This chapter considers DC-modulated AC/AC converters and sub-envelope modulation method to reduce total harmonic distortion (THD) for matrix AC/AC converters. Single-stage AC/AC converters are the most popular structure widely applied in various industrial applications. These AC/AC converters are traditionally implemented by voltage regulation technique, cycloconverters, and matrix converters. However, they have high THD, low power factor, and poor power transfer efficiency. The mathematical modeling for DC/DC converters is a historic topic that accompanies the DC/DC converter development. The DC-modulated single-stage buck-type AC/AC converter can only convert an input voltage to a lower output voltage. For certain applications, the output voltage needs to be higher than the input voltage. In order to offer more information to readers, a DC-modulated positive output Luo converter and a two-stage boost-type AC/AC converter have been designed. Classical modulation methods such as Venturini method and space vector modulation method using AC network maximum-envelop modulation can execute matrix conversion successfully.