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Abstract

A trigger circuit is coupled to a gas discharge lamp having anode and cathode terminals, a minimum anode voltage and a minimum holding voltage. The trigger circuit periodically transmits a trigger voltage pulse to the lamp to provide first stage ionization of the gas in the lamp. A power supply circuit charges a boost storage capacitor to a first voltage and an energy storage capacitor to a second voltage above the minimum holding but below the minimum anode voltage. The sum of the first and second voltages exceeds the lamp minimum anode voltage. A voltage controlled capacitor switching circuit includes input terminals coupled across the boost storage capacitor and across the energy storage capacitor and output terminals coupled to the anode and cathode terminals of the lamp. This switching circuit operates in a first state to apply a boost voltage exceeding the minimum anode voltage across the lamp anode and cathode terminals to allow energy to flow into the lamp after the first stage ionization of the lamp by the trigger circuit to provide second stage ionization of the lamp. The capacitor switching circuit switches into a second state after the boost voltage falls below the minimum anode voltage but before it falls below the minimum holding voltage to couple the energy storage capacitor across the lamp anode and cathode terminals to enable the energy storage capacitor to discharge additional energy into the lamp.

First Claim