Hello

What voltage range are you interested in obtaining?

Do you just want to adjust the output to 37 Volts?

Is there a plus or minus limit?

I am not seeing a lot of lm317 circuit examples for output voltages of greater than 37volts due to the lm317's input voltage limit of 40 Volts.

There is a lm317HV version that has a input voltage limit of 60V.

There is also the heatsink problem to contend with.

Well output need to vary between 3 to about 35V,but with my circuit I got 43V which is even better than what I thought it will be!

 

I am not seeing a lot of lm317 circuit examples for output voltages of greater than 37volts due to the lm317's input voltage limit of 40 Volts.

This is incorrect information. Unlike previous generations of three-terminal regulators, the LM317 has no input voltage limit with respect to GND, because it does not have a GND pin. It does have an input-to-output differential voltage limit of 37 V, but that is a very different thing. It is entirely possible to use an LM317 to regulate a bulk DC supply voltage of 923 Vdc with 10 V pp- ripple down to a nice clean 900 Vdc.

ak

 

OK, good to know. I kinda wondered about this.

I do not think we are going to get 3 to 37VDC at 1 AMP out with a lm317 tho.

The TI Data Sheet does say that 40v input is a MAX spec. I was basing my comments upon reading it.

 

The TI Data Sheet does say that 40v input is a MAX spec. I was basing my comments upon reading it.

No, it doesn't. Re-read it. The line item is:

Input-Output Voltage Differential +40 V, -0.3 V

ak

 

Hi Kuki,
This simulation shows a typical variable regulated Vout supply, using a LM317 voltage regulator.
Note what Albert points out regarding the 10meg.

E

And yes,i wanted to ask whats maximum resistance of R3.

 

And yes,i wanted to ask whats maximum resistance of R3.

hi KK,
If you mean the R3 potentiometer in the LM317 circuit I posted, R3 could be set to 0 Ohms, so Vout would be approx 1.25V as stated in the LM317 d/s.
E