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    power supply residual voltage

    I have a tdk lamda power supply CUT35-522, which is 230V input, 5V,+/-12V output. I am using +12V output to power my arduino board with LCD. It works fine.
    The power supply claimed immunity to surge and EFT. To my surprise, when the supply was subjected to 2kV surge, residual voltage of +/-25V appeared at +12V output. This lead to resetting of arduino board and garbage characters displayed in LCD. I am looking for a solution to reduce this surplus voltage and prevent garbage characters in LCD. Kindly suggest.

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    Re: power supply residual voltage

    Your claims don't seem reasonable. How could a residual voltage of '+/-25V' appear on a 12V output?
    Are you saying it went up to 37V or down to -13V and under those conditions how could your Arduino or LCD survive?

    Brian.
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    Re: power supply residual voltage

    Hi

    The residual voltage was additional +/-12V over 12V DC supply. This lasts for about 10us. Arduino regulator output gets reset in this situation.



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    Re: power supply residual voltage

    How are you testing this? How are you applying a "2KV surge"? How are you measuring it? What are its characteristics? Are you picking up something with your scope (or whatever you're using) rather than seeing what's really coming out of the power supply? And what the heck is "residual voltage"? Do you, perhaps mean a transient? Does the power supply specify 2KV immunity?



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    Re: power supply residual voltage

    I believe that you are using an incorrect problem description.
    What I believe you are describing, based on your description, is an input transient voltage caused the supply to produce a brief output pulse.

    But I have to ask: how did you apply the 2Kv transient to the Lambda supply? What waveform (8X20, 1.2X50, 1000Khz ringwave)? What location service category, A, B, C?

    BTW, you have to define also what you mean by immunity. The lowest immunity level *only* means that the device will not suffer permanent damage, but can misbehave and require user intervention to restore functionality.
    An enhanced immunity level the device can still misbehave but will recover its functionality automatically, and for the highest level the device not only will not suffer any damage, but functionality will not be impaired at all.

    Depending on the answers above, there will be different levels of upstream or downstream protection requirements. It could be as simple as an enhanced physical ground (earth), or as complex as a motor generator set which completely isolates the device from the grid. There is a whole spectrum of protection levels.
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    Re: power supply residual voltage

    Hi,

    The residual voltage was additional +/-12V over 12V DC supply. This lasts for about 10us.
    I donīt think this is possible.
    Most probably the power has a a capacitor at the ouput.
    It needs a lot of power to charge this capacitor to +/-12v within 10us.

    And negative voltages at a usually positive power supply output may kill the power supply immediately.

    --> I assume this is a measurement error.

    Klaus
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    Re: power supply residual voltage

    I could kind of solve this issue a bit. I just connected the power supply chassis ground to protective earth and I could get a criteria-A performance for 4kV surges. However, arduino resets for EFT level of 1kV. All my observations are in oscilloscope (in trigger mode, ac coupling). Except EFT, all events are captured for the transient event. Could you please explain how to connect PCB ground to protective earth. Is is necessary? How to resolve for EFT?



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