Ac step down

[Fahime]

Hi,
I'm looking for an Ac step down Ic. That converts 220Vac to 4Volts.
Do you know this IC?

 

[Nigel Goodwin]

It's called a mains transformer!.

 

[Fahime]

It's called a mains transformer!.

I can't use transformer. Because my circuit is often standby (no load operation) and it push current few seconds when is used. As the circuit in installed in a block box and there is no air movement, the heat of transformer will hurt the circuit elements. So I need an ac/ac converter that is in form of an IC or by using some electonic elements.

 

[Nigel Goodwin]

A correctly designed transformer will run fairly cool, and probably more so than most other methods. As your requirement is for AC out, a transformer is really the only solution - unless you get REALLY complicated with a switchmode design (using a high frequency transformer), rectify it, then convert it to a crude AC electronically.

 

[dinesh.s]

What is u r current rating.

 

[RODALCO]

I second Nigels comments.

If by whatever means you want to reduce 220 Volts AC to 4 volts AC in an IC you will be in for smoke, or an early faillure of your circuit because of mains spikes.

Any mains driven timing applications which have a 'directly' mains driven IC, usually have a rectifier diode like 1N4007, to reduce powerdissipation, series resistor, and zener to supply the IC with DC.
All IC's i know off require DC at the supply rail for correct operation
Then whatever oscillator drives gates from the IC to generated AC at 4 volts.

 

[dinesh.s]

It is not necessarly used to use a power dissipation resistor, which dissipates hell lot of energy.

 

[Aily Sajjad]

What current you need out from the IC/Circuit? If you consider cost, a transmformer is cheaper than the circuit you will have to make for reducing 200 V to 4 VAC. Further, it is always better to employ some means of isolation from the mains (like transformer).

Fruthermore, What do you mean by Standby? No load? Then you can use a mains disconnecting relay to keep the transmformer disconnected whenever there is no load. It will be easy and will be safer than AC/AC down converters.

Decision is upto, which ever way you go... all will help you... (Except when you are about to fall from the hill.. all will back up then to call ambulance )...

Aily

 

[Fahime]

The current I need is 100mA.
Regarding with NO LOAD, I mean the times that the key is not hitted and so the speaker doesn't works. Is it clear now?

 

[Fahime]

Hi, I've found an IC that converts 220vac to 5 volt dc. It would be exelent. It doesn't need any dc voltage to run. But the problem is the cost. The IC number is BP5041A5.
I was wondering if there are another IC's like that or even is just ac/ac converter.

 

[dknguyen]

I don't understand what you have against transformers:

1. they ARE AC/AC converters
2. they are the most efficient converters available- meaning they heat up LESS the other converters
3. why on earth would a transformer heat up (and damage nearby components) if it was on standby? It's driving no load, it's providing no current. It's just sits there!
4. Not only do other converters draw more current on standby, they are less efficient so they heat up MORE than a transformer
5. They're cheaper than other converters
6. They provide isolation
7. I'm also pretty sure they have faster transient response than other converters

Do not mistake complexity and cost for efficiency and performance. Just because something is simple and has been around a long time doesn't mean it can't beat the pants off everything else- that's probably why it's been around for so long. By not using a transformer you are basically ignoring THE advantage of AC.

Come to think of it, before reading this post, I wasn't even aware there was any other AC/AC converter other than transformers (except for regulators)- I just don't see why anyone would bother.

 

[ericgibbs]

hi,
downloaded the data sheet for the BP +5v device.
You should realise that this device is NOT mains isolated.
The mains neutral is the common 0v/gnd line !.

If its ever connected to an incorrectly wired mains outlet [reversed L and N], the common line will be at 220v/240v ac, ( and so will YOU) depending upon your local mains voltage.

Use a mains isolating transformer, is your life or someone elses worth less
than $10 ?

Regards
EricG

Update:
have a look at the dc power supplies that are incorporated into the mains plug assembly.
a range of voltages can be selected, with current ratings of upto 1 amp
prices about $10.

 

[Papabravo]

The current I need is 100mA.
Regarding with NO LOAD, I mean the times that the key is not hitted and so the speaker doesn't works. Is it clear now?

No it most certainly is not clear. What key? What speaker?
I strongly urge you to desist from this foolish quest for an IC to apply to your problem. You're buying youself nothing but heartache.

 

[dinesh.s]

There is a way only by using bridge wave rectifier, few capacitor and other components we can build a power supply (without any inductor and switching), but i am not sure wether it will support 100 ma.

 

[dinesh.s]

Capacitor C1 has to be designed properly such that it offers 2300ohm at 50 hz and your load should be appropriately connected. i would like to hear things from other enggineer also.

 

[kchriste]

Hi, I've found an IC that converts 220vac to 5 volt dc. It would be exelent. It doesn't need any dc voltage to run. But the problem is the cost. The IC number is BP5041A5.

I wouldn't really call the BP5041A5 an IC. It is a switching regulator modual with a built in inductor. So I guess if you are looking for a more cost effective solution, you could look for a switching regulator IC and roll your own.

 

[ericgibbs]

hi dinesh,
I have used this method in the past, BUT I would NOT recommend that it
be built/used by anyone who has not a clear understanding of the potential
safety hazard. The psu is NOT isolated from the incoming mains supply.

Ready built mains input psu's with a regulated, selectable dc voltages are
readily available for a few $$. You can buy the 'inline' , enclosed type psu or
a psu built into the mains power plug assembly.

REMEMBER: when you are designing and/or building mains powered, or units
capable of generating lethal voltages, SAFETY is paramount.
As the designer of the equipment you may be aware of the danger,but
others may not.

Regards
EricG

 

[Fahime]

Could any one explain me what's wrong with asking question when you don't know something or not sure about that. I'm just doing consult about the things that may are fatal or hazardous. Why everyone should use strong language to convince the others. We are here to friendly help each other. Is it right or I might have been completely wrong!!!!!
Any way, according to the comments I think that transformer is the best choose. I used a 2pins transformer 220V~5V, A diod bridge and a capacitor. The max current is 100mA. For a 0.5V ripple, according to the formula: I=C dV/dt we have (100x0.001)=Cx0.5/(16.7/2x0.001) then: C=1670uF
I think a large capacitor is required. Right?
Mean while the output current of the transformer is not constant so the output voltage will change. These changes are not desired. Is there any way to prevent the voltage change?

 

[Nigel Goodwin]

You really need to tell us what you're wanting to feed - it makes all the difference!.

Posters are very careful and worried about people asking for help with transformerless power supplies, as I said in a previous thread "if you have to ask, you shouldn't be attempting it".

 

[Fahime]

You really need to tell us what you're wanting to feed - it makes all the difference!..

I have a melody Ic, an audio amplifier and a 8ohms loadspeaker. The supply voltage should be about 4volts.