Device for detecting a capacitance variation and capacitive sensor for detecting the presence of a user using such a device

A user presence detection device, integrated in a motor vehicle, for detecting a variation in the capacitance of a variable capacitive structure (Cx), comprising:

• a generator for generating voltage pulses;
• a capacitor for charging the variable capacitive structure by means of said voltage pulses;
• a resistor for discharging said variable capacitive structure toward a reference capacitor;
• a comparator for detecting a voltage threshold across the terminals of the reference capacitor;
• a counter for determining a number of charges and discharges of said variable capacitive structure corresponding to said voltage threshold;
• and
• an ECU for detecting a variation in said number of charges and discharges with respect to a number of charges and discharges previously obtained.