Power supply design considerations for maintaining a minimum sustaining current in a vortex water wall high pressure argon arc lamp

Abstract

Vortex water wall high-pressure argon arc lamps are used to generate intense light and are capable of operating at radiative efficiencies greater than 50%. These lamps are being considered for use in a pulsed DC mode of operation in the next generation of rapid thermal processing applications. The results of a series of experiments have shown that the breakdown to arc transition consists of a prethermionic electrode emission phase and a nonlocal thermodynamic equilibrium positive column phase. The large dynamic voltage and current range between the breakdown phase and the arc phase necessitates the use of the following power circuit topologies: a high voltage ignition circuit connected in series with an arc sustaining power source; and an arc sustaining current source consisting of a step down hysteresis current controlled DC/DC power converter cascaded with a constant off-time output voltage controlled step up DC/DC power converter. The current controlled power converter supplies the minimum arc sustaining current whereas the step-up power converter provides the minimum post ignition pre-arc positive column voltage. A switch placed across the high voltage supply is closed after ignition and allows a reduction of the current ratings of the high voltage circuit components. Finally experimental verification of the circuit operation and design guidelines are provided.