US 6,958,590 B1Granted

Temperature compensated battery charger current

AssigneeNational Semiconductor Corporation

InventorJarmo Antero Vaananen

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Abstract

A battery charger circuit is arranged to charge batteries in a constant current mode. A charging current flows from a power device through a sense resistor to a battery. The voltage across the sense resistor is used to measure the charging current. The temperature of the sense resistor changes either because of a change in ambient temperatures or as the result of the charging current creating thermal energy in the sense resistor. The measured charging current from the sense resistor changes because of the temperature coefficient of the sense resistor, creating inaccuracies. A temperature compensation block uses a set of controllable current mirror banks to adjust reference signals such that the effects of the temperature coefficient in the sense resistor are minimized and an accurate charging current measurement is achieved.

Claims20

Dependent claims

An apparatus for controlling an output current that is delivered to a load, the apparatus comprising:

a first transistor circuit that is coupled between a first node and a second node, wherein the first transistor circuit has a control terminal that is coupled to a third node;
a sense resistor circuit that is coupled between the second node and the load, wherein the sense resistor circuit is arranged to generate a first voltage drop in response to the output current;
a reference resistor circuit that is coupled between the second node and a fourth node, wherein the reference resistor circuit is arranged to generate a second voltage drop in response to a reference current;
a first amplifier circuit that has an input that is coupled to the load, another input that is coupled to the fourth node, and an output that is coupled to third node, wherein the first amplifier circuit is arranged to cooperate with the first transistor circuit to control the output current such that the first voltage drop is approximately equal to the second voltage drop;
and
a temperature compensated reference current generator circuit that is coupled to the fourth node, wherein the temperature compensated reference current generator circuit is arranged to dynamically adjust the reference current such that the output current is stabilized with respect to an operating temperature of the apparatus.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/713,609Filed 13 Nov 2003
Granted: 25 Oct 2005
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H01M 10/46
Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells: accumulators structurally combined with charging…
H01M 10/48
Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells: accumulators combined with arrangements for…
H02J 7/04
For charging batteries from AC mains by converters: regulation of charging current or voltage
H02J 7/975
The charge cycle being controlled or terminated in response to non-electric parameters: in response to temperature