AC-DC Power Supply Output Connection

1. refer to the simplest rectifier circuit (here I am attaching one from wiki, not feeling like drawing it )

As you must be aware that the earthing (or grounding) of the neutral point (here it is the negative terminal) will avoid the floating on user end.

This will alse create less stress on the insulations (with respect to the grounded parts of the transformers and other cirsuit elements). This is more clear from the rectified voltage diagram. Look at it and tell which point you want to ground? +ve or -ve?

SB,

?

No both don't belong to each other, the wave is a 3 phase rectifier output voltage.

That, my friend appears to be an illustration of full wave rectified three phase AC. I have no idea of its application to this discussion though! TT3

sb I have copied your ckt for some more illustration.Hope you don't mind

Some adition to what sb had said, There is a parasitic capacitance between primary and secondary of every transformer. If you don't ground secondary coil or circuit, this parasitic capacitance will keep secondary coil and circuit at floating voltage that is equal to primary coil voltage, as you may know that capacitor can pass current on AC voltage.

It is unneccessary to ground the secondary side of transformers in double-insulated systems, shown on proprietary equipment by the standard square-within-a-square symbol. Indeed, no earth wire is provided in the power lead.

Sometimes the effect of parasitic capacitance can be felt by touching metallic parts of the double-insulated equipment. The sensation is interesting, though not dangerous.

Sometimes the effect of parasitic capacitance can be felt by touching metallic parts of the double-insulated equipment. The sensation is interesting, though not dangerous.

Undoubtedly not dangerous for human, but how about if there is a C-mos device assembled in the circuit board? touch and go!!!!!!!

I think its always advisable however one can live with out it.

by touching metallic parts of the double-insulated equipment. The sensation is interesting, though not dangerous.

Undoubtedly not dangerous for human, but how about if there is a C-mos device assembled in the circuit board? touch and go!!!!!!!

____________________________________

What are you touching, guys?

• The front bezel of a small television set.
• The front bezel of a domestic stereo audio amplifier.
• Etc.

Yeah, I knew that! Just trying to make a joke, apparently not a good one.

<...how about if there is a C-mos device assembled in the circuit board...>

Unless the equipment were faulty, there would be no access to the C-mos device connections with the cover in place, so the possibility need not be considered.

Earthing is for personal protection in the event of a fault inside the equipment. No earth wire is provided for double-insulated equipment.

Were the device energised with the circuit board accessible, the presence of C-mos devices is secondary to the safety need of being wary of, and avoiding contact with, mains-voltage electrical connections with an ingress protection rating lower than IP2x. Such conditions would safely be under the direction of a competent person, not the general user.

"Earthing is for personal protection in the event of a fault inside the equipment. No earth wire is provided for double-insulated equipment."

There was the short answer...

Some power supplies are double insulated, some are not. Usually the cheaper ones are not.

Would someone please briefly explain what "Double Insulation" is?

Thanks

http://en.wikipedia.org/wiki/Appliance_classes

Thanks guys for all the fruitful information. As to summarize, I think we should ground the secondary neutral/common point regardless of whether it is a double insulated or single insulated transformer right guys? as for the safety of the components as well as to human touch.