Abstract: A power supply for a gas discharge lamp that provides a constant current to the lamp even when there are variations in a DC input voltage includes an inverter having a drive transformer that is controlled without negative feedback to operate close to its resonance condition, which permits a substantially constant load current even for large variations of the DC input voltage to the power supply.

Abstract: A power supply for powering a neon sign assembly includes a ground fault detection circuit having a current sensing circuit that produces a voltage that is proportional to the current that flows from a center tap of an output transformer, a phase-sensitive rectifier that receives output from the current sensing circuit and a reference voltage from the transformer and produces an output voltage that depends on the magnitude of the output from the current sensing circuit and the phase angle between the output from the current sensing circuit and the reference voltage, and an amplitude comparator that produces an output to a latch circuit only when an output voltage from the phase-sensitive rectifier is equal to or greater than a pre-set ground fault current limit.