STX83003
Product Page
STX93003 Product Page
Among electronic driven lighting equipment available today,
CFLs (Compact Fluorescent Lamps) are the most popular and widespread
in the consumer market. Thanks to their significant energy saving,
coupled with a very simple and cost effective electronic design,
CFLs are having evident success with a yearly growth rate higher
than 20%.
In order to maintain the leadership in the lighting market,
ST is now proposing a new solution that involves both new circuit
and silicon development to cut further costs and simplify the
design.
| The Self Oscillating Topology |
The
electronic ballast can be schematised in three parts: The “Bridge
+ Filter”, the “DC to AC Converter” and the inductance
and the capacitor in series with the lamp.
The core of the electronic ballast is the DC to AC converter where,
when a self-oscillating solution is used, a saturable core auxiliary
transformer and a start up network are enclosed. In order to correctly
fix the operating frequency, the maximum flux density of the core
of the transformer and the storage time of the transistors have
to be taken into consideration.
The new proposed solution allows lamp ballast designers to eliminate
the saturable core auxiliary transformer as well as the start
up network.
It is based on a half bridge voltage fed topology and works using
an auxiliary winding on the inductor in series with the lamp,
in order to generate the waveform of the resonant driving circuit.
The effect of the variation of the storage time is drastically
reduced leading the transistors to operate with good switching
performances.
| The New Complementary Pair |
The DC-AC converter associated to the lamp is realized using the
new complementary pair of power bipolar transistors, with a relatively
high gain characteristic, that is unique in the market for this
application. The new devices are the STX83003 and STX93003.
They are NPN and PNP respectively, and are in TO-92 package, but
they are also available in SOT-32, IPAK and DPAK packages, and
are suitable for CFLs power range from 17W to 21W.
