A fan regulation circuit configuration includes an input receiving an input voltage
(proportional to fan current and forms a first comparison voltage), a low-pass
filter (filters input voltage and a filter output voltage is tapped off as second
comparison voltage), a first comparison device for commutation identification (outputs
signal indicating a commutation if value of one of the comparison voltages multiplied
by first factor is greater than the other comparison voltage), and a regulator
(outputs a control voltage dependent upon identified commutation pulses). The circuit
has self-adjusting sensitivity adaptation and a second comparison device outputting
a signal if the value of one of the comparison voltages multiplied by a second
factor is greater than the other comparison voltage, the second factor being less
than the first factor. A control device decreases the first and second factors
in the event of an output signal of the second comparison device being received
to reduce the sensitivity of the commutation identification.