Analysis and design consideration of using current sensing transformer in forward converter with synchronous rectification

Current sensing in a forward converter with synchronous rectification using current sensing transformer is analyzed. That the mechanism about how DC bias of the magnetizing current in the current sensing transformer´s core is developed in light or no load condition and how the core could be saturated is also analyzed. To solve the problem, maximum reset resistor value is derived and a better solution replacing the rectifying diode by a MOSFET switch is also presented and analyzed. Experimental data was also collected and presented in the paper to confirm the analysis.