CHARGE CONTROL CIRCUIT AND CHARGING CIRCUIT

PROBLEM TO BE SOLVED: To generate a voltage for charging a secondary battery having a full charge voltage higher than an input voltage.SOLUTION: The charge control circuit includes first and second comparator circuits for comparing the voltage of a secondary battery with first and second comparison voltages, a first transistor for supplying an input current to the inductor of a step-up DC-DC converter, a first control circuit for controlling the first transistor, and a second control circuit for controlling step-up operation of the step-up DC-DC converter. When the voltage of a secondary battery is equal to or goes above a first comparison voltage, the first transistor is turned on, and second and third transistors for increasing and decreasing the inductor current are switched complementarily so that the step-up DC-DC converter performs step-up operation. When the voltage of a secondary battery goes below a second comparison voltage, inclination of an inclined wave compared with an error signal is made steep. When the voltage of a secondary battery goes below a first comparison voltage, the first transistor is controlled so that the input current has a predetermined value thus turning the second transistor off and turning the third transistor on.