Importance

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Abstract

The present invention relates to an over-discharge preventing circuit, especially an over-discharge over-current preventing circuit, and more specifically relates to an over-discharge over-current preventing circuit comprising an over-discharge preventing circuit having a FET and an over-current preventing circuit for protecting the FET. The invention includes a primary or secondary battery containing such a circuit, and a battery pack containing such a circuit. The batteries comprising an over-discharge over-current preventing circuit according to the present invention have (1) an electrolyte, (2) a pair of electrode members forming a negative electrode member and a positive electrode member which electrically contact the electrolyte, (3) a pair of external connection terminals respectively electrically connected to corresponding electrode members and (4) a PTC element and FET with a source terminal and drain terminal serially connected between one of the electrode members and the corresponding external connection terminal, the gate terminal being connected to the other electrode member. The FET prevents over-discharge by stopping the supply of current to the external connection terminal when the voltage between the electrode members becomes lower than a predetermined value. The PTC element prevents over-current by stopping the supply of current to the external terminal when the current between the electrode members exceeds a predetermined value, thereby also protecting the FET from being destroyed by such an over-current.

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First Claim