Is there any IC chip solution to convert AC/DC?

[wylee]

I am having trouble of converting AC supply to 9V-15V DC supply

I know one can do the conversion by using a transformer and a bridge rectifier, but buying a transformer is costly and space consuming.

So I wonder, is there any off the shelf IC which can do this? I just want to use the DC voltage to power a PIR (passive infra-red) and a 555 timer...under 30mA

 

[IanP]

You can provide unisolated power but for safety reason a transformer is recommended.
But .. for I≤30mA:
You have to connect 6800Ω(10W) resistor or 470nF(rated for 250Vac) capacitor to Active (230Vac) in series with a rectifier diode (rated for 400V) and 10V zener diode between rec. diode and Neutral. You will have to add a smoothing capacitor, say, 100µF/63V .. and here is your supply voltage ..

 

[wylee]

IanP, but would it be possible if I can get an IC which does the conversion? what IC can I use

what is the 'safety reason' for using a transformer anyway?

 

[IanP]

You have no isolation, and a transformer presents one, from dangerous mains voltage. In "open circuit" situation you are exposed to full 230Vac ..
I don't know of any IC without external components that will convert 230Vac to 10(or so) Vdc @ 30mA ..

 

[seyyah]

There are some ics making conversion isolated or nonisolated but they need external components and/or transformer. But transformer will be smaller due to high frequency. But it will also cost more than a linear supply. If you don't care isolation then you should consider IanP's suggestion as you need low power.

 

[wylee]

seyyah,

my main consideration is minimizing my PCB size and lowering component cost....and also weight

could you tell me what is the part no. of the ICs you mentioned? I want to take a look on their datasheet

 

[seyyah]

This firm has related products:
http://www.powerint.com/

 

[lastdance]

there's no magic, you have to sacrifice some board space for this purpose.
I wonder if u wanted just a crude supply and up to 30mA of current, why couldn't u get it from ur system supply? u got to have one, otherwise, where is your system powered from?
However, i do not know ur app, u may have specific reasons to do so.
I am sure the simplest and most area effective method has been presented to u, you may not want to waste time to explore an IC solution.

 

[seyyah]

In addition you must have enough knowledge to make it work properly. It'll be more difficult than other solutions.

 

[prinsloo]

Look at cell phone charger circuits,yuo will find all you want to know.