Abstract: A combination electronic ballast designed to operate a metal halide lamp and a high-pressure sodium gas discharge lamp is disclosed. The ballast includes a primary and secondary coil coupled to a magnetic core. The primary is adapted to be connected to an ac power source and the secondary is adapted to be connected to a metal halide lamp and a high-pressure sodium lamp. The primary and secondary coils are connected together using a capacitance circuit including two capacitors and a switch. The capacitance circuit is designed to connect both of the capacitors between the primary and secondary coil when a high pressure sodium lamp is connected to the ballast and to connect only one of the capacitors in parallel when a metal halide lamp is connected to the ballast. In an alternative embodiment, the primary is adapted to be connected to one of four different ac power sources.

Abstract: A zero current crossing capacitive switching scheme for controlling the switching of a capacitor into and out of an HID lead ballast circuit at a time when a current through the capacitor is at or near zero. The capacitor switching enabling bi-level operation of an HID lamp such that the HID lamp operates at full power mode or in a reduced power mode. The zero current crossing is achieved by delaying the capacitor switching, a duration equal to about 5.degree. to 10.degree. lag from the zero volt crossing. The device can be used in a method of controlling a plurality of HID lamps using an isolated class 2 wiring scheme. Potential damage to the HID lamp caused by aborted lamp ignitions is also disclosed. The method includes suppressing off input signals during the warm up period.

Abstract: A low cost power supply for neon lamps provides enhanced safety protection. The power supply has a transformer with a return path which is separate from the earth ground so that a fault current can be detected. The power supply has a mid-point connected secondary coil design which operates a mid-point connected neon lamp configuration. A protection circuit detects the fault current flowing between the output terminals and the earth ground. When the fault current is detected, the protection circuit disconnects the input power from the primary winding. An input power reset is required to restart the power supply once the protection circuit has operated.