Variable intensity control apparatus for operating a gas discharge lamp

Apparatus for energizing a gas discharge lamp having a pair of electrodes which comprises:

• a rectified AC voltage supply circuit;
• a switching device;
• a resistor;
• means connecting said electrodes, said switching device and said resistor in series across said supply circuit;
• an inductor connected in parallel with said electrodes;
• a one-shot multivibrator having a first fixed time output state and a second variable time output state;
• means connecting the output of said multivibrator to said switching device to close said switching device during said first output state and to open said switching device during said second output state;
• and
• means responsive to a rise in voltage across said resistor and to the output of said rectified AC voltage supply for triggering said multivibrator to said second state to vary the peak current through said inductor and said lamp in accordance with the varying AC voltage of said AC voltage supply.

Apparatus for energizing a gas discharge lamp from an AC power source, comprising:

• an inductor connected in parallel with said lamp;
• means for generating an alternating current signal having a frequency substantially higher than the frequency of said AC power source and a fixed time period during one half cycle;
• means for modulating the peak level of said alternating current signal to provide a current waveform which varies at said higher frequency and maintains said fixed time period half cycle, but which has an average current which varies at said power source frequency;
• and
• means for energizing said lamp and said inductor with said alternating current signal.