Cold cathode lamps use is mostly in decorative lighting that often feature flashing sequencers which would create a huge stress on the filter capacitor, what would be killing for the lamp, but as well as for the sequencer switch, so their ballasts just do not use them. Being cold cathode, there is no penalty extinguishing and reigniting the discharge, so there is no need to sustain the arc over the mains zero cross to prevent excessive wear (as with the high efficacy optimized hot cathode designs). Consequently they power the lamp only when there is enough voltage at the mains waveform, so not around the zero crossing. The consequent flicker is in the decorative use not considered as a problem with the targeted application, on the other hand the inrush current of a ballast featuring the filter capacitor killing the sequencer and even the lamps would be quite a show stopper for such lamp.
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