| 摘要 |
PROBLEM TO BE SOLVED: To implement a current detection system using a single element, by avoiding increase in a switching loss.SOLUTION: Current detection control means 35, when a current detection rate is high in the case that a motor is in a low speed rotation region, uses a first detection system in which a two-phase PWM signal is made to be output, and current detection means 27 is made to detect current of one phase at fixed timing and current of another phase at variable timing. The current detection control means, when the current detection rate is low, uses a second detection system in which a three-phase PWM signal is made to be output, and the current detection means 27 is made to detect current of two phases at fixed timing. The current detection control means, when the current detection rate is in an intermediate state, uses a third detection system. In the third detection system, when a duty of one of two phases, to which a duty pulse is output in a carrier wave period and which is a second and third phase, has reduced to disable current detection of the two phases, in a state in which a two-phase PWM signal is made to be output to make current detection of one phase be at variable timing; a duty pulse of the first phase is made to be generated by a predetermined value, duty pulses of the second and third phases are made to increase by a predetermined value, and current detection of another one phase is made to be at variable timing.SELECTED DRAWING: Figure 1 |
