Pulse density modulation using pulse pattern approach for zero-cross switch control

An approach of the pulse density modulation allowing a high modulation factor for the zero-cross switch control is proposed. The pulse pattern for the pulse density modulation is determined over an interval of several clock to allow a high modulation factor. The noise shaping filter is designed utilizing a continuous-time one to realize a high effective resolution of the modulation. In the presented example, the effective resolution is above 20 levels with the bandwidth of the Nyquist frequency using eight-clock pulse patterns with a third order noise shaping filter.