| 摘要 |
PROBLEM TO BE SOLVED: To prolong the using time of a battery power source by turning off a current supplied to a back light in the case the supplied power source voltage is lower than a reference voltage supplied from a stabilized power source. SOLUTION: A comparator 12 compares the reference voltage value with the voltage value of the battery 9. As a result, when the voltage value of the battery 9 is larger than the reference voltage value, the comparator 12 transmits a signal H to the base of a transistor 13 and a CPU 1. As to the transistor 13, the base receives the signal H, a collector is turned on, a current from the battery 9 is transmitted to the back light 10 so as to turn on the back light 10, and an easy-to-view LCD screen can be obtained. When the voltage of the battery 9 is lower than the reference voltage in the case the comparator 12 performs comparison, a signal L is outputted from the comparator 12 to the base of the transistor 13 and the CPU 1, and a power source circuit supplying power source current to the back light 10 from the battery 9 is turned off, and the power source of the battery 9 can be saved. |
