EFS Datasheet, PDF (6/14 Pages) STMicroelectronics – STARLIGHT-KIT

EFS
EFS STARLIGHT-KIT APPLICATION NOTE
1/ THE AC POWER SWITCH: FUNCTIONAL DESCRIPTION
he Starter is a bi-directional switch which performs two functions:
n the preheat of the tube,
n the ignition of the tube.
1
BALLAST
FLUORESCENT
TUBE
220V / 50HZ
PREHEAT
2
V strike
3
The mains voltage is applied
Preheating of the tube
During the preheat period, the ASD™ is fully
conducting. The tube lamp is short circuited by the
starter, and the current flows through its filaments.
In these conditions, the lamp can not light up, but
the temperature of the lamp electrodes increases.
At the end of the preheat period, lamp filaments
are warm enough to emit electrons in the gas and
to permit the lamp ignition in good conditions. The
ASD™ switches off the preheating current . At this
moment, the ballast is equivalent to a current
generator (I=I_SO, I_SO = Switched Off current). As
the ASD™ switches off, the starter voltage
increases. The amplitude of this high voltage spike
is then clamped by the ASD™ (V_BR′1350 V). As
the starter and the lamp are in parallel, the striking
pulse is directly applied to the lamp. The
electromagnetic energy of the ballast is then
discharged through the lamp and the ASD™.
Striking pulse
2/ WHAT’S NEW IN THIS SWITCH?
The AC SWITCH merges an auxiliary power
supply for the driver, a power clamping device
(1350V) and a bi-directional switch with his
execution pilot block.
NEW EFS ASD
G1
ON / OFF
G2
DRIVER
Striking of the tube
TUBE
Vcc
Power supply
GND
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