A novel winding coupled-buck converter for high-frequency, high step-down DC/DC conversion

The buck converter is popularly used for stepdown DC/DC conversion when there is no isolation requirement. However, for high step-down, large output current applications such as voltage regulation modules (VRMs), it is no longer suitable, especially at high switching frequencies. The too-small duty cycle and large switching-related loss limit its performance. This paper proposes a novel topology, which is based on the use of additional coupled windings and can solve all these problems. An integrated magnetic structure is proposed for these windings so that the same magnetic cores can be used as in the buck converter. Furthermore, it is easy to implement a lossless clamp circuit to limit the device turn-off voltage spike and to recover inductor leakage energy. Experimental results obtained with a 12 V to 1.5 V/25 A VRM prove the significant improvement of the proposed topology at switching frequencies in excess of a megahertz.