To protect a load from overvoltage even if a battery is removed by a method wherein, when the battery is not connected to first and second connection terminals, the first connection terminal is connected to the other electrode of a solar cell.
A solar cell 1 is connected to a mini-jack 61 which is a first terminal and a load through a reverse current block diode 4. A battery 2 is connected to the mini-jack 61 through a mini-plug 62 which is a second terminal so as to have the battery 2 removed and attached easily for maintenance, etc. Further, while the mini-jack 61 and the mini-plug 62 are not mated with each other and the battery 2 is removed, a terminal (a) and a terminal (c) are brought into contact with each other to short-circuit both electrodes of the solar cell 1. With this constitution, even if the battery 2 is not connected, the possibility of applying an overvoltage to a load can be eliminated.
TAKEHARA NOBUYOSHI
FUKAE KIMITOSHI
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