Battery-operated Secondary Battery Charging and Adapter / Battery Selection Circuits

摘要

Disclosed herein is an adapter / battery selection circuit of a system operated by a DC voltage optionally provided from a rechargeable battery pack and an AC adapter. The selection circuit has an input terminal for receiving a DC voltage provided from the AC adapter and an output terminal for outputting the DC voltage to the system. Furthermore, the selection circuit outputs a blocking diode that cuts off the current flowing from the output terminal to the input terminal, and a detection signal indicating whether the AC adapter is connected to the input terminal by detecting the voltage level of the input terminal. A detection unit; A first switching unit connected in parallel with the blocking diode and connecting the input and output terminals such that a charge current corresponding to the DC voltage bypasses the blocking diode in response to a first switch control signal; And a first switching control unit generating the first switch control signal in response to the detection signal to control a switch-on / off operation of the first switching unit. In addition, the voltage level lowered by the first switching unit is relatively smaller than the voltage level lowered by the blocking diode.