US 7,253,589 B1Granted

Dual-source CMOS battery charger

AssigneeNational Semiconductor Corporation

InventorsVladislav Potanin, Elena Potanina, Khosrow Vijeh, Richard Dye

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Abstract

A circuit for charging a battery by selecting among two available power sources while providing overcharging and temperature protection to the battery and managing a charging current is described. A power pass and sense circuit is arranged to provide charge voltage from either power source based on control voltages from a current/voltage control circuit, which receives control signals from a logic control and timer circuit, a sensed voltage from a current setting circuit and reference and temperature voltages from a voltage reference and thermo-sense circuit. Differential amplifiers controlling power pass transistors are turned on and off depending on a power source availability and selection. A power supply circuit provides global supply voltages to all subcircuits preventing reverse current to power sources and stable supply independent of a power source availability. A pair of transistors arranged to operate as body-switcher protect power pass and sense transistors against reverse bias current.

Claims14

Dependent claims

A circuit for providing a charge voltage and current to a battery, comprising:

a logic control and timer circuit that is arranged to select at least one of at least two available power source voltages and provide a first and a second control voltages indicating the selection;
a current/voltage control circuit that is arranged to provide one of a first error voltage and a second error voltage in response to the first and second control voltages, such that:
if a first power source voltage is selected, the first error voltage controls, in part, regulation of the charge voltage and current;
and
if a second power source voltage is selected, the second error voltage controls, in part, regulation of the charge voltage and current;
a power pass and sense circuit that is arranged to provide the charge voltage and current in response to the selected power source voltage and the corresponding error voltage,
a sense determination circuit that is arranged to receive a portion of the charge voltage, to receive a reference voltage, and to provide a sense voltage;
and
a multiplexer that is arranged to multiplex a voltage based on at least one limit current and the portion of the charge voltage, and to provide a feedback voltage, wherein the current/voltage control circuit is arranged to receive the sense voltage, the feedback voltage, a temperature voltage, a reference voltage, and a first enable voltage and a second enable voltage;
and wherein the current/voltage control circuit is further arranged to provide the first error voltage and the second error voltage to the power pass and sense circuit, wherein current/voltage control circuit is further arranged to:
select a smaller of the reference voltage, the temperature voltage, and the sense voltage;
combine the selected voltage with the feedback voltage;
and
select at least one of the at least two available power source voltages based on the first and the second enable voltages.

11 more elements

A circuit for providing a charge voltage and current to a battery, comprising:

a logic control and timer circuit that is arranged to select at least one of two available power source voltages and provide a first and a second control voltages indicating the selection;
a current/voltage control circuit that is arranged to provide one of a first error voltage and a second error voltage in response to the first and second control voltages, such that:
if a first power source voltage is selected, the first error voltage is provided for regulation of the charge voltage and current;
and
if a second power source voltage is selected, the second error voltage is provided for regulation of the charge voltage and current;
a power pass and sense circuit that is arranged to provide the charge voltage and current in response to the selected power source voltage and the corresponding error voltage;
a power supply circuit that is arranged to receive the at least one of two available power source voltages and to provide a global supply voltage to the circuit;
a voltage reference and thermo-sense circuit that is arranged to provide a plurality of reference voltages and a temperature dependent voltage to the current/voltage control circuit and to the logic control and timer circuit;
a current setting circuit that is arranged to receive a sense current and a setting current, and to provide a sense voltage to the current/voltage control circuit such that a regulation of the charge voltage and current is based on a sensed current, the setting current, a temperature of the circuit, and a reference voltage;
and
a reconfiguration circuit that is arranged to reconfigure an operation mode of the current/voltage control circuit to a low-voltage-dropout voltage regulation mode, if the battery is disconnected, wherein the setting current is provided by at least one of an internal current source or another current source external to the current setting circuit, and wherein a first variable resistor is employed to determine a value of an internally supplied setting current and a second resistor is employed to determine a value of an externally supplied setting current.

8 more elements

Dependencies are inferred from the claim text.