Patent ID: 7570026

Claim:
A protection circuit comprising: a second circuit to be connected to a first circuit, the first circuit including: a first reference voltage generating circuit configured to generate a first reference voltage; a first comparing voltage generating circuit configured to generate a first comparing voltage to be compared with a battery voltage of a secondary battery to be charged based on the first reference voltage; a first comparator configured to output a first comparing output voltage corresponding to relation in magnitude between the first comparing voltage and the battery voltage; and a first control circuit configured to control supply of a charging voltage to the secondary battery corresponding to the first comparing output voltage, the second circuit including: a second comparing voltage generating circuit configured to be input with the first reference voltage and to generate a second comparing voltage to be compared with the battery voltage based on the first reference voltage; a second comparator configured to output a second comparing output voltage corresponding to relation in magnitude between the second comparing voltage and the battery voltage; and a second control circuit configured to control the supply of the charging voltage to the secondary battery corresponding to the second comparing output voltage.