A New Transformer-Based Non-Isolated Topology Optimized for VRM Application

The duty cycle of conventional multi-phase buck converters becomes extremely small as the output voltage becomes lower and lower. This is a severe challenge with the switching frequency goes up. This paper introduces a non-isolated half bridge converter which can extend the duty cycle to a favorable range. Thus, the converter will have symmetrical dynamic response ability. The switching loss will reduce dramatically. The primary current is directly transferred to the output. The energy transferring is more effectively then that of conventional isolated half bridge converter. In addition, the voltage stress of the primary MOSFETs equals to the input voltage, which is much lower than that of non-isolated forward or push-pull topologies. A 12 V input, 0.8 V/30 A output, 500 kHz prototype was built to demonstrate the advantages