vainajala

TINA Pro didn't have it :( But I'll try one more program: 5Spice

Ante: I'm downloading TINA Pro demo version, I'll have to check if it has the model...

Ante: I thought that too, but I don't have the program. Do you know some good simulation program?

[move]this is off-topic[/move] At school we tried to "fry" some cheap LEDs with a 30V / 4A supply, some leds sent nice smoke signals, but some even exploded! Of course that wasn't very wise, but entertaining indeed ::)

Ante, Yes, it just a matter of how short time they are illuminated. But what if somehow the circuit fails and continuos 2A goes through the LEDs... :-X

I made the circuit with Eagle and modified it a bit. I have some MJ15004 transistors, so I'll propably use one of those Diode is ultrafast type, rated at 200V/8A Most propably I'll take the inductor from an old PC power supply I only hope that the Hfe of MJ15004 is high enough (about 25)... maybe I should try darlington connection? If you notice any errors, please tell me and I'll try to fix ;)

Luxeon Star LEDs driven by some sort of oscillator circuit like in Ante's attachment might be really powerful! :) These are the only LEDs i know with up to 5 watt of power capability, too bad that they are very expensive... :P

Thank you very much! :) Yes, i was aware that after rectifying and filtering the voltage might be too high for the IC to handle. However I found this picture in the datasheet, which is the solution:

Hi all, I thought about building a power supply for a thermoelectric (peltier) cooler element, which maximum power is 122W @ 15,7V (~7,8A). I have a toroidal transformer whose ratings are 300VA and 2x35VAC, so dropping the voltage from about 40VDC (or something, I don't know the exact voltage which comes from the transformer after rectifying&filtering) to around 12-14 volts would most propably produce tremendous amount of heat to the linear pass transistor(s)... (40V-13V) * 6,5A = 175,5 W of heat if i calculate correctly. That could make good heater though :) So I started planning a switching power supply. TL494 might be good choice as a controller IC, so i downloaded the datasheet and started designing with EAGLE... Only problem is that the circuit presented in the datasheet has output voltage of +5VDC and current capability of 200mA. I understand that the output voltage and current are both "sensed" by the TL494's on-board operational amplifiers, which control the PWM "chopping" process... changing resistor values might do the trick! I think that by changing the resistor values, switching transistor, output coil, capacitors and the current sense resistor would solve my problem. Would someone give me some advice ??? TL494's page: http://www.onsemi.com/site/products/summary/0,4450,TL494,00.html