A switched mode power supply (SMPS) includes a filter (202), a power factor correction (PFC) circuit (204), and a control circuit (206, 406) configured to determine various electrical parameters of the SMPS. In some embodiments, the control circuit (206, 406) is configured to determine a power line frequency and an AC input voltage based on an AC line voltage and an AC neural voltage. In other embodiments, the control circuit (206, 406) is configured to determine an AC input current based on a reactive current flowing through the filter (202) and a PFC AC current. In further embodiments, the control circuit (206, 406) is configured to report a value of an electrical parameter if value is determined to be accurate. Other example switch mode power supplies, control circuits and methods are also disclosed.