The present technology provides a high-pressure sodium lamp lighting device that reduces occurrence of the acoustic resonance phenomenon. A high-pressure sodium lamp lighting device of one aspect of the present invention comprises a high-pressure sodium lamp of arc length AL within the scope of 142.8 mmAL167 mm. The lighting device also includes an electronic ballast configured to supply a high frequency AC voltage to the high-pressure sodium lamp. A lighting frequency of the electronic ballast is a frequency that avoids a first and a second acoustic resonance occurrence bands f1 kHz and f2 kHz determined based on equations from an arc tube inner diameter D mm of the high-pressure sodium lamp. The equation for f1 is a range of f1min to f1max=(7.4D+130) to (8.3D+156). The equation for f2 is a range of f2 min to f2max=(11.5D+200) to (10.0D+197).

A projector which configured to project a horizontally long image and a vertically long image, includes a cooling unit configured to cool a discharge lamp according to an installation attitude of the projector, a detection unit configured to detect the installation attitude, and a controller configured to control a discharge lamp driving unit and the cooling unit, in which the installation attitude includes a first attitude for projecting the horizontally long image and a second attitude for projecting the vertically long image, and in which the controller is configured to put out the discharge lamp in a case where the installation attitude detected by the detection unit is a third attitude which is different from both of the first attitude and the second attitude.

A discharge lamp driving device includes a discharge lamp driving unit configured to supply a driving current to a discharge lamp, and a control unit configured to control the discharge lamp driving unit. The discharge lamp driving device is configured to provide a first hybrid period and a second hybrid period each alternately including a first AC period in which an AC current is supplied and a first DC period in which a DC current with a first polarity is supplied. The control unit, in the first hybrid period, is configured to change a ratio of length of the first DC period to length of the first AC period to be increased, and in the second hybrid period, is configured to change a ratio of the length of the first AC period to the length of the first DC period to be increased.

In a discharge lamp driving device, a mixed period is provided, in which a first period in which an alternating current is supplied and a second period in which a direct current is supplied are alternately repeated and a third period alternately including a first direct current period and a second direct current period in which a direct current having a polarity opposite to a polarity of the direct current in the first direct current period is supplied. Length of the second direct current period is smaller than 0.5 ms. A total of lengths of the first direct current periods in the third period is larger than length of the second period. The third period is not provided at least when the inter-electrode voltage is smaller than a first predetermined value or when a cumulative lighting time of the discharge lamp is smaller than a second predetermined value.

A discharge lamp driving device includes a discharge lamp driving section configured to supply a driving current to a discharge lamp including a first electrode and a second electrode and a control section configured to control the discharge lamp driving section. The control section is configured to repeat a unit period. The unit period includes a direct current period including a first direct current period in which a direct current having a first polarity is supplied to the discharge lamp and a second direct current period in which a direct current having a second polarity is supplied to the discharge lamp, and an alternating current period provided between the first direct current period and the second direct current period, an alternating current being supplied to the discharge lamp in the alternating current period. The control section is configured to temporally change length of the direct current period.

A discharge lamp driver includes a discharge lamp driving unit configured to supply drive current to a discharge lamp and a control unit configured to control the discharge lamp driving unit. The drive current has a modulation drive period in which a first period in which AC current having a frequency higher than 1 kHz is supplied and a second period in which DC current is supplied are alternately repeated. In the modulation drive period, the control unit periodically changes length of a first DC period included in the second periods and in which DC current of a first polarity is supplied, and length of a second DC period included in the second periods and in which DC current of a second polarity is supplied, and increases one of the length of the first DC period and the length of the second DC period while decrease the other one.

A discharge lamp driving device according to one aspect of the invention includes a discharge lamp driving section configured to supply a driving current to a discharge lamp including electrodes and a control section configured to control the discharge lamp driving section. The control section controls the discharge lamp driving section such that a mixed period is provided in which a first period in which an alternating current having a first frequency is supplied to the discharge lamp and a second period in which a direct current is supplied to the discharge lamp are alternately repeated. The first frequency includes a plurality of frequencies different from one another. The control section temporally changes the length of the first period.

There is provide a discharge lamp lighting apparatus that comprises a discharge lamp and a power supply device configured to drive a regular lighting mode and the low electric power lighting mode in a switchable manner. The power supply device configured to control a power supply to the discharge lamp such that, in the low electric power lighting mode, after a secondary protrusion forming process in which an alternating current having a frequency equal to or greater than the basic frequency in the regular lighting mode is supplied, the low electric power lighting mode transitioning to a secondary protrusion maintaining process in which a high frequency alternating current having a frequency higher than the basic frequency in the regular lighting mode, and a low frequency alternating current having a frequency lower than the frequency of the high frequency alternating current is alternately supplied.

The present disclosure relates to a light attenuation controlling apparatus for a CDM lamp, comprising: a full-bridge inverter as a power source to supply an output to the CDM lamp; a driving circuit for driving the full-bridge inverter; a single-chip microcomputer connected to the driving circuit; a tube voltage sensing module, one end of which is connected to the full-bridge inverter so as to sense a tube voltage currently outputted by the full-bridge inverter to the CDM lamp, and through the other end of which the tube voltage of the CDM lamp is outputted to the single-chip microcomputer. The present disclosure provides a novel light attenuation controlling apparatus for a CDM lamp, which can effectively control light attenuation of the CDM lamp by constantly regulating the output of the full-bridge inverter, thereby enhancing duration of the CDM lamp.

A projector which configured to project a horizontally long image and a vertically long image, includes a cooling unit configured to cool a discharge lamp according to an installation attitude of the projector, a detection unit configured to detect the installation attitude, and a controller configured to control a discharge lamp driving unit and the cooling unit, in which the installation attitude includes a first attitude for projecting the horizontally long image and a second attitude for projecting the vertically long image, and in which the controller is configured to put out the discharge lamp in a case where the installation attitude detected by the detection unit is a third attitude which is different from both of the first attitude and the second attitude.