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Per Westermark
02/29/12 03:00
Modified:
  02/29/12 04:11

Read: 526 times
Sweden


 
Msg Score: +1
 +1 Good Answer/Helpful
#186273 - Not a good design - and expensive
Responding to: Oliver Sedlacek'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?

List of 27 messages in thread
TopicAuthorDate
AC Powered LEDs + strobe      Chico Magalh„es      02/28/12 22:58      
   Isolated Switch      Jim Granville      02/28/12 23:39      
      Switching      Chico Magalh„es      03/15/12 00:41      
   Some basics      Oliver Sedlacek      02/29/12 00:54      
      Not a good design - and expensive        Per Westermark      02/29/12 03:00      
         Answers + need some explantion      Chico Magalh„es      02/29/12 23:55      
      Cap voltage      Chico Magalh„es      03/01/12 00:03      
         More than 280V      Oliver Sedlacek      03/02/12 04:30      
            Measurement      Chico Magalh„es      03/15/12 00:45      
               Measurement correct      Erik Malund      03/15/12 07:54      
   two caps polarity reversed on DC!! ?      Erik Malund      02/29/12 07:13      
      More common long time ago      Per Westermark      02/29/12 08:33      
         I was around then      Erik Malund      02/29/12 09:21      
            Some polarized capacitors survives AC but not reversed DC      Per Westermark      02/29/12 10:01      
               POOOOOOOOOF      Erik Malund      02/29/12 10:27      
                  Yes, very likely a failure      Per Westermark      02/29/12 11:10      
                     that need bold face      Erik Malund      02/29/12 11:44      
            Back to back connection...      Kai Klaas      03/02/12 17:05      
   And another thing...      Andy Neil      02/29/12 15:30      
      Pseudo-CC with resistor requires much % V over resistor      Per Westermark      02/29/12 16:52      
      chip      Chico Magalh„es      03/01/12 00:11      
         one of these      Erik Malund      03/01/12 08:00      
         Chips      Andy Neil      03/01/12 14:33      
   PC PSU      Chico Magalh„es      03/15/12 00:47      
      Definitely better with lower voltage design      Per Westermark      03/15/12 01:11      
         PSU      Chico Magalh„es      03/15/12 18:37      
            Some bricks can inform about rating      Per Westermark      03/16/12 02:21      

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