Need Help analysing block diagram, please help.

Discussion in 'Homework Help' started by rccengr, Jul 9, 2009.

  1. rccengr

    Thread Starter New Member

    Jul 4, 2009
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    0
    Hi Guys,
    Good day.
    I'm working on a power supply for my school assignment and having problem interpreting the block diagram of the IC -switching regulator LM2674 I'm going to use. Can someone help me analyze the block diagram in the link below i.e. how does the comparators work and the reference voltage. Any help is greatly appreciated. Thank you.

    Link for block diagram: http://www.national.com/images/pf/LM2674/10004117.pdf

    Link for data sheet of LM2674 - http://www.national.com/ds/LM/LM2674.pdf
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. rccengr

    Thread Starter New Member

    Jul 4, 2009
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    Thanks for the reply. I'm actually wondering if someone can interpret the diagram of the IC itself. Any help is greatly appreciated. Thanks
    again
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    There are 13 elements in the block diagram. Which functions do you not get?
     
  5. rccengr

    Thread Starter New Member

    Jul 4, 2009
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    0
    Thanks for your help again. I have some what idea as to how the over all diagram works but not very concrete. I would like to at least get people's analysis of the whole diagram and from there I can compare with my own. The part in which I'm having difficulty the most to understand is the comparator side, I noticed there are at least 3 comparators in the diagram. Would it be ok if you provide your analysis regarding the whole diagram? That would really great. Thanks for your help in advance.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    GM1 trips then the voltage between R2 & R1 exceeds the level of the voltage reference. GM2's exact operation is hard to determine. Operation is almost like GM1, except the compared signal is applied to the other input. The gain compensation is a bit mysterious.

    The PWM comparator gets turned off when the output voltage is at the setpoint, as determined by R2.

    As far as operation goes, here is what National Semi has to say - www.national.com/appinfo/power/files/f5.pdf
     
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