Direct current magnetic polarization component compensation circuit for constant voltage/frequency power supply apparatus

Claim 1

A constant voltage/frequency power supply circuit comprising a constant voltage/frequency output circuit including a converter for DC (direct current)-converting an AC (alternating current) output of an AC power source, and an inverter for AC-inverting the DC converted output, and a control circuit for supplying a control signal to said inverter by superimposing a reference sine wave on a triangle wave, characterized by further comprising: a correction circuit connected to an output side of said constant voltage/frequency output circuit and said control circuit, which correction circuit supplies a correction command for correcting the AC output of said inverter by a correction amount corresponding to a DC magnetic polarization amount contained in the AC output of said constant voltage/frequency output circuit, wherein said correction circuit includes: a filter connected to the output of said constant voltage/frequency output circuit for deriving only a DC component from the AC output of said constant voltage/frequency output circuit; an amplifying circuit connected to said filter for detecting the DC magnetic polarization amount from the filter output so as to obtain a correction amount corresponding to said DC magnetic polarization amount; and, an adder connected to said amplifying circuit for adding said correction amount to said reference sine wave and for deriving a correction command signal so as to delete a DC component of the reference sine wave.