CIRCUIT FOR PROTECTING BATTERY AGAINST OVERCHARGE

摘要

PURPOSE: A circuit for protecting a battery against overcharge is provided to protect a battery against overcharge even though a battery voltage detecting terminal is opened and a battery voltage is not inputted. CONSTITUTION: A secondary battery charge voltage detecting part(20) compares a charge voltage of a battery to a set secondary reference voltage, amplifies them and detects a charge voltage level of the battery. In the secondary battery charge voltage detecting part(20), the input secondary reference voltage is applied to a non-inverting input terminal of an op amp. The battery is connected to the an inverting input of the op amp through a resistance(R21) and an output terminal of the op amp is feedback connected to an inverting input terminal of the op amp through the resistance. The output terminal of the op amp is also connected to an anode of a diode such that a secondary battery detect voltage is applied to a non-inverting input terminal of a comparator(14) along with an output signal of a secondary battery charge voltage detecting part(10).