| 摘要 |
PURPOSE: A lithium ion battery charging circuit for reducing a charging time is provided so that a whole charging time can be reduced by sensing a battery voltage applied to both ends of the battery, and constantly charging the battery with a constant current to a maximum charging limit voltage(generally 4.35V). CONSTITUTION: A DC/DC converter(12) converts a DC voltage from a DC power unit(11) to a predetermined DC voltage. The DC voltage output from the DC/DC converter(12) charges a lithium ion battery(13). An output voltage distributing circuit(23) includes resistances(R1,R2) connected in series between the output terminal of the DC/DC converter(12) and a ground, a resistance(R3) connected in parallel to the resistance(R2), and a constant voltage constant current control FET(22). Here, the output voltage distributing circuit(23) distributes the output voltage from the DC/DC converter(12) through the resistances(R1,R2,R3), and inputs the distributed voltage from the resistance(R2) to a DC/DC converter control unit(14). The DC/DC converter control unit(14) receives the voltage from the output voltage distributing circuit(23), and compares the voltage with a reference voltage. When the voltage is below the reference voltage, the DC/DC converter control unit(14) enables the DC/DC converter(12) to charge the battery with the constant current. When the voltage is over the reference voltage, the DC/DC converter control unit(14) enables the DC/DC converter(12) to charge the battery with the constant voltage.
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