| 摘要 |
In a first embodiment an electronic ballast system is provided for two gas discharge tubes (202, 202 min ), the ballast system comprising a first transformer (238) powered by an AC source (204) via wave bridge (218). Transformer (238) comprises primary and secondary windings (240 and 242) which establish an oscillating signal. Two transistors (256, 258) are coupled in feed-back relation to the transformer for switching a current signal in response to the oscillation signal. Two inverter transformers (210, 212) establish an induced voltage signal responsive to the current signal which is passed to the tubes via capacitors (308, 310). Capacitance tuning circuits embodying capacitors (312, 314; 316, 318) serve to modify the resonance frequency and duty factor of the signal pulse generated by each inverter transformer. …<??>In a second embodiment, tube (12) is powered by a ballast system comprising transformer (T) connected to AC power source (14) via rectifying diode (D1). Primary winding (22) of transformer (T) is connected in series with the power source (14) and filament (30) of tube (12) via capacitor (C2). Secondary winding (24) of transformer (T) is connected in positive feed-back relation with the base (44) and emitter (42) of a transistor (Tr). The collector (38) of the transistor (Tr) is connected to the capacitor (C2). Second capacitor (C3) is connected in series with the transformer secondary winding (24) to apply a pulse voltage to the second filament (32) of the tube (12). |
