Abstract: By detecting a temperature abnormality of a power semiconductor by using the power semiconductor as a temperature sensor, it is possible to detect deterioration and an abnormality of elements, a drive circuit and a cooling system, prevent a failure during an operation by taking an appropriate measure in advance, and make a system operational life long. More specifically, a power converting device which includes the power semiconductor and an arithmetic operation circuit which gives a drive instruction to the power semiconductor detects the temperature abnormality of the power semiconductor based on the drive instruction of the power semiconductor and a delay time of a control drive voltage applied to the power semiconductor to protect the power converting device.

Abstract: A protective layer has, on its back side, an electron emissive layer formed of magnesium oxide crystals. Based on a front view of discharge cells C, there are defined intersection regions (first regions) where display electrode pairs (each including a sustain electrode X and a scan electrode Y) and address electrodes Z intersect and a remaining region (a second region) E1 excluding the intersection regions. The surface density of the magnesium oxide crystals forming the electron emissive layer over the intersection regions (the first regions) is equal to or lower than half the surface density of the magnesium oxide crystals forming the electron emissive layer over the remaining region (the second region) E1 excluding the intersection regions.