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    7310/3510 supervisor chip with overcurrent protection

    In the past I have read comments from those who criticize power supplies as being cheap POS because of the 7510/3510 supervisor chip which has no overcurrent protection. The purpose of this thread is to challenge this generalized complaint to prove it just is not true. Half bridge power supplies I have worked on do not use the 7510/3510 supervisor chip. It is often used in the current forward class of power supplies. That being said (and can be disputed), I am using a very commonly found Bestec ATX-250 12Z as a reference for the circuit description which follows. Below is a drawing of the overcurrent protection circuit.
    Attached Files
    Last edited by everell; 12-14-2020, 09:27 AM.
    Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

    #2
    Re: 7310/3510 supervisor chip with overcurrent protection

    Referring to Figure 1, a comparator chip has inputs attached to the input and output of the PI output coil. The voltage across the PI output coil determines whether the output of the comparator chip goes hi or low. For normal operation, the output is high. When overcurrent is detected the output goes low. The Bestec ATX-250 12Z uses a LM358 chip which has two op-amp comparators, one used for the +5 volt line and one used for the +12 volt line. The value of resistor R1 in Figure 1 sets the overcurrent limit amount. I don't have a formula available for determining its value...I will leave that to our Romanian engineer!
    Attached Files
    Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

    Comment


      #3
      Re: 7310/3510 supervisor chip with overcurrent protection

      Referring to Figure 2, a simple voltage divider consisting of R1, R2, and R3 is between the +12 volt line and ground. The voltage across R3 sets the voltage going to pin 6 of the 7510/3510 chip at 5.3 volts. This is well within spec for what the 7510/3510 chip expects as normal. In Figure 3 diode D1 is added between the +5 volt line and the junction of R1 and R2. The voltage at this junction is normally 5.6 volts. If the voltage on the +5 volt line goes below 5 volts, diode D1 begins conducting. The reduced voltage on the 5 volt line goes to pin 6 of the 7510/3610 chip until the supervisor chip reaches its cutoff point and shuts down the power supply. The purpose of R2 is to compensate for the 0.6 volt drop across the diode.
      Attached Files
      Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

      Comment


        #4
        Re: 7310/3510 supervisor chip with overcurrent protection

        Referring to Figure 4, the output of one of the comparators is added to the circuit. When circuit operation is normal, the output of the comparator chip is high (open collector output) and 5.3 volts is at pin 6 of the 7310/3510 chip. When an overcurrent condition is detected the comparator chip switches and goes low taking pin 6 of the 7310/3510 chip to ground causing the supervisor chip to shut off the power supply. Both overcurrent comparator outputs are connected to pin 6 of the supervisor chip, either directly or through a diode as in the case of the Bestec ATX=250 12Z.
        Attached Files
        Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

        Comment


          #5
          Re: 7310/3510 supervisor chip with overcurrent protection

          The explanation of this circuit is as simple as I could make it. The figures have also been simplified for explanation. This circuitry is used in the Bestec ATX-250 12E, ATX-250 12Z, ATX-300 12E, ATX-300 12Z, ATX-400, and several other Bestec models. I don't know if any other brands and models are using this type of overcurrent circuitry. This forum is for power supply design and engineering. So it is possible to take a cheapo POS without overcurrent protection and add an outboard overcurrent circuit on a small piece of perf board. Very few changes need to be made to the main circuit board. Anyone up to the challenge???
          Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

          Comment


            #6
            Re: 7310/3510 supervisor chip with overcurrent protection

            There are lots of ways to do fun stuff with chips trying to squeeze in more functionality. Figure 2 appears to be a very common UVP plan - using one pin to check two voltages. I believe this is on one of the datasheets on one of the supervisory chips I've seen this as a reference design.

            Figure 4 only works if the comparator is one of those open collector output units like LM393 or LM339 instead of a full op amp like LM358 / LM324. However without a full op amp, a lot of the amplification/"virtual ground" tricks won't work. You may need to mix between the two types.

            However the OCP in figure 1 looks a bit suspicious. While I don't disagree it does have the intended effect of OCP but it's tough to tailor to the right current. "R1" is not the only value that needs to be used to calculate the OCP current - the rest of the circuit does too. I have a hard time believing this will work reliably for many common SMPS chips. What SMPS chip does it use?

