A novel control method for multilevel converter used inenvelope tracking power supply

The topology of a multilevel converter in series with a linear regulator is a hybrid solution for envelope tracking power supply. A novel control method based on Walsh Transformation of envelope reference was proposed for the multilevel converter. The needed voltage levels for multilevel converter can be derived from the linear combinations of Walsh coefficients and the number of voltage levels can be determined by the order of Walsh basis. The overall power losses of the hybrid topology was analyzed and an algorithm for the optimization of the voltage levels was explained. The proposed control method is simple and can effectively reduce the ratio between the switching frequency and the bandwidth of envelope reference, especially for the periodic signal. A prototype was built for the hybrid solution, which can reproduce any signal with maximum spectral component of 1MHz and give instantaneous maximum power of 50W.