Generating 48V@50mA from 5V for microphone phantom power...

Discussion in 'Electronic Design' started by Jaye Gallagher, Dec 28, 2004.

  1. Hi there,

    I need to generate a fairly clean 48V at around 50mA to be used for phantom
    power for up to four microphones. The source voltage I need to step up
    somehow is the 5V output of a battery driven DC-DC step up. Whilst I've
    looked around for parts and schematics for this, any help or comments would
    be much appreciated.

    Thanks,
    Jaye.
    Jaye Gallagher, Dec 28, 2004
    #1
    1. Advertising

  2. I read in sci.electronics.design that Jaye Gallagher
    <> wrote (in <41d0d5b3$0$3603$61c65585@un-
    2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    from 5V for microphone phantom power...', on Tue, 28 Dec 2004:

    >I need to generate a fairly clean 48V at around 50mA to be used for
    >phantom power for up to four microphones. The source voltage I need to
    >step up somehow is the 5V output of a battery driven DC-DC step up.
    >Whilst I've looked around for parts and schematics for this, any help or
    >comments would be much appreciated.


    If your 5 V-48 V converter were 100% efficient, you would draw 480 mA
    from your battery. Can you supply a current significantly larger than
    that?
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #2
    1. Advertising

  3. John Woodgate wrote:
    > I read in sci.electronics.design that Jaye Gallagher
    > <> wrote (in <41d0d5b3$0$3603$61c65585@un-
    > 2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating
    > 48V@50mA from 5V for microphone phantom power...', on Tue, 28 Dec
    > 2004:
    >
    >> I need to generate a fairly clean 48V at around 50mA to be used for
    >> phantom power for up to four microphones. The source voltage I need
    >> to step up somehow is the 5V output of a battery driven DC-DC step
    >> up. Whilst I've looked around for parts and schematics for this, any
    >> help or comments would be much appreciated.

    >
    > If your 5 V-48 V converter were 100% efficient, you would draw 480 mA
    > from your battery. Can you supply a current significantly larger than
    > that?


    Hmm. You're right, that's a lot. Perhaps I'm confused about the amount of
    power required for a single phantom power supply? I've seen phantom power
    supplies that claim to power a mic. for 10-30 hours from 2 AA batteries. (Or
    thought I had in my net trawling.)

    I haven't been able to find any hard specs on the current that should be
    available via phantom power. Anyone have any idea?

    Thanks,
    Jaye.
    Jaye Gallagher, Dec 28, 2004
    #3
  4. Jaye Gallagher wrote:

    > Hmm. You're right, that's a lot. Perhaps I'm confused about the
    > amount of power required for a single phantom power supply? I've seen
    > phantom power supplies that claim to power a mic. for 10-30 hours
    > from 2 AA batteries. (Or thought I had in my net trawling.)
    >
    > I haven't been able to find any hard specs on the current that should
    > be available via phantom power. Anyone have any idea?


    Have just trawled around a bit more. Seems that 2mA per mic. is a more
    reasonable estimate of the average current drawn by professional condenser
    microphones. Some draw more, some less (see
    http://www.sounddevices.com/tech/phantom.htm).

    So, let's say that I want a supply circuit that can set up +5V to +48V and
    provide probably around 10mA in total, but have capacity to provide up to
    50mA (if the end-user plugs in power hungry microphones, that's their
    business).

    Thanks,
    Jaye.
    Jaye Gallagher, Dec 28, 2004
    #4
  5. Jaye Gallagher

    Rich Grise Guest

    On Tue, 28 Dec 2004 17:05:30 +1100, Jaye Gallagher wrote:

    > Hi there,
    >
    > I need to generate a fairly clean 48V at around 50mA to be used for phantom
    > power for up to four microphones. The source voltage I need to step up
    > somehow is the 5V output of a battery driven DC-DC step up. Whilst I've
    > looked around for parts and schematics for this, any help or comments would
    > be much appreciated.


    As long as you already have batteries, just get 5X 9V "transistor radio"
    batteries and clip them in series. Voila! 45V painlessly! If 45V isn't
    enough, 6 in series will give you 54V, which you could regulate down
    to 48.

