+ Post New Thread
Results 1 to 2 of 2
  1. #1
    Full Member level 6
    Points: 4,898, Level: 16

    Join Date
    Nov 2003
    Location
    Brazil
    Posts
    399
    Helped
    0 / 0
    Points
    4,898
    Level
    16

    Corwbar with LM723 triggered SCR

    This is a new crowbar circuit at least to me, this application of the LM723 I've never seen before. This is a redraw of a Spanish magazine so I don't know about copyright it is just an amateur post. If someone have any observation against this circuit, please post it. In the article is said SCR activation time 1us or 2us too fast isn't it???
    73 to all Fernando PU2PLL - Brazil

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 34,834, Level: 45
    Achievements:
    7 years registered Created Blog entry Created Album pictures
    SunnySkyguy's Avatar
    Join Date
    Sep 2007
    Location
    Richmond Hill, ON, Canada
    Posts
    6,729
    Helped
    1679 / 1679
    Points
    34,834
    Level
    45
    Blog Entries
    7

    Re: Corwbar with LM723 triggered SCR

    uA723 is an ancient Linear voltage regulator chip with many pins.

    In this case the regulated Power Supply is external and just flows across the top 30A Fuse.

    This circuit is a precision OVP or over voltage protection circuit that blows the fuse to probably a >300W power supply.

    The chip uses a pot on the left to select the trip voltage of the output on top right. The OUTPUT is in the comparator loop while the VZ is the Output minus a 6.2V zener to pull up the SCR and blow the fuse. Since an old electrolytic cap opening up could result in Over Voltage Spikes ( or some other failure) which could cause other things to fail in the LOAD , the designer needed a really fast OVP., So he uses this precision SCR controlled fuse blower.

    Not very elegant , but safe and effective.

    This sounds like it came from a vintage 1978 magazine.
    A best design is easily achieved with good test specs™
    A better question deserves a better answer. ™
    ... so include all your acceptance criteria ( values, % tolerance) and assumptions in your question or any design.

    ... Tony Stewart EE since 1975
    - slightly north of Toronto



--[[ ]]--