[amsat-bb] AMSAT: RFI from LED bulbs?

[Robert Bruninga]

My take on LED bulbs is that the conventional ones use a DC switching
supply, but the ones with the new "orange filaments" which are actually
strings of series LEDs that add up to about 90 volts and then I assume a
resistor in the base (no switching?)

I dont think one can use a capacitor reactance to drop voltage reliably
(without additional safety limiting devices) because the drop at 60 Hz
might be fine, but the drop when a 1ms high joule transient comes along,
the energy goes right through the capacitor and dumps all that transient
into the LEDs with no protection...Just my theory, I have not proved it in
practice.  I do remember reports in the 60's when people were building
their first LED clocks and using a small capacitor to sync to the 60 Hz
line.  That sooner or later, a high-rise transient would wipe out the clock?

just theorizing...

> My understanding is that many LED bulbs use series strings of diodes
> > with the current limited by the reactance of a capacitor. This seems
> > like it ought to be quieter than the ~20 kHz AC inverter commonly used
> > in CFLs.
>
>