Circuit configuration for fan regulation

A circuit configuration for identifying positive and negative commutation pulses, comprising:

• an input for receiving an input voltage, proportional to a current and forming a first comparison voltage;
• a low-pass filter connected to said input and filtering the input voltage, said filter having an output at which a filter output voltage is tapped off as a second comparison voltage;
• a first comparison device connected to said input and to said filter for commutation identification and having an output at which a signal indicates a commutation if a value of one of said first and second comparison voltages multiplied by a first factor is greater than the other one of said first and second comparison voltages;
• a regulator outputting a control voltage in a manner dependent upon identified commutation pulses;
• a second comparison device connected to said input and to said filter and having an output at which is provided an output signal if a value of one of said first and second comparison voltages multiplied by a second factor is greater than the other one of said first and second comparison voltages, said second factor being less than said first factor;
• a control device connected to said outputs of said first and second comparison devices, said control device decreasing said first and second factors in the event of receiving said output signal of said second comparison device for reducing a sensitivity of the commutation identification;
• to identify positive commutation pulses, the input voltage is said one of said comparison voltages multiplied by said first and second factors and said other one of said comparison voltages is said filter output voltage;
• and
• to identify negative commutation pulses, said filter output voltage is said one of said comparison voltages multiplied by said first and second factors, and said other one of said comparison voltages is the input voltage.