Circuit for detecting remaining battery capacity

A circuit for detecting remaining battery capacity, comprising:

• a current detection unit detecting a charge and discharge current of a battery;
• a remaining capacity measurement unit including a central processing unit (CPU), the remaining capacity measurement unit measuring remaining capacity of the battery by integrating the charge and discharge current at first time intervals and at second time intervals shorter than the first time intervals, and the CPU performing a digital filter process and a remaining capacity measurement process;
• an interrupt signal generation unit generating an interrupt signal to the CPU of the remaining capacity measurement unit when the charge and discharge current exceeds a reference value and instructing the remaining capacity measurement unit to measure remaining capacity of the battery, the interrupt signal allowing the CPU to enter an awake status from a sleep status;
• a voltage detection unit connected to the battery and providing a voltage detection signal;
• a temperature detection unit connected to the battery and providing a temperature detection signal;
• a current detection unit connected to the battery and providing a current detection signal;
• a sigma-delta modulator;
• and
• a multiplexer which selects a selected detection signal from one of the voltage detection signal, the temperature detection signal, and the current detection signal, and provides the selected detection signal to the sigma-delta modulator, wherein the selection is performed based on a control signal from the CPU;
• wherein the CPU judges, following the measurement of remaining capacity, whether the charge and discharge current exceeds a predetermined value, and if the charge and discharge current is not more than the predetermined value and maintained for a predetermined time, the CPU sets the time intervals for measuring the remaining capacity of the battery to the first time intervals and if the charge and discharge current exceeds the predetermined value, the CPU sets the time intervals to the second time intervals.