Method for determining a predefinable wave form of a lamp current for operating a discharge lamp of a projection arrangement, and projection arrangement

A method for determining a predefinable wave form of a lamp current for operating a discharge lamp of a projection arrangement in at least one operating mode, wherein the projection arrangement has a predefined rotatable color wheel and the discharge lamp for illuminating the color wheel, wherein the discharge lamp has two electrodes, wherein the projection arrangement has a ballast for the discharge lamp, which ballast, during the operation of the projection arrangement, provides for the discharge lamp a lamp current embodied as alternating current and having the predefinable wave form, which has a predefinable commutation scheme, such that a polarity of the electrodes is commutated in accordance with the predefinable commutation scheme, the method comprising:

• providing at least one wave form having a commutation scheme, wherein the commutation scheme is constituted in such a way that it has an even number of commutations in a predefined time interval, wherein the time interval is predefined by the color wheel rotating twice during the operation of the projection arrangement in this time interval;
• checking whether operation of the discharge lamp with a lamp current having the at least one wave form satisfies a criterion which relates to a lifetime of the discharge lamp;
• if at least the one criterion is satisfied, storing the at least one wave form in a memory of the projection arrangement, and providing the at least one wave form as the predefinable wave form at the ballast for the discharge lamp.

A projection arrangement comprising:

• a predefined rotatable color wheel;
• a discharge lamp for illuminating the color wheel, said discharge lamp having two electrodes;
• wherein the projection arrangement has a ballast for the discharge lamp, which ballast is designed to provide, during the operation of the projection arrangement, for the discharge lamp a lamp current embodied as alternating current and having a predefined wave form, which has a predefined commutation scheme, such that a polarity of the electrodes is commutated in accordance with the predefined commutation scheme;
• a memory, in which the predefined wave form is stored, wherein the predefined wave form stored in the memory is embodied in such a way that one criterion with regard to a lifetime of the discharge lamp and a further criterion with regard to a flicker amplitude of the discharge lamp are satisfied during operation of the discharge lamp with a lamp current having the predefined wave form.

A projection arrangement comprising:

• a predefined rotatable color wheel;
• a discharge lamp for illuminating the color wheel, said discharge lamp having two electrodes, wherein the projection arrangement has a ballast for the discharge lamp, which ballast is designed to provide, during the operation of the projection arrangement, for the discharge lamp a lamp current embodied as alternating current and having a predefined wave form, which has a predefined commutation scheme, such that a polarity of the electrodes is commutated in accordance with the predefined commutation scheme;
• and
• a memory, in which the predefined wave form is stored, wherein the predefined commutation scheme is constituted in such a way that it has an even number of commutations in a predefined time interval, wherein the time interval is predefined by the color wheel rotating twice during the operation of the projection arrangement in this time interval, wherein the predefined wave form stored in the memory is furthermore embodied in such a way that one criterion with regard to a lifetime of the discharge lamp is satisfied during operation of the discharge lamp with a lamp current having the predefined wave form.