A Low-Current Power Supply for the 71M65XX Metering ICs


Capacitor-coupled power supplies have been used for a long time in low-cost single-phase residential meters. These power supplies work without transformers and generate a voltage drop across a high-voltage capacitor that is typically in the 200nF to 680nF range. This approach is simple and economical, but efficiency is low, as it does not allow load currents of more than a few milliamperes. This application note presents an improved design for the capacitive power supply of Teridian's single-phase energy meters.