    Good Luck!
    Rich
    Rich Grise, Dec 28, 2004
    #5
  6. Rich Grise wrote:

    >> I need to generate a fairly clean 48V at around 50mA to be used for
    >> phantom power for up to four microphones. The source voltage I need
    >> to step up somehow is the 5V output of a battery driven DC-DC step
    >> up. Whilst I've looked around for parts and schematics for this, any
    >> help or comments would be much appreciated.

    >
    > As long as you already have batteries, just get 5X 9V "transistor
    > radio" batteries and clip them in series. Voila! 45V painlessly! If
    > 45V isn't enough, 6 in series will give you 54V, which you could
    > regulate down
    > to 48.
    >
    > Good Luck!
    > Rich


    Well, I'm hoping to use a single battery source for this device, as it's
    supposed to be portable. Hence the requirement that the 48V be derived from
    my existing 5V supply.

    Thanks anyway, though,
    Jaye.
    Jaye Gallagher, Dec 28, 2004
    #6
  7. I read in sci.electronics.design that Jaye Gallagher
    <> wrote (in <41d0f50d$0$3601$61c65585@un-
    2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    from 5V for microphone phantom power...', on Tue, 28 Dec 2004:
    >John Woodgate wrote:
    >> I read in sci.electronics.design that Jaye Gallagher
    >> <> wrote (in <41d0d5b3$0$3603$61c65585@un-
    >> 2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating
    >> 48V@50mA from 5V for microphone phantom power...', on Tue, 28 Dec
    >> 2004:
    >>
    >>> I need to generate a fairly clean 48V at around 50mA to be used for
    >>> phantom power for up to four microphones. The source voltage I need
    >>> to step up somehow is the 5V output of a battery driven DC-DC step
    >>> up. Whilst I've looked around for parts and schematics for this, any
    >>> help or comments would be much appreciated.

    >>
    >> If your 5 V-48 V converter were 100% efficient, you would draw 480 mA
    >> from your battery. Can you supply a current significantly larger than
    >> that?

    >
    >Hmm. You're right, that's a lot. Perhaps I'm confused about the amount of
    >power required for a single phantom power supply? I've seen phantom power
    >supplies that claim to power a mic. for 10-30 hours from 2 AA batteries. (Or
    >thought I had in my net trawling.)


    That may refer to powering simple electret microphones that draw less
    than 1 mA.
    >
    >I haven't been able to find any hard specs on the current that should be
    >available via phantom power. Anyone have any idea?
    >

    The famous IEC/EN 61938, Table 11. Specification 48 V +/- 4V, maximum
    current 10 mA (per microphone). Typically, the 48 V supply is fed to the
    microphone via two 6.8 kohm resistors that are effectively in parallel.
    Many microphones do not draw as much as 10 mA. but some do.

    There is a significant problem with phantom supplies, even in some
    mixing desks, that have inadequate current capacity. Also, there are two
    lower voltage supplies standardized in IEC 61938 Table 11:

    12 V +/- 1 V, maximum current 15 mA;
    24 V +/- 4 V, maximum current 10 mA.

    The 24 V standard is no longer used, it appears, by any microphone
    manufacturer.
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #7
  8. I read in sci.electronics.design that Jaye Gallagher
    <> wrote (in <41d0f7ff$0$5269$61c65585@un-
    2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    from 5V for microphone phantom power...', on Tue, 28 Dec 2004:

    >Well, I'm hoping to use a single battery source for this device, as it's
    >supposed to be portable. Hence the requirement that the 48V be derived
    >from my existing 5V supply.


    But what is your actual *battery* voltage? It can't be 5 V. If you run
    your 48 V converter directly from the battery you will get a much higher
    efficiency overall.
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #8
  9. John Woodgate wrote:

    >> Well, I'm hoping to use a single battery source for this device, as
    >> it's supposed to be portable. Hence the requirement that the 48V be
    >> derived from my existing 5V supply.

    >
    > But what is your actual *battery* voltage? It can't be 5 V. If you run
    > your 48 V converter directly from the battery you will get a much
    > higher efficiency overall.


    Oh, if I could find a way to step the battery voltage (2.4V, two NiMh cells)
    up to 48V, that'd be ideal, but all of the parts I've looked at so far seem
    to have around 5V minimum input voltages.

