US 6,476,585 B1Granted

Battery charger

OwnerNeil S. Simmondsinventor

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Abstract

A charging circuit and method for charging a lithium-ion cell or battery at a charging voltage that is varied during the charging of the cell or battery from a selected minimum charging voltage to a predetermined maximum charging voltage. The charging circuit includes a transformer for transforming line voltage applied to the primary winding thereof to a lower AC secondary winding voltage, the transformer being selected to limit secondary winding output current when the charging voltage is not less than the selected minimum charging voltage to a value not exceeding a selected upper limit for the lithium-ion cell; a rectifier sub-circuit connected to the secondary winding of the transformer for rectifying the secondary winding voltage; and a charge-voltage regulator sub-circuit connected to the rectifier sub-circuit for receiving the rectified secondary winding voltage and providing an output charging voltage that is limited to the predetermined maximum charging voltage.

Claims29

Dependent claims

A charging circuit for charging a lithium-ion cell or battery (335, 435) at a charging voltage that varies during the charging of the cell or battery (335, 435) from a selected minimum charging voltage to a predetermined maximum charging voltage, comprising:

(a) a selected suitable transformer (305, 405) for transforming AC line voltage applied to the primary winding (303, 403) thereof to a lower AC secondary winding voltage;
(b) a rectifier sub-circuit (309, 409) connected to the secondary winding (307, 407) of the transformer (305, 405) for rectifying the secondary winding voltage;
and
(c) a charge-voltage regulator sub-circuit (323, 423) connected between the rectifier sub-circuit (309, 409) and the lithium-ion cell or battery (335, 435) for receiving the rectified secondary winding voltage and providing an output charging voltage that is limited to the predetermined A maximum charging voltage;
the charge-voltage regulator sub-circuit (323, 423) being connectable to the lithium-ion cell or battery (335, 435) for charging the lithium-ion cell or battery (335, 435) by applying the output charging voltage across the lithium-ion cell or battery (335, 435);
wherein
(d) the charging circuit in operation provides charging current to the cell or battery (335, 435) in two successive stages, viz
(i) a first stage, during which the charge-voltage regulator sub-circuit (323, 423) operates in non-regulating mode thereby to apply output charging voltage across the lithium-ion cell or battery (335, 435) at a value below the predetermined maximum charging voltage;
and
(ii) a second stage, during which the charge-voltage regulator sub-circuit (323, 423) operates in a voltage-regulating mode thereby to apply output charging voltage across the lithium-ion cell or battery (335, 435) at a value limited to the predetermined maximum charging voltage;
and wherein the charge-voltage regulator sub-circuit (323, 423) changes its mode of operation from non-voltage-regulating mode to voltage-regulating mode when the voltage charging voltage across the lithium-ion cell or battery (335, 435) reaches the predetermined maximum charging voltage;
further characterized in that
(e) the transformer (305, 405) is selected to limit secondary winding output current when the charging voltage is greater than the selected minimum charging voltage so that the secondary winding output current will not exceed a selected upper limit for the lithium-ion cell (335, 435);
(f) the charge-voltage regulator sub-circuit (323, 423) is connected to the rectifier sub-circuit (309, 409) for receiving the rectified secondary winding voltage;
and
(g) wherein when the charge-voltage regulator sub-circuit (323, 423) operates in non-voltage-regulating mode, the charge circuit provides charging current to the cell or battery which is limited by means of the loading effect of the transformer (305, 405).

13 more elements

A charging circuit for charging a lithium-ion cell or battery at a charging voltage that varies during the charging of the cell or battery from a selected minimum charging voltage to a predetermined maximum charging voltage, comprising:

(a) a selected suitable transformer for transforming AC line voltage applied to the primary winding thereof to a lower AC secondary winding voltage;
(b) a rectifier sub-circuit connected to the secondary winding of the transformer for rectifying the secondary winding voltage;
and
(c) a charge-voltage regulator sub-circuit connected between the rectifier sub-circuit and the lithium-ion cell or battery for receiving the rectified secondary winding voltage and providing an output charging voltage that is limited to the predetermined maximum charging voltage;
the charge-voltage regulator sub-circuit being connectable to the lithium-ion cell or battery for charging the lithium-ion cell or battery by applying the output charging voltage across the lithium-ion cell or battery;
wherein
(d) the charging circuit in operation provides charging current to the cell or battery in two successive stages, viz:
(i) a first stage, during which the charge-voltage regulator sub-circuit operates in non-regulating mode thereby to apply output charging voltage across the lithium-ion cell or battery at a value below the predetermined maximum charging voltage;
and
(ii) a second stage, during which the charge-voltage regulator sub-circuit operates in a voltage-regulating mode thereby to apply output charging voltage across the lithium-ion cell or battery at a value limited to the predetermined maximum charging voltage;
(e) wherein the charge-voltage regulator sub-circuit changes its mode of operation from non-voltage-regulating mode to voltage-regulating mode when the voltage charging voltage across the lithium-ion cell or battery reaches the predetermined maximum charging voltage;
(f) the transformer is selected to limit secondary winding output current when the charging voltage is greater than the selected minimum charging voltage so that the secondary winding output current will not exceed a selected upper limit for the lithium-ion;
(g) the charge-voltage regulator sub-circuit is connected to the rectifier sub-circuit for receiving the rectified secondary winding voltage;
(h) when the charge-voltage regulator sub-circuit operates in non-voltage-regulating mode, the charge circuit provides charging current to the cell or battery that is limited by means of the loading effect of the transformer;
and
(i) the minimum charging voltage is selected to be less than the predetermined nominal voltage of the lithium-ion cell or battery and greater than the initial charging voltage of the lithium-ion cell or battery when the charging current is held at a constant level equal to the 1.0 C rate for the lithium-ion cell or battery.

13 more elements

Dependencies are inferred from the claim text.