Patent ID: 8143831

Claim:
Electronic control system, controlled by a pulse width-modulated signal (SG) related to earth, for regulating the voltage (Umot) across a high-side load (M), in particular a fan control unit for motor vehicles, wherein the circuit part that converts the pulse width-modulated signal (S 1 ) into the reference input variable (U−) needed for the regulation uses the positive potential of the supply voltage (V 2 ) as reference potential, so that the reference input variable (U−) is likewise related to the positive potential of the supply voltage and the control signal (S 1 ) is converted by means of a Zener diode (D 1 ) and by means of a resistance (R 5 ) connected parallel to the Zener diode (D 1 ) into a control signal related to the positive supply potential and is further converted with a low pass filter (R 7 , C 1 ) into a linear control signal, which serves as input reference variable (U−).