Please, I need, if possible, a transformerless circuit for 220VCA to 12 VDC at 1 Amp

[rocarbri]

Please, I need, if possible, a transformerless circuit for 220VCA to 12 VDC at 1 Amp .
This circuit is for 96 5mm diameter high bright leds ( 8 x 12 in series of
3 leds) forming a ceiling light.
The total power required is less than 800 mA.
I can´t use a transformer for reasons of weight and volume.
Thanks to all.

 

[mtwieg]

Is an inductor permissible? What kind of size are you going for?

 

[Orson Cart]

POwer integrations has some good buck converter circuits straight off the line...

 

[emontllo]

Hello,

what you are looking for is called "offline LED Driver" and you will find many circuits, specific IC's application notes and demo boards! Some examples:
- National LM3445
- Allegro LC5210D

If size is important, having the LEDs in series rather than in parallel would increase output voltage and therefore, reduce inductor size.
What you have to decide too is, if you need high power factor and also if the circuit should be dimmable.

Ermest

 

[rocarbri]

It´s permissible. The height no more than 25 mm. Other measures no problem.

 

[moataz fouad]

It´s permissible. The height no more than 25 mm. Other measures no problem.

But you can find some transformers with hight less than 25mm, you can use EE12 cores.
You can use PI Expert tool from Power Integration to help you optimize your design, check this link:
**broken link removed**

 

[ea.arun]

you can also choose some designs from PI as in the below link......small changes only might be required....

**broken link removed**

this link has some buck derived solutions which must be of small size....

**broken link removed**

 

[rocarbri]

thanks to all that help me

 

[Orson Cart]

It is also possible to do a capacitor dropper (e.g. a 680nF, 275Vac, 2 x 220 ohm 2W, and a diode bridge of 2 zeners (24V say) and 2 diodes & a 220uF cap (35V) to get 50mA say at 24V, this can then be connected to a very small uncontrolled 100-250kHz square wave driver (full bridge or half bridge) and thru a very small transformer to the secondary and more importantly ISOLATED side where it can be rectified with little 35V 1A schottkies to give 12VDC at nearly 100mA which will be quite stable for voltage due to the zeners on the mains side and will work over 190-265Vac quite well - the 2 x 220ohm, 2W res are for surge and ripple freq protection.
Regards, Orson Cart.