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3-5V DC @50mA from 230V AC without transformer

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Advanced Member level 3
Jan 11, 2006
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tinyswitch transformerless

Can any one suggest a Circuit for getting
3-5V DC @50mA from 230V AC without transformer
or any other ways.

You may use some ideas from here:

Is a great link and teaches a lot.

I would like to know how to increase and ensoure safety of the circuit using this power supply

There is almost no way to increase safety in transformer-less power supplies ..

In some circuits there is a second fuse between N(eutral) and E(arth) and the GND of the whole circuit is referred to Earth (not to Neutral). If, for some reasons, this fuse blows, the RCD (Residual current device=safety switch) device, if you have any, in your electrical installtion should trip, as your circuit becomes a "leakage" path from Active to Earth ..


what are the means to protect my circuit from the mains abnormalities like mains transients, spikes, surges, etc..


I will be glad to have more details

I assume you are talking about something hooked up to your 220V mains, so it's a power supply circuit with a lot of amps it can push into your circuit. In that case please, please, please, step back and take a look at what you're asking. If you could safely do what you're asking, companies would do it and save themselves the cost of a big expensive xformer. You need the xformer for isolation (safety). I've seen that Microchip pdf and I shudder to even think about it. There is a reason why my 2 HP, 230 V milling machine has a $200 magnetic starter switch attached to it. There is a reason why companies put circuitry on their equipment so that the user controls are 12VDC or less while the equipment runs at 110AC or 220AC or above. There is a reason why a cheap 110VAC radio still has a transformer in it and not that Microsoft appnote stuff. A magnetic field gives you isolation. Nothing else does. The Xformer you need should only cost 5-6 dollars new.

i donot have problem with money only but i have problem with size also.

I will try to use the smallest transformer, or switcher like ckt so the small transformer can be used.
As my circuit require only 20mA@5V.

I think you shouldn't be so scared ..
The transformer-less solution is as good as any other ..
Of course, safety use of electricity is always very important but without unnecassary exaggeration ..


thanks IanP for giving me courage so can u suggest me some safety tips for protecting my circuit IC and other components,

One more things my PIR Sensor module is KC778x is sensitive to power line noise. i.e is when i switch load then there is false ouput.
So I want to suppress all transients, spikes etc which could reach to my system.

If you use MOV on input and zener diode + a decent smooting capacitor, perhaps as big (not in size) as 1000µF, the mains noise shouldn't affect your PIR sensor ..
Also, you can add, say, 1mH inductors (RF choke) on both supply lines and connect a 100nF ceramic + 10µF tantalum just next to PIR ..



    Points: 2
    Helpful Answer Positive Rating
The all things pointed here are ok!See fig10 in Microchip 00954a.pdf.Is a cllasic aplication,the only thing is to have a good rated zenner,cause,without load,the current is flowing through it!-This means an minimum 1 watt zenner![better 2 watt].The condenser .47uF should be taken at 275 V AC current,or 400[600] V in DC.

For 220V use a 250V RMS MOV. If you have 230V or 240V use a 260 or 275V RMS MOV ..
As an example, have a look at NTE2V250: **broken link removed**

The size of a MOV usually indicates it's power dissipation capacity which normally corresponds to it's rating in kA, kilo (1000) Amperes, during a very short period. Remember, Power = Voltage * Current. Use the biggest MOV that will fit the PCB ..


shortly I will send my prototype ckt to u for validity and more improvement.

Do X10 products are using power from transformerless power supply.
I am not talking for all of them but few.
if you know plz provide me links for x10 products which are using transformerless power supply.

i have already gone through microchip site and there transformerless designs.

I will be glad to know other products of x10 range using similar techniques.

IanP thanks for replying to my questions sometimes they are really dumb.

from the link
I was wondering how small are the charges
and we can have such in our system
I will also search forum for charger ckt.
If some u alreay know then plz provide links.

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