For certain specific applications, it is desirable to operate arc lamps, having a short arc spacing, in series because the voltage drop of such lamps is relatively low (15-18 volts). Operating multiple arc lamps individually (i.e., connected in parallel) results in inefficient high current transfer to the lamps due to increased switching loss of the associated power train circuitry associated with modulating the lamps in a high current mode. By connecting the arc lamps in series, a low voltage is presented across the power train circuitry, thus reducing the V.cndot.I losses and the I.sup.2 R losses associated with power train circuits. Improved efficiency is of utmost importance when modulating arc lamps at high power levels (e.g., 400 amps peak and duty cycles approaching 50 percent).
Operating arc lamps in a series configuration, however, can present a prohibitive condition during ignition of the arc lamps when a number of arc lamps are connected in series. The ignition voltage for typical arc lamps is on the order of 11,000 volts. Thus, in order to ignite a series string of arc lamps, voltages of 22,000 volts for two series lamps, 33,000 volts for three series lamps, etc., would be required. In applications common to certain high altitude airborne infrared tracking jammers, voltages greater than 2,300 volts at altitude have proved to be prohibitive due to the necessary voltage standoff distances required in order for ambient air to prevent arcing to the structure of the jamming system. Series ignition of multiple lamps requiring 22,000 volts, 33,000 volts, etc., is prohibitively expensive due to the extensive dielectric insulation required within the mechanical assembly of the airborne structure.
The basic circuit structure of this invention includes modifications and improvements on the co-owned circuit disclosed in U.S. Pat. No. 5,495,150 to Zawislak et al., Feb. 27, 1996. The disclosure of which is hereby incorporated by reference. Among the differences and distinctions to be noted, Zawislak did not employ voltage clamping devices, anode dielectrics, nor multiple lamp state measurement for individual control of the intermediate simmer current regulators.
USPTO Backgrounds
USPTO Backgrounds