Abstract: The power supply to a starter of a motor vehicle engine is cut off when the power supply voltage to the starter reaches a threshold value. On closing of the starter power contacter, a time window is commenced, and during this time window the maximum value assumed by the supply voltage is measured. The threshold value is determined as a function of the maximum value measured during this time window, and may also be a function of the value of the supply voltage prior to initiation of the starting process, and/or a function of operating temperature.

Abstract: A circuit for measuring the duration of a cut-off period in the power supply to an electronic system, for example the control system of a motor vehicle starter, comprises a voltage splitting bridge and a processing unit receiving the output of the splitting bridge. The bridge supply voltage is derived from the power supply to the electronic system, and the bridge has a branch which includes a temperature variable resistor. The processing unit determines the duration of the cut-off period as a function of the value of the output voltage from the splitting bridge at the end of a cut-off period.