| 摘要 |
A self oscillating inverter drives a fluorescent lamp 8 connected in series in an L-C resonant circuit 10b, 7, the inductor 10b of the resonant circuit forming a primary winding of a feedback transformer 10. Gate drive signals for alternately conducting FET's 5, 6 (or bipolar transistors, or IGBT's) are derived from secondaries 10a, 10c of the transformer 10 via L-C resonant circuits 21, 22 and 15, 16. The resonance frequency of circuits 15, 16 and 21, 22 is preferably higher than the switching frequency of FET's 5, 6 (eg. resonance frequency of 100KHz and switching frequency in the range 10KHz to 75KHz). The gate-to-source drive voltage of the FET's 5, 6 is limited by zener diodes 19, 20 and 17, 18. The zener diodes may give equal positive and negative limit voltages (Fig.4). Preferably, however, the positive limit voltage is higher than the negative limit voltage (Fig.5), thereby preventing shoot-through by ensuring that there is a dead time (TD) between turn-off of one transistor and turn-on of the other transistor. An alternative inverter has a single transistor driven by an L-C resonant circuit.
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