High voltage buck converter topology for common mode voltage reduction

A new DC buck power converter topology to actively reduce common mode voltage applied to the load is presented in this paper. The supply is designed to interface universal input DC-DC power supplies to a rectified 480 VAC (700 VDC) bus. By minimizing the common mode voltage produced, the size and cost of the passive filter elements can be significantly reduced. In the topology presented, an additional switching device to cancel the common mode voltage augments the traditional buck converter. Canceling the common mode voltage reduces the EMI filter requirements. It is shown that the switching losses remain unchanged while the voltage rating of the switching devices can be reduced. By using de-rated devices, the cost of the converter is reduced.