Dimmer and ground fault interruption for solid state neon supply

A dimmable power supply for neon and other gaseous luminous tubes including means for generating substantially periodic pulse groups, each pulse group comprising one or more high frequency pulses, the amplitude of the pulses being that required to produce substantially full illumination of a gaseous tube load during said pulses, the pulse groups having a repetition rate lower in frequency than that of the high frequency pulses;

• the means for generating pulse groups including a high frequency, high voltage step-up transformer having a secondary for connection to a gaseous luminous tube and a primary, dc power supply means, switch means for connecting the dc power supply to the transformer primary and for reversing the polarity of such connection in response to signals on the inputs of the switch means, a high frequency oscillator, digital gate means for selectively connecting the high frequency oscillator to the switch means inputs whereby full amplitude high frequency pulses are applied to the luminous tube when the high frequency oscillator is thus connected and whereby no output pulses are applied to the luminous tube when the digital gate means disconnects the high frequency oscillator from the switch means input;
• low frequency oscillator means having a periodic output between first and second output states, the output thereof being operatively connected to the digital gate means whereby the high frequency oscillator is gated to the switch means input in correspondence with one of said low frequency oscillator output states;
• control means for varying the relative durations of the first and second low frequency output states whereby luminous tube intensity may be adjusted by selectively adjusting the relative duration of full intensity high frequency pulse groups applied to the luminous tube.