    Jaye.
    Jaye Gallagher, Dec 28, 2004
    #9
  10. On Tue, 28 Dec 2004 17:05:30 +1100, in sci.electronics.design "Jaye
    Gallagher" <> wrote:

    >Hi there,
    >
    >I need to generate a fairly clean 48V at around 50mA to be used for phantom
    >power for up to four microphones. The source voltage I need to step up
    >somehow is the 5V output of a battery driven DC-DC step up. Whilst I've
    >looked around for parts and schematics for this, any help or comments would
    >be much appreciated.
    >
    >Thanks,
    >Jaye.
    >

    the feeble phantom, bottom of the page
    http://www.rycote.com/information/default.htm
    gives a lot of P48 info




    martin

    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
    martin griffith, Dec 28, 2004
    #10
  11. I read in sci.electronics.design that Jaye Gallagher
    <> wrote (in <41d1164a$0$3611$61c65585@un-
    2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    from 5V for microphone phantom power...', on Tue, 28 Dec 2004:
    >John Woodgate wrote:
    >
    >>> Well, I'm hoping to use a single battery source for this device, as
    >>> it's supposed to be portable. Hence the requirement that the 48V be
    >>> derived from my existing 5V supply.

    >>
    >> But what is your actual *battery* voltage? It can't be 5 V. If you run
    >> your 48 V converter directly from the battery you will get a much
    >> higher efficiency overall.

    >
    >Oh, if I could find a way to step the battery voltage (2.4V, two NiMh cells)
    >up to 48V, that'd be ideal, but all of the parts I've looked at so far seem
    >to have around 5V minimum input voltages.
    >

    Oh, if you are starting from 2.4V, you have a REAL BIG problem. Have you
    considered social work as a career? (;-)
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #11
  12. On Tue, 28 Dec 2004 12:18:13 +0000, in sci.electronics.design John
    Woodgate <> wrote:

    >I read in sci.electronics.design that Jaye Gallagher
    ><> wrote (in <41d1164a$0$3611$61c65585@un-
    >2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    >from 5V for microphone phantom power...', on Tue, 28 Dec 2004:
    >>John Woodgate wrote:
    >>
    >>>> Well, I'm hoping to use a single battery source for this device, as
    >>>> it's supposed to be portable. Hence the requirement that the 48V be
    >>>> derived from my existing 5V supply.
    >>>
    >>> But what is your actual *battery* voltage? It can't be 5 V. If you run
    >>> your 48 V converter directly from the battery you will get a much
    >>> higher efficiency overall.

    >>
    >>Oh, if I could find a way to step the battery voltage (2.4V, two NiMh cells)
    >>up to 48V, that'd be ideal, but all of the parts I've looked at so far seem
    >>to have around 5V minimum input voltages.
    >>

    >Oh, if you are starting from 2.4V, you have a REAL BIG problem. Have you
    >considered social work as a career? (;-)

    2.4v will be a problem, but some people use PP3's and still get next
    to no life out of them
    http://www.canford.co.uk/commerce/productdetails.aspx?productid=20-752
    quote
    "providing at least 5 hours life (at 2 x5mA microphone current) from
    an alkaline battery."

    That is a miserable performance. Have a long lunch break, and you have
    lost your P48!


    martin

    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
    martin griffith, Dec 28, 2004
    #12
  13. Jaye Gallagher

    Sharptop Guest

    Sharptop, Dec 28, 2004
    #13
  14. Jaye Gallagher

    Tim Wescott Guest

    Jaye Gallagher wrote:

    > Hi there,
    >
    > I need to generate a fairly clean 48V at around 50mA to be used for phantom
    > power for up to four microphones. The source voltage I need to step up
    > somehow is the 5V output of a battery driven DC-DC step up. Whilst I've
    > looked around for parts and schematics for this, any help or comments would
    > be much appreciated.
    >
    > Thanks,
    > Jaye.
    >

    Why pay the efficiency hit twice, one on the 5V switcher and one on the
    phantom power supply? Why not just power the phantom supply straight
    from the batteries?

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com
    Tim Wescott, Dec 28, 2004
    #14
  15. Jaye Gallagher

    Tim Wescott Guest

    Jaye Gallagher wrote:

    > Jaye Gallagher wrote:
    >
    >
    >>Hmm. You're right, that's a lot. Perhaps I'm confused about the
    >>amount of power required for a single phantom power supply? I've seen
    >>phantom power supplies that claim to power a mic. for 10-30 hours
    >>from 2 AA batteries. (Or thought I had in my net trawling.)
    >>
    >>I haven't been able to find any hard specs on the current that should
    >>be available via phantom power. Anyone have any idea?

