| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce a loss by a PWM in high Duty-ratio control in complementary PWM control. <P>SOLUTION: An output Duty determining circuit 14 determining and outputting a Duty ratio command signal in response to an accelerator operation, a carrier frequency determining circuit 15 lowering a carrier frequency in response to an increase in a Duty ratio when the Duty ratio command signal is a fixed value or more and a negative-phase time determining circuit 16 setting the time of a negative-phase PWM reducing a motor current at the fixed value to a positive-phase PWM increasing the motor current are provided to the motor control unit. A dead time simultaneously turning off each switching element 1a and 1b on a high side and a low side is set for a fixed time when a positive phase and a negative phase are changed over. In the case of a fixed Duty ratio or more, the frequency is lengthened owing to a decrease in a PWM carrier frequency and the rate of the dead time in a negative-phase time can be lowered owing to a fixed negative-phase time. Consequently, the loss of the PWM in the high Duty ratio control in the complementary PWM control can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT |
