Patent ID: 7378929
Filing Date: 2008-05-27
Classification: H01F,H02M

Abstract:
1. A power supply, comprising: an energy transfer element including an input winding, an output winding, an electrically conductive shield and a cancellation winding, the input winding coupled to a first input voltage terminal, the electrically conductive shield and the cancellation winding coupled to a second input voltage terminal, the cancellation winding wound such that a first displacement current to flow from the cancellation winding to the output winding substantially offsets a second displacement current to flow from the output winding to the second input voltage terminal to result in a substantially zero net displacement current between an input circuit coupled to the input winding and an output circuit coupled to the output winding; a switch coupled between the energy transfer element input winding and the second input voltage terminal; and control circuitry coupled to a control terminal of the switch, the control circuitry to control the switch in response to the output circuit coupled to the output winding.