| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and apparatus detecting abnormity of a cooling fan for cooling a heat sink. SOLUTION: Temperatures (Tx) and (Ty) of a heat sink at a time when current is (Ix) and (Iy) are detected, respectively. Element losses (Px) and (Py) of a switching element on the heat sink at a time when the current is (Ix) and (Iy) are calculated. The temperatures (Tx) and (Ty) and the element losses (Px) and (Py) are assigned to a relational expression consisting of a temperature (T) of the heat sink, an element loss (P), a thermal resistance (R) of the heat sink, and a surrounding temperature (T<SB>0</SB>) of the heat sink to set up two simultaneous equations. The thermal resistance (R) of the current heat sink is calculated by solving the two simultaneous equations, and the thermal resistance (R) of the current heat sink is compared with a thermal resistance (R) of the heat sink in a normal state of the cooling fan. When the current thermal resistance (R) is larger than the thermal resistance (R) of the heat sink in the normal state of the cooling fan, determination that an airflow of the cooling fan is deteriorated is carried out. COPYRIGHT: (C)2009,JPO&INPIT
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