Portable electronic calculator power supply

Claim 2

For use in a portable, hand-held calculator, a power supply comprising positive, negative, and reference terminals, a plurality of batteries connected electrically in series between one of said positive and negative terminals and said reference terminal for producing at said one of said terminals a first direct current voltage of predetermined polarity, and means coupled to said batteries and between the other of said positive and negative and said reference terminals for generating at said other of said terminals a direct current voltage which is of a polarity opposite said predetermined polarity with respect to the voltage occurring at said reference terminal, said generating means including an oscillator circuit having an input circuit coupled to said positive terminal, an output circuit, a rectifier circuit, and means coupling said rectifier circuit to said output circuit, the current capacity of said generating means being substantially less than the current capacity of said batteries.

Claim 3

The power supply of claim 1 wherein said coupling means includes a transformer having an input and an output winding, said input winding having end taps and a center tap, said oscillator including a pair of transistors coupled in push-pull configuration to said end taps, said center tap being connected to said one of said terminals, said rectifier means being coupled to said output winding.

Claim 4

The power supply of claim 2 wherein said output winding includes two end taps and a center tap, said rectifier means including a full wave rectifier having two input terminals and an output terminal, said input terminal being connected to said last mentioned end tap, said output terminal being connected to said other of said terminals, said center tap being connected to said reference terminal, said transformer further including a feedback winding having end taps and a center tap, said transistors having their bases connected to opposite ones of said feedback winding end taps, respectively, there being a first capacitor coupled between said feedback winding end taps, a second capacitor connected between said common connected elements of said transistors and said feedback winding center tap and a resistor connected between said feedback winding and said input winding center taps.

Claim 5

For use in a portable, hand-held calculator, a power supply comprising positive, negative, and reference terminals, a plurality of batteries connected electrically in series between said positive terminal and said reference terminal, and means coupled to said batteries and between said negative and reference terminals for generating at said negative terminal a direct current voltage which is negative with respect to the voltage occurring at said reference terminal, said generating means including an oscillator circuit having an input circuit coupled to said positive terminal, an output circuit, a rectifier circuit, and means coupling said rectifier circuit to said output circuit, a charging circuit disengageably coupled to said power supply, said charging circuit including means for connecting said charging circuit to a source of alternating current, means coupled to said connecting means for generating a unidirectional, filtered current signal having a predetermined voltage level, means coupled to said generating means for regulating said voltage level, said regulating means including an output circuit, and means for simultaneously and selectively coupling said output cirCuit to said positive terminal and coupling said battery positive terminal to said generating means and disconnecting said battery positive terminal from said positive terminal when said module is coupled to said power supply and for connecting said battery terminal to said positive terminal when said module is disconnected from said power supply.

Claim 6

For use in a portable, hand-held calculator, a power supply comprising positive, negative, and reference terminals, a plurality of batteries connected electrically in series between said positive terminal and said reference terminal, and means coupled to said batteries and between said negative and reference terminals for generating at said negative terminal a direct current voltage which is negative with respect to the voltage occurring at said reference terminal, said generating means including an oscillator circuit having an input circuit coupled to said positive terminal, an output circuit, a rectifier circuit, and means coupling said rectifier circuit to said output circuit, a charging circuit disengageably coupled to said power supply, said charging circuit including means for connecting said charging circuit to a source of alternating current, means coupled to said connecting means for generating a unidirectional, filtered current signal having a predetermined voltage level, means coupled to said generating means for regulating said voltage level, said regulating means including an output circuit, and means for simultaneously and selectively coupling said output cirCuit to said positive terminal and coupling said battery positive terminal to said generating means and disconnecting said battery positive terminal from said positive terminal when said module is coupled to said power supply and for connecting said battery terminal to said positive terminal when said module is disconnected from said power supply.

Claim 7

The power supply of claim 4 wherein said coupling means includes a single-pole, single-throw switch having first, second, and common contacts, said common contact being connected to said positive terminal, said first contact being connected to said battery positive terminal, said second contact being disengageably connected to said output circuit, said battery connecting means including a diode having its cathode connected to said battery positive terminal and a resistor connected in series between said signal generating means and the anode of said diode.

Claim 8

The power supply of claim 5 wherein said regulating means includes a resistor and a zener diode connected electrically in series between said signal generating means and said reference terminal, a transistor having its collector and emitter connected electrically in series between said generating means and said module positive terminal and its base connected to the cathode of said zener diode, and a capacitor connected between said base and said reference terminal.

Claim 9

The power supply of claim 5 wherein said coupling means further includes a multi-pin plug having selectively engageable male and female portions, said common contact being normally connected to said first contact, said plug including means for connecting said common contact to said second contact and disconnecting said common contact from said first contact when said male and female portions are engaged.