The circuit we use makes use of Linear Technology's LT3080 (www.linear.com) which consists of a three- and five-terminal regulator available in both TO-220 and SOT-23 enclosures and has a low voltage drop. Its input can reach 40 V and the voltage drop displayed in the drive is only 300 mV. In the figure we have the practical circuit of application. The Rset resistor has typical values in the range of 100 k ohm to 300 k ohm.
