According to one embodiment, the circuit CTRL is configured to detect the nominal value of the voltage V_AC, and to adapt the threshold Vth_l to the detected nominal value of the voltage V_AC. This detection may be done by comparing, when the voltage V_T is, in absolute value, above the threshold Vth, the value of the voltage V_T to a first threshold determined by a first nominal value of the voltage V_AC and to a second threshold determined by a second nominal value of the voltage V_AC. Indeed, when the first nominal value, for example, 110 V, is lower than the second nominal value, for example, 230 V, the first threshold is, in absolute values, lower than the second threshold. The comparison of the steady value of voltage V_T to the first and second thresholds thus allows us to determine which of the first and second nominal values the voltage V_AC has.

According to one embodiment, when the circuit CTRL detects that the voltage V_T is between the threshold Vth et Vth_l, the circuit CTRL is configured to send a message to the load 400 (FIG. 1) coupled to the interface 214, via the communication terminals CC1 and CC2. The message informs load 400 that mains 201 is lost, and that interface 214 will soon stop providing a power supply to load 400. Preferably, the message is an ALERT message according to the USB Power Delivery Specification Revision 3.0.