Importance

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Abstract

A ballast circuit for energizing a lamp includes an inverter circuit with a start up circuit which provides a repeating start up sequence until a lamp lights. The start up circuit includes a start up switching element coupled across a start up capacitor which initiates operation of the inverter. A rapid start capacitor is charged as the inverter applies a signal to the lamp and the voltage on the rapid start capacitor determines the conduction state of the start up switching element. The inverter applies an increasing strike voltage to the lamp until the lamp lights or until the lamp voltage becomes greater than a predetermined level. After the restart capacitor discharges, the start up capacitor charges to re-initiate operation of the inverter. The ballast thereby applies a strike voltage to the lamp having a relatively small duty cycle for reduced stress on the circuit components.

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First Claim