            Comment


              #7
              Re: 7310/3510 supervisor chip with overcurrent protection

              Originally posted by eccerr0r View Post
              Figure 4 only works if the comparator is one of those open collector output units like LM393 or LM339 instead of a full op amp like LM358 / LM324. However without a full op amp, a lot of the amplification/"virtual ground" tricks won't work. You may need to mix between the two types.
              The drawing in the first post is from a Bestec ATX-250 12Z which does use a LM358 chip. Notice that there is a diode between the op-amp output and pin 6 of the supervisor chip. Therefore the LM358 does not need to be open collector output. The Bestec ATX-400 uses a LM339 which is open collector and therefore does not need the diode between the op-amp output and pin 6 of the supervisor chip.
              Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

              Comment


                #8
                Re: 7310/3510 supervisor chip with overcurrent protection

                Yeah, need to be a bit more clear which is being used in the sample.

                Really what does one want for OCP anyway, just instant shutdown when max current is reached?

                Technically the current sense resistor on the primary side also plays a role in OCP, but it's more of a wattage limit of the whole supply. But if that is properly integrated into the works, that too will limit how much current will flow through the secondary before the whole supply starts leaking magic smoke.

                Comment


                  #9
                  Re: 7310/3510 supervisor chip with overcurrent protection

                  eccerr0r and everell

                  I might be taking this post off topic if I am please for give me for doing so but I find this topic very interesting and wanting to know more about it

                  I have a question for both of you and that is could you take a supervisor chip and change it voltage parameters for different voltages and if you can how / what would you have change for it to work correctly
                  ( in reference to computer power supply ) [ even if this means that I would have to make a daughter board for it ]

                  ( I know that when you change the voltage all power rails will change I well aware of this fact )

                  I have quite a few computer power supply that are the same exact model number and for a long time I have wanted to modify a computer power supply for a different voltage output but have not like the fact that you have to disable the protection circuit in order to do this but reading what this post is about got me thinking that there might be a way to do it and keep the protection circuit still functioning so I am very interested in your post

                  I found this part very interesting

                  “ Technically the current sense resistor on the primary side also plays a role in OCP, but it's more of a wattage limit of the whole supply. But if that is properly integrated into the works, that too will limit how much current will flow through the secondary before the whole supply starts leaking magic smoke.”
                  Last edited by sam_sam_sam; 12-16-2020, 02:17 PM.
                  9 PC LCD Monitor
                  6 LCD Flat Screen TV
                  30 Desk Top Switching Power Supply
                  10 Battery Charger Switching Power Supply for Power Tool
                  6 18v Lithium Battery Power Boards for Tool Battery Packs
                  1 XBox 360 Switching Power Supply and M Board
                  25 Servo Drives 220/460 3 Phase
                  6 De-soldering Station Switching Power Supply 1 Power Supply
                  1 Dell Mother Board
                  15 Computer Power Supply
                  1 HP Printer Supply & Control Board * lighting finished it *


                  These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                  1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                  2 Hem Saw Computer Stack Board

                  All of these had CAPs POOF
                  All of the mosfet that are taken out by bad caps

                  Comment


                    #10
                    Re: 7310/3510 supervisor chip with overcurrent protection

                    For the most part it's difficult in general to predictably change a circuit without knowing the whole circuit. Depending on the supervisory chip, some of them don't specify the impedance of the input (even in the datasheets, because it's assumed that the voltage input is tied directly to a power rail) and without that bit of data, is impossible to tweak the offset and best you can do is use a variable resistor and tune it to the right value.

                    The ones that implement OVP/UVP discretely, it's much easier because now the circuit is exposed instead of this random IC and you can make good assumptions that op amp inputs have high impedance and your circuit can generally be whatever you want and ignore the opamp contribution.

