DC Voltage Regulators for 400VDC....

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

  1. Link555

    Link555 Well-Known Member

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    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

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    "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

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    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

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

    Link555 Well-Known Member

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    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.

    Cheers

    Ian
     
  7. Link555

    Link555 Well-Known Member

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

    rmburrow Active Member

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    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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