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440v to 12 v transformerless circuit

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I guess you help defining all the input and output requirements 1st.

power, dynamic load, ac or dc in, ripple, EMI conducted and radiated , PFC etc.
 

Friends thanks to your reply my requiring is 2 phase In put (R-230 V & Y-230 V) Out Put 12 v 150 or 200 Ml Amp Actually I want to Operate only 12 v DC S P D T relay & One LED
 

Power integrations have plenty of solutions for this in a simple buck switcher, have a search of their site...
 

Dear sribangaram,
you can design transformer less 12 v supply but it has very low op current capacity.
can you tell me how much current you required for relay coil & led?
 

find attached image.
but op current is low.
ps.png
 
Hi,

you should be experienced to work with that high and dangerous voltage!!

Below is a schematic. Be warned: It is a cheap and dirty solution.
It is meant for fixed connection of LED and relay. Don´t disconnect relay or LED while power is on the input side. (Else C2 will explode!!!)
12VDC.jpg

Don´t use this circuit if you are not aware of the risks!!

Klaus

Klaus
 

There is an inherent load regulation problem with Capacitive loaded DC bridge and switched load using a smaller high impedance cap. in the source.

With no load it pumps up to input Peak voltage and 1k load only reduces it by impedance ratio with 1.2uF to 20% of peak voltage or almost 100Vdc

There is a way to improve this somewhat using a capacitive transformer method.

but, tell us why you cannot use an 440Vac AC coil contactor, which is an obvious solution.
 

Friend I have to connected one bridge rectifier with 2 phase out put voltage showing is 1000 v ........ now how to convert 1000 v to 12 v Please enplane me
 

2 phase OUTput voltage?

Apart from the obvious dangers of high voltage, this appears to be a circuit connected across two phases of a three phase + Neutral (3P&N) system. The 440V RMS will be subject to variation depending on load but even at 440V, it's peaks will be ~625V so a series capacitor should be rated at considerably higher voltage the 630V in the last schematic. It probably also needs a series inductor and varistor across the AC input to supress spikes which are likely to far exceed 440V in amplitude. If this is a 'normal' 3-phase distribution network, spikes are likely to deliver several Amps of current.

I have to ask, why are you connecting across two phase lines? If it is to detect a phase loss, bear in mind that some voltage will be returned from the load side and current can still flow via the other phases and Neutral. They may be enough operate the relay if one phase disconnected at source.

Brian.
 

Friend Actually i need timer triggering circuit I have to don that job But that circuit require 12 v DC but their is Only 3 phase supply don't have a neutral & don't want to use neutral & Earth any how I want to get 12 v dc from three phase supply at low cost I have 440 v transformer but that's cost is 70 Rupees I want to make low cost power supply Please give me any suggestion

- - - Updated - - -

2 phase OUTput voltage?

Friend I have to connected one bridge rectifier to '2' PHASE'S Means L1-230 V & L2- 230 V That time Bridge rectifair out put "+" & "-" is showing 1000 v now I am asking how to get 12v and 0.3 Amp from 1000 v DC Please excuse me for poor english
 

He wants the circuit to be extremely cheap and does not care about having any safety from electrocution.
I think this thread requirement is too unsafe and should be closed!
 
Hi Audioguru,

i feel sorry for posting the schematic.
You are correct, i also think it´s better to close the thread ... to safe the OP and other people from being hurt...

Klaus
 
Before condemning it for being unsafe, there may be another option which gives a degree of isolation.

Sribangaram, if all you need is the closure of relay contacts when the AC is present, you might be able to do it using an opto-isolator instead of a relay. It reacts faster, uses less power and still gives good safety isolation. What it does NOT do is provide any usable power whatsoever but you can use it as a switch that can be part of a circuit that gets it's power from elsewhere. Would that be any use to you?

Brian.
 

Audioguru said:
He wants the circuit to be extremely cheap and does not care about having any safety from electrocution.
I think this thread requirement is too unsafe and should be closed!
Click to expand...

These Circuits are No less safe than the OLD "AC/DC TV Sets".

As long as BOTH the circuit and Load are built in a SEALED INSULATED BOX with No Metal Exposures to the Outside, they are Quite Safe.
 

sribangaram said:
Friend Actually i need timer triggering circuit I have to don that job But that circuit require 12 v DC but their is Only 3 phase supply don't have a neutral & don't want to use neutral & Earth any how I want to get 12 v dc from three phase supply at low cost I have 440 v transformer but that's cost is 70 Rupees I want to make low cost power supply Please give me any suggestion

- - - Updated - - -

2 phase OUTput voltage?

Friend I have to connected one bridge rectifier to '2' PHASE'S Means L1-230 V & L2- 230 V That time Bridge rectifair out put "+" & "-" is showing 1000 v now I am asking how to get 12v and 0.3 Amp from 1000 v DC Please excuse me for poor english
Click to expand...

Unless this is for high volume (10k) , this requirement of 1000V to 12V@0.3A is not feasible.

70 rupees =1.3 USD is a cheap solution.
 

I would never buy a very cheaply made transformer that costs only $1.30 (70 rupees?) since it would probably burn down my home.
But I forgot that I bought some excellent surplus Name-Brand and certified SMPS power supplies (from an Indian surplus store) and they cost only $1.75 each. They were made for powering a dial-up modem (remember them?).
 

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