's rather than FET's - about 450v rated or so. I've used them in the past for high current drivers for coils , and they seem to work fine at 12v levels ( and they cope with the inductive spikes well too...)
you will almost certainly have to rewind the transformer - leave it overnight in acetone and the core will come apart without a fight. don't be tempted to get rough with it 'cos they're very brittle.
I'm currently using one as a high voltage driver for a bike CDI project, it works wonderfully in a 250v 50kHz inverter.
you should have no problem finding any number of xx494 designs to work with.
remember to use fast rectifiers on the output , normal ones will fry at the frequency you'll be running the thing at ( 20kHz+ , or the transformer isn't efficient).
have fun , don't be discouraged by all the components you will probably fry in the design process
check your waveforms on the scope - and then check 'em again.
you can't afford to get things wrong with a SMPS , when they go pop they do it very quicky.
Ray
you'll probably find that those transistors *are* quite suitable, provided you don't expect to run get 250W+ from the PSU
The ones I've taken out of old PC PSU's are all high voltage BJT's rather than FET's - about 450v rated or so. I've used them in the past for high current drivers for coils , and they seem to work fine at 12v levels ( and they cope with the inductive spikes well too...)
you will almost certainly have to rewind the transformer - leave it overnight in acetone and the core will come apart without a fight. don't be tempted to get rough with it 'cos they're very brittle.
I'm currently using one as a high voltage driver for a bike CDI project, it works wonderfully in a 250v 50kHz inverter.
you should have no problem finding any number of xx494 designs to work with.
remember to use fast rectifiers on the output , normal ones will fry at the frequency you'll be running the thing at ( 20kHz+ , or the transformer isn't efficient).
have fun , don't be discouraged by all the components you will probably fry in the design process
check your waveforms on the scope - and then check 'em again.
you can't afford to get things wrong with a SMPS , when they go pop they do it very quicky.
Ray
have alook at
http://www.ee.mut.ac.th/datasheet/tl494.pdf
for a datasheet on the TL494
a Google search should turn up a bunch of designs.
ray
http://www.ee.mut.ac.th/datasheet/tl494.pdf
for a datasheet on the TL494
a Google search should turn up a bunch of designs.
ray
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