Capacitive voltage divider power supply

Discussion in 'Power Electronics' started by jymmm, Jul 10, 2018.

  1. jymmm

    Thread Starter New Member

    Jul 10, 2018
    3
    0
    Hi Forum,

    I'm just messing around with a little led indicator circuit to act as an 'on' light. I thought to use a cap divider circuit to limit the current and drop the voltage down (see attached). But I'm not sure on the placement of the inrush resistor R4 and the discharging resistor R3. Any thoughts appreciated.
    Jim.
     
  2. crutschow

    Expert

    Mar 14, 2008
    19,552
    5,451
    R4 placement is fine as an inrush limiter.

    You don't need R3 or C3.

    Just select the value for C2 to give the LED current you want.
     
  3. jymmm

    Thread Starter New Member

    Jul 10, 2018
    3
    0
    Is there no benefit in dropping the voltage down for the LEDs? As well as bleeding the caps when switched off?
     
  4. crutschow

    Expert

    Mar 14, 2008
    19,552
    5,451
    Can't think of any.

    The LED is basically a current operated device.
    If you control the current to the desired value (by using the proper capacitor value), the voltage will be whatever the LED forward drop voltage is.

    What's the reason to bleed the caps when switched off?
     
  5. jymmm

    Thread Starter New Member

    Jul 10, 2018
    3
    0
    I guess i'm just over egging the pudding on this one.

    I'll drop the cap divider and the bleed R.

    Thanks for your input.
     
Loading...