In the case exemplified in FIGS. 5A and 5B, the modulating waveform V_fm does not present a symmetrical triangular plot, as in the case of FIG. 3A, where the modulating signal V_fm has (this choice being, moreover, non-imperative) rising and falling edges with constant angular coefficient (that is the same, but for the sign, which is positive for the rising edges and negative for the falling edges).

In the case exemplified in FIGS. 5A and 5B, the modulating waveform V_fm has, instead, a plot (which may be defined as a sort of “mixed” triangular plot), where:

the rising edges initially have a first value of angular coefficient, which is followed, when a value of approximately 0.3 V is reached (i.e., below the half-amplitude value of 0.5 V), by a second value of angular coefficient, higher than the first; i.e., the slope is steeper;

the falling edges have a symmetrical plot (also but for the positive and negative sign, for the rising and falling edges) and initially have an angular coefficient corresponding to a steeper slope, which is followed by an angular coefficient corresponding to a gentler slope, also in this case when the falling edge reaches a value of approximately 0.3 V (i.e., below the half-amplitude value of 0.5 V, which corresponds to a value of the frequency of the frequency-modulated PWM signal equal to the average between the minimum value and the maximum value of the frequency resulting from the modulation).