Hi. Long time no see.
First of all, let me tell you I do not intend to build this. So this is a theoretical discussion. And I'm not an expert on this, so don't try to build it.
The thing is all transformerless supplies are considered dangerous and I really don't understand why there's so much fuss about this. So I'm trying to design a schematic (attached to this post) that, along with proper building, would provide enough safety.
The green box labeled "Permanent insulation" contains all the components that should be encased in something like a permanent plastic case that cannot be opened. If something blows up inside (e.g. the fuse), you're supposed to throw it away and buy another one.
The schematic goes like this... C1 and C2 block any DC component that might be present on the power lines, just like a transformer. D1-D3 are avalanche diodes (somewhat like higher voltage Zeners): D1 and D2 step the voltage down, while D3 blows the fuse in case:
Outside the box, we filter the voltage in a way similar to other supplies. The input waveforms to the filter are different than in a regular supply (due to the way we lower the voltage with D1 and D2), but it can be worked around it.
As far as I can tell, the user would not be in any danger, except if D3 isn't properly connected or F1 does not blow and another failure occurs, which can't be handled anymore. Multiple D3 diodes could provide enough redundancy to reduce the probability of dangerous situations.
What do you think about this? Am I right?
First of all, let me tell you I do not intend to build this. So this is a theoretical discussion. And I'm not an expert on this, so don't try to build it.
The thing is all transformerless supplies are considered dangerous and I really don't understand why there's so much fuss about this. So I'm trying to design a schematic (attached to this post) that, along with proper building, would provide enough safety.
The green box labeled "Permanent insulation" contains all the components that should be encased in something like a permanent plastic case that cannot be opened. If something blows up inside (e.g. the fuse), you're supposed to throw it away and buy another one.
The schematic goes like this... C1 and C2 block any DC component that might be present on the power lines, just like a transformer. D1-D3 are avalanche diodes (somewhat like higher voltage Zeners): D1 and D2 step the voltage down, while D3 blows the fuse in case:
- There's a voltage spike on the power lines.
- Any other components fail and the voltage would rise to dangerous levels.
Outside the box, we filter the voltage in a way similar to other supplies. The input waveforms to the filter are different than in a regular supply (due to the way we lower the voltage with D1 and D2), but it can be worked around it.
As far as I can tell, the user would not be in any danger, except if D3 isn't properly connected or F1 does not blow and another failure occurs, which can't be handled anymore. Multiple D3 diodes could provide enough redundancy to reduce the probability of dangerous situations.
What do you think about this? Am I right?
Attachments
-
40.2 KB Views: 100