Mini Switcher - about 500mA

DJG · 28th January 2003, 08:59 AM

Hello!

I need a schematic for a mini switcher with a few components only. It has to be powered by AC 220V in has to produce DC 12V.
It will be used as PSU for one relay and IC 4027. I supose that 500mA should be enough.
Does anyone have an idea how should this be done? I was hoping that i could use an IC, but i'm not sure that it is possible.

Regards,
DJG

alvaius · 28th January 2003, 06:49 PM

For a relay and a single gate, you probably need more like 20 mA, not 500. Just buy the smallest transformer you can find or buy a small AC\DC power supply. ST has a linear regulator that I believe you can get 20mA out of. Designing a switcher for AC use is just not worth it at low volumns.

DJG · 28th January 2003, 07:38 PM

Would you perhaps know the exact label of that ST? Or do you might have a schematic of it?

thx

BeanZ · 29th January 2003, 02:46 PM

National Semiconductor LM2954 series of "Simple Switchers" will work great for your application.

BeanZ · 29th January 2003, 08:38 PM

No, it wont. disregard that last post. I forgot about your 220V input requirement.

BeanZ · 29th January 2003, 08:40 PM

Try making a Royer Converter from the rectified AC line. It would require a transformer with a primary, a secondary, and two aux windings. Also, two resistors and two transistors. Your transformer should be a "square" B-H material such as Permalloy 80 or Orthonol. Good Luck!!

Helix · 29th January 2003, 08:52 PM

what about one of these ?

http://www.futura-shop.com/pdf_eng/1350-VB409SP.pdf
- only about 30 mA tho
Or

You can use a cap. to reduce mains voltage.

Be careful with mains plz

DJG · 30th January 2003, 07:17 AM

Yes, this VB409 is the right thing for me!

-Just one question - where to buy?
I looked over all the shops in Slovenia, but they don't have it

DJG

BeanZ · 30th January 2003, 01:03 PM

If you are only driving a relay and a mini IC, it would be best to just use a low frequency main transformer with rectifier and cap filter. The previously mentioned part will dissipate huge amounts of power and will require a heatsink. Also the minimum output current on this part is 80mA much higher than your required minimum. You may have trouble there.

DJG · 30th January 2003, 06:40 PM

I don't know... I realy don't want to use a transformer.
I guess I'll have to ask directly: How should I build a button-switch, witch would control 1kW toroidal trans.?

DJG

28th January 2003, 08:59 AM	#1
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Mini Switcher - about 500mA Hello! I need a schematic for a mini switcher with a few components only. It has to be powered by AC 220V in has to produce DC 12V. It will be used as PSU for one relay and IC 4027. I supose that 500mA should be enough. Does anyone have an idea how should this be done? I was hoping that i could use an IC, but i'm not sure that it is possible. Regards, DJG

29th January 2003, 02:46 PM	#4
BeanZ diyAudio Member Join Date: May 2002 Location: Cincinnati, OH now Columbus,OH USA	National Semiconductor LM2954 series of "Simple Switchers" will work great for your application. __________________ BeanZ

29th January 2003, 08:38 PM	#5
BeanZ diyAudio Member Join Date: May 2002 Location: Cincinnati, OH now Columbus,OH USA	No, it wont. disregard that last post. I forgot about your 220V input requirement. __________________ BeanZ

29th January 2003, 08:40 PM	#6
BeanZ diyAudio Member Join Date: May 2002 Location: Cincinnati, OH now Columbus,OH USA	Try making a Royer Converter from the rectified AC line. It would require a transformer with a primary, a secondary, and two aux windings. Also, two resistors and two transistors. Your transformer should be a "square" B-H material such as Permalloy 80 or Orthonol. Good Luck!! __________________ BeanZ

30th January 2003, 01:03 PM	#9
BeanZ diyAudio Member Join Date: May 2002 Location: Cincinnati, OH now Columbus,OH USA	If you are only driving a relay and a mini IC, it would be best to just use a low frequency main transformer with rectifier and cap filter. The previously mentioned part will dissipate huge amounts of power and will require a heatsink. Also the minimum output current on this part is 80mA much higher than your required minimum. You may have trouble there. __________________ BeanZ


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28th January 2003, 06:49 PM	#2
alvaius diyAudio Member Join Date: Feb 2002 Location: Toronto	For a relay and a single gate, you probably need more like 20 mA, not 500. Just buy the smallest transformer you can find or buy a small AC\DC power supply. ST has a linear regulator that I believe you can get 20mA out of. Designing a switcher for AC use is just not worth it at low volumns.

28th January 2003, 07:38 PM	#3
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Would you perhaps know the exact label of that ST? Or do you might have a schematic of it? thx

29th January 2003, 08:52 PM	#7
Helix diyAudio Member Join Date: Jul 2001 Location: UK	what about one of these ? http://www.futura-shop.com/pdf_eng/1350-VB409SP.pdf - only about 30 mA tho Or You can use a cap. to reduce mains voltage. Be careful with mains plz

30th January 2003, 07:17 AM	#8
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Yes, this VB409 is the right thing for me! -Just one question - where to buy? I looked over all the shops in Slovenia, but they don't have it DJG

30th January 2003, 06:40 PM	#10
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	I don't know... I realy don't want to use a transformer. I guess I'll have to ask directly: How should I build a button-switch, witch would control 1kW toroidal trans.? DJG __________________ Mosfet rules! In any prospect!

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