POWER SOURCE SWITCHING UNIT WITH INTEGRATED CHARGING CIRCUIT FOR SELECTIVELY COUPLING AN EXTERNAL POWER SOURCE, A COMPUTER LOAD, AND BATTERIES, FOR PROVIDING TEMPORARY POWER DURING COUPLING, AND FOR CHARGING BATTERIES

摘要

To obtain a power source switching unit that is capable of cost and size reduction, and also supplying electric power reliably even when external power supply is intercepted, and to obtain a computer that is capable of avoiding shutdown that results from the interception of the external power supply. The power source switching unit is equipped on a power supply line with an AC adapter detection circuit and outputting a #AC-ADAP signal, and a temporary power supply circuit for temporarily supplying electric power to a DC-DC converter when the power supply is intercepted. The switching unit is further equipped with a battery switching circuit for switching the states of FET 1 , FET 2 , FET 3 , and FET 4 so that main and second batteries are both connected to the DC-DC converter in response to a change in the #AC-ADAP signal when the AC adapter is disconnected from the switching unit.