Transformerless Power Supply.

[lord loh.]

**broken link removed**

from aaron cake site...

If I need to draw 5A DC, do I need to draw 5A from my 220v line? I would like to have a powersupply as compact as possible and yet want it to deliver a clean 5A current.

If I decide to use an SMPS IC, I still need atleast 15v unregulated DC to regulate between 12vDC and 5VDC...

Please help.

 

[Nigel Goodwin]

**broken link removed**

from aaron cake site...

If I need to draw 5A DC, do I need to draw 5A from my 220v line? I would like to have a powersupply as compact as possible and yet want it to deliver a clean 5A current.

Yes you do, and that horribly crude circuit wouldn't be any good for it.

If I decide to use an SMPS IC, I still need atleast 15v unregulated DC to regulate between 12vDC and 5VDC...

If you're doing it SMPS, then have two secondary windings on the transformer (or one tapped winding) - assuming you want 5V and 12V, if you just want variable 5V to 12V, you can probably design the supply to adjus that much.

But in any case you need a transformer, and for SMPS almost certainly a hand wound one.

 

[akg]

5A amps.!! ..tooooo difficult . these ckt are good only some mA of current

 

[JRoque]

Hello. Be aware that if you don't use a transformer there will be a high potential (about 57V) on the ground output terminal. That means that if you try to hook that circuit to anything else that's common grounded, sparks will fly. The DC output will be about 170V. If you want a lower output, D1 will have to dissipate the difference and could be significant.

JR

 

[penoy_balut]

how about a simple phase control circuit that uses SCR

 

[mvs sarma]

**broken link removed**

from aaron cake site...

If I need to draw 5A DC, do I need to draw 5A from my 220v line? I would like to have a powersupply as compact as possible and yet want it to deliver a clean 5A current.

If I decide to use an SMPS IC, I still need atleast 15v unregulated DC to regulate between 12vDC and 5VDC...

Please help.

Lord loh did not ndicate that th psu is variable- neither has he responded-- if we assume the requirement as 5VDC with 5 amps load, it is better to go for a simple smps with latest ICs, e.g., TOP246 of power integration inc or Viper series of ST micro. etc.,

the smps need not have seperate regulator as the loops takes care with aux winding and a zenor ref or TL431.

25watts from transformerless at such low voltage (5V) calls for either a bulky linear transormer and heavy electrolytic or smps.

 

[Hero999]

how about a simple phase control circuit that uses SCR

Exactly the same applies, it'll work for low currents only (though a little higher than this crude circuit) and it isn't isolated.

 

[Nigel Goodwin]

Exactly the same applies, it'll work for low currents only (though a little higher than this crude circuit) and it isn't isolated.

Plus SCR's have a poor reliability record - plan for it going S/C!.

 

[Hayato]

It is better to build this power supply with a 7.5V 35VA transformer. You gonna get a nice power supply for almost the same price than a very poor quality transformerless power supply.