2
\$\begingroup\$

As above, what are the disadvantages, risks and dangers involved in modding a class II switch mode power supply i.e. a double insulated laptop charger that is ungrounded to have the dc- output shorted directly to earth?

I know this question has been asked countless times before here, but I did not feel that there was a satisfactory conclusion.

Some of the threads I have reading with more elaborate answers are listed:

How to safely ground a switching power supply with floating outputs?

What does the Y capacitor in a SMPS do?

What I gather now is that what the mod essentially does is bypassing the y-capacitor and I will probably lose all of the EMI insulation class II designs provide. My primary concern here, though, is safety, not just in normal operation but when a fault occurs e.g. loose/frayed wires, shorts.

I may be very wrong, so please correct me where I'm totally mistaken.

Not so necessary background information: I want the power supply output dc- to be referenced to earth to stop the tingle/small shock from touching devices with metal casings powered by such power supplies. I have scouted around for grounded power supplies that supply 15V but they are hard to find and expensive.

\$\endgroup\$
  • 1
    \$\begingroup\$ There is an interesting paragraph in one of the answer in the second question you linked about class 1 PSUs. \$\endgroup\$ – ratchet freak Sep 22 '17 at 14:25
  • \$\begingroup\$ Thanks, I saw it but it is pertaining to a class 1 psu as you mentioned. However, I am looking to short the dc- output of a class 2 power supply to earth (or by any other better means to reference it to earth voltage) and I'm not sure if that recommendation applies to me \$\endgroup\$ – Xbing Sep 23 '17 at 3:20
  • 2
    \$\begingroup\$ Shorting one of the legs of a class 2 power supply to ground turns it into a class 1 at the worst. It's still a safe device or it would not be standard practice for desktops. \$\endgroup\$ – ratchet freak Sep 23 '17 at 8:08
1
\$\begingroup\$

It's fine, there will be a slight leakage to earth but that leakage should be much lower than with many class 1 power supplies.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.