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Type: Posts; User: E-design

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  1. Closed: Re: TPS54331 oversupply output no load voltage is not proper

    The application circuit in the data sheet seems to simulate well on 6 V with a high-value load resistance. It will go into a burst-mode of operation at light loads as shown.

    You should use the...
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    [SOLVED]Closed: Re: Simetrix/Simplis Elements help

    Go to transient advanced options and tick "Skip DC bias point" and it should work.
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    [SOLVED]Closed: Re: Simetrix/Simplis Elements help

    The software sometimes will complain about floating nodes and convergence, so I usually place large resistances referenced to the circuit GND. You can place fixed probes or probe a device pin or...
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    [SOLVED]Closed: Re: Simetrix/Simplis Elements help

    Here is a typical transformer and rectifier setup. You can play with the values to suit your needs.
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    Closed: Re: Push-Pull Convertor load steps

    Your control loop may not have enough gain to deal with the resonant bump from the output filter. If you have a 1000 uF/400V electrolytic available, try to add that with a 2.2 ohm in series over the...
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    Closed: Re: Understanding switched mode power supplies

    You will select the proper feedback value capacitor on the error amplifier opamp to reduce the total gain to 0 dB at the desired crossover frequency.
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    Closed: Re: Understanding switched mode power supplies

    It is usually only a problem that comes up with indirect transfer converters, like boost, buck-boost and flyback. Operating deep into CCM will make the problem worse, and as stated the crossover must...
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    Closed: Re: 4-20mA current loop with common ground

    Yes, and most probably have used a better opamp with jfet inputs and higher resistances.
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    Closed: Re: Dell 255W PSU 8.3V on source power MOSFET

    Well, we can substitute from an external power supply the voltage that the bias supply would normally supply, and measure if there are any activity around the PFC/switching chip once we can look up...
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    Closed: Re: Dell 255W PSU 8.3V on source power MOSFET

    Make sure your standby/bias supply is working. This is using the TNY280 chip. Without this giving the correct power, the rest of the circuits may not start up correctly. Also identify the...
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    Closed: Re: 4-20mA current loop with common ground

    Here is another circuit (like we don't have enough already), which seems happy operating with either an MOSFET or BJT. It shows no stability problems from simulation results and phase margin stays...
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    Closed: Re: 4-20mA current loop with common ground

    Yep, similar frustrations this side. The best stable version was 10, before they added a lot of new features. Often it will plot graphs on top of each other with no way to separate them. Then when...
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    Closed: Re: 4-20mA current loop with common ground

    Nice circuit! I thought of using a controlled current source using a LM334 or similar but could not find any simulation models for it.

    Which version of TINA are you using?
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    Closed: Re: 4-20mA current loop with common ground

    Yes, I think the 75 k helped a lot. I found adding a 1n after the 75 k, level out the phase nicely. TINA seems a bit over optimistic on the gain margin (62 dB). Other sim says 44 dB, which I tend to...
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    Closed: Re: 4-20mA current loop with common ground

    It appears that it should be possible to trim out most of the loading and base current errors by adding a error-compensation resistor after the 75k to the diff amp like shown. Linearity or stability...
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    Closed: Re: 4-20mA current loop with common ground

    Here is the final circuit. I rolled off the response around U1 as was also suggested and increased R2 to 75k. All the peaky square wave response vanished as expected. As can be seen that the...
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    Closed: Re: 4-20mA current loop with common ground

    Well today after work I decided to breadboard (hate these things) the circuit in the lab and test it. When I powered up and checked I could not see any obvious problems. I then simulated the circuit...
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    Closed: Re: 4-20mA current loop with common ground

    I looked at this Motorola model, and I could get it to go unstable under certain conditions. I updated the diagram with values that seems to give good margins with all five different models I tested...
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    Closed: Re: 4-20mA current loop with common ground

    I never said that. I agree if there are obvious problems with the simulation results, then there is a good chance that you will have problems. If you have simulation results that seemed good with...
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    Closed: Re: 4-20mA current loop with common ground

    Which model did you use? I actually made a similar circuit with opto-isolated coupling in the past (it is posted somewhere in a thread), which I expected to have stability problems, but performed...
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    Closed: Re: 4-20mA current loop with common ground

    I can't give you a number, since I have not checked it. I did check the squarewave (100 Hz) response because of the zener action in the circuit and I could just observe very low level...
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    Closed: Re: 4-20mA current loop with common ground

    You can sense the current on the high side using a differential amp. Values of R7/8/9/10 must be well matched. The 4 mA offset resistor can be a trim-pot for better adjustment.

    The total loop...
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    Closed: Re: Negative Topologie Converter

    There are chips available that can provide positive and negative boost voltages. Take a look at the ADP5071, which works with up to 15 V input. If you search for a bit more you may find a similar...
  24. Closed: Re: UC3842 simulation problem in Proteus 8.0Version

    It appears that it is just some experiment controlling the current though the LED. The chip itself can drive 500 mA or more at its output and is usually used to drive an MOSFET when used in a...
  25. Closed: Re: Help needed to repair a Sony Trinitron KV-2165MT power failure

    The part e-music showed looked like a 10mm or less pin spacing, so it is most probably rated at a lower voltage. I don't expect to see a very high-voltage requirement as this capacitor is in series...
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