Two new power conversion techniques, the constant-frequency zero-voltage-switching multiresonant-converter (CF ZVS-MRC) technique and the zero-voltage-switching technique that uses the magnetizing inductance of the power transformer as a resonant element {ZVS {LM)) are proposed. analyzed, and evaluated for high-frequency applications. In addition, a novel design optimization approach for resonant type converters is introduced.
Complete dc analysis of CF forward and half-bridge {HB) ZVS-MRCs are given, and the dc voltage-conversion-ratio characteristics for each of these two converters are derived. Graphic design procedures that maximize the efficiency and minimize current and voltage stresses are established. The design guidelines are verified on a 50 W CF forward ZVS-MRC operating with a switching frequency above 2 MHz, and on a 100 W HB ZVS-MRc operating with a switching frequency of 750 kHz.
The ZVS (LM) technique is developed to eliminate the need for a large, inefficient external resonant inductor in ZVS resonant converters. This new family of isolated converters can operate with zero-voltage-switching of the primary active switches only (quasi-resonant (QR) operation) or with soft-switching of all semiconductor devices (multi-resonant (MR) operation).
Furthermore, variable and constant frequency operation of all topologies in this new family of dc/dc converters are possible.
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