Wide dimming range gas discharge lamp drive system

Dimmable backlighting for a display panel comprising:

• a fluorescent lamp;
• a power supply having a relatively high frequency AC output;
• igniter means disposed external of but in proximity to substantially all of said fluorescent lamp for ionizing the gases in said fluorescent lamp when a high voltage pulse of a relatively short duration with respect to the frequency of the high frequency AC output is applied to said igniter means;
• drive means for applying a short duration, high voltage pulse to said igniter means and for connecting said power supply to said fluorescent lamp while its gases are ionized to turn said fluorescent lamp on;
• and,
• control means for controlling said drive means for varying the time said power supply is connected to said fluorescent lamp for varying the average light output of said fluorescent lamp.

A dimmable fluorescent lighting system comprising:

• a fluorescent lamp;
• an external igniter disposed on said fluorescent lamp for causing ionization of lamp gases when the external igniter has a high voltage pulse applied thereto;
• a relatively high frequency AC voltage source;
• gate means for applying said AC voltage source to the fluorescent lamp;
• and,
• control means for triggering said gate for selected time periods to control the average light output of said fluorescent lamp and for applying a short duration, high voltage pulse to said external igniter at the start of each selected time period to start said fluorescent lamp.

A method of controlling the average light output of a gas discharge lamp which can be excited from an AC voltage source comprising the steps of:

• (a) disposing an external igniter in close proximity to the gases within the gas discharge lamp;
• (b) applying a short duration, high voltage pulse having a rapid rate of rise to the external igniter to ionize the gases in the gas discharge lamp when the lamp is to be turned on;
• (c) applying to the gas discharge lamp while its gases are ionized the AC voltage source for selected periods of time which are a function of the desired average light output;
• and
• (d) varying the length of the periods of time when the AC voltage source is applied to the gas discharge lamp to vary the average light output of the lamp.

A method of controlling the light output of a fluorescent lamp which periodically has an AC voltage applied thereto for variable time periods comprising the steps of:

• disposing an external igniter on substantially the entire length of the fluorescent lamp;
• applying a short duration high voltage pulse having a rapid rate of rise to the external igniter to ionize the gases in the fluorescent lamp in conjunction with immediately thereafter applying the AC voltage to the fluorescent lamp causing the lamp to turn on;
• and
• varying the time periods during which the AC voltage is applied to the gas discharge lamp to change the average light output of the lamp.