| 摘要 |
A high-frequency, lightweight, solid-state ac ballast for operating arc discharge lamps such as fluorescent lamps. An ac ballast in accordance with the invention includes a single transistor and a storage capacitor interconnected with a lightweight air-gap ferrite core transformer provide a blocking oscillator circuit capable of high-frequency ac operation. To initiate operation of the blocking oscillator circuit, low-frequency (e.g., 50-60 hertz) ac input voltage signals are converted to a dc voltage and applied to a starting circuit for producing a voltage for charging the storage capacitor. When the voltage developed across the capacitor reaches a predetermined value, the transistor is forward biased into conduction thereby initiating operation of the blocking oscillator circuit. After a predetermined period of time, the transistor is reversed biased by a voltage produced across a regenerative feedback winding of the air-gap transformer thereby terminating operation of the blocking oscillator circuit. During the operation of the blocking oscillator circuit through several cycles, high-frequency ac voltage signals (e.g., 20 kilohertz) are produced across a load winding of the air-gap transformer for operating a pair of fluorescent lamps.
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