Abstract: A charging control unit decides the number of battery cells on the basis of an output voltage of a battery pack, and an output voltage of a charging circuit is determined in accordance with the decided number of battery cells. Even though supply of an external power supply is detected, when a battery connection is not detected, the power supply circuit of the charging control unit is set in a stop state. In addition, when disconnection of the battery is detected, a canceling voltage for canceling a cutoff state caused by overdischarging of the battery is output. In a power supply device for a portable terminal, a capacitor electrically charged by an output voltage of main DC/DC converter is connected as an auxiliary power supply of a backup DC/DC converter to make exchange of the auxiliary battery unnecessary.

Abstract: An apparatus is installed in a portable terminal to isolate hardware and power source problems and to quickly find the cause of a given problem occurring in the terminal. In the apparatus, a monitoring circuit (1) monitors and measures the voltages of power sources of the terminal at predetermined intervals. A memory (2) keeps a log of the measured voltages. An output circuit (3) provides the log outside. A controller (4) controls the monitoring circuit, memory, and output circuit and provides the log outside in response to a request. The monitoring circuit, memory, output circuit, and controller are energized by a backup power source of the terminal.

Abstract: In data communication with power furnished from a built-in battery, the residual battery capacity is detected as power that can be currently supplied by the battery. In addition, power necessary for communication is forecast from the quantity of data for communication. The currently residual battery capacity and the necessary power for communication are compared. If the former is in excess of the latter, the communication operation is allowed, while otherwise it is inhibited. When the communication operation is inhibited, functions of parts irrelevant to communication operation are suppressed or reduced. When function suppression is done, the necessary power for communication is re-forecast for comparison from current consumed by other parts than those functions suppressed or reduced.