Hysteresis battery charger

Claim 2

A battery charging circuit comprising: a source of unidirectional charging current; a series pass element having a control terminal, said series pass element characterized by respective conducting and substantially nonconducting states for controlling charging current to the battery; means connected across said battery for producing a voltage proportional to the voltage exhibited by the battery; a voltage reference element exhibiting a non-linear voltage drop thereacross dependent upon the magnitude of current being conducted by the non-linear element; means for comparing said proportional voltage to said voltage reference element and thereby producing a control signal representative of the difference between said proportional voltage and the voltage exhibited by the voltage reference element; means responsive to said control signal for rendering said series pass element through its control terminal either in its conducting state or in its substantially non-conducting state; means for varying the state of current conduction in the voltage reference element between a relatively high conduction state when the series pass element is in its conducting state and a relatively low conduction state when the series pass element is in its substantially non-conducting state; said voltage reference element exhibiting a relatively higher voltage thereacross when said series pass element is in its conducting state and a relatively lower voltage thereacross when said series pass element is in its substantially nonconducting state; whereby when said proportional voltage is at or below a first predetermined value the battery charging circuitry initiates delivering high rate charging current to the battery and ceases to deliver high rate charging current to the battery when said proportional voltage reaches or exceeds a second predetermined value which is greater than said first predetermined value.

Claim 3

The circuit of claim 1 wherein the series pass element is a transistor whose emitter to collector path is shunted by a low rate series pass element.

Claim 4

The circuit of claim 1 wherein said means for producing the proportional voltage includes a voltage divider having a variable tap connected to the base of a first transistor switching means which serves as said means for comparing the proportional voltage to the voltage exhibited by said non-linear element.

Claim 5

The circuit of claim 1 wherein the voltage reference element exhibits a negative temperature coefficient.

Claim 6

The circuit of claim 3 wherein said responsive means includes a second transistor switching means having its base connected to said first transistor switching means for receiving said control signal, and having its emitter/collector terminals connected in shunt between said control terminal and said non-linear element.

Claim 7

The circuit of claim 5 wherein the collector of said first transistor switching means is connected to the base of said second transistor switching means and the emitter of said first transistor switching means is connected to said non-linear element.

Claim 8

The circuit of claim 6 wherein resistance means is connected between one side of the series pass element and the junction formed between the base of said second transistor switching means and the collector of said first transistor switching means.

Claim 9

The circuit of claim 5 wherein a resistance means is connected between said control terminal and said non-linear element, in series with the emitter/collector path of said second transistor switching means.

Claim 10

The circuit of claim 1 wherein a current limiting resistance means is connected in series with said series pass element, and diode means are connected across the current limiting resistance means to the control terminal of the series pass element to form a substantially constant current source when the charger is in its high rate charging mode.

Claim 11

The circuit of claim 8 wherein diode means are connected between the base of said second transistor switching means and across said resistanCe means to form a substantially constant current shunt when said series pass element is in its conducting state.

Claim 12

The circuit of claim 1 wherein said non-linear element is a unidirectional diode means.

Claim 13

A circuit having first and second output charging terminals for delivering unidirectional current to a battery connected across the terminals comprising: a source of unidirectional current; a high rate charging path connected between the current source and the first output terminal of the battery and including a series pass element having a control terminal, said series pass element switchable between a conducting mode and a substantially non-conducting mode; a voltage reference element exhibiting a non-linear voltage drop thereacross dependent upon the magnitude of current being conducted by the non-linear element; said control terminal connected through a first shunt path to the second output terminal through said voltage reference element; a second shunt path connected from the high rate charging path through said voltage reference element to the second output terminal; means for voltage sensing the state of charge of the battery; control circuitry including a first conducting path connected from said high rate charging path to said first shunt path which is in a state of conductivity when said series pass element is in its conduction mode, and a second conducting path connected from said sensing means to said second shunt path which is in a state of conductivity when said series pass element is in its substantially non-conduction mode; means for varying the state of current conduction in the voltage reference element between a relatively high conduction state through said first shunt path when the series pass element is in its conducting mode and a relatively low conduction state through said second shunt path when the series pass element is in its substantially non-conducting mode; said voltage reference element exhibiting a relatively higher voltage thereacross when said series pass element is in its conducting mode and a relatively lower voltage thereacross when said series pass element is in its substantially non-conducting mode.