    >
    >
    > Have just trawled around a bit more. Seems that 2mA per mic. is a more
    > reasonable estimate of the average current drawn by professional condenser
    > microphones. Some draw more, some less (see
    > http://www.sounddevices.com/tech/phantom.htm).
    >
    > So, let's say that I want a supply circuit that can set up +5V to +48V and
    > provide probably around 10mA in total, but have capacity to provide up to
    > 50mA (if the end-user plugs in power hungry microphones, that's their
    > business).
    >
    > Thanks,
    > Jaye.
    >
    >

    You can certainly do this, but you'll pay a cost in efficiency,
    component cost and size -- a switching power supply takes a certain
    standing power whether it's delivering power or not, and that standing
    power generally increases as the design power output of the switcher
    goes up. In addition you'll need larger, more expensive magnetics and
    semiconductors to implement the thing for 2.5W instead of 0.5W -- but
    requirements is requirements.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com
    Tim Wescott, Dec 28, 2004
    #15
  16. Jaye Gallagher

    Tim Wescott Guest

    Jaye Gallagher wrote:

    > John Woodgate wrote:
    >
    >
    >>>Well, I'm hoping to use a single battery source for this device, as
    >>>it's supposed to be portable. Hence the requirement that the 48V be
    >>>derived from my existing 5V supply.

    >>
    >>But what is your actual *battery* voltage? It can't be 5 V. If you run
    >>your 48 V converter directly from the battery you will get a much
    >>higher efficiency overall.

    >
    >
    > Oh, if I could find a way to step the battery voltage (2.4V, two NiMh cells)
    > up to 48V, that'd be ideal, but all of the parts I've looked at so far seem
    > to have around 5V minimum input voltages.
    >
    > Jaye.
    >
    >

    Check for a chip that'll let you power the chip from 5V (small drain)
    and your power section from 1.8V at 1.4A (two NiMh cells in the middle
    of the discharge knee) or 2.0V (two NiMh cells on the leading edge of
    the discharge knee).

    Where do you get your D-size NiMh cells?

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com
    Tim Wescott, Dec 28, 2004
    #16
  17. Jaye Gallagher

    Ben Bradley Guest

    On Tue, 28 Dec 2004 10:08:18 +0000, John Woodgate
    <> wrote:

    >I read in sci.electronics.design that Jaye Gallagher
    ><> wrote (in <41d0f50d$0$3601$61c65585@un-
    >2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating 48V@50mA
    >from 5V for microphone phantom power...', on Tue, 28 Dec 2004:
    >>John Woodgate wrote:
    >>> I read in sci.electronics.design that Jaye Gallagher
    >>> <> wrote (in <41d0d5b3$0$3603$61c65585@un-
    >>> 2park-reader-02.sydney.pipenetworks.com.au>) about 'Generating
    >>> 48V@50mA from 5V for microphone phantom power...', on Tue, 28 Dec
    >>> 2004:


    Gee, that's lots of lines of attribution. Keep reading, my original
    content is further down...

    >>>> I need to generate a fairly clean 48V at around 50mA to be used for
    >>>> phantom power for up to four microphones. The source voltage I need
    >>>> to step up somehow is the 5V output of a battery driven DC-DC step
    >>>> up. Whilst I've looked around for parts and schematics for this, any
    >>>> help or comments would be much appreciated.
    >>>
    >>> If your 5 V-48 V converter were 100% efficient, you would draw 480 mA
    >>> from your battery. Can you supply a current significantly larger than
    >>> that?

    >>
    >>Hmm. You're right, that's a lot. Perhaps I'm confused about the amount of
    >>power required for a single phantom power supply? I've seen phantom power
    >>supplies that claim to power a mic. for 10-30 hours from 2 AA batteries. (Or
    >>thought I had in my net trawling.)

    >
    >That may refer to powering simple electret microphones that draw less
    >than 1 mA.


    And that's different from the phantom power standard, it's usually
    called "bias power" and is used for electret condenser mics plugged
    into soundcards and minidisc recorders with their 1/8" miniphone
    connectors, as well as in built-in mics for telephone answering
    machines.

