| 摘要 |
Methods and apparatus for powering a dimmable ballast operating a gas-discharge bulb in a cold cathode mode of operation, that is, without requiring heating of filaments. The ballast circuit includes a rectifier, bypass capacitor, driver circuit, and a tank circuit that includes a resonant circuit that are configured to ionize a light source, such as a fluorescent lamp, every half cycle of the input voltage. The bypass capacitor supplies energy to produce a high frequency current introduced into the resonant circuit to continually recycle energy in the resonant circuit, resulting in a ballast with a high power factor. A tank circuit comprising a tapped inductor operating in a non-saturated or limited saturated mode provides additional voltage to the bulb to ionize the bulb. The ballast may be dimmed and combined with other energy savings circuitry.
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