osazee ogbeide
New Member
i want to design a mobile phone charger without a transformer
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zachtheterrible said:the only way i can see is lots of resistors or 1 big resistor, which would be a HUGE waste of electricity. You would also need to make the ac dc and even out the supply so ur gonna need capacitors, chokes, etc.
indecided said:I have a ton of compatible manufacture mobile phone chargers, and all it is is a transformer, with 1 transistor, and 4 1n4008's.
no point playing with rectifiers and all.
Nigel Goodwin said:indecided said:I have a ton of compatible manufacture mobile phone chargers, and all it is is a transformer, with 1 transistor, and 4 1n4008's.
no point playing with rectifiers and all.
:?: the 4 1N4008's are rectifiers.
There are various ways to avoid the use of transformers, but none of them are as good as a transformer, nor probably as safe either!.
Someone Electro said:my dads charger is as light as a fether and its 1 cm thick so there codnt be a transformer in there.
i know i should open it but it has odd shaped screws.
samcheetah said:my mobile phone charger is simillar to the one mentioned by Someone Electro. it says that it outputs 5.7V @ 800mA and its really really light and as thin as my mobile phone itself. so does that use a switching regulator with a switchmode transformer. i highly doubt there will be anything like a transformer in there because as i said its very light. i know i should open it but it has odd shaped screws.
Nigel Goodwin said:samcheetah said:my mobile phone charger is simillar to the one mentioned by Someone Electro. it says that it outputs 5.7V @ 800mA and its really really light and as thin as my mobile phone itself. so does that use a switching regulator with a switchmode transformer. i highly doubt there will be anything like a transformer in there because as i said its very light. i know i should open it but it has odd shaped screws.
They will be security screws, there are various types, and you can buy sets of tools to undo them.
Switchmode transformers are very light, they use ferrite cores rather than iron, and the high frequencies employed make them small. Your charger output is only 4.5W, so it's a very low power supply, a switchmode transformer for that could be tiny.
It's also possible it uses a simple capacitive dropper off the mains, but this doesn't provide proper isolation, and the dropper is likely to be fairly large.
indecided said:I also have a large number of car chargers for handphones, they are nothing more then a 8pin IC, a couple of caps, and a ferrite winding.
It's also possible it uses a simple capacitive dropper off the mains, but this doesn't provide proper isolation, and the dropper is likely to be fairly large
samcheetah said:yeah i have heard about that. but ive also heard that switchmode supplies do not necessarily want any dropper. they just take the 220VAC (or 110VAC) and convert it into DC voltage.