Battery charger shunt regulator with dual feedback control
AssigneeNational Semiconductor Corporation
InventorGregory J. Smith
Life of this patent
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Abstract
An apparatus and method is related to a shunt regulator that includes two feedback control loops. The shunt regulator provides a charging current to a battery cell from a power source. The input voltage from the power source is limited by the first feedback control loop to ensure that the input voltage does not exceed the breakdown voltage of the shunt regulator. The output voltage from the shunt regulator is limited by the second feedback control loop to ensure that the output voltage does not exceed the maximum rated voltage of the battery. The dual feedback control loops provide maximum charging current to the battery, while protecting the shunt regulator and the battery from damage. The shunt regulator is suitable for implementation in an integrated circuit.
Claims14
An apparatus that regulates a power source and provides an output current to a load, comprising:
- a first feedback circuit that is arranged to provide a first feedback signal in response to a first voltage that is associated with the power source;
- a second feedback circuit that is arranged to provide a second feedback signal in response to a second voltage that is associated with the load;
- an amplifier circuit that is arranged to provide a control signal when at least one of a first operating mode and a second operating mode is selected, wherein the first operating mode is selected in response to a first reference signal and the first feedback signal, and the second operating mode is selected in response to a second reference signal and the second feedback signal;
- and
- a shunt circuit that is arranged to selectively couple power from the power source to a circuit ground in response to the control signal when active such that the first feedback circuit, the amplifier circuit, and the shunt circuit are part of a first control loop, and the second feedback circuit, the amplifier circuit, and the shunt circuit are part of a second control loop.
A method for regulating a power source and providing an output current to a load, comprising:
- determining when a voltage associated with the load exceeds a first predetermined level to indicate a first condition;
- determining when another voltage associated with the power source exceeds a second predetermined level to indicate a second condition;
- activating a control signal in response to at least one of the first condition and the second condition;
- and
- decreasing the voltage associated with the power source in response to the control signal.
An apparatus that regulates a power source and provides an output current to a battery, comprising:
- a first means for monitoring that is arranged to provide a first feedback signal in response to a voltage that is associated with the power source;
- a second means for monitoring that is arranged to provide a second feedback signal in response to another voltage that is associated with the battery;
- a means for controlling that is arranged to provide a control signal when at least one of a first operating mode and a second operating mode is selected, wherein the first operating mode is selected in response to a first reference signal and the first feedback signal, and the second operating mode is selected in response to a second reference signal and the second feedback signal;
- and
- a means for shunting that is arranged to selectively couple power from the power source to a circuit ground in response to the control signal when active such that the other voltage associated with the battery is limited to a predetermined maximum and the voltage associated with the power source is limited to another predetermined maximum.
Dependencies are inferred from the claim text.