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    #21
    Re: I Don't Understand

    Is it really pulsing? What is the ON time and OFF time of the pulse being applied to the LED's?
    And are you using that constant current source circuit as you have shown to drive the LED's?
    What did you use to limit the current to the LED's? Just remember that LED is current device, you have to manage the current flowing through it, you do not hook them up to constant Voltage source and hoping it will not blow up, you use constant current source to drive LED.
    That power supply board looks like capacitive dropper type.
    Are there any parts on the bottom side of the board.
    Last edited by budm; 11-05-2018, 10:28 AM.
    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


      #22
      Re: I Don't Understand

      Originally posted by budm View Post
      Is it really pulsing? What is the ON time and OFF time of the pulse being applied to the LED's?
      So this is kind of interesting ... here is the voltage with the stock circuit powering the new LEDs with no other modifications:



      and here is the same exact thing with an added 400Ω resistor in series



      it definitely pulses on and off with the resistor in series ... by the way I tested this earlier with my ammeter and it still draws 170ma even with a series resistor in place and even when it flashes...

      Originally posted by budm View Post
      And are you using that constant current source circuit as you have shown to drive the LED's?
      NO I canned that circuit.

      Originally posted by budm View Post
      What did you use to limit the current to the LED's? Just remember that LED is current device, you have to manage the current flowing through it, you do not hook them up to constant Voltage source and hoping it will not blow up, you use constant current source to drive LED.
      That power supply board looks like capacitive dropper type.
      Are there any parts on the bottom side of the board.
      I am well aware that LEDs are a current sourcing device and that exceeding the rated current is bad juju and I know that you should never run them without a limiting resistor OR a constant current power supply.

      and NO there is nothing on the underside of the board.
      Attached Files

      Comment


        #23
        Re: I Don't Understand

        I do not understand the 'ORIGINAL CIRCUIT', what is the ORIGINAL CIRCUIT? The power supply module? You should also shows the bottom side of the board so we can see how the output section is setup, it may be setup as constant current source already.
        So the second picture shows ripple (5V P-P) riding on top of 12.5VDC. at what test point is that?
        15V source (based on you scope showing 5V per division with compensation with x10 PROBE) with 400 Ohms so the max shorted current will be 15V/400 Ohms = 37.5mA so how many LED's are connected in series with that resistor?
        Last edited by budm; 11-05-2018, 02:38 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


          #24
          Re: I Don't Understand

          Originally posted by budm View Post
          I do not understand the 'ORIGINAL CIRCUIT', what is the ORIGINAL CIRCUIT? The power supply module? You should also shows the bottom side of the board so we can see how the output section is setup, it may be setup as constant current source already.
          So the second picture shows ripple (5V P-P) riding on top of 12.5VDC. at what test point is that?
          15V source (based on you scope showing 5V per division with compensation with x10 PROBE) with 400 Ohms so the max shorted current will be 15V/400 Ohms = 37.5mA so how many LED's are connected in series with that resistor?
          ORIGINAL CIRCUIT = Driver circuit installed in the lamp from the factory ... the "original" ... no modifications, and no additions to the output etc.

          OK, so when I said there was nothing on the underside of this board, I made a mistake ... I was thinking of my other thread about the flashlight circuit ... this one does have stuff on the bottom ... here is the picture... I reversed one of the images so that the components line up properly ... you'll see what I mean ...

          I have NINE LEDs in series but only 4 are working now ... here are the exact LEDs that I'm using:

          Attached Files

          Comment


            #25
            Re: I Don't Understand

            Hey Budm,

            What do you think about replacing this circuit with a capacitive dropper as STJ suggested?

            Comment


              #26
              Re: I Don't Understand

              That looks to be non-isolated constant current power supply (HOT chassis, so I hope you are using scope without the safety connected which is dangerous or connect this board to isolation transformer), what are the P/N of IC U1, U2?
              Last edited by budm; 11-05-2018, 10:44 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


                #27
                Re: I Don't Understand

                recap that psu - the small ones anyway.

                Comment


                  #28
                  Re: I Don't Understand

                  OK, so when I said there was nothing on the underside of this board, I made a mistake ...
                  offcourse you did, there were no semiconductors on the top side, so nothing to rectify mains ac etc.

                  that small smps pos(like "cheap chinese piece of shit") has no power and that's why it starts to pulse as soon as you (over)load it, and it doesn't take much.

                  can you power it from pc psu?

                  [i like the signature signature, used to have same thing at another forum...]
                  Last edited by i4004; 11-06-2018, 02:13 PM.

                  Comment


                    #29
                    Re: I Don't Understand

                    Originally posted by budm View Post
                    That looks to be non-isolated constant current power supply (HOT chassis, so I hope you are using scope without the safety connected which is dangerous or connect this board to isolation transformer), what are the P/N of IC U1, U2?
                    Look at the attached image ... the power comes in through that ... im assuming thats an isolation transformer?

                    U1
                    BP2326A
                    16D30A
                    DEG26 or OEG26 or CEG26

                    U2
                    BP5602
                    16C14A
                    BRG23
                    Attached Files

                    Comment


                      #30
                      Re: I Don't Understand

                      looks like a connector block ..
                      p.s there seems to be a stray bare wire melted into the wire nut .

                      Comment


                        #31
                        Re: I Don't Understand

                        unless i am thinking wrong the isolation transformer goes before the scope . or is the DUT ?

