US Patent 7449840 Ignitor turn-off switch for HID ballasts

The instant invention relates to an ignitor turn-off switch for ballasts for high intensity discharge (HID) lamps to prevent damage to ballasts by disconnecting the ignitor if a lamp has failed or is missing. The ignitor turn-off switch circuit comprises an AC power source, a full-wave bridge rectifier circuit, a voltage regulator circuit, a first solid state integrated circuit as a timer circuit, and a second solid state integrated circuit as a switch circuit. The second solid state integrated circuit comprises an optically-coupled triac and light emitting diode wherein the optically-coupled triac is driven by a beam generated by the light emitting diode.