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Transformerless Power Supply of 1A at 5Volts!
The topic of P.S. direcly from the mains is very dangerous and I do not recommed to do so.
But there are cases that this is unavoidable.
Current designs have the dis-advatage that are of low current.
The attached one is a clever design from Elektor and gives about 1A at 5Volts.
I repeat that all parts are live and should never be touched!
Ioannis
Microchip has examples...
The Microchip website has examples of running micros off the AC line... search the app notes...
Re: Transformerless Power Supply of 1A at 5Volts!
The circuit of Elektor will NOT work when input voltage is rising above 39 or so volts. So it will work perfectly well if input AC voltage is just up to 110. No need to change anything, or almost anything. May be just the R5 changed to a lower value, say 15 ohms.
The circuit is very clever and the SMPS is disabled by the pass transistor wheninput voltage is greater than 39 so volts. Beware it is not isolated.
Ioannis
Re: Transformerless Power Supply of 1A at 5Volts!
Did anyone try to build this circuit? Can this work at 230v AC
Re: Transformerless Power Supply of 1A at 5Volts!
It is mainly for 230 VAC
Ioannis
Re: Transformerless Power Supply of 1A at 5Volts!
It is not AC but rectified AC to result in DC. Also note the Zener that drops the voltage.
Re: Transformerless Power Supply of 1A at 5Volts!
Please review the circuit more carefully. The circuit works from zero up to about 39 volts. After that point it cuts off.
It works very good from 230 VAC.
Ioannis
Re: Transformerless Power Supply of 1A at 5Volts!
Be interesting to see what happens from 90Vac to 304Vac.
Re: Transformerless Power Supply of 1A at 5Volts!
Agreed, I'd be interested in 110VAC range.
Robert
Edit: Did you guys check Melanie's design?
http://www.picbasic.co.uk/forum/show...7531#post17531
Re: Transformerless Power Supply of 1A at 5Volts!
Quote:
Originally Posted by
jmgelba
Be interesting to see what happens from 90Vac to 304Vac.
As I said it does not do anything above 39 or so volts. So where is the problem?
After the sine wave has reached the 38-39 volts the circuits is not powered any more from the power line.
Ioannis
Re: Transformerless Power Supply of 1A at 5Volts!
Very interesting circuit, however, a think it is not going to work very well, look at T2 ( BUZ41A or IRF730) , both have a maximum 20V VGS, so when voltage get bigger than 20 , T2 gate get damage. Maybe it work for a time, but T2 VGS is out of specification.
Re: Transformerless Power Supply of 1A at 5Volts!
It won't get that high for long time to destroy the Mosfet. Also the Zener is not a switch but it does start to operate at lower that rated voltage.
It does work with great success and efficiency.
If you are concerned about Vgs, there are other Mosfets (sure more expensive) to replace this one.
Ioannis
Re: Transformerless Power Supply of 1A at 5Volts!
"voltage at few places seem to be as high as 280-300V"
No so.
Do you realise the current taken by a globe (and lots of other devices) will increase considerably as the voltage increases. When the voltage rises by say 10%, the current will rise by much more than 10% and this will put a very heavy burden on the generator and in most cases the generator will not be able to supply the load. This is why the voltage will not rise as you have stated.
Globes and radiators are not linear devices, but if they were, a 1,000 watt radiator at 250v would take 1250 watts at 280v. This is 25% increase in wattage for 13% increase in voltage.
The figures would be much higher for 230v supply.