| ??? 02/29/12 10:00 Modified: 02/29/12 11:11 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#186273 - Not a good design - and expensive Responding to: ???'s previous message |
I guess you have found this schematic on the net somewhere.
The AC-side caps are there as current limiters. This design is illegal in many countries. 1) It is illegal because the lack of isolation. 2) It is illegal because of the irregular load on mains, affecting the wave form. Third is that with high-intensity LEDs, control of voltage/current is much more important that with old LEDs. You don't have much margin between "optimum light" and "dead". As noted, transients can kill all your diodes. But so can a slightly higher mains voltage in case you have a three-phase system that gets unbalanced unless you are willing to have enough voltage margin on the series resistor that it can swallow that extra voltage with the LEDs still within proper current range. Why not create a real solution and use chains of maybe 80V instead? How fast do you need to flash them - can't you use a current-controlled driver? What is a cost of one (1) accident that burns 50% of your LEDs? What is the cost if someone manages to touch the circuit and comes after you for compensation? What is the cost if some inspector sees this design and orders it immediately removed? |
