Regarding the data sheet of this SMPS power supply. In the first page it says:

2 x MOPP Medical safety according to AAMI/ANSI ES 60601-1:2005(R) and IEC/EN 60601-1 3rd edition

Then I googled to read about IEC 60601 and I found this article.

In the article it is written:

It is the MOP (Means of Protection) used for medical device requirements to protect both the operator and the patient from electric shock.

As you know most of the power supplies have leakage parasitic capacitance and a phantom voltage can be measured sometimes upto 100VAC between any of DC terminals and the earth. This sometimes causes unpleasant electric shock which is not dangerous. But it can still be unpleasant.

My question is, is this medical approved power supply does not have this problem? Or by "medical safety" do they mean dangerous electric shock not the parasitic capacitive coupling?

  • \$\begingroup\$ What about people with pacemakers? How would a pacemaker handle a 100V spike? I'm guessing handling this case will be about the same thing as handling ESD protection, pretty much (high voltage low current). \$\endgroup\$
    – Lundin
    Commented Feb 26, 2018 at 15:33
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    \$\begingroup\$ The standard varies on requirements depending on the application the power supply is being used for. It looks like the rules are based on leakage current of 500uA for medical devices that do not make contact with a patient body. Patient attached (Body Floating) and cardiac floating applications have additional requirements (like full isolation transformers). This PDF has some additional info: cui.com/catalog/resource/… \$\endgroup\$ Commented Feb 26, 2018 at 15:38
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    \$\begingroup\$ The power supply has an associated certification zip file. You could read that to get a better idea. \$\endgroup\$
    – Andy aka
    Commented Feb 26, 2018 at 15:53
  • \$\begingroup\$ I tried this power supply, it has around 90VAC between its DC power terminals and earth. So it has nothing to do with the parasitic capacitance effect i.e ghost voltage. It is still there. Damn isn't there any power supply type on earth(besides battery) which does not have this ghost voltage issues? \$\endgroup\$
    – user16307
    Commented Mar 5, 2018 at 19:53
  • \$\begingroup\$ Did AnalogKid's answer answer your question? \$\endgroup\$ Commented Aug 17, 2022 at 18:16

1 Answer 1


If the supply is designed, tested, and certified to meet the requirements of 60601, then it does not have that problem. First, the Y capacitors in the power line filter and the output stage have a smaller value, which increases the leakage current impedance and reduces the earth ground current. Second, look into SELV:


In my experience, supplies and systems that meet 60601 have the power supply output ground firmly bolted (literally) to the earth/chassis ground.

  • \$\begingroup\$ 60601 class II supplies are fully isolated. \$\endgroup\$ Commented Mar 3, 2019 at 15:06
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    \$\begingroup\$ True, but a fully isolated supply still can have lethal leakage currents; or almost none if you design them out. \$\endgroup\$
    – AnalogKid
    Commented Apr 1, 2022 at 16:38

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