Alternative Transistors for LM317 High Current Voltage Regulator Circuit

Thread Starter

sribasu

Joined May 10, 2017
18
Hi,
I am referring the below circuit diagram to make a High Current Linear Voltage Regulator circuit. This circuit is given in LM317's datasheet.


I need the regulator circuit to handle no more than 5 AMP Output Current. I find TIP73 a little overestimate for this current. Moreover, I do not have this transistor handy. For 5 AMP output, what would be the alternatives for TIP73 and 2N2905 transistors in this circuit?
Can I replace them with 2N3055/TIP3055 and TIP42/MJE2955 respectively? Would 2N3055/TIP3055 cause any interference to the LM317 to regulate the output voltage?
 

Thread Starter

sribasu

Joined May 10, 2017
18
Yes your selection of alternative transistors will work just as well.
Thanks Dodgydave for your response. I have a followup question. I am new to Electronics. I learned the other day that 2N3055 has high leakage, so do I need to attach a load everytime (just like the one shown in the diagram) to measure the output voltage?
If yes, what is a practical value and wattage rating of the recommended load resistor to use when measuring the output voltage?
 

crutschow

Joined Mar 14, 2008
27,755
Make sure the 3055 is mounted on a good heatsink as it will dissipate ≈(Vin-Vout)*Iout watts.

Also that circuit is not short-circuit protected.
 

bertz

Joined Nov 11, 2013
327
Hi,
I am referring the below circuit diagram to make a High Current Linear Voltage Regulator circuit. This circuit is given in LM317's datasheet.


I need the regulator circuit to handle no more than 5 AMP Output Current. I find TIP73 a little overestimate for this current. Moreover, I do not have this transistor handy. For 5 AMP output, what would be the alternatives for TIP73 and 2N2905 transistors in this circuit?
Can I replace them with 2N3055/TIP3055 and TIP42/MJE2955 respectively? Would 2N3055/TIP3055 cause any interference to the LM317 to regulate the output voltage?
The circuit shown will NOT be able to handle 5 amps! In fact it will not even handle 3 amps. You need at least two pass transistors in parallel mounted on a hefty heat sink with fan cooling as shown in the attached photo. The TO-3 case has much better heat dissipation capability than the TO-220.
As Crutschow correctly points out this circuit has no short circuit protection or current limit capability. I suggest you take the time to view this tutorial on power supply design.
DSC00277.JPG DSC00341.JPG
 

Picbuster

Joined Dec 2, 2013
1,027
Hi,
I am referring the below circuit diagram to make a High Current Linear Voltage Regulator circuit. This circuit is given in LM317's datasheet.


I need the regulator circuit to handle no more than 5 AMP Output Current. I find TIP73 a little overestimate for this current. Moreover, I do not have this transistor handy. For 5 AMP output, what would be the alternatives for TIP73 and 2N2905 transistors in this circuit?
Can I replace them with 2N3055/TIP3055 and TIP42/MJE2955 respectively? Would 2N3055/TIP3055 cause any interference to the LM317 to regulate the output voltage?
It is, due to efficiency, not useful to use linear power supplies above the 1 Amp.
Advice use a step down see TI's step down pages call simple switches one coil few cap and two resistors.

Picbuster
 

Tegra

Joined May 18, 2017
2
I agree with Picbuster, linear supplies are out of date. A small switcher will be smaller, cheaper to build and actually save a substantial amount in power consumption. (Saving even 1 watt will save $1 a year, your circuit will likely "waste" $20 a year)

T
 

Thread Starter

sribasu

Joined May 10, 2017
18
Thanks for replying. Unfortunately I can't use a SMPS for my purpose. I got it working with 2N3055 transistor TO-3 package along with a TIP2955 (I know I could have chosen a smaller one).
Thank you all for responding to my question. I really appreciate your help!

I made a PCB layout of LM317 power supply. Sharing it here, if it helps anyone else!
 
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