                    Comment


                      #11
                      Re: 7310/3510 supervisor chip with overcurrent protection

                      Do you have any part number that should be looking at

                      Thanks
                      9 PC LCD Monitor
                      6 LCD Flat Screen TV
                      30 Desk Top Switching Power Supply
                      10 Battery Charger Switching Power Supply for Power Tool
                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                      1 XBox 360 Switching Power Supply and M Board
                      25 Servo Drives 220/460 3 Phase
                      6 De-soldering Station Switching Power Supply 1 Power Supply
                      1 Dell Mother Board
                      15 Computer Power Supply
                      1 HP Printer Supply & Control Board * lighting finished it *


                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                      2 Hem Saw Computer Stack Board

                      All of these had CAPs POOF
                      All of the mosfet that are taken out by bad caps

                      Comment


                        #12
                        Re: 7310/3510 supervisor chip with overcurrent protection

                        Possibly TI's TPS3514, https://cdn.badcaps-static.com/pdfs/...b9d41c4c39.pdf
                        PeteS in CA

                        Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
                        ****************************
                        To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
                        ****************************

                        Comment


                          #13
                          Re: 7310/3510 supervisor chip with overcurrent protection

                          Originally posted by PeteS in CA View Post
                          Thank you for your reply

                          Can I ask you one more question what brand of computer switching power supply was this chip found in
                          9 PC LCD Monitor
                          6 LCD Flat Screen TV
                          30 Desk Top Switching Power Supply
                          10 Battery Charger Switching Power Supply for Power Tool
                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                          1 XBox 360 Switching Power Supply and M Board
                          25 Servo Drives 220/460 3 Phase
                          6 De-soldering Station Switching Power Supply 1 Power Supply
                          1 Dell Mother Board
                          15 Computer Power Supply
                          1 HP Printer Supply & Control Board * lighting finished it *


                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                          2 Hem Saw Computer Stack Board

                          All of these had CAPs POOF
                          All of the mosfet that are taken out by bad caps

                          Comment


                            #14
                            Re: 7310/3510 supervisor chip with overcurrent protection

                            The switching power supply that I quit a few of them has this supervisor ic chip



                            This ic chip is on it own little board that has three pots which one of them I have traced it to pin 7 which if I am correct it to one of voltage senes pins


                            I have to recap one of to see what these adjustment pots controls
                            Last edited by sam_sam_sam; 12-17-2020, 11:48 AM.
                            9 PC LCD Monitor
                            6 LCD Flat Screen TV
                            30 Desk Top Switching Power Supply
                            10 Battery Charger Switching Power Supply for Power Tool
                            6 18v Lithium Battery Power Boards for Tool Battery Packs
                            1 XBox 360 Switching Power Supply and M Board
                            25 Servo Drives 220/460 3 Phase
                            6 De-soldering Station Switching Power Supply 1 Power Supply
                            1 Dell Mother Board
                            15 Computer Power Supply
                            1 HP Printer Supply & Control Board * lighting finished it *


                            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                            2 Hem Saw Computer Stack Board

                            All of these had CAPs POOF
                            All of the mosfet that are taken out by bad caps

                            Comment


                              #15
                              Re: 7310/3510 supervisor chip with overcurrent protection

                              Hello sam_sam_sam. Your comments/questions concerning a power supply using the PS223 chip shows the problem we are discussing. The PS223 chip has overvoltage/undervoltage protection AND overcurrent protection. The 7510/3510 chip used in cheapo POS power supplies has overvoltage/undervoltage protection BUT NO overcurrent protection. It was my intent to show that most Bestec power supplies have overcurrent protection using the circuitry I have been describing.

                              I spent much time working a problem on a Bestec ATX-400 power supply which turned out to be in the overcurrent circuitry. Having never seen this kind of problem before, I changed all capacitors and some of the chips. The overcurrent circuit on the two 12 volt rails were sensed by special "shunt" resistors. Thank you Bestec for puting your famous white glue all over the sensing shunts. Here is my drawing of what I found - not the best in the world and with perhaps a few errors. But it does show the basis of what they were trying to accomplish.
                              Attached Files
                              Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                              Comment


                                #16
                                Re: 7310/3510 supervisor chip with overcurrent protection

                                Here is a figure showing the waveforms I found on the Bestec ATX-400. On the left is what was on the 7510 chip and on the right what was on the outputs of the 12, 5, and 3.3 volt rails. The only difference was the waveform on pin 6 of the 7510 chip and the 5 volt rail. The voltage waveform tried to increase but shutdown in about 5 milliseconds. This time corresponds to one quarter of a sign wave at 60 hertz. This is the time it takes for the voltage to go from zero to maximum during one cycle. This is the amount of time required for the circuit to react to an overcurrent problem. Not bad for a "cheap" power supply!
                                Attached Files
                                Last edited by everell; 12-17-2020, 04:51 PM.
                                Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                                Comment

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