    >>I haven't been able to find any hard specs on the current that should be
    >>available via phantom power. Anyone have any idea?
    >>

    >The famous IEC/EN 61938, Table 11. Specification 48 V +/- 4V, maximum
    >current 10 mA (per microphone). Typically, the 48 V supply is fed to the
    >microphone via two 6.8 kohm resistors that are effectively in parallel.
    >Many microphones do not draw as much as 10 mA. but some do.


    A few microphones may have a center-tapped transformer output,
    which would effectively ground both resistors (these of course should
    not have phantom power applied, but that's another topic). This would
    give 14mA per microphone, or 42mA total if three such microphones are
    plugged in (thus the OP's 50mA spec isn't too far off for absolute
    worst-case conditions). Also, each of these 6.8k's will be dissipating
    0.34 watts with the full 48V across them, so it's a good idea to use
    1/2W resistors.

    >There is a significant problem with phantom supplies, even in some
    >mixing desks, that have inadequate current capacity. Also, there are two
    >lower voltage supplies standardized in IEC 61938 Table 11:
    >
    >12 V +/- 1 V, maximum current 15 mA;
    >24 V +/- 4 V, maximum current 10 mA.
    >
    >The 24 V standard is no longer used, it appears, by any microphone
    >manufacturer.


    Some mics are designed to work over the 12V to 48V range, but there
    may be lower performance at 12V.

    -----
    http://mindspring.com/~benbradley
    Ben Bradley, Dec 28, 2004
    #17
  18. I read in sci.electronics.design that Ben Bradley <ben_nospam_bradley@mi
    ndspring.com> wrote (in <>)
    about 'Generating 48V@50mA from 5V for microphone phantom power...', on
    Tue, 28 Dec 2004:

    Jaye Gallagher wrote:

    >>>Hmm. You're right, that's a lot. Perhaps I'm confused about the amount of
    >>>power required for a single phantom power supply? I've seen phantom power
    >>>supplies that claim to power a mic. for 10-30 hours from 2 AA batteries. (Or
    >>>thought I had in my net trawling.)

    >>
    >>That may refer to powering simple electret microphones that draw less
    >>than 1 mA.

    >
    > And that's different from the phantom power standard, it's usually
    >called "bias power" and is used for electret condenser mics plugged into
    >soundcards and minidisc recorders with their 1/8" miniphone connectors,
    >as well as in built-in mics for telephone answering machines.


    No-one claimed that it was the same as *standardized* 48 V phantom
    power. Some such mics are powered on the unbalanced signal conductor,
    some have 'A-B' phantom power.
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #18
  19. I read in sci.electronics.design that Tim Wescott
    <> wrote (in <.
    com>) about 'Generating 48V@50mA from 5V for microphone phantom
    power...', on Tue, 28 Dec 2004:

    >Where do you get your D-size NiMh cells?


    I think 'Flag' size cells would be better!
    --
    Regards, John Woodgate, OOO - Own Opinions Only.
    The good news is that nothing is compulsory.
    The bad news is that everything is prohibited.
    http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
    John Woodgate, Dec 28, 2004
    #19
  20. On Tue, 28 Dec 2004 17:15:25 GMT, Ben Bradley
    <> wrote:

    >On Tue, 28 Dec 2004 10:08:18 +0000, John Woodgate
    ><> wrote:
    >>The famous IEC/EN 61938, Table 11. Specification 48 V +/- 4V, maximum
    >>current 10 mA (per microphone). Typically, the 48 V supply is fed to the
    >>microphone via two 6.8 kohm resistors that are effectively in parallel.
    >>Many microphones do not draw as much as 10 mA. but some do.

    >
    > A few microphones may have a center-tapped transformer output,
    >which would effectively ground both resistors (these of course should
    >not have phantom power applied, but that's another topic). This would
    >give 14mA per microphone, or 42mA total if three such microphones are
    >plugged in (thus the OP's 50mA spec isn't too far off for absolute
    >worst-case conditions). Also, each of these 6.8k's will be dissipating
    >0.34 watts with the full 48V across them, so it's a good idea to use
    >1/2W resistors.


    It's possibly a bad idea to use 1/2W resistors, as these aren't
    usually available in the close tolerances required. The match (but
    not the actual value) of the two resistances needs to be very
    accurate.

    It is possible to make up the desired power rating by using a number
    of lower powered precision resistors in parallel or series.

    Regards,
    Allan
    Allan Herriman, Dec 29, 2004
    #20
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