Abstract: A lighting device for lighting a high-pressure discharge lamp 2 having an outer tube, an interior of which is substantially under vacuum. The lighting device includes a ballast 3 having at least a current limiting element and a high-voltage pulse generating circuit 4 for generating a high-voltage pulse, and also includes a lighting discriminating means 8 for discriminating between lighting and non-lighting of the discharge lamp 2, a timer circuit 9 for setting a predetermined period of time, and a pulse-stop control means 10 for stopping generation of the high-voltage pulse. When the lighting discriminating means 8 discriminates non-lighting after lighting has been discriminated, generation of the high-voltage pulse is stopped within the predetermined period of time set by the timer circuit 9.

Abstract: A level shift IC (3b) of a power supply/shutoff section (3) is operable, when a shutoff signal (Sa) is input from a timer circuit (8) for a time T during an ON state of a discharge lamp (7), to turn off a MOSFET (3a) so as to shut off power supply to a smoothing capacitor (4). When a detection signal (Sb) of a capacitor voltage is lowered to a value less than a reference voltage Vr1 during input of the shutoff signal (Sa), an output of a comparator (10) is changed from an H level to an L level in an inverted manner. In conjunction with this change, respective outputs of an auxiliary control circuit (12) and a NOT element (12a, 12b) are changed from an L level to an H level in an inverted manner. As a result, a current flows from the NOT element (12a) to an LED (13b) through a resistor (13a) to turn on the LED (13b). Thus, a life end of the smoothing capacitor 4 is annunciated, and a main control circuit (6) is operable to suppress an output of an inverter main circuit (5).

Abstract: Even if a DC output voltage of a step-down chopper circuit (3) is lowered from a value in a non-lighted state or a no-load state due to a discharge occurring between conductors (105a) in a cable (104), the turn on detection circuit (26a) can discriminates between lighted and non-lighted states without erroneously determining such a discharge as a discharge in a discharge lamp (4). This allows an operation of the timer (29) to be continued, so that high-voltage pulses are intermittently applied to prevent continuous discharge between the conductors (105) and abnormal heat generation in the cable (104). Further, even if a discharge occurs in an outer tube of the discharge lamp (4), the turn on detection circuit (26a) never erroneously discriminates this discharge as the lighted state. Thus, the lighting device of the present invention can suppress abnormal heat generations in the components and a socket (102).

Abstract: A level shift IC (3b) of a power supply/shutoff section (3) is operable, when a shutoff signal (Sa) is input from a timer circuit (8) for a time T during an ON state of a discharge lamp (7), to turn off a MOSFET (3a) so as to shut off power supply to a smoothing capacitor (4). When a detection signal (Sb) of a capacitor voltage is lowered to a value less than a reference voltage Vr1 during input of the shutoff signal (Sa), an output of a comparator (10) is changed from an H level to an L level in an inverted manner. In conjunction with this change, respective outputs of an auxiliary control circuit (12) and a NOT element (12a, 12b) are changed from an L level to an H level in an inverted manner. As a result, a current flows from the NOT element (12a) to an LED (13b) through a resistor (13a) to turn on the LED (13b). Thus, a life end of the smoothing capacitor 4 is annunciated, and a main control circuit (6) is operable to suppress an output of an inverter main circuit (5).

Abstract: A lighting device for lighting a high-pressure discharge lamp 2 having an outer tube, an interior of which is substantially under vacuum. The lighting device includes a ballast 3 having at least a current limiting element and a high-voltage pulse generating circuit 4 for generating a high-voltage pulse, and also includes a lighting discriminating means 8 for discriminating between lighting and non-lighting of the discharge lamp 2, a timer circuit 9 for setting a predetermined period of time, and a pulse-stop control means 10 for stopping generation of the high-voltage pulse. When the lighting discriminating means 8 discriminates non-lighting after lighting has been discriminated, generation of the high-voltage pulse is stopped within the predetermined period of time set by the timer circuit 9.

Abstract: Even if a DC output voltage of a step-down chopper circuit (3) is lowered from a value in a non-lighted state or a no-load state due to a discharge occurring between conductors (105a) in a cable (104), the turn on detection circuit (26a) can discriminates between lighted and non-lighted states without erroneously determining such a discharge as a discharge in a discharge lamp (4). This allows an operation of the timer (29) to be continued, so that high-voltage pulses are intermittently applied to prevent continuous discharge between the conductors (105) and abnormal heat generation in the cable (104). Further, even if a discharge occurs in an outer tube of the discharge lamp (4), the turn on detection circuit (26a) never erroneously discriminates this discharge as the lighted state. Thus, the lighting device of the present invention can suppress abnormal heat generations in the components and a socket (102).

Abstract: A device for operating a high pressure gas discharge lamp with an electronic ballast having a lamp power factor of substantially 1.0. The device utilizes a lamp equi-luminescence performance curve X which is obtained for the lamp to give a lamp voltage and a lamp wattage that can vary along the curve X while keeping an arc luminescence of an arc developing between electrodes of the lamp at substantially constant level. The arc luminescence is defined as a maximum luminescence of the arc having varying luminescence along the length of the arc. The constant level determined to be the luminescence that the lamp gives at the rated lamp voltage. The curve X is analyzed to determine a specific lamp voltage Va at which curve X gives a maximum lamp wattage Wa. The lamp is operated in accordance with a first load characteristic for controlling to increase the lamp wattage substantially along the lamp performance curve X until the lamp voltage increases to the specific lamp voltage Va.