I'm trying to build a +/- 150V battery powered DC power supply variable power supply.

I have two of these 150V nixie power supplies: http://desmith.net/NMdS/Electronics/NixiePSU.html

And was thinking about putting two of them in series, and setting ground to the middle which gives me -150V and +150V. I would then feed these into two IRF740A MOSFETs (same as those used in the PSU). The IRF740s would then receive an external control voltage to control the output. In my mind the MOSFETs kind of work as a voltage divider. Here is the basic schematic:


Does this idea make sense? What have I missed?

  • \$\begingroup\$ You're going to fry those MOSFETs. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 23 '14 at 3:19
  • \$\begingroup\$ @IgnacioVazquez-Abrams thanks for you comment? But why? They are rated to 400V (VDS). \$\endgroup\$ – new299 Oct 23 '14 at 3:22
  • \$\begingroup\$ Yes, but they're only rated to 125W. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 23 '14 at 3:22
  • \$\begingroup\$ @IgnacioVazquez-Abrams ah, I only plan to draw maybe 5mA. But in this configuration will they end up dissipating more? I don't fully understand. \$\endgroup\$ – new299 Oct 23 '14 at 3:25
  • \$\begingroup\$ You may end up drawing only 5mA from the output, but in order to do so some current will have to go through the divider. I suggest you be very careful about your control voltages. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 23 '14 at 3:28

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