Method for controlling an electrical light source by pulse width modulation

A method for controlling an electrical light source by pulse width modulation of a supply voltage, the method comprising:

• measuring a supply voltage (U) or a parameter (I,P) dependent thereon;
• controlling a pulse width as a function of the measured supply voltage or parameter;
• generating a characteristic curve of the light source's brightness as a function of the supply voltage or the parameter dependent thereon;
• determining with a characteristic curve an actual brightness valued from the measured supply voltage or the parameter dependent thereon;
• and
• comparing the actual brightness value a brightness given value and the pulse width is controlled as a function thereof so as to maintain the light source's brightness independent of the measured supply voltage or wherein the supply voltage (U) or the parameter dependent thereon is measured at least twice during a pulse scope width (T) and the pulse width (T (n), T (n+1)) of the current or a subsequent pulse is matched subject to the recorded values of the supply voltage or the parameter dependent thereon.