Green Wire Ground Current Attenuation Circuit
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
This attenuation circuit substantially eliminates green wire ground (GWG) current (IGWG) resulting from the line-to-frame ground capacitors C1-C2 of an electromagnetic interference filter (EMI). Such EMIs are often used with the switching regulator (SW REG) of a computer system or the like. In general, the circuit technique involves reproducing the voltage waveform at a preselected one of the EMI input terminals 1A or 3A with respect to the frame ground (FRAME GND), feeding it to the input winding of a transformer (TX) and applying the resultant voltage at the TX's output winding between the EMI node 2 and FRAME GND. As a result, the line or utility voltage across either of the capacitors C1 and C2 is approximately zero and hence the IGWG is also substantially zero.