| 摘要 |
PURPOSE: To control a brushless DC motor stably, even in a light-load, low- number-of-revolution region. CONSTITUTION: The controller for a brushless direct current motor has a group of switching elements 2-4 to which the brushless DC motor 5 is connected at connecting points 20, 30, and 40, and a PWM comparator 613 for comparing the amplitude of a signal wave 64 with a carrier wave 65, and a PWM control circuit 6 for controlling the group of switching elements 2-4 is provided. And when a CPU 615 detects that the duty factor of a PWM signal 66 has decreased to the lower limit value (2%) at the current carrier frequency (10kHz), it increases (from 2% to 5%) the duty factor of the PWM signal 66 to a value where the output duty factor (6%) does not change considering the operation delay time (4μs) of the group of switching elements 2-4, and the CPU 615 directs a multiplexer 611 to perform switching-over to a clock CL 2 side, and switches the frequency of the carrier 65 to a lower frequency (2.5kHz). |
