Abstract: A ballast (11) includes a variable output DC converter source (12) and an inverter circuit (14) arranged to provide AC output voltage to an electro-luminescent (EL) lamp (16). A Q factor of EL lamp can characterize the age of the EL lamp. A series resonance-parallel loaded circuit and two voltage detector (18, 20) are constructed to measure the Q factor. A processor (17) controls the output of DC voltage source in accordance with a look-up table containing constant brightness algorithm based on the derived voltage and Q relationship.

Abstract: A double-shielded electroluminescent panel includes an electroluminescent device, an upper electrical shield and a lower electrical shield. The upper electrical shield is a transparent conductive material, and is overlaid on the illuminating surface of the electroluminescent device. The lower electrical shield is an electrical conductive material, and is mounted on the non-illuminating surface of the electroluminescent device. The upper electrical shield and lower electrical shield are together connected to the ground line of a power source. Therefore, the occurrence of electromagnetic interference and an electric shock is avoided.

Abstract: A ballast (11) includes a variable output DC converter source (12) and an inverter circuit (14) arranged to provide AC output voltage to an electro-luminescent (EL) lamp (16). A Q factor of EL lamp can characterize the age of the EL lamp. A series resonance-parallel loaded circuit and two voltage detector (18, 20) are constructed to measure the Q factor. A processor (17) controls the output of DC voltage source in accordance with a look-up table containing constant brightness algorithm based on the derived voltage and Q relationship.