I'm looking for a high-efficiency replacement for the LM317.

Thread Starter

saltdoll

Joined Mar 14, 2022
10
A switch mode regulator.
Thank you.
I have considered it, but the switching regulator is troubled by the problem that the circuit becomes somewhat complicated.

The main reason I want to change the LM317 is because of the heat.
 
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dendad

Joined Feb 20, 2016
4,135
LM2596Buck.jpg
Something like these are available on Ebay quite cheaply.
There are many others.
A linear regulator, no matter what the IC in use, will still have the same losses.
 
Last edited:

dendad

Joined Feb 20, 2016
4,135
The regs in post #6 are quite small but have lower input voltage limits than these as in post #4.

LM2596S_Buck.png
And the Ebay price is under $5 for one. That is pretty hard to beat.
Otherwise, the only thing you can do is to try to run the LM317 on lower input volts or use larger heat sinks or a fan.

EDIT: Fot less noise, if that is a problem, install one of these in front of the LM317, and set the switch mode supply output volts to 7V.
 

Thread Starter

saltdoll

Joined Mar 14, 2022
10
The regs in post #6 are quite small but have lower input voltage limits than these as in post #4.

View attachment 262718
And the Ebay price is under $5 for one. That is pretty hard to beat.
Otherwise, the only thing you can do is to try to run the LM317 on lower input volts or use larger heat sinks or a fan.

EDIT: Fot less noise, if that is a problem, install one of these in front of the LM317, and set the switch mode supply output volts to 7V.
The reason I can't use a switching regulator is because of the EMC test.
 

Thread Starter

saltdoll

Joined Mar 14, 2022
10
Well, it is back to a better heat sink.
But, switch mode regs can be made to pass EMC tests ok. Have the tests been done already?
Does your device have a metal case or chassis the LM317 can be mounted on?
Since the equipment (case) has already been completed, it seems impossible to cover the case with limited space.
 

Thread Starter

saltdoll

Joined Mar 14, 2022
10
Well, it is back to a better heat sink.
But, switch mode regs can be made to pass EMC tests ok. Have the tests been done already?
Does your device have a metal case or chassis the LM317 can be mounted on?
Thank you very much for your previous comments.
I'm considering LDO now.
 

Wolframore

Joined Jan 21, 2019
2,541
Linear regulators are very quiet but have an efficiency issue because you are basically burning off the excess voltage/current as heat. If you need higher efficiency your only option is some form of switching convertor. Power supply should never be an afterthought.

An LDO is a linear regulator just like the LM317 is.
 

Thread Starter

saltdoll

Joined Mar 14, 2022
10
Linear regulators are very quiet but have an efficiency issue because you are basically burning off the excess voltage/current as heat. If you need higher efficiency your only option is some form of switching convertor. Power supply should never be an afterthought.

An LDO is a linear regulator just like the LM317 is.
Thank you very much for your comments.
 

dendad

Joined Feb 20, 2016
4,135
I'm considering LDO now.
That will not help at all.
If the input voltage is the same, and the output is still the same power, exactly the same power will need to be dissipated.
A low drop out regulator is used when the input voltage is very close to the output voltage.
It will not help you here.
the only ways to reduce the power dissipation, (assuming the same load), is to lower the input voltage or use a switch mode buck regulator.
 

Thread Starter

saltdoll

Joined Mar 14, 2022
10
That will not help at all.
If the input voltage is the same, and the output is still the same power, exactly the same power will need to be dissipated.
A low drop out regulator is used when the input voltage is very close to the output voltage.
It will not help you here.
the only ways to reduce the power dissipation, (assuming the same load), is to lower the input voltage or use a switch mode buck regulator.
Ah... I see.....
 
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