| 摘要 |
PROBLEM TO BE SOLVED: To obtain a PWM control apparatus which can output a PWM voltage following a small voltage instruction while a minimum ON-pulse width is being ensured. SOLUTION: A triangular-wave-phase generation part 15 outputs a triangular-wave phase θp on the basis of a triangular-wave frequency fsw. A DC-bias-voltage generation part 14 generates a DC bias voltage Vbias whose polarity is changed alternately so as to correspond to the cycle of the triangular-wave phase θp. A DC-bias-voltage addition part 12 adds the voltage Vbias to respective phase-voltage instructions VuRef, VvRef, VwRef from a three-phase-voltage-instruction computing part 11, and respective new phase-voltage instructions Vu, Vv, Vw are formed. A positive-side triangular-wave generation part 17 outputs positive-side triangular waves TRIp on the basis of the input of the phase θp, and a negative-side triangular-wave generation part 18 outputs negative-side triangular waves TRIn on the basis of the input of a triangular-wave phase θn. The phase θp and the phase θn are deviated by a phase difference of δ=π A triangular-wave comparison part 13 outputs respective phase-PWM voltage instructions VuPWM, VvPWM, VwPWM on the basis of the comparison of a magnitude relationship between the respective phase-voltage instructions Vu, Vv, Vw and the triangular waves TRIp, TRIn. |
