01-08-2015, 08:39 AM
Nick (surrey) I've just been looking at the LM317 data sheet, apparently it's a floating device so that means it can be used for HT regulation, but only over a certain voltage range, that range is governed by it's maximum voltage differential rating (voltage difference between Vin & Vout) for a bog standard LM317 it's 40 volts, there is a higher differential voltage version the LM317HV which has a maximum voltage differential rating of 60 volts.
A wider range of HT voltage can be obtained by tying the LM317 up with a pre regulator, TI (Texas Instruments) do a notes sheet for it in the link below, it shows a variable HT supply with an output range of 1.2 volts to 160 volts at 25 ma, if the minimum voltage setting could be increased then that might give a voltage range more suited for plotting valve characteristics if a voltage of more than 160 volts is required, the output current can be increased above 25 ma if needed as per the TI notes.
http://www.ti.com/lit/an/snva583/snva583.pdf
Food for thought.
Lawrence.
A wider range of HT voltage can be obtained by tying the LM317 up with a pre regulator, TI (Texas Instruments) do a notes sheet for it in the link below, it shows a variable HT supply with an output range of 1.2 volts to 160 volts at 25 ma, if the minimum voltage setting could be increased then that might give a voltage range more suited for plotting valve characteristics if a voltage of more than 160 volts is required, the output current can be increased above 25 ma if needed as per the TI notes.
http://www.ti.com/lit/an/snva583/snva583.pdf
Food for thought.
Lawrence.
