voltage regulator

[Lory]

regulator


























































































































































































































































































































































need some help here.
I built a voltage regulator to drop 16 DC V to 8.25 DC V using a LM 317 but I am losing to much power to the heat sink. this is a portable unit.
Any ideas...?
Thanks for any info.
Lory johnson

 

[MikeMl]

You cant violate the Laws of Thermodynamics. The power dissipated in the regulator is (Vin-Vout)*Iload.

 

[ronv]

It may be hot but should be ok. Get a heatsink good for 5 or 6 degrees C per watt and it should run at 100 C. or so at 1.5 amps.

Just don't touch it. :=)

Post the whole circuit. Maybe we can cheat a little.

 

[Lory]

I was just hoping their might be a more efficient voltage regulator out there. the device I am using draws about 800ma and it seems like nearly the same amount of current is going into the heat sink. I was just hoping for a little more run time.

I will just keep the second battery on the charger and do it that way.

Lory

 

[Jon Chandler]

As MikeMI said, the power dissipation in any linear regulator is (Vin - Vout) * Iload. All linear regulators must follow this relationship.

The options are to reduce the voltage drop across the regulator or reduce the current. And use a big heat sink.

The alternative is to use a switching regulator. With the linear regulator, you're dissipating as much power in the regulator as in the load. A switching regulator can improve efficiency to 80 - 90%.

 

[Lory]

Thanks Jon
I looked into a switching regulater and it might be over my head but i have a guru friend that might help me build one.
Thanks
Lory

 

[Jon Chandler]

Here's something that might help you out for less than $10:

**broken link removed**

 

[Lory]

Hi Jon
I looked at #LM2596 and it seemed to output 5 volts only but I need 8.25 volts so I googled ( #LM2596 ) and looked around the net and found (#LM2576/LM2576HV ) which seems to have adjustable output voltage....looks good to me ..?.as long as it comes with instructions. at least it would be good for an experiment.
Lory

 

[Jon Chandler]

Excellent. Glad you found the right thing. I've ordered a number of items from Sure Electronics via ebay and have been very happy with them.