Apparatus for monitoring power of battery to supply electric power to load

An apparatus for monitoring power of a battery which supplies an electric power to a load, said apparatus comprising:

• a micro current detection resistor Rs1 which is inserted in a signal line connecting a plus terminal of said battery and said load such that current flow through said resistor generates a detection voltage V1 across said resistor that is proportional to a battery discharge current Id flowing from said battery to said load;
• a current converting circuit having an operational amplifier to which said detection voltage generated across said current detection resistor is inputted through an input high resistor Rf, said current converting circuit including an FET which is driven by an output of said operational amplifier and which outputs a micro discharge detection current Is which is derived by multiplying said battery discharge current Id with a ratio Rs1/Rf;
• an integrating circuit for charging a capacitor by the discharge detection current Is of said current converting circuit and forming an integration voltage;
• a comparing circuit for resetting said integrating circuit and outputting one pulse signal when the integration voltage of said integrating circuit reaches a reference voltage indicative of a unit charge amount;
• and
• a measuring unit for counting the number of pulse signals outputted from said comparing circuit and generating a count value, and measuring the discharge charge amount of the battery on the basis of said count value.