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.