| 摘要 |
Controlled DC supply voltage is provided to a self-oscillating FET bridge inverter ballast from a pre-converter and by way of an inductor having two separate windings on a common magnetic core-with one winding being positioned in each leg of the DC supply. The inverter is loaded by way of a parallel-tuned L-C circuit connected across the bridge inverter's output, thereby providing a special AC output voltage thereat. This special AC output voltage is characterized in that it exhibits an unusually high rate of voltage change at its cross-over points but otherwise has a substantially sinusoidal waveshape. An instant-start fluorescent lamp is connected via a current-limiting capacitor across the bridge inverter's output. The magnitude of the DC supply voltage is so chosen as to cause the magnitude of the AC output voltage to be such as to effectuate proper instant-starting of the fluorescent lamp. Because the AC output voltage is balanced with respect to ground, U.L. requirements are met without the need for an isolation transformer. Each of the four FET's is driven by providing a sinusoidal AC voltage directly from a positive feedback winding on the tank-inductor of the L-C circuit.
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