| 摘要 |
PROBLEM TO BE SOLVED: To provide a constitution for suitably protecting glow plugs from the inverse connection of a battery, with a simple constitution, without increasing an installation space. SOLUTION: This glow plug protection circuit has switch means 21-24 for switching current-carrying/non-current-carrying to the glow plugs 31-34 when the battery 3 is normally connected and carrying an electric current in the inverse direction when the battery is inversely connected, a control means 10 for controlling ON/OFF of the switch means so as to make a maintaining current flow for maintaining the glow plugs at the predetermined temperature by turning on the switch means for a predetermined timeτso as to make a temperature rise starting current flow for quickly raising the temperature of the glow plugs, and PTC thermistors 51-54 having a resistance change rate smaller than a resistance change rate of the glow plugs in at least the predetermined timeτ. Ordinary operation is performed when the battery is normally connected, and when the battery is inversely connected, since resistance of the respective PTC thermistors increases in response to a temperature rise by a backward current Ir, the respective glow plugs are protected. COPYRIGHT: (C)2009,JPO&INPIT
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