| 摘要 |
PROBLEM TO BE SOLVED: To elongate the life time of a heat generating part and reduce its size, by providing a protective element in its vicinity. SOLUTION: When a diode 2 is overheated and, e.g. the temperature of the diode 2 becomes a first predetermined value of it having the possibility of its heat destruction, examining the temperature distribution surrounding the diode 2 on a printed board, a protective element 1 is mounted in a position B wherein the temperature of the protective element 1 becomes the temperature value coinciding with a second predetermined temperature value whereat its resistance value increases remarkably. In this case, the position B becomes the vicinity of a position A of the diode 2. Doing in this way, the temperature of protective element 1 becomes the temperature value whereat its resistance value increases remarkably, when the temperature of the diode 2 becomes the temperature value of it having the possibility of its heat destruction. Since the protective element 1 is connected in series with the load-power feeding route of a power supply unit, the current flowing in the load-power feeding route is also limited to a very small current value. Therefore, the current flowing in the diode 2 of a heat generating part is restricted to make preventable its heat destruction. Also, the provision of any radiation part is made unnecessary to make reducible the size of the power supply unit.
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