Battery charging circuit
OwnerPhilip A. Hoffmaninventor
Life of this patent
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Abstract
Disclosed is a battery operated hand tool which has incorporated directly into its housing a novel battery charging circuit. The charger normally operates off a conventional household power outlet and comprises a solid state switching circuit for recharging the battery with a series of electrical impulses. In some special cases, it can be operated in a non-switching state. External inductance is eliminated by charging the battery through the hand tool motor.
Claims18
A battery operated hand tool comprising a housing, an electrical motor in said housing for operating said tool, means in said housing for coupling said motor to a rechargeable battery, a battery charging circuit in said housing coupled to said motor for charging a battery in said housing in series with an inductance of said motor, said charging circuit comprising a pair of input terminals, a solid state switch connected to said terminals for causing the current from said terminals to flow through said motor, said charging circuit comprising means for automatically varying the charging rate in accordance with the charge on a battery, said solid state switch comprising a transistor, said automatic rate varying means comprising a positive feedback resistor coupling one side of said motor to the emitter-collector circuit of said transistor, and a negative feedback transistor coupling the other side of said motor to the base of said transistor.
A charging circuit for a battery comprising first and second input terminals, a rectifier and transistor amplifier coupling said first terminal to one side of said battery, a solid state switch coupled to said amplifier for controlling the flow of current through said amplifier to said battery, means coupling said switch to said terminals for operating said switch during a portion of each cycle of an AC input applied to said terminals, means coupling the second of said input terminals to the other side of said battery, an inductance, said inductance comprising a winding of an electric motor, said charging circuit including means for coupling said battery and said motor winding in series between said amplifier and said second input terminal, said solid state switch comprising a transistor, a voltage divider coupling said terminals to the base of said transistor, a positive feedback resistor coupling said inductance and battery to the emitter-collector circuit of said transistor, and a negative feedback resistor coupling said inductance and battery to the base of said transistor.
A battery charging circuit comprising first and second input terminals, a rectifier coupled to said terminals for rectifying an AC input applied to said terminals, a battery, a transistor amplifier coupling said rectifier to said battery whereby rectified current from said terminals flows through said amplifier to said battery, a transistor switch having first and second controlled terminals connected in parallel with said amplifier and battery, said switch having a third control terminal, and means coupling said control terminal to said rectifier whereby said switch is rendered conductive and shunts current around said amplifier and battery when the input voltage exceeds a predetermined value, said switch being rendered non conductive when the input voltage falls below said predetermined value, said switch permitting current flow through said amplifier to said battery when a conventional 60 Hz household outlet electrical source is applied to said input terminals only during those portions of a source cycle when the source voltage is below a predetermined voltage level substantially less than its maximum.
Dependencies are inferred from the claim text.