| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce auditory noise, with high efficiency over a wide range of the fluctuating rotational speed of a motor. <P>SOLUTION: For an oscillator 4, the oscillating frequency of output pulses fluctuates, depending upon the magnitude of the differential value between a torque command signal input terminal 1 and a torque command reference signal input terminal 2. The oscillating frequency of this oscillator 4 changes to be lower, when the differential output value of an amplifier 3 is small and to be higher, when the differential output value of the amplifier 3 is large. When the differential output value of the amplifier 3 is large for the purpose of high-speed rotation, PWM frequency becomes high, and the ripple amplitude value of a motor phase current, that is, the ripple component energy is suppressed, and auditory noise is decreased. Moreover, when the differential output value of the amplifier 3 is small for the purpose of low-speed rotation, the PWM frequency is decreased, and it reduces the switching loss ratio is reduced and the efficiency at low speed is improved; and even if the lower limit value in ON period exists by the minimum PWM, the motor can be rotated slowly. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
