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DC Voltage Regulators for 400VDC....

Discussion in 'Electronic Repair Modifications DIY' started by Link555, Apr 6, 2010.

  1. Link555

    Link555 Well-Known Member

    What are some of your favourite circuit for this voltage?
    Has anyone used the Linear Regs like the Supertex inc. LR8?
  2. Boswell

    Boswell Moderator Distinguished Member

    "Favourite" is stretching things a bit - I don't like precision regulating at this voltage unless I really have to. The LR8 does a good job up to 10mA of output current, which is enough for the V+ in most double-triode circuits, but not enough for a power stage. One thing I have done is to float a medium-voltage regulator up to a high potential, but you have to be very careful to surround it with diodes so it does not get overvoltage under startup/shutdown or fault conditions.

    Apart from valve (tube) HT supplies, the majority of designs I have done at this voltage have been in the input end of direct off-line switching power supplies. In these cases, you are dealing in phase-controlled high frequency FET switching, for which there are reference designs and a whole raft of available devices for the purpose.
  3. Link555

    Link555 Well-Known Member

    Thanks for the info!

    There are a lot of options in the switching power supply world, and with proper filtering they work quite well. However I am interested in linear regulation at this point.
  4. Boswell

    Boswell Moderator Distinguished Member

    That's odd - I thought you had said something about a double triode, but maybe I dreamed it.
  5. Link555

    Link555 Well-Known Member

    I thinking of 12AX7 based pre-amp, but I will need a lower rail for that. Most older designs I see do not use a regulator on the plate supply, however a few newer design use switchers, but I never seen a linear regulator on the plate supply, although I am sure someone has done it.
  6. ruffrecords

    ruffrecords Guest

    I like the Texas TL783. Works OK for phantom power too.


  7. Link555

    Link555 Well-Known Member

    783 is good for more than 125v?
  8. rmburrow

    rmburrow Active Member

    Preamp regulator: Look in the UTC transformer catalog; there are schematics of tube type regulated power supplies for tube gear. For low current "cheap and dirty" using gas filled regulator tubes, two 0D3 and a 0C3, all in series, will regulate 20 ma or so at 405 v....a series resistance from unregulated HT to the VR-tube string is required. The value of the series resistor depends on the unregulated DC supply voltage, and the sum of the maximum VR-tube current and the load.

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