| 摘要 |
PURPOSE: To accurately discriminate the service life of a power semiconductor by taking the temperature difference between a semiconductor element and heat spreader caused by an abrupt change of an electric current into account by calculating the service life by using the outputs of an arithmetic means for calculating thermal stress caused by temperature changing range and another arithmetic means for calculating thermal stress caused by temperature changing rate and the allowable thermal stress peculiar to the semiconductor element. CONSTITUTION: An arithmetic section 22a for calculating service life of transistor adds the number of thermal stresses caused by temperature changing range calculated and integrated by an arithmetic section 21 for calculating thermal stress caused by temperature changing range of a transistor to the number of thermal stresses caused by temperature changing rate calculated and integrated by an arithmetic section 23 for calculating thermal stress caused by temperature changing rate of the transistor. Then the section 22a compares the calculated sum with the allowable number of thermal stresses of a transistor found from the service life peculiar to the transistor set in a service life setting section 39 and, when the sum exceeds the allowable number, the section 22a performs warning operation by issuing an warning displaying command indicating that the service life of the transistor has expired, etc., to a display section 140. The same system applies to a diode also. |
