Voltage regulator

[RodneyB]

I have a 40 Volt DC power supply and need to be able to reduce it to 30 Volts. I usually use the LM317T to adjust the voltage but the maximum input voltage of this regulator is 40 Volts which worries me cause its at its max.
Can you suggest a circuit that I can use

 

[jpanhalt]

How much current do you need to supply? Have you tried the parametric search engines at Mouser, DigiKey, etc.? There are several linear regulators that have 60 or 80V limits. Also, many 40-volt regulators will have a rating for short-term overvoltage.

John

 

[RodneyB]

In total I need 2 Amps I was going to switch the current through a power transistor

 

[jpanhalt]

A voltage drop of 10V at 2A is 20W. Have you considered a switching regulator to save on the heat?

John

 

[RodneyB]

In total I need 2 Amps I was going to switch the current through a power transistor

A voltage drop of 10V at 2A is 20W. Have you considered a switching regulator to save on the heat?

John

I would like to try and build on, can yo direct me to a suitable diagram

 

[jpanhalt]

I have used the LM2678 and similar ones in that series. The datasheets give detailed schematics and charts for part selection. Design input is up to 40V; maximum allowable is 45V.

Just go to your supplier (I use DigiKey.com), search on voltage regulator, select switching, and then enter your specifications.

John