| 摘要 |
Disclosed is a power supply unit that can properly prevent a reverse current from a battery to an external power source and that is employed for an electronic system, such as a notebook computer, which is activated by both an external power source and an incorporated battery, and a method for controlling such a power supply unit. A power supply unit for an electronic system, to which power is supplied by both an external power source and a battery, comprises: voltage detection means for detecting an output voltage of the external power source; current detection means for detecting an output current of the external power source; logical sum means for outputting a logical sum of the detection results of the voltage detection means and the current detection means; and connection/disconnection means for connecting and disconnecting the external power source in response to the output of the logical sum means. Since the external power source is disconnected when only the battery is active, a reverse current from the battery is properly prevented. The connection/disconnection means of the external power source includes only an FET switch, does not require a Schottky barrier diode, so that heat generation will not occur. <MATH> |
