Battery charging circuit

Claim 2

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.

Claim 3

A hand tool according to claim 1 including a capacitor in parallel with said positive feedback resistor.

Claim 4

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.

Claim 5

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.

Claim 6

A charging circuit according to claim 3 including a capacitor coupled to said positive feedback resistor to increase the switching speed of said transistor.

Claim 7

A charging circuit according to claim 4 wherein said capacitor forms part of a blocking oscillation circuit for imparting a plurality of charging impulses to said battery during each cycle of the AC input.

Claim 8

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.

Claim 9

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.

Claim 10

A charging circuit according to claim 6 including a relatively large resistor in series with said transistor switch whereby current flow through said switch when in its conductive state is minimized.

Claim 11

A charging circuit according to claim 7 including 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 one of said input terminals.

Claim 12

A charging circuit according to claim 7 including a battery operated hand tool comprising a housing, an electric motor in said housing for operating said tool, means in said housing for coupling said motor to said battery, said charging circuit being wholly contained within said housing whereby said battery may be recharged from a 117 volt 60 Hz household outlet by a simple cord connection to said housing.

Claim 13

Apparatus according to claim 9 including an inductance in said housing, said inductance comprising the armature winding of said motor, said charging circuit including switch means in said housing for charging said battery in series with said armature winding.

Claim 14

Apparatus according to claim 10 including a rectifier diode coupled to said battery for sustaining current flow through said battery after current flow from said input terminals has been directed through said amplifier.

Claim 15

A charging circuit according to claim 7 including an oscillator coupling said input terminals to said battery whereby a plurality of charging impulses pass through said battery during each cycle of the AC input to said terminals.

Claim 16

A charging circuit according to claim 7 wherein said means coupling said input terminals to said switch control terminal comprises a voltage divider.

Claim 17

A charging circuit according to claim 13 including a rectifier diode coupling said input terminals to said amplifier.

Claim 18

A charging circuit according to claim 14 wherein said amplifier comprises a Darlington amplifier.

Claim 19

A charging circuit according to claim 14 wherein said switch comprises a transistor having as controlled terminals an emitter and collector, and as a control terminal a base.

Claim 20

A charging circuit according to claim 14 including an automatic charging rate controlling circuit coupling said battery to said switch.

Claim 21

A charging circuit according to claim 17 wherein said automatic charging rate controlling circuit comprises a transistor and a zener diode.