what is the easiest and cheapest method for 13 -50V to 10V, conversion

DC voltage from SMPS

 

At what current?

 

below 100mA

 

The easiest way (and the least efficient) is with a LM7810 1A voltage regulator.

https://www.fairchildsemi.com/produ...ositive-voltage-linear-regulators/LM7810.html

50V is too high for this device but you could put a suitably rated 20V zener diode in series with the input to bring the voltage within range. A heatsink will also be required to dissipate the power.

 

With a 20 V zener it will not operate at 13 V in.

ak

 

Hello,

You could have a look at the LM317HV.
This may have an input voltage of 60 Volts.
If you want to go higher, look at the TL783.
This may have an input voltage upto 125 Volts.

See the datasheets for more info.

Bertus

 

With a 20 V zener it will not operate at 13 V in.

ak

Good point, I conveniently ignored the lower voltage limit