Step-UP ZVS converter with bi-transformer

In this paper, a step-up active-clamp SEPIC with bi-transformer is presented for battery sourcing application. Two voltage double circuits are connected in series at secondary side, thus, the output voltage could be increase compared with the conventional isolated SEPIC converter. The voltage double circuit at secondary side provides high voltage gain and limits the voltage spike on output diodes. The interleaved operation in output side reduces ripple current and output capacitance. The active-clamp technique is used to reduce voltage stresses on switches and achieve ZVS for main and auxiliary switches and recycle the stored energy of resonant inductance and magnetizing inductance. The leakage inductance of the transformer and additional resonant inductance are used to achieve ZVS during the dead time. Therefore, high conversion efficiency can be obtained. The analysis and design consideration of the proposed converter are shown in detail. Experimental results are shown to prove prototype with input 48V and 200V / 2A output.