Abstract: A power system within a portable electronic device is disclosed. In order to discharge electricity stored in a rechargeable battery within the portable electronic device to a discharge cutoff voltage, a charge booster charges the rechargeable battery with electric power coming from an AC/DC adaptor. When the AC/DC adaptor is detached, the charge booster performs boosting operation to supply power to a load from the rechargeable battery. The charge booster operates only when input voltage of the load decreases. A direct discharge circuit operates in conjunction with the charge booster, and when the charge booster does not perform any boosting operation, electric power is supplied directly from the rechargeable battery to a DC/DC converter. The charge booster can keep the input voltage of the DC/DC converter until the voltage reaches a discharge cutoff voltage of the rechargeable battery, and then stops operation when electric power is being supplied from the direct discharge circuit.

Abstract: A method for controlling the clock frequency of a processor while suppressing performance degradation is disclosed. The processor receives power from a battery to operate at a high clock frequency HFM(f) or a low clock frequency LFM(f). An allowable current Im is set for the discharge current of the battery. The time during which the processor operates at the HFM(f) and the time during which the processor operates at the LFM(f) are controlled by PWM. As the feedback current Ifb increases, the time during which the processor operates at the LFM(f) become longer than the time during which the processor operates at the HFM(f).

Abstract: A power system within a portable electronic device is disclosed. In order to discharge electricity stored in a rechargeable battery within the portable electronic device to a discharge cutoff voltage, a charge booster charges the rechargeable battery with electric power coming from an AC/DC adaptor. When the AC/DC adaptor is detached, the charge booster performs boosting operation to supply power to a load from the rechargeable battery. The charge booster operates only when input voltage of the load decreases. A direct discharge circuit operates in conjunction with the charge booster, and when the charge booster does not perform any boosting operation, electric power is supplied directly from the rechargeable battery to a DC/DC converter. The charge booster can keep the input voltage of the DC/DC converter until the voltage reaches a discharge cutoff voltage of the rechargeable battery, and then stops operation when electric power is being supplied from the direct discharge circuit.

Abstract: A method for controlling the clock frequency of a processor while suppressing performance degradation is disclosed. The processor receives power from a battery to operate at a high clock frequency HFM(f) or a low clock frequency LFM(f). An allowable current Im is set for the discharge current of the battery. The time during which the processor operates at the HFM(f) and the time during which the processor operates at the LFM(f) are controlled by PWM. As the feedback current Ifb increases, the time during which the processor operates at the LFM(f) become longer than the time during which the processor operates at the HFM(f).