"Burning off" 9V at 6A

[truenoteno]

I have a 312 watt switchmode power supply that i would like to make use of.

It supplies upto 48V at 6amps.
I would lke to use an LM338 voltage regulator but the max input voltage is 40v. How could I chew up about 9V at 6amps ?
I could only think of having about 13 6A rectifiers but that is too expensive, takes up room and leaves more room for error.

thanks

 

[stevez]

Do the power regulation in steps - take the 48 to 40 volts or so then go from there. My recollection is that the 338 is limited to 5 amps max - as long as you don't exceed power dissapation ratings. It would seem that you could "wrap" a power transistor or two around an LM317 - see datasheet for ideas on that.

 

[bogdanfirst]

how about using a 2n3055 transistor hooked with a zenner diode and another transistor. since the regulation is done with the LM then you dont need to have 40V regulated.
i guess that another solution is to buy 13 diodes rated at 6 amps, or 7 bridge rectifiers.....wich might be cheaper than the diodes.....
i think that the first solution is the best.....
what do you think?

 

[Sebi]

Use L4970 SMPS from ST. It can deliver 10A, but the input also 40V.

 

[Mosfet]

Pre-regulator
Transistor Q1 can be any power NPN similar to a 2N3055 or MJE3055.
Transistors Q2 & Q3 could be TIP31C's, I happen to have a lot of them.
Or Q1 & Q2 could be a power Darlington instead.
Resistor R1 should be a 2 watt package.
Zener diode D1 sets the output voltage and could be lower.
Mount the transistors close by on the same heatsink as your LM338 [electrically insulated].
That way the thermal overload circuit in the LM338 will protect them also.

 

[truenoteno]

thanks for your help