| 摘要 |
<p>In accordance with the invention, there is provided a ballast circuit for a gas discharge lamp. The circuit comprises means for providing a d.c. bus voltage on a bus conductor with respect to ground. The circuit includes a resonant load circuit incorporating a gas discharge lamp and including first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. Further included is a converter circuit coupled to the resonant load circuit so as to impress a bi-directional voltage thereacross and thereby induce a bi-directional current in the resonant load circuit. The converter comprises first and second switches serially connected between the bus conductor and ground, and having a common node coupled to a first end of the resonant load circuit and through which the bi-directional load current flows. A current-sensing winding senses at least a portion of the current flowing in the resonant load circuit. A feedback arrangement generates a feedback signal in response to current flowing in the current-sensing winding, and re-generatively controls the first and second switches in response to the feedback signal. A starting circuit superimposes a starting current pulse through the current-sensing winding, so as to achieve the re-generative control of the first and second switches.</p> |
