Is there a cheap alternative for step-down transformers?

[einstamas]

Hello, dear forum members. I am an electronics student but most likely i learn it in my freetime.
I am working on a light project, and i need to convert 230V AC to 5-12V AC or DC(building a rectifier isn't really hard), but i need a high current of 15-20 amps on the secondary coil of the transformer. I found some transformers which are capable of this, but they are pretty expensive for me.

Is there a way of "transforming" down voltages without using a transformer? I was thinking about thing such as PWM with a capacitor on it, but i don't even know if that would work and i guess it wont be capable of supplying me a current this high.

I've seen some chinese LED light bulbs working without a transformer, and i am thinking about it for a long time.
I know the most secure way would be to use a transformer, and if there is no other option i will do that. But i am really curious if there is another way to solve this problem.

Thanks for the read and for any help! Have a nice day!

 

[augustinetez]

You'll be looking at a Switch Mode Power Supply as an alternative at those sorts of currents.

This is one example Ebay SMPSU 12V 30A

 

[Diver300]

Is there a way of "transforming" down voltages without using a transformer? I was thinking about thing such as PWM with a capacitor on it, but i don't even know if that would work and i guess it wont be capable of supplying me a current this high.

I've seen some chinese LED light bulbs working without a transformer, and i am thinking about it for a long time.

Tranformerless power supplies won't increase the current like a transformer will. Also, transformerless power supplies are not a practical solution when the current output is more than about 50 mA. They also don't isolate, so there is a safety issue. Transformerless supplies often need shunt regulators, so the power consumed is the same for any load up to the maximum, and that means that they are very inefficient at low loads.

Inside an LED light it is quite easy to put many LEDs in series, so the voltage needed is quite high and the current is quite low, so a transformerless supply is practical. There is also no issue with isolation, as the lamp housing is all plastic. Finally, the load is constant, it's just the LEDs, so there are few problems with a tranformerless supply, and they are often used.

 

[Pommie]

I have a(n) smps that is 12V and 30A - 360W. I have no problem with isolation etc. Where did the 50mA come from?

Mike.

 

[Nigel Goodwin]

I have a(n) smps that is 12V and 30A - 360W. I have no problem with isolation etc. Where did the 50mA come from?

Mike.

I think you're both a little confused with each other

The 50mA was referring to a transformerless PSU, NOT an SMPSU - and he was confiused as the original reply by augustinetez proposed an SMPSU and not a transformerless one. The only actual transformerless reference was to mains LED bulbs by the OP.

However, as so often in thiese kinds of threads it's all very vague, and we've little idea of what he's actuially wanting or trying to do?.

 

[Pommie]

I'm guessing with a 50mA limit we're talking a resistor and zener type regulator - or capacitive divider. The OP states a much higher current and it was explained that an smps supply is probably needed. No confusion at all.

Mike.
BTW, is an smps not transformerless? Guess that depends on the smps but I think of them as transformerless as they don't have a huge transformer.

 

[shortbus=]

BTW, is an smps not transformerless? Guess that depends on the smps but I think of them as transformerless as they don't have a huge transformer.

Wouldn't that just make them(SMPS) transformer lite not transformer less? Kind of like lite beer?

 

[Nigel Goodwin]

I'm guessing with a 50mA limit we're talking a resistor and zener type regulator - or capacitive divider. The OP states a much higher current and it was explained that an smps supply is probably needed. No confusion at all.

Mike.
BTW, is an smps not transformerless? Guess that depends on the smps but I think of them as transformerless as they don't have a huge transformer.

Most of them have a transformer, it's just smaller because of the higher frequency.

 

[tomizett]

PC power supplies are always a good option if you can use 5V. You can often find scrap ones for free. There are plenty of instructions on line about how to connect them up.