OVERMODULATION PREVENTING CIRCUIT IN PWM MODULATION

摘要

PROBLEM TO BE SOLVED: To provide an overmodulation preventing circuit in a PWM modulation.;SOLUTION: The overmodulation preventing circuit 20 includes a maximum modulation factor pulse signal generating means 12 for comparing the level V_B of the triangular wave 3 of a PWM modulator 1 with a high voltage side voltage level V_H corresponding to the maximum modulation factor allowed at the high voltage side of a modulation factor 2 by a comparator Comp1, outputting a high voltage side maximum modulation factor pulse signal V_D synchronized with the triangular wave 3, comparing the level V_B of the triangular wave 3 with the low voltage side voltage level V_L corresponding to the maximum modulation factor allowed at the low voltage side of the modulation factor 2 by a comparator Comp2 and outputting the low voltage side maximum modulation factor pulse signal V_E synchronized with the triangular wave 3; and a maximum modulation factor pulse signal injection means 12 having an AND circuit 13 for outputting a pulse signal V_F of the AND of a PWM output signal 4 after the PWM modulation and the high voltage side maximum modulation factor pulse signal V_D and an OR circuit 15 for outputting the pulse signal V_G of the OR of the pulse signal V_F and the low voltage side maximum modulation factor pulse signal V_E as a PWM output signal 14.;COPYRIGHT: (C)2006,JPO&NCIPI