High-efficiency design of multiphase synchronous mode soft-switching converter for wide input and load range

A four-phase interleaved bidirectional dc-dc converter with coupled inductor is adopted in both boost- and buck-mode operations. The circuit allows synchronous mode operation to achieve zero-voltage switching. Together with the use of low R ds-on power MOSFET as the switching device, ultra high efficiency can be obtained. This paper shows a high-voltage example system operating completely in synchronous mode with 99.2% efficiency at the full load, but only 93% at 10% load. A low-voltage system example is then proposed to operate in synchronous mode under light-load condition and in continuous conducting mode under heavy load condition to achieve high efficiency over a wide load range. The peak efficiency of the second example system reaches 99.5% in between 10 and 20% load and maintains above 98% throughout the rest of load range.