                        Comment


                          #32
                          Re: I Don't Understand

                          You will plug the device to be tested into the Isolation transformer (L and N are floated).
                          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


                            #33
                            Re: I Don't Understand

                            https://www.badcaps.net/forum/attach...8&d=1541545003
                            Looks like line filter, rated at 3A 12VAC.
                            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


                              #34
                              Re: I Don't Understand

                              U1 BP2326:
                              https://cdn.badcaps-static.com/pdfs/...aa1495d297.pdf

                              U2 BP5602: http://bpsemi.com.cn/uploads/file/20...170036_863.ppt


                              Looking at the board layout, it looks like U1 (BP2326) is set up as the Buck converter to supply the Voltage to run the U2 (BP5602) LED driver.
                              Resistors (R13/R13 1 (2R20 Ohms in parallel = 1.1 Ohms) connected in parallel) at CS pins 7 & 8 of BP5602 determine the LED current setting.
                              Formula: Rcs = 0.2V/Iout, that means it is set for about 180mA (Iout = 0.2V/1.1 Ohms) of constant current which is what you have found out in the earlier test. So when you put 400 Ohms in series, there is no way the circuit can force 180mA through 400 Ohms resistor + the LED's, the power supply does not have enough Voltage to force 180mA through, 400 Ohms x 0.18A = 72V so no way it will happen.
                              Attached Files
                              Last edited by budm; 11-06-2018, 11:32 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


                                #35
                                Re: I Don't Understand

                                Originally posted by petehall347 View Post
                                looks like a connector block ..
                                p.s there seems to be a stray bare wire melted into the wire nut .
                                Actually, it ended up being the on off switch...

                                Comment


                                  #36
                                  Re: I Don't Understand

                                  Originally posted by budm View Post
                                  https://www.badcaps.net/forum/attach...8&d=1541545003
                                  Looks like line filter, rated at 3A 12VAC.
                                  Ended up being the on off switch ... I'll take a BIG FAT ZERO for that one ...

                                  Comment


                                    #37
                                    Re: I Don't Understand

                                    Originally posted by budm View Post
                                    So when you put 400 Ohms in series, there is no way the circuit can force 180mA through 400 Ohms resistor + the LED's, the power supply does not have enough Voltage to force 180mA through, 400 Ohms x 0.18A = 72V so no way it will happen.
                                    When I dropped the series resistor down low enough to make it stop blinking, it still drew 170ma ... and when I had the 400 in there, it drew 170ma ... just not constantly (obviously) ... its as if a series resistor didn't do Diddley squat for limiting current ... which kind of makes sense if the power supply is a CC at 180ma .... what respectable CC power supply would give two craps about a pesky series resistor ... just another obstacle to overcome for the power supply is all ... it's gonna deliver 180ma come hell or high water ... or pulse on and off like a whiney two year old if the load is too heavy ... but at least it's putting forth a valiant effort...

                                    So all of this analysis of the circuit was fun and all ... but the question is still on the table: How do I take 120V AC and kick out some decent DC voltage at roughly 100 to 120 milliamps in the small space I have to work in? Remember STJ recommended the capacitive dropper ... what are your thoughts on that option?

                                    OR, are you thinking we could modify the existing power source to put out less current so my LEDs don't go belly up? .... THAT actually sounds like FUN!
                                    Last edited by EasyGoing1; 11-07-2018, 07:31 AM. Reason: Added a thought...

                                    Comment


                                      #38
                                      Re: I Don't Understand

                                      It cannot force 180mA through 400 Ohms resistor if the power supply cannot go up high enough to force 180mA through the resistor, the Voltage across the load is varied to maintain constant current.
                                      "How do I take 120V AC and kick out some decent DC voltage at roughly 100 to 120 milliamps in the small space I have to work in? Remember STJ recommended the capacitive dropper ... what are your thoughts on that option?"
                                      First question will be what is the load? 1 LED? 10 LEDs, 100 LED's? You need to know what the load requirement is first, you already know what the required current but now you need to know the load requirement is so you can make power supply that puts out enough Voltage to force 120mA through the load.
                                      So what are you going to do with that power supply? It is a good CC power supply that should be re-capped with good caps.
                                      Last edited by budm; 11-07-2018, 10:36 AM.
                                      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


                                        #39
                                        Re: I Don't Understand

                                        Originally posted by budm View Post
                                        First question will be what is the load?
                                        I was thinking 9 LEDs in series ... rated at 3v / 150ma so I'm thinking the power supply should be able to supply roughly 30 volts at 150ma?

                                        Originally posted by budm View Post
                                        So what are you going to do with that power supply? It is a good CC power supply that should be re-capped with good caps.
                                        What's your definition of "good caps"? and where would I get them?

                                        Comment


                                          #40
                                          Re: I Don't Understand

                                          I would run constant current of 120mA (80% of the max spec.).
                                          The VF of the LED will vary withe current flwoing through the LED, temperature all affect Vf, that is why you should use constant current source, 30V may be OK it depends on the Vdrops of the Constant current active control element at the needed current and variation of the total Vf of the LED string, you want it to have head room for the Output Voltage to go up and down as needed to maintain constant current.
                                          See page 12 of the graph which is typical spec provided by the LED manufacturer which I doubt if you have it for your LED. If you have constant current power supply then you do the measurement and see what you get with your LEDs you will be using.

                                          https://cdn.badcaps-static.com/pdfs/...7f6e02e49a.pdf

                                          Good caps: I.E. Panasonic FM/FC/FR series, and many other Japanese manufacturer.
                                          Last edited by budm; 11-07-2018, 10:11 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

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