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Ioannis,
Unless I am missing something here, K1 in your schematics seems to be a transformer. The datasheet for the LM2595 gives a maximum input voltage for this chip of 40V. If K1 is not a transformer, it looks like you would fry this chip with a power supply input of 230Vac.
Robert
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Robert.
K1 is a connector!
As for the 2595, yes you are right on the max input voltage. BUT, look carefully at the schematic.
The 2595 will get a max of 40 volts and nothing more than this. Zener, T1 and T2 will make sure that it stays in safety region.
Thats why I stated that the circuit is clever.
Ioannis
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Ioannis,
Yes, you are right about T1 and T2 keeping the voltage low on the LM2595 chip. However, I am still not convinced with this circuit. After looking at the datasheet for T2, it seems to me like the Drain and the Source inputs should be swapped for a proper grounding on LM2595. The current should be flowing away from the ground in LM2595, not towards it.
Also, the maximum VGS voltage on T2 is 20V, so if for some reason T1 fails T2 would also be fried. I don't know why Elektor designed this circuit without a transformer, and I agree with you that this is very dangerous.
Robert
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Technically the circuit is correct. No need for pin swaping. It is OK as it is.
At first I know it is a bit confusing but trust me it is very clever trick.
The purpose of zener and the 2 transistors is to let the voltage raise up to say 40 volts on the capacitor and 2595 input. Then T1 is biased and switches off T2 so that the raising voltage cannot hurt the 2595.
This is repeated again on the next half period.
As for the dangerous this refers to the live voltages all over the circuit and the circuits connected to this. Other than this I consider it "safe" in a matter of speaking to use it.
Ioannis
Last edited by Ioannis; - 8th December 2010 at 22:42. Reason: Typos
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Microchip has examples...
The Microchip website has examples of running micros off the AC line... search the app notes...
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I know some places have extreme voltage drop. Will this circuit work if AC voltage drops to lets say 160V from 230V & also if it rises to Lets say 300V from 230 V? Thanks
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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.
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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
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Re: Transformerless Power Supply of 1A at 5Volts!
Be interesting to see what happens from 90Vac to 304Vac.
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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
Last edited by Demon; - 12th December 2013 at 23:36.
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Re: Transformerless Power Supply of 1A at 5Volts!
As I said it does not do anything above 39 or so volts. So where is the problem?Originally Posted by jmgelba
After the sine wave has reached the 38-39 volts the circuits is not powered any more from the power line.
Ioannis
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