Transformerless power supply

Discussion in 'Electronics Resources' started by hany, Aug 29, 2008.

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  1. hany

    Thread Starter New Member

    Aug 29, 2008
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    hi all during searching for files talking about Transformerless power supply
    i found this good files


    link removed by moderator

    enjoy
    [​IMG]

    i hope to be active member
     
    Last edited by a moderator: Sep 24, 2008
  2. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    In my oppinion, transformerless powersupplies are pretty dangerous.
    They are directly connected to the mains.
    If a series capicitor fails and makes a short the mains will get on the output.

    Greetings,
    Bertus
     
  3. frechetn

    New Member

    Sep 14, 2008
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    Thanks Hany! I have been looking for something of this nature for some time now.

    I would have to agree with bertus that these types of power supplies can be dangerous. However figures 10 and 11 do try to address those saftey concerns a some degree.

    Thanks
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Be careful -that application note shows a 470 uF capacitor connected between the Line and Ground! A sure fire way to cause a fire, or at least blow a fuse (you are going to use a fuse or two, aren't you?).

    I suspect that L and N got reversed, but I leave it to the experts to explain.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    These are VERY DANGEROUS circuits, and should NOT be built! They are not correct!
    Figures 1, 5, 10, 11 and 12 are all in error!

    L1, or 120VAC, will be connected directly to the output, and the "virtual ground" will be floating at about 5v less.

    It is not simply a matter of reversing the L and N inputs to correct the errors.

    This is the worst application note I have ever read in my entire life.

    [eta]
    I have put in a technical request ticket on Microchip's website, requesting them to withdraw the application note pending review.
     
    Last edited: Sep 24, 2008
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    From the very first page of the document under discussion:
    Is your life and safety really worth less than the cost of a transformer?
     
  7. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Did you happen to notice the load values in the Index.

    Like "Figure 2: Vout at Startup with a 10kW Load" :eek:

    Similar for Figures 3., 4, 6, 7, and 8. The text at least is correct...load values in Ohms.

    Ken
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    I haven't had time to analyze every word of the AN yet. Just quick glances at the schematics were enough for me to realize that they were absurdly dangerous.

    Take Figure 1 for example. Line voltage is connected directly from the input to the output, and the "ground" is isolated from the Neutral line via R1 and C1. This means that VOUT will be at a 120VAC potential, and the "ground" will be riding about 4.3v to 4.9v below VOUT, depending upon what kind of diode is used for D2.

    R1, C1 and D2 need to be moved from the Neutral line to L, and D2 turned around. However, there will still be some voltage on the N line, depending on whatever other loads are using N for a power return. This can cause great problems if attempting to connect a circuit powered by such a supply to another circuit.

    See the attached.

    Schematics removed by moderator

    [eta]
    Corrected Figure 5 attached; similar problems still exist.
     
    Last edited by a moderator: Sep 24, 2008
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