LED circuit

Discussion in 'General Electronics Chat' started by SVS, Jul 18, 2014.

  1. SVS

    Thread Starter Member

    Aug 16, 2012
    89
    4
    Hallo Everyone,

    I wanna design a status LED for 300V DC..

    Normally the low voltage status LED 's (5V and 12 V) are designed using a resistance in series to the supply voltage as it creates the required voltage drop.

    But for 300 V DC , a resistance in series is not the economical way due to high loss.....
    can someone please give me other suggestions???
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,133
    267
    The super easy way to do it would be to buy a small 240 VAC input switching power supply, a "wall wart" - connect an LED to the output (and maybe a dummy load to reduce the time it takes to turn off) - Done.

    The switching supply will care not that it's getting DC.
     
  3. SVS

    Thread Starter Member

    Aug 16, 2012
    89
    4
    I am looking for a simple circuit that would solve this issue so that I could integrate it in my PCB..
    Thanks anyways..
     
  4. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,133
    267
    Ahh. got it.

    Now it's a bit more tricky. Beyond a resistor, the next level is still 10 X more complex and expensive, a switching buck regulator.

    It doesn't have to regulate well or isolate, so it could be a simple design.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,813
    1,105
    Why not use a neon instead of the LED? But even a LED should do, if its's an ultra-bright type which will give reasonable light at very low current.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,156
    3,062
    Is your 300VDC really pure DC? If it has even a small AC component, you might be able to harvest a little power off that.
     
  7. EVBuilder1

    New Member

    Jul 18, 2014
    4
    0
    I'm not really familiar with CB design, but I'll throw
    out an idea....What if you used a current meter to sense the current and turned on the LED with a relay or IC?
     
  8. SVS

    Thread Starter Member

    Aug 16, 2012
    89
    4
    Something like a LED which works at 1-2mA?

    I found a LED , which has a forward voltage drop of 1.9V,@2mA.

    If my supply voltage is 300 V DC,
    then I would need a 150 K Ohm resistor with a power handling capability of 1W in series to my supply voltage.

    The loss is estimated to be 0.6 W

    Is this loss too much??
    I have also attached a datasheet from VISHAY. Please check :)

    Thank you..
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    That LED looks fine; but I'd try running it at, say, ~1mA. R = 330k 1W, loss = 0.27W. 300V is potentially LETHAL. Take due safety precautions.
     
  10. SVS

    Thread Starter Member

    Aug 16, 2012
    89
    4
    Thanks for your help and concern..

    And I have attached my circuit which explains the need of such status LEDs , where MOSFETs are used as high side switches.
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I note the company name on the paper in the pdf. Hope there's no confusion when customers were expecting to buy condoms ;).
     
  12. SVS

    Thread Starter Member

    Aug 16, 2012
    89
    4
    Let me know if you need free samples..:D:D
     
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