| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the following problem: when carrying out inverter control with higher accuracy, it is required to shorten a carrier frequency and carry out complicated computation using CPU and thus shorten an AD conversion time; in present AD conversion control circuits, it is possible only to set a channel on which conversion is started and a channel on which conversion is terminated and it is impossible to select optimal two phases corresponding to a state with hardware; and, therefore, there is no choice but carrying out AD conversion of three phases and it takes time more than necessary to carry out AD conversion. <P>SOLUTION: An AD conversion circuit includes: a selector 11 for selecting a signal to be input to an AD converter 12 from among multiple analog input signals Sa; an AD conversion timing control circuit 14 that controls timing with which the AD converter starts AD conversion; a duty ratio comparison circuit 17 that compares the values on the three duty ratio setting registers of a PWM circuit 10a; and an AD conversion channel selection circuit 15 that selects two channels for controlling the selector 11 on which AD conversion is carried out based on the result of the comparison. <P>COPYRIGHT: (C)2008,JPO&INPIT |
