Emergency Lighting Fluorescent Lamp

 The 8W emergency lighting converter
shown here CAN be constructed at a
fraction of the cost of older TO220
transistor based designs. Using the
ZTX851 which has a saturation voltage
of only 150mV at 4A (the cycle by cycle
peak current seen with this design), the
circuit runs with an efficiency of over
70%, a key feature for these battery
operated circuits. Care with the
transformer design and construction will
allow the use of the higher gain ZTX869 BR>which will raise efficiencies even
higher.The ZTX851 and ZTX869 are
available in the E-Line (TO92 style)
package which has a 1.2W power rating
for these device types.This permits
significant space savings to be made
since the bulky TO220 Transistors and
corresponding heatsinks CAN be
eliminated. The operating frequency has
been limited to around 25kHz to
minimise transformer losses, yet
ensuring the converter is inaudible.
Emergency lighting systems provide
illumination in the event of mains failure
and consist of a monitor circuit, a battery
pack with trickle charging, and a DC-AC
inverter. The inverter is used with the
existing fluorescent tubes or an
additional smaller tube, and is enabled
by the monitor circuit.
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Emergency Lighting Fluorescent Lamp application circuits
Emergency Lighting Fluorescent Lamp application circuits



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