For a transformerless power supply how to increse current

[rajaram04]

Hello sir
There are a number of transformesless power supplies available on net & working very nicely but having a very very poor current parameter . . so how to increase the current in any of them ? i mean just to drive simple transistorised or 555 ic circuits , very simple circuits i am taking about

 

[Genovator]

There are lots of ways involved for high current output. One example is shown here...

**broken link removed**

 

[rajaram04]

hmm kk boss i got that , well i found a one statment there

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

what it actually means ?

 

[_Eduardo_]

hmm kk boss i got that , well i found a one statment there

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

what it actually means ?

If you did not understand that paragraph --> Please do not use this power supply, use transformer.

 

[rajaram04]

hmm ya sir i am using transformer presently but i want to use this kind of power supply for very low small circuits & i need too much sources for that & its not possible that all i ve to go fo 50 60 transformers thats why i am trying to design that , please help me with some other tech.

 

[godfreyl]

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

what it actually means ?

It means you might get killed if you touch any part of your circuit, even the "low voltage" part.

 

[rajaram04]

hehehe :grin::grin::grin::grin:
kk kk i ll be carefull all the way . . kk tell me some options other than this . .
any link etc

 

[tpetar]

Interesting way to get to know Mr. Death or a full team of firefighters.

 

[rajaram04]

hmm ya sir dats why please tell some other option

 

[Genovator]

There is no other 'good' option for high current without using a transformer. Other options are little risky or inefficient. If you use simple resistor as voltage divider, then around 50W to 75W resistors are required, which are larger in size and cost in respect to transformers...
You can use small smps circuits as they use small transformer for high frequency. They will consume a little less space.


Another thing you can do is using a high current triac from AC line, adjust it to minimum voltage, then rectify & filter properly to get a high current output... Some triacs are BT136, BTA40 series, etc. Proper heat sinking is required...

 

[rajaram04]

hmm kk can u explain diagramatically the procedure u ve described in last para ?

 

[godfreyl]

Another thing you can do is using a high current triac from AC line, adjust it to minimum voltage, then rectify & filter properly...

Except that that that's just as dangerous as a "normal" transformerless supply, but it's more complicated and more expensive, and will cause much worse EMI, unless great care is taken (more complication and expense).

 

[ZASto]

If you don't follow this:

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

the following might happen: **broken link removed**

 

[Genovator]

Yes, I agree with godfreyl. That is why I mentioned 'There is no other 'good' option for high current without using a transformer'.

Anything you do without transformer to get "high" current, it will be as like doing an eye surgery with a bone doctor....

I will advise you to use SMPS adapters, something like the laptop adapters, to minimize the size and risk...