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

    Senior Member

    Jun 19, 2012
    1,511
    403
    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

    Senior Member

    Jun 19, 2012
    1,511
    403
    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
    7,095
    1,478
    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
    13,607
    4,402
    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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