FEATURES
• Reliable lamp starting, due to well defined
inrush-current generated time delay
• Accurate resistance for ease of circuit design
• Small size and durable
• Available bulk-packed or taped-on-reel
• Long life: More than 20 000 starts for a 20 W
CFL lamp
• Material categorization: for definitions of compliance
please see www.vishay.com/doc?99912

APPLICATIONS
Fluorescent lighting and lighting ballasts for:
• CFL 5 to 25 W range
• TL HF-ballasts

DESCRIPTION
Positive temperature coefficient (PTC) thermistors for
overload protection have proved to be the ideal electronic
ballast component for increased lamp life-time.
When the rectified mains is first applied, the PTC thermistor
is cold, so its resistance is low. The lamp voltage will be
below the necessary ignition value, so the current will flow
through the cathodes, heating them to their emission
temperature. At the same time, the PTC thermistor will heat
up to its switch temperature, whereupon its resistance will
rise rapidly, allowing the lamp voltage to reach its ignition
value and light the lamp.
Once the lamp is lit, the cathodes are fed by a
high-frequency lamp supply, to avoid flicker and improve
efficiency. The PTC thermistor plays no further part until the
lamp is switched off, whereupon it is ready to resume its
smooth-starting function.
We supply a range of lighting PTC thermistors for this
application offering a wide choice of voltage and switch
times.