New high efficiency power conversion circuits using transient current build-up soft switching technique

Abstract

To solve the non-ZVS operation of main power switch, many techniques are suggested. However, theses techniques require additional conduction loss, additional core loss, additional voltage and current stress, additional components and degraded core utilization. Therefore, this dissertation suggests three new step-down ZVS converters and two new step-up converters. First, new active clamp forward converter with improved ZVS performance is proposed. Since it uses the output inductor current ripple for the ZVS operation of main power switch, the ZVS operation is achieved by both of the ripple of magnetizing current and output inductor current. Therefore, more easy ZVS operation is guaranteed compare to the conventional one which uses only the ripple of magnetizing current for the ZVS operation of main power switch. Secondly, high efficiency active clamp forward converter with transient current build-up (TCB) ZVS technique is proposed. The structure of the proposed converter is the same as that of the conventional active clamp forward converter. However, since it controls the secondary synchronous switch to build up the primary current during the very short period of them, the ZVS operation can be easily obtained without any additional conduction losses in transformer and clamp circuit. Furthermore, there are no additional circuits required for the ZVS operation of power switches. Therefore, the proposed TCB ZVS forward converter can achieve the high efficiency, high power density and low switching noise. Thirdly, a new full ZVS-range variable transient current build-up (VTCB) asymmetrical half bridge converter is proposed. Since it controls the secondary synchronous switch to build up the current for the ZVS operation in a very short period of time, the ZVS operation of all power switches is easily achieved through all load condition without any additional conduction losses of magnetizing current. And also, large leakage inductor or additional components ar...