Fan cooling device

A fan cooler for electric or electronic sub-assemblies has a control circuit with a control stage for controlling the speed of rotation of a fan motor connected to the control stage depending on set values. To achieve a polyvalent operation with a simple design, the fan motor is a phase-controlled asynchronous motor, the control circuit has a micro-controller that controls the control stage, an optic coupler is connected between the control stage and the micro-controller, and the micro-controller determines the operating angle for controlling the fan motor on the basis of the set values and the zero crossing of a control signal.