| 摘要 |
PURPOSE:To simplify circuit constitution, and to charge a battery effectively by connecting a field effect transistor, to which a voltage drop element having a temperature coefficient is connected, in series with the battery. CONSTITUTION:A voltage drop element 3a having a negative temperature coefficient on a FET 2a operated at positive gate voltage and a voltage drop element 3b having a positive temperature coefficient on a FET 2b operated at negative gate voltage are connected among the FETs 2a, 2b operated at positive or negative gate voltage and gates G and sources S for the FETs 2a, 2b in series with batteries. Constant drain currents determined by voltage Vgs at both ends of the elements 3a, 3b having negative or positive temperature characteristics flow through the batteries 1 and constant current charging is conducted, thus simplifying circuit constitution, then miniaturizing a battery charging circuit.
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