Abstract: Circuit arrangement for supplying power to a fan and/or battery from solar energy generator in a motor vehicle. A DC voltage converter using impedance matching between the solar energy generator and the fan or the battery includes a switch that is alternately opened and closed by a pulse-width-modulated operating signal, and is part of the circuit arrangement. To generate the operating signal, a microprocessor, a frequency generator and a pulse width modulator, which is acted on by the output signal of the frequency generator and a control signal of the microprocessor, are provided. These components also are used as components of an actuating device to displace a movable part of a sun roof, a changeover signal switching between use for charging a battery and/or powering a fan and use operating the sun roof. Thus, the circuit arrangement is able to fulfill multiple functions.