Safety Circuit for Line Frequency Leakage Current
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
An inductor and the equivalent input capacitance of a filtered input switching regulator (SR) are configured as a parallel resonant circuit to mitigate line frequency leakage current in the ground return. In SRs using a single- or multiple-phase input house supply, it is customary to provide a half-section type LC filter in each phase input to attenuate any RFI noise, which is generated by the SR, and thus prevent its propagation into the house supply, as required by FCC and/or other regulatory bodies. For example, in the illustrated single-phase application, RFI half-section filter L1C1 is connected between the single-phase 60-cycle house supply 1 and SR 2. C1 is connected to the return wire GWG (green wire ground) which is also grounded to the machine frame 3.