Adding current boost to voltage regulator TL783

[jhanus]

Hi,

I found at my local shop voltage regulator TL783 (http://www.ortodoxism.ro/datasheets/texasinstruments/tl783.pdf), it can regulate from 0-125V, I can't use any other regulator because my input voltage is 40VDC.

Problem is that this regulator from characteristics can only deliver around 700mA output at input-to-output voltage differentials of 25 V, but I need 3A.

So can somebody help me to add current boost like it's done here (http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm#317pass.gif), under title "LM317T Voltage Regulator with Pass Transistor".

In datasheet there is circuit for current boost, but I would prefer method above.

How to calculate this components would be of great help, because there is high probability that I can't buy the same transistors.

Thank you.

[audioguru]

The TL783 has a dropout voltage of about 12V. So current-boosting transistors must be paralleled to be able to dissipate the high amount of heat.

[jhanus]

Thanks for response,


Let say that I will be satisfied even if I get 1.5A at 10V (40VDC-30VDC).

Can you put equation for calculating current-boosting transistors or schematic?!