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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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In what place of earth can municipal power lines go from 230V to 300V?Originally Posted by Megahertz
I can understand 240 or even at max 260, but 300? Such a case would end up for compensation in court.
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