The proposed method is based on burst dimming and
decreases the inverter output voltage during the burst-off period by changing
the switching pattern of the inverter.
Consequently, the lamp can be turned
OFF, while the filaments of lamp are kept preheated without adding an inverter
for preheating.
Once the lamp is turned OFF, N-times resonant mode
(where N means a natural number) occurs because the characteristic of
the resonant circuit (which depends on lamp impedance) changes drastically.
This mode keeps the root mean square of filament currents large enough to
ensure long lamp life. Moreover, the inverter operates in
zero-voltage-switching resonant mode during both the burst-on and burst-off
periods.
The proposed method thus contributes to
achieving long lifetime, small size, and low cost of lighting system for HCFLs.
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