Transformerless Power Supply (230 volt to +12v/500ma)

[betwixt]

I sense this thread is going nowhere.

Bjtpower, you are basically asking for a physically large, very expensive, potentially very dangerous and always inefficient power supply.

You seem to be heading down the wrong design path and failing to observe all the pitfalls previously mentioned.

Can I ask what you are trying to achieve? What is the intended use of this power supply?

Brian.

 

[Bjtpower]

Hi Brian

We are making Proof of concept for all Kind of power supply.

For the Demonstaration against switch mode power supply,Linear Supply and capacitive power supply.

That will help us to classified different types of Power supply design possibility.


Thanks
Marx

 

[FvM]

O.K., can be at least instructive. You need to calculate the component values in a proper design process to get valid information.

It has been previously suggested to use a full wave bridge because the capacitor value can be halved. It's not quite clear if you require a common mains terminal with DC- which would enforce half wave? But anyway, after setting an AC capacitor value of 15 to 22 µF (half wave rectifier) or 8 to 10 µF (full wave), you'll search a suitable type with 250 V AC rating. You'll also care for inrush current and possible mains surges and select a series resistor with sufficient power rating and pulse handling.

 

[betwixt]

We are making Proof of concept for all Kind of power supply.

OK, that make the question more reasonable. By far the most important concern you should mention in your report is that transformerless supplies do not provide any voltaic barrier between the incoming AC and the output connections. It makes them extremely dangerous and they should never be used in a situation where any part of the PSU or it's load can be touched or any part of the load can be linked to any other equipment. You can not ground the output of a transformerless supply, it has be left 'floating' and potentially can attain lethal voltages with little or no current limit.

They are fine in situations where they are completely enclosed and have no external connections but useless anywhere else. You will find them in low energy light bulbs and some very low power but completely encapsulated circuits but nowhere else, at least legally! They can be cost effective in low power applications but the high cost and large size of the capacitor makes them impractical at more than a few tens of mA load current.

Brian.