In a discharge lamp driver, a control section is configured to alternately repeat a first period in which an AC current is supplied and a second period in which a DC current is supplied, and when a first drive power lower than a rated power of the discharge lamp is supplied and an accumulated lighting time of the discharge lamp is shorter than a predetermined time, the control section is configured to set the length of the first period to be greater than that in a case where the first drive power is supplied and the accumulated lighting time is equal to or longer than the predetermined time, and set the frequency of the AC current during the first period to be higher than that in the case where the first drive power is supplied and the accumulated lighting time is equal to or longer than the predetermined time.

A projector according to the invention includes a discharge lamp, a cooling section, and a control section. The control section is configured to execute a first cooling control in which a number of revolutions of the cooling section does not depend on an inter-electrode voltage of the discharge lamp and a second cooling control for controlling the cooling section based on first control information indicating a relation between the inter-electrode voltage and the number of revolutions. The number of revolutions in the first cooling control is equal to or smaller than the number of revolutions in the second cooling control. When the inter-electrode voltage is larger than a first voltage value or when a cumulative lighting time of the discharge lamp is larger than a first time, the control section configured to switch the control of the cooling section from the first cooling control to the second cooling control.

A discharge lamp lighting device includes: a storage unit that stores information; a lamp drive unit that supplies drive power to the discharge lamp; a voltage detection unit that detects the lamp voltage of the discharge lamp; and a control unit that, on the basis of the voltage detection value supplied from the voltage detection unit, stores in the storage unit error log information that indicates the operating state of the discharge lamp when change of the lamp voltage indicates a predetermined voltage characteristic.

Described is dynamic control of the temperature of the envelope of an HID lamp in order to stabilize the output color temperature of the lamp. As the lamp power is changed, or environmental factors alter the lamp envelope temperature, the system senses these changes and adjusts the lamp cooling systems so as to move the lamp envelope temperature back to the desired point.

A projector includes a discharge lamp, a discharge lamp lighting device adapted to supply the discharge lamp with a drive current for driving the discharge lamp, a timer section adapted to count lighting time of the discharge lamp, and a control section adapted to control the discharge lamp lighting device to select and then perform either of a plurality of operation modes different in drive current to be output to the discharge lamp from each other, and the control section selects the operation mode based on the lighting time counted by the timer section.

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.

This projection-type image display device is provided with: a lamp drive unit that drives a lamp; a lamp voltage detection unit that detects a lamp interelectrode voltage (hereinafter referred to as a lamp voltage); an image correction unit that corrects image qualities of image signals to be supplied to an image display element; and a control unit that controls a correction quantity of the image correction unit on the basis of the lamp voltage detected by means of the lamp voltage detection unit. Consequently, deterioration of visibility of a projection image can be suitably suppressed.

An electronic circuit for protecting a load against over-voltage is disclosed. The electronic circuit comprises an input port for receiving a voltage and an output port for feeding the voltage to the load. The electronic circuit further comprises a switching unit arranged to switch on and off the voltage from the input port. Moreover, the electronic circuit comprises a capacitive component arranged to receive the voltage when the switching unit is switched on and is otherwise arranged to feed voltage to the output port. Furthermore, the electronic circuit comprises a comparing unit configured to control the switching unit to be switched off when a value at the output port exceeds a first threshold; and to control the switching unit to be switched on when the value is below a second threshold.

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.

A discharge lamp lighting apparatus is provided with a pulse generation part, and a power supply part converts DC applied voltage into alternating current corresponding to a frequency of the pulse, and supplies the alternating current to the discharge lamp. The pulse generation part is structured to alternately output a first pulse and a second pulse that has a lower frequency than the first pulse. The frequency of the second pulse is set to a predetermined reference frequency when a value of the applied voltage coincides with a predetermined reference value, is set to a lower frequency than the reference frequency when the value of the applied voltage exceeds the reference value, and is set to a frequency that is equal to or lower than the reference frequency when the value of the applied voltage falls below the reference value.