Switched-capacitor-based quasi-resonant converter operating at constant switching frequency

A soft-switching DC-DC converter, in which the resonant capacitor is realized by a switched-capacitor (SC) circuit, is proposed. The SC circuit plays a regulation role. Consequently, the zero-current switching quasi-resonant converter operates at a constant switching frequency. An analogue feedback circuit is used, allowing for discrete changes in the equivalent resonant capacitance, and thus, in the resonant frequency f_r. By adjusting f_r, the output voltage can be kept constant despite large variations in line and load. The control circuit is much simpler than that used in frequency-controlled quasi-resonant converters. Additional advantages of the above idea are: the soft-switching condition is fulfilled even for large load or small line values; the current stress does not increase with the line. High efficiency, as proved by the experimental results on a buck converter, is obtained