| 摘要 |
PROBLEM TO BE SOLVED: To maximize the battery drive time of a portable telephone set by acquiring the voltage of a battery and controlling the ON time of a back light on the basis of that voltage. SOLUTION: When the initial factor is a back light ON request, a peripheral circuit control LSI 12, which receives the acquisition request of a battery voltage from a back light power source control program 01 through an internal bus 61, requests acquisition of the battery voltage of the portable telephone set at present to a battery voltage acquiring circuit 41. The battery voltage acquiring circuit 41 measures the terminal voltage of a battery 42, converts it to a digital value through A/D conversion and gives it to the peripheral circuit control LSI 12. The peripheral circuit control LSI 12 sends the battery voltage through the internal bus 61 to the back light power source control program 01. The back light power source control program 01 acquires back light ON time and a back light ON current corresponding to the battery voltage from a back light power source control table 02 through the internal bus 61. |
