A device for detecting the presence of a user for the unlocking of an access point to a motor vehicle, includes a first generator of a first supply voltage, a detection capacitor adapted to be charged on account of the presence of a user, and a storage capacitor defining at the terminals thereof a storage voltage. The device also includes an intermediate capacitor, elements for charging the detection capacitor from the first supply voltage and the storage voltage, elements for discharging the detection capacitor into the intermediate capacitor, elements for charging the storage capacitor, the elements being configured so that the charge of the storage capacitor is equal to the charge of the intermediate capacitor, and elements for detecting the presence of a user for the unlocking of an access point to the motor vehicle on the basis of the charge of the storage capacitor.