Claim 14

A circuit having first and second output charging terminals for delivering unidirectional current to a battery connected across the terminals comprising: a source of unidirectional current; a high rate charging path connected between the current source and the first output terminal of the battery and including a series pass element having a control terminal, said series pass element switchable between a conducting mode and a substantially non-conducting mode; a voltage reference element exhibiting a non-linear voltage drop thereacross dependent upon the magnitude of current being conducted by the non-linear element; said control terminal connected through a first shunt path to the second output terminal through said voltage reference element; a second shunt path connected from the high rate charging path through said voltage reference element to the second output terminal; means for voltage sensing the state of charge of the battery; control circuitry including a first conducting path connected from said high rate charging path to said first shunt path which is in a state of conductivity when said series pass element is in its conduction mode, and a second conducting path connected from said sensing means to said second shunt path which is in a state of conductivity when said series pass element is in its substantially non-conduction mode; means for varying the state of current conduction in the voltage reference element between a relatively high conduction state through said first shunt path when the series pass element is in its conducting mode and a relatively low conduction state through said second shunt path when the series pass element is in its substantially non-conducting mode; said voltage reference element exhibiting a relatively higher voltage thereacross when said series pass element is in its conducting mode and a relatively lower voltage thereacross when said series pass element is in its substantially non-conducting mode.

Claim 15

The circuit of claim 12 wherein said first shunt path includes a resistance means in series with the emitter/collector path of first control transistor means.

Claim 16

The circuit of claim 12 wherein said second shunt path includes a resistance means in series with the emitter/collector path of a second control transistor means, one side of said resistance means connected to said high rate charging path and the other side connected to said first shunt path along said first conducting path.

Claim 17

The circuit of claim 14 wherein said second conducting path is connected from the base of said second control transistor means to a variable tap of a potentiometer connected across the battery and serving as said sensing means.

Claim 18

A hysteresis battery charging network comprising: a source of unidirectional charging current; a series pass transistor switch characterized by respective conducting and substantially non-conducting states connected between the unidirectional source and one side of a battery to be charged, the base of the series pass transistor serving as a control terminal; voltage divider means connected across the battery and having a tap; a first shunt path connected between the base of the series pass transistor and the other side of the battery through a first resistance means, the emitter/collector path of a first control transistor and a voltage reference element which exhibits a non-linear voltage drop thereacross dependent upon its relative state of current conduction; and a second shunt path connected between one side of said series pass transistor and the other side of said battery through a second resistance means, the emitter/collector path of a second control transistor and said voltage reference element, the base of said second control transistor connected to said tap, and the base of said first control transistor connected to the juncture formed between said second resistance means and the collector of said second control transistor; said voltage reference element exhibiting a relatively higher voltage thereacross when said series pass transistor is in its conducting state and a relatively lower voltage thereacross when said series pass transistor is in its substantially non-conducting state.

Claim 19

A hysteresis battery charging network comprising: a source of unidirectional charging current; a series pass transistor switch characterized by respective conducting and substantially non-conducting states connected between the unidirectional source and one side of a battery to be charged, the base of the series pass transistor serving as a control terminal; voltage divider means connected across the battery and having a tap; a first shunt path connected between the base of the series pass transistor and the other side of the battery through a first resistance means, the emitter/collector path of a first control transistor and a voltage reference element which exhibits a non-linear voltage drop thereacross dependent upon its relative state of current conduction; and a second shunt path connected between one side of said series pass transistor and the other side of said battery through a second resistance means, the emitter/collector path of a second control transistor and said voltage reference element, the base of said second control transistor connected to said tap, and the base of said first control transistor connected to the juncture formed between said second resistance means and the collector of said second control transistor; said voltage reference element exhibiting a relatively higher voltage thereacross when said series pass transistor is in its conducting state and a relatively lower voltage thereacross when said series pass transistor is in its substantially non-conducting state.

Claim 20

The network of claim 16 wherein the series pass transistor is shunted by resistive means providing a trickle or float charge bypass to the battery.

Claim 21

The network of claim 16 wherein said non-linear element has shunted thereacross resistive means for reducing the difference between the relatively higher voltage and the relatively lower voltage exhibited by the non-linear element.

Claim 22

The network of claim 16 wherein said second resistance means has a substantially higher ohmic value than said first resistance means.

Claim 23

The network of claim 16 wherein said non-linear element is a diode.

Claim 24

The network of claim 16 wherein the voltage reference element exhibits a negative temperature coefficient.

Claim 25

The network of claim 16 wherein said voltage divider means has a variable tap.