| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that, although the peak current constant control of a PM motor by V/f control requires a peak hold circuit consisting of a diode and CR separately from a circuit for amplifying a shunt resistance terminal voltage using a high-speed amplifier, for detecting a peak value of each phase current, the CR effects responsiveness of the high-speed amplifier, while extra diode and CR are required for constituting an external circuit, and a cost rises due to enlarged substrate area. <P>SOLUTION: A means is disclosed in which a peak value is acquired with no use of a peak hold circuit. An AD conversion unit 7 allows successive conversions of the same CH. Maximum value storing buffers 12a, 12b, and 12c are provided in addition to normal conversion buffers 11a, 11b, and 11c. A value of a conversion buffer is compared with a value of the maximum value storing conversion buffer for each conversion during successive conversions. If the value of conversion buffer is larger, it is stored in the maximum value storing conversion buffer. <P>COPYRIGHT: (C)2010,JPO&INPIT |
