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

saltdoll

Joined Mar 14, 2022
10
Hello,
I'm looking for a high-efficiency replacement for the LM317.
What will it be?

Joined Feb 20, 2016
4,135
A switch mode regulator.

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.

Last edited:

Joined Feb 20, 2016
4,135

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:

ericgibbs

Joined Jan 29, 2010
15,526
hi salt,
Please post a circuit diagram of the project.
E

Joined Feb 20, 2016
4,135

These too.

saltdoll

Joined Mar 14, 2022
10
hi salt,
Please post a circuit diagram of the project.
E
Here is the LM317 circuit.

Attachments

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Joined Feb 20, 2016
4,135

saltdoll

Joined Mar 14, 2022
10

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.

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.

Joined Feb 20, 2016
4,135
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?

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.

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?
I'm considering LDO now.

saltdoll

Joined Mar 14, 2022
10
hi salt,
Please post a circuit diagram of the project.
E
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.

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.

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.
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.

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.
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.....

DickCappels

Joined Aug 21, 2008
8,710
Power dissipation = Load current x (input voltage - output voltage)

You are stuck.