Abstract: A power-supply apparatus, or ballast, for starting and operating a high-pressure gas discharge lamp is fed from a battery and has at least one current- and/or power-controlled voltage converter which is coupled to a high-pressure gas discharge lamp via an ignition device and to a current/power control device via input and output terminals. A comparator of the current/power control device produces a switching signal dependent upon a lamp voltage input signal, and a capacitor, dependent upon the switching signal, is charged with a circuit having a first time constant and discharged with a circuit having a second time constant. The charge voltage of the capacitor is applied to the output to determine the level and duration of additional power supplied to the high-pressure gas discharge lamp after ignition. When the power-supply apparatus is turned off, the capacitor is coupled to a second reference voltage source and is charged by means of the first time constant.

Abstract: A circuit arrangement for a motor vehicle headlight including a reflector and/or a lens, a light source coupled to a voltage providing device (W), at least one electrically conductive heating element (H) mounted on or in an enclosing light-transmissive shield coupled to the voltage source, and a switching-on apparatus (E) for the heating element will, in addition to avoiding a coating and ice build-up, in an uncomplicated and cost effective manner provide a dependable, security-increasing, crack monitoring of the light transmissive shield in that the heating element is electrically coupled with an analyzing apparatus (A) which includes a light-transmissive-shield, crack-monitoring device formed as a current or voltage measuring device.