Abstract: A DC-to-AC electric power converting apparatus including an invertor circuit having a plurality of switching elements, a transformer connected to the invertor circuit, and a cyclo-converter circuit for converting the frequency of the output from the transformer. A carrier signal generator is provided for generating a carrier signal of a predetermined frequency.

Abstract: A phase-locked loop circuit adapted to produce a stable output signal having the same frequency and phase as those of an input signal. Phase comparator means measures the time difference between the rising edge of the input signal and the falling edge of the feedback signal, and calculator means executes a phase control calculation twice per cycle on the basis of the measured time difference. Then a variable-frequency oscillator circuit produces, in accordance with the result of such calculation, an output signal whose frequency and phase are locked to those of the input signal.