A method for operating a discharge lamp by modulating a current signal is presented. The discharge lamp is operated with at least two different frequencies. At first a probability distribution function for a first number of first frequency periods and a second number of second frequency periods is defined. Next, the first number of first frequency periods and the second number of second frequency periods are determined depending on the probability distribution function by at least one random number. The current signal is modulated by applying the first number of first frequency periods and the second number of second frequency periods to the current signal for operating the discharge lamp.

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.

A discharge lamp driving device includes a discharge lamp driving unit configured to supply a driving current to a discharge lamp including electrodes, a controller configured to control the discharge lamp driving unit, and a voltage detection unit configured to detect an inter-electrode voltage of the discharge lamp, in which the controller controls the discharge lamp driving unit so that the driving current includes a hybrid period in which a first period for supplying an AC current with a first frequency to the discharge lamp and a second period for supplying a DC current to the discharge lamp are alternately repeated, in which the first frequency includes a plurality of different frequencies, and in which the controller changes the first frequency on the basis of at least one of the detected inter-electrode voltage and driving power supplied to the discharge lamp.

According to the present disclosure, a method for operating a discharge lamp of a projection arrangement is provided. The method includes storing the first commutation scheme in the ballast, such that the first commutation scheme fulfils a specification with respect to a first criterion, wherein the first criterion represents an electrode burnback; storing of the second commutation scheme in the ballast, such that the second commutation scheme fulfils a specification with respect to a second criterion; and operation of the discharge lamp with the alternation of the first and the second commutation schemes; characterized in that, a periodic brightness fluctuation in the discharge lamp is employed as the second criterion.

The discharge lamp lighting device for supplying alternating current to a discharge lamp includes: a power supply control part having a segment signal generation part, a peak value control part, and a frequency control part; and a power supply part. The peak value control part sets a specific segment period, which indicates a value where a value of integral corresponding to a product of the length of the segment period and a peak value set in a segment period is most deviated from an average value of the values of integral within the specific period, to a period other than a final segment period positioned at the final end of the specific period, among a plurality of segment periods belonging to the specific period.

A discharge lamp lighting device includes a control unit adapted to control a frequency of the AC electric current supplied to a discharge lamp by a feeding unit, in different manners within a first term and a second term which are alternately repeated, the control unit is adapted to control the frequency of the AC electric current such that, within the first term, the frequency of the AC electric current becomes at least one frequency out of plural set frequencies, and is further adapted to control the frequency of the AC electric current, based on a predetermined frequency and an electric current within the previous first term, such that, within the second term, the frequency of the AC electric current becomes a frequency lower than this predetermined frequency.

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 drive device includes a resonant circuit section connected to a discharge lamp, a power conversion section configured to convert direct-current power into alternating-current power, and supply the discharge lamp with the alternating-current power via the resonant circuit section, and a control section configured to supply the discharge lamp with the alternating-current power having a first frequency and a second frequency higher than the first frequency in a lighting start period until the discharge lamp reaches a steady lighting state, the first frequency is a frequency for causing a resonance of the resonant circuit section, and the second frequency is a quasi-resonant frequency.

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, a control section configured to control the discharge lamp driving section, and a voltage detecting section configured to detect an inter-electrode voltage. The control section supplies a driving current including a first alternating current when the inter-electrode voltage is equal to or higher than a first voltage, supplies a driving current including a second alternating current having a frequency which is lower than a frequency of the first alternating current when the inter-electrode voltage is lower than the first voltage and equal to or higher than a second voltage lower than the first voltage, and supplies a driving current including a third alternating current having a frequency which is higher than the frequency of the first alternating current when the inter-electrode voltage is lower than the second voltage.