An input of the comparator 605 receives voltage Vth_h′ and another input of the comparator 605 receives the voltage V_T′. A binary signal C3 is outputted by the comparator 605. Signal C3 is at a first level when the voltage V_T′ is above the voltage Vth_h′, which indicates that the voltage V_T is, in absolute value, above the threshold Vth_h, signal C3 being at a second level when the voltage V_T′ is below the voltage Vth_h′, which indicates that the voltage V_T is, in absolute value, below the threshold Vth_h. In this example, the voltage V_T′ is received by the inverting input (?) of the comparator 605 and the voltage Vth_h′ is received by the non-inverting input (+) of the comparator 605. As a result, the binary signal C3 is at a high level when the voltage V_T′ is below the voltage Vth_h′ and at low level when the voltage V_T′ is above the voltage Vth_h′.

Based on the value or level of the signals C1, C2, and C3, the circuit CTRL determines whether there is an issue on the mains.

In this example, when the signal C1 is at its high level, the circuit CTRL determines that there is an issue with the mains if one of the signals C2 and C3 is at its low level.

In an embodiment where the voltage V_T is not compared to threshold Vth_h, the comparator 605 of the circuit 600 is omitted.