US Patent 7696743 Zero-phase current detecting apparatus

In a zero-phase current detecting apparatus, a feedback loop is made up of a pulse generating unit, a current detecting unit, a peak detecting unit, an adding unit, and a current regulating unit. The adding unit outputs a difference between a target value and a peak value detected by the peak detecting unit. A zero-phase current is detected based on the difference output from the adding unit as a result of regulation of the peak value so as to be the target value in the adding unit.