A Two-Stage AC-DC Converter with $\Delta-\sum$ Configuration for Wide Output Voltage Range Applications

A two-stage AC-DC converter with $\Delta-\Sigma$ configuration is studied for wide output voltage range application. A three-port rectifier (TPR) with two output ports is employed to realize power factor correction and create two paths for input power. One path goes through a LLC resonant converter, the other path goes through an unregulated DC-DC transformer (DCX), The converter improves the efficiency by two ways. First, the TPR itself reduces voltage stress for switches and diodes, which reduces switching loss. Second, the DCX process a part of power which is good for overall efficiency. Dual loop control and dual carrier modulation are used to regulate the TPR. The selection methods of the voltage range of the TPR output is also been discussed to achieve relatively high efficiency under wide output range. Experimental results based on a 1KW prototype are provided to evaluate the effectiveness and advantage of the analyzed method.