Input voltage control device

An input voltage control device comprising:

• a first power line to which a first potential is applied;
• a second power line divided into one part and the other part, to said one part a second potential being applied to;
• a third power line;
• a constant voltage generator operating on the first potential supplied by said first power line and the second potential supplied by said one part of the second power line and outputting to said third power line a third potential having a constant potential difference from said second potential;
• a reference potential generator connected to said third power line and said one part of the second power line, generating a reference potential on the basis of said third potential and said second potential and outputting said reference potential;
• a comparative potential generator connected to said first power line and said one part of the second power line, generating a comparative potential on the basis of said first potential and said second potential and outputting said comparative potential;
• a comparator operating on the third potential supplied by said third power line and the second potential supplied by said one part of the second power line and alternately outputting a conducting potential or an interrupting potential depending on the comparison between said reference potential and said comparative potential;
• and
• a semiconductor device with one terminal of its current path connected to said one part of the second power line, the other terminal connected to said other part of the second power line and a control terminal connected to the output terminal of said comparator, the semiconductor device making said current path conductive when the conducting potential is inputted to said control terminal and non-conductive when the interrupting potential is inputted to said control terminal.