How are inverter boards controlled ?

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  • 120volts
    Senior Member
    • Oct 2013
    • 57
    • USA

    #1

    How are inverter boards controlled ?

    Hi I'm new to the Badcaps forum.

    I took a four years coarse in electronics at a tech trade school and then worked for over fifteen years for various companies as a bench tech.

    Here's my question.

    On the typical CCFL backlight inverter board how is the brightness controlled?

    Is it by raising or lowering the control voltage or is it controlled by varying pulse width?
    Dan "TV Tinkerer"
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: How are inverter boards controlled ?

    The DIM signal an analog voltage typically from 0 - 3.3V which controls brightness from approx 10% to 100%, or a PWM signal (pulse width modulation.)

    Note minimum brightness around 10% for CCFL because they cannot go below that without having to re-ignite which takes about a second to occur.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment

    • 120volts
      Senior Member
      • Oct 2013
      • 57
      • USA

      #3
      Re: How are inverter boards controlled ?

      Thanks for the replay Tom.
      Time to get the scope up and running.
      Dan "TV Tinkerer"

      Comment

      • 120volts
        Senior Member
        • Oct 2013
        • 57
        • USA

        #4
        Re: How are inverter boards controlled ?

        Ok, when I turn on this DX-LCD32-09 Dynex I get sound but back-light for only 1 sec.

        The inverter board is getting the 24V and 5V. and on the PWM I get a steady +3.4V
        with the scope I don't see any pulse or frequency at all.
        Dan "TV Tinkerer"

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: How are inverter boards controlled ?

          That is the 2-second to black problem which can be the MOSFET, Inverter transformer, CCFL, etc.
          https://www.badcaps.net/forum/showthread.php?t=10419
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment

          • 120volts
            Senior Member
            • Oct 2013
            • 57
            • USA

            #6
            Re: How are inverter boards controlled ?

            OK thanks for the links but, my question was should I be seeing a control pulse?
            I bought a used inverter board and was told it was working 100% and the TV still has the same problem.
            Dan "TV Tinkerer"

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: How are inverter boards controlled ?

              The PWM is about 200Hz. But does it also has another connection for the analog dimming? Set your meter to AC to see if you will get any AC voltage. Board P/N?
              Is this the board, which only has PWM only.
              http://www.shopjimmy.com/vit68001-95...t-inverter.htm
              According to what I found about your LCD panel spec, the PWM can be fed with Anolag signal.
              https://cdn.badcaps-static.com/pdfs/...4256d2d602.pdf
              3.3VDC = Max brightness. If this is the panel you have.
              Attached Files
              Last edited by budm; 10-21-2013, 09:07 PM.
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: How are inverter boards controlled ?

                You probably have "2 seconds to black". This occurs when the set detects an open or shorted bulb in the panel, which causes it to shut down after the ignition phase (2 seconds.)
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #9
                  Re: How are inverter boards controlled ?

                  I agree.
                  Never stop learning
                  Basic LCD TV and Monitor troubleshooting guides.
                  http://www.badcaps.net/forum/showthr...956#post305956

                  Voltage Regulator (LDO) testing:
                  http://www.badcaps.net/forum/showthr...999#post300999

                  Inverter testing using old CFL:
                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                  http://s807.photobucket.com/user/budm/library/

                  TV Factory reset codes listing:
                  http://www.badcaps.net/forum/showthread.php?t=24809

                  Comment

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