A ZVT cell for high-frequency quasi-resonant converters in ON-OFF mode for solar applications

In this paper, a fully ZVT auxiliary cell for boost type resonant converters is proposed to achieve soft switching in ON-OFF control mode. In conventional ON-OFF methods, transient and switching losses at the beginning and end of each power pulse decrease the overall efficiency of the system at high modulation frequencies. This ZVT cell offers zero voltage switching without imposing extra resonant current. This structure can be implemented in most boost type resonant converters such as class E, φ
₂
and quasi-resonant DC-DC converters. The fully ZVS operation, the absence of inductive components, and low voltage and current stress are main advantages of this cell. Thus, the ON-OFF control can be implemented at higher modulation frequencies without any significant drop in the efficiency. Simple structure and timing are other advantages of the proposed cell, which makes it useful for solar applications. The operation of the proposed auxiliary cell is analyzed in individual intervals. To verify the mathematical analysis, the proposed cell is implemented in a 3 MHz quasi-resonant boost converter. A maximum efficiency of 95.8% is obtained at 385 watts output and the efficiency drops about two percent at 80 watts at 500 kHz